Regenerative heat exchanger with low pressure drop for use in heat or energy recovery ventilation

Abstract

A heat exchanger of the regenerative type which is capable of being utilized for transferring heat between incoming and outgoing building ventilation air. The article includes internal elements into which heat is transferred from the air, and from which heat is transferred to the air (3), between and around which air may flow. It preferably includes staggered internal heat exchange elements within a certain range of dimensions, elements for structural support of the heat exchange elements (4), and an outermost external wall (5).

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of provisional patent application Ser. No. 63 / 597,160 filed 2023 Nov. 8, by the present inventor(s), which is incorporated by reference in its entirety. The title of the provisional patent application is “Non-rotating regenerative heat exchanger for use in heat or energy recovery ventilation.”STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINT INVENTOR

[0002] There are no joint inventors involved in this patent application.

[0003] The disclosures the inventor has made on the subject have been after the inventor submitted the provisional patent application mentioned in this application.

[0004] These are limited disclosures made to other companies, without detail regarding dimensions or geometry of the article, while discussing their potential interest in licensing the the technology.TECHNICAL FIELD OF THE INVENTION

[0005] The embodiments described here relates primarily to a regenerative heat exchanger. More particularly, the invention relates to the transfer of heat energy between two volumes of building ventilation air to transfer heat energy and water vapor from one volume of air to another volume of air.BACKGROUND AND DISCUSSION ON PRIOR ART

[0006] Roughly 20% of all greenhouse gas emissions are a result of the energy expended on heating or cooling fresh air being brought into buildings. Bringing in clean air is the only practical way to control the levels of many types of indoor air pollutants such as carbon dioxide and volatile organic chemicals. Other habitable spaces such as vehicle cabins also benefit from outdoor air being brought in.

[0007] An energy recovery ventilator is known and designed to transfer heat energy from polluted, outgoing ventilation air to incoming, relatively clean, air. This greatly reduces the energy that is lost or expended to maintain adequate indoor air quality in a habitable volume, compared with straightforward transfer of air into or out of the volume with no heat or energy recovery.

[0008] A large fraction of buildings, residential or commercial, merely use a fan or the wind to blow or suck air in and expel it during winter, along with all its heat energy, to the outdoors. A similar but inverted situation arises with air conditioning in summer, where unwelcome heat and water vapor intrudes into the building when fresh air is brought in. These problems generally apply to other habitable indoor / inside spaces, such as vehicle cabins or recreational vehicles.

[0009] A decentralized / ductless / push-pull type energy recovery ventilator uses a reversible air moving device to move air through a regenerative heat exchanger, while periodically reversing airflow direction. Heat is stored from one volume of air in the solid structure of the heat exchanger and then released into the other air volume. Water vapor is similarly transferred. These ventilators are usually used in pairs, with one ventilator blowing air out of the dwelling while the other blows air in, to prevent any net changes in indoor air pressure that would lead to an egress or ingress of air through cracks etc. in the building envelope. However, both units operate in reverse direction in synchrony periodically.

[0010] The regenerator surface can be coated with a small amount of silica gel adsorbent or zeolite based material, like the common 3A molecular sieve material, lithium chloride, calcium chloride or another material which captures and releases water vapor effectively when exposed to higher / lower surrounding humidity.

[0011] All commercially produced regenerative heat exchangers that are currently available are produced form a cylindrical block of alumina with round, square or hexagonal channels. They suffer from poor airflow and poor efficiency of heat and water vapor transfer, generally making the machines they are used in uneconomical. Such machines generally have very long or infinite payoff periods i.e. periods before a return on investment is seen on heating costs. The fans also make more noise than is generally acceptable, to achieve the flow rates they do.

[0012] None of the commercially available devices used in decentralized push-pull type units allow effective water vapor transfer. They only transfer small amounts of water vapor between air streams due to condensation / deposition and evaporation / sublimation.

[0013] The use of regenerative heat exchangers in rotating thermal wheel type devices is well known in the art, and the heat exchange elements in them are usually made of corrugated metal, sometimes with adsorbents. In this type of device, the heat exchanger is rotated while air flows in one direction on one side of the exchanger and another direction on the other side. Thus, the fan does not need to reverse direction, but the heat exchange elements inside the heat exchanger still “see” periodic direction reversal. The demands placed on the performance and properties of these heat exchanger wheels are different in many ways from non-rotating devices, but the physics at a small scale are very similar. Far more effort in general has been put into the development of rotating devices.BRIEF SUMMARY OF THE INVENTION AND DIFFERENT EMBODIMENTS

[0014] The embodiments described herein relate to regenerative type heat exchangers that are designed to store heat in the solid structure of the device while it transfers heat and water vapor from one volume of air to another volume of air. The fluid, in this case air, passes by the internal elements used for heat exchange (e.g. walls) (3) in alternate directions at different times.

[0015] Without wishing to be bound by theory, in one of the embodiments, the regenerative type exchangers are particularly suitable and meant for use in ductless / push-pull / decentralized energy- and heat-recovery ventilator devices, which are used to transfer heat energy from outgoing building ventilation air to incoming air, or vice versa. However, a person skilled in the art would understand that the exchangers can be used in any other ventilator systems.

[0016] In one of the embodiments, the exchangers have external walls (2), and internal heat exchange elements (3), which are staggered which are capable of dividing the air flowing lengthwise along the device i.e. along the direction of travel repeatedly as the air flows lengthwise (axially) along the device. However, the design can be varied as needed depending on the ventilator system, the type of facility it's being used in, and its eventual use.

[0017] Very little of the cross section of the inner region of the pipe which passes through a building wall, allowing access to clean outdoor air, and in which the exchanger is typically inserted, is not available for air flow and heat exchange. This is advantageous over prior art devices which have thick outer housings walls or collars or foam collars between the actual heat exchanger and the inner diameter of the pipe. This is because producing new devices of custom size is costly, the outer walls of ceramic devices need to be thick and strong enough to resist cracking, and the ceramic is very rigid, and thus large nominal clearances must be left to allow for out-of-roundness and other variations in pipe geometry, so that the heat exchanger will reliably fit in the pipe segments it encounters in the real world.

[0018] Through additive manufacturing, custom and optimized designs can be produced for a given application with low tooling and manageable production cost, especially from polymers, and powder-filled polymers such as steel, copper, or alumina filled polymers.

[0019] The “tuning” of the length, diameter, and internal feature dimensions, is dependent on the application, but the parameters used in the first embodiment are a good compromise for typical residential decentralized ventilation.

[0020] The first embodiment may integrate an adsorbent, for instance Zeolite 3A, Type A Silica gel, or any other similar material, into the surface of the walls, bonded to the polymer material, to adsorb water vapor from one volume of air and subsequently release the water vapor into the air volume which is passed through the device in the opposite direction. A person skilled in the art would know that many variations of this embodiment with other adsorbent materials are encompassed within this disclosure.

[0021] The second embodiment is the same general design as the first embodiment, but the structure is made from a different material, for instance Alumina or any other similar material, to increase thermal mass and allow larger volumes of air to be passed in each direction during operation, making its use as a retrofit device in ventilators with long fan reversal times more practical. Zeolite or another adsorbent may be bonded to the surface with adhesive or through other means, or simply allowed to cling to the surface through weak forces such as van der waals forces.

[0022] The third embodiment is made of a cellular structure with a stack of segments, each segment similar to a conventional prior art device but much shorter. Each segment is rotated about 90 degrees relative to the last in the stack, or is slightly different in design, or rotated about 180 degrees (the walls can be offset from center such that 180 degree relative rotation of each slice places them in a manner such that they are staggered, even if the slices are identical), so that the walls split the air streams lengthwise repeatedly as the air flows lengthwise down the device. Any other variation of rotation between 30 degrees to 210 degrees is encompassed within the scope of this invention. Again, adsorbent may be added to it in a manner similar to any of the other embodiments. This embodiment plugs into existing manufacturing methodologies well because each segment or “slice” in the stack is basically the same as a conventional device, but heat flux is improved and axial conduction losses are greatly reduced. Indeed, a crude example can probably be made just by cutting a conventional device into segments, rotating each segment suitably, and then taping them back together.

[0023] The various embodiments described in this document have the following advantages over prior art devices, specific to the embodiments indicated:

[0024] The exemplary first, second and third embodiments are capable of transferring heat between volumes of air with higher efficiency, for a given average air flow rate.

[0025] The first, second and third embodiments described impede air flow through the device to a lower degree for a given flow rate. That is, the pressure drop is lower for a given flow rate.

[0026] The first embodiment is low cost to manufacture and requires only small amounts of capital to start manufacturing of a given design i.e. has low tooling costs associated with its manufacture, and any changes.

[0027] The first, second and third embodiments exhibit higher sound attenuation from indoor side to outdoor side than prior art devices of equal internal surface area and mass due to staggering of the internal heat exchange elements, causing reflections and attenuation of the sound waves.

[0028] The first embodiment additionally attenuates sound to a higher degree than prior art devices of equal mass due to the damping effect of the polymer material it is made from being larger than that of ceramics or metals.

[0029] There are a few publications that discuss regenerative heat exchangers in general. U.S. Pat. No. 5,050,667A shows a typical assembled ductless energy recovery ventilator with heat exchanger in place. U.S. Pat. No. 3,367,406A describes the heat exchanger with very thin walls and narrow channels, but for a purpose quite different than the goal of the present invention. U.S. Pat. No. 3,369,592A describes generically the purpose of a rotating heat exchanger device and provides broadly the role and nature of the corrugated heat exchange elements in that context, without providing any specifics. U.S. Pat. No. 9,404,689B2 shows the staggering of some elements but not all of the heat exchange surface, and the device is rotating, specifically made only of metals, and not for decentralized ventilation. US20140033924A1 talks briefly about heat element staggering but only of lattice elements made of sintered material. Other element types are not considered, and the value is not recognized, and it is for a purpose different than the goal of the present invention. No mention of the drag to efficiency ratio is mentioned. U.S. Pat. No. 2,558,752A shows limited staggering of some sections of the heat exchange surface, but only of small regions. The invention briefly discusses the effect of the heat element staggering, but not quantitatively. U.S. Pat. No. 3,369,592A only briefly discusses the staggering effect. Moreover, the reynolds number that helps predict fluid flow patterns are a bit unclear and different from the goal of the present invention. U.S. Pat. No. 3,965,695 briefly discusses staggering of heat elements for the purpose of interrupting axial flow which is only limited to metals with only random offset, not to split the air stream in half or thirds. U.S. Pat. No. 5,580,370 discusses a typical total sorption wheel. WO2018233775A1 describes a push-pull type heat exchanger made only of metals and ceramic, and does not teach staggering, and EP3401610B1 discusses interruption of heat flow axially along their proposed device. DE102013020758 shows addition of adsorbent to the interior surface of channels. GB1567239A shows a brief staggering effect but only for some fraction of the heat exchange elements, and only for a rotating device, and mentions polymers only in passing.EMBODIMENTS

[0030] The present invention overcomes the various problems and deficiencies of the prior art.

[0031] In an embodiment of the invention, an article or a device is provided which is a regenerative heat exchanger for transferring heat between volumes of building ventilation in a 6 decentralized manner.

[0032] The article comprises a plurality of solid elements as means for heat exchange, past which air may flow (3). The article also comprises means to hold said solid elements in position relative to each other. The solid elements as means for heat exchange (3) are staggered, thereby splitting the air stream flowing along the device longitudinally, along the nominal axis of the air flow one or more times as it flows through the device, whereby said staggering leads to increased ratio of the amount of heat energy and or water vapor transferred between air volumes and the air pressure needed to cause a predetermined rate of air flow through said article. In an exemplary embodiment the air flow channels or gaps between said solid elements as means for heat exchange have less than 4.8 mm in the shortest dimension. A person skilled in the art would understand that other variations of this device are encompassed within the scope of the present disclosure.

[0033] In a further embodiment, the solid elements as means for heat exchange are in the form of flat plates, spiral walls, concentric circles, concentric squares, airfoil like elements, rods, or any structure of equivalent or nearly equivalent geometry for heat transfer purposes. The solid elements may be fixed and non-rotating.

[0034] In a further embodiment, the article further includes an adsorbent or other material as means to retain and release water vapor in the process of transferring it between air volumes, such as zeolite, silica gel, or calcium or lithium chloride. The solid elements may be fixed and non-rotating.

[0035] In a further embodiment, said solid elements as means for heat exchange are made primarily of polylactic acid or any other similar material that's coated with an adsorbent to aid the transfer of water vapor. The solid elements may be fixed and non-rotating.

[0036] In a further embodiment, said solid elements as means for heat exchange are made primarily of a material of high volumetric heat capacity, such as alumina, polylactic acid, another plastic, iron, or some combination thereof, and which is fixed and non-rotating. Any other material with similar volumetric heat capacity as the ones noted above are also encompassed within the scope of this invention.

[0037] In a further embodiment, said solid elements as means for heat exchange are solid walls around air channels of hexagonal, square, round, triangular, or any other shape equivalent for the purpose of heat transfer, and which is fixed and non-rotating.

[0038] In a further embodiment, said solid elements as means for heat exchange are solid walls around air channels of hexagonal, square, round, triangular, or any other shape equivalent for the purpose of heat transfer, which is used in a rotating thermal wheel type configuration rather than non-rotating, in which more than 80 percent, of the active surface area of said elements as means of heat exchange are staggered relative to surfaces encountered by the most previous single set of elements upstream.

[0039] In a further embodiment, said solid elements as means for heat exchange are solid walls around air channels of hexagonal, square, round, triangular, or any other shape equivalent or nearly equivalent for the purpose of heat transfer, which is used in a rotating thermal wheel type configuration rather than non-rotating, and wherein said elements as means for heat exchange consist partly or primarily of a polymer or any other similar material fit for the intended purpose.

[0040] In a further embodiment, the solid material of which it is primarily constructed may be made primarily of any suitable material for heat storage and release, which in an exemplary embodiment may be a thermoplastic such as polyethylene terephthalate or polypropylene, and which may be combined with alumina or any other suitable material that fits the intended purpose.

[0041] In a further embodiment, the article may further include small elements to encourage mixing of the air within the air channel as it flows, thereby improving the ratio of flow impediment or flow drag to heat exchange efficiency. Other modifications that may allow similar result of improving the ratio of flow impediment or drag to heat exchange efficiency are also intended within the scope of the invention.

[0042] The invention further describes an article or a device, which is a regenerative heat exchanger for transferring heat between volumes of building ventilation in a decentralized manner. The article may comprise internal solid walls or elements as means for heat exchange with interspersed air channels. The interspersed air channels may be less than 1 mm-4 mm in the shortest dimension, more preferably less than 1.7 mm in the shortest dimension. The article or device may further comprise means for holding such solid elements in position relative to each other, which may be the elements themselves, and which is fixed and non-rotating.

[0043] In a further embodiment, the internal solid walls or element of the article as means for heat exchange are of thickness less than 0.3 mm-0.9 mm in the shortest dimension, preferably 0.65 mm in the shortest dimension.

[0044] In a further embodiment, the article may be composed primarily of alumina. In a further embodiment, the article may be composed primarily of any suitable material, which may be a thermoplastic such as polylactic acid, polyethylene terephthalate or polypropylene, and which may be combined with alumina or other material.

[0045] In a further embodiment, the air channels are less than 0.5 mm to 1.9 mm, preferably 1.35 mm in the shortest nominal dimension. In a further embodiment, the article may be made primarily of any suitable material, which may be a thermoplastic such as polylactic acid, polyethylene terephthalate or polypropylene, and which may be combined with alumina or other material, and which is coated with zeolite or another adsorbent or other material such as calcium chloride, to aid the transfer of water vapor. A person skilled in the art would understand that other suitable article materials or coating materials could be used as replacements that fit the intended purpose.

[0046] In another embodiment, the article may also comprise air flow channels or gaps between said solid elements as means for heat exchange having less than 2 mm to 6 mm in the shortest dimension, preferably less than 4.8 mm in the shortest dimension.BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The above and other aspects, features and advantages of the invention will become more readily apparent from the following description of the accompanying drawings. However, a person skilled in the art would understand that these figures are merely for representative purposes only and other variations of the embodiments shown and described may be possible.

[0048] FIG. 1 shows an exemplary primary embodiment.

[0049] FIG. 2 shows a cross section of the exemplary primary embodiment. It consists of many sections or “segments”, stacked. The thickness of the heat exchange elements is not to scale.

[0050] FIG. 3 shows a close up of the cross sectional view, showing the way the internal heat exchange elements are staggered and spaced, dividing the air stream lengthwise as it traverses the length of the device.

[0051] FIG. 4 shows the front view of the exemplary first embodiment, showing thin walls and thin air channels. The number of spiral rotations, thickness, and air gap is not exact.REFERENCE NUMERALS

[0052] The various parts shown in the figures and described herein are referred to by means of reference numerals throughout the description.

[0053] Notch to allow the passage of wires past the device after inserting it into a pipe is referred to by reference numeral referred to by reference numeral 1.

[0054] External wall is referred to by reference numeral 2.

[0055] Internal heat exchange element is referred to by reference numeral 3.

[0056] Internal supporting wall is referred to by reference numeral 4.

[0057] Segment of the assembly is referred to by reference numeral 5.DETAILED DESCRIPTION OF THE INVENTION

[0058] The following description is of preferred embodiments by way of example only and without limitation to the combination of features necessary for carrying the invention into effect.

[0059] All terms are intended to be understood as they would be understood by a person skilled in the art. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosure pertains. The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0060] Although various features of the present disclosure can be described in the context of a single embodiment, the features can also be provided separately or in any suitable combination. Conversely, although the present disclosure can be described herein in the context of separate embodiments for clarity, the present disclosure can also be implemented in a single embodiment.

[0061] Reference in the specification to “some embodiments,”“an embodiment,”“one embodiment”, “alternate embodiment”, or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments, of the present disclosures.

[0062] In the design of decentralized energy recovery ventilators, the space the device consumes in the wall it is built into is at a premium. For this reason, the methods usually employed in rotating heat exchangers, such as increasing diameter and size of the heat exchanger, which reduces velocity in the channels thus improving the flow to pressure relationship for a given efficiency, become less viable.

[0063] Additionally, simplicity and low cost of each device becomes more important. Additionally, noise production of the machine becomes considerably more important. The so-called dead space, which is the volume of air that is contained in the heat exchanger and sometimes adjoining duct or other volumes, also becomes more important compared with centralized ventilation systems.

[0064] The staggering of the heat exchange elements (3) to split the air stream lengthwise in two nearly equal parts improves all of these factors, if all else is kept constant to whatever degree practical.

[0065] Splitting the air stream in three equal or nearly equal parts is also an improvement over not staggering them at all, but overall it is fundamentally usually more useful in the context of decentralized building ventilation to split the air streams in half and then adjust the other parameters of the exchanger to adapt it to a given application if higher heat flux or flows are warranted.

[0066] Although the description uses the terms first embodiment, second embodiment etc, no superiority or order of any embodiment over another is implied or intended by these terms.

[0067] The inventor believes that the reason these developments were not uncovered before is fundamentally a lack of exploration, which is an outgrowth of, the inventor believes cultural ideas about the priorities in business, the lack of realization that increased performance was practical, and the high cost of manufacturing devices of novel design through conventional means, and lack of knowledge about additive manufacturing both during prototyping and for use during final manufacture.

[0068] The progress the inventor has made is by employing significant knowledge of several unrelated fields to even understand progress is possible and that the devices developed could be worth the investment and economically viable to produce and sell, and considerable amounts of human and monetary capital and time to actually realize such progress. They are also interrelated and one will not realize the potential without undertaking the more nuts and bolts stages. Together, these undertakings, which led to this superior result are best described as, simply, exploratory activity. Some credit should also go to relatively recent developments in manufacturing and prototyping techniques opening new doors.Exemplary First Embodiment

[0069] The first embodiment could be made of Polylactic Acid (PLA), or any material with similar properties, and the internal heat exchange elements (3) may be coated with a layer of zeolite 3A powder, silica gel powder, or a similar material to adsorb and desorb water vapor. Polylactic Acid is both low cost, easy to process and has a high volumetric heat capacity among the common polymers.

[0070] The zeolite can be bonded to the PLA by coating the plastic with a mixture of solvent and adhesive, allowing the solvent to evaporate, and then applying the powdered zeolite, which sticks to the adhesive permanently. The total mass of zeolite that sticks to the surfaces can be controlled by adjusting the particle size. There are many other usable methods for coating a surface with powder which are also suitable. After various rounds of testing, the inventor was able to get about 54 grams of powder onto the prototypes of the first embodiment, which is a good quantity for the purpose.

[0071] The internal walls (3) to which heat is transferred into from the air, and subsequently out of to the air, may be a spiral shape, with a width of 0.25 mm and about 98 rotations of the spiral. The width of the air channel between heat exchange element surfaces may be 1.25 mm. It is functionally very similar to a stack of flat plates, for this purpose. The spiral path is just faster and easier to manufacture through additive manufacturing. Flat plates also work and are equivalent in terms of their heat transfer and drag or fluid flow related properties in almost every way. One exception is that the air exiting from the fan is usually rotating, i.e. exhibiting a twisting motion. When this interacts with a stack of plates, it leads to a non-uniform pressure on the intake side of the heat exchanger. This tends to push an excessive amount of air through some areas and not as much through others. Spirals and concentric circles avoid this concern. The supporting walls can be rotated relative to each other in each slice, to reduce this effect, as well, or minimized in size. A person skilled in the art would understand that the dimensions provided are merely exemplary and could be modified to fit the intended design and purpose.

[0072] Each set of internal walls in each section (3) similar to the individual slice / segment (5) in the finished, assembled, device, is rotated 180 degrees relative to the ones in adjacent slices. This causes the heat exchange elements to be “staggered” i.e. to split the air stream lengthwise, as indicated in FIG. 3. This is due to the spiral nature of the heat exchange elements, in this case, as a spiral rotated in this way will combine with a non-rotated spiral path such that the path of the second spiral lies in between the paths of the first. However it can be accomplished through other means if concentric circles or other designs are used.

[0073] As can be seen from the drawings, except for the supporting walls (4) and the outermost wall (2), the elements which serve as means of heat exchange do not have walls which are colinear or coplanar in most areas. That is, a large fraction of the wall surfaces used for heat exchange are staggered or offset from each other. Additionally, the heat exchange elements (3) split the air stream in half. If higher internal surface areas are desired, rather than splitting the air stream into thirds, the air channel width or other parameters may be changed while maintaining the approach of splitting the air stream in half. This halfing brings the under-tapped center of the air stream into contact with the heat exchange elements effectively.

[0074] There is a notch (1) at the top of the device to allow the passage of wires for a fan, sensors and valves etc. on the other side of the heat exchanger while it is installed in a pipe.

[0075] Inside the air channel, air flows down the length of the device. Heat is transferred into or out of the heat exchange elements (3) by various mechanisms, mostly conduction and radiation. The influence of convection is limited because the gas flow is mostly laminar due to channel geometry and gas velocity, which is usually in the range of 0.3 to 2.2 meters per second, but can deviate from this.

[0076] The inventor has found, through simulation and experimentation, that the primary impediment to heat flow from the bulk of the gas to the internal regions of the wall is within the gas stream itself. The center of the gas stream in each segment of the device, or in the whole of a prior art device, has a low rate of addition or loss of heat because the heat mostly diffuses through the gas sideways. When the channel is made thinner, this effect is reduced. However in the completed device, if the entire cross section is filled with channels and all else is held constant, the viscous drag also increases, and thus we are limited in how thin we can practically make the channel.

[0077] If a positive displacement air moving device such as a piston is used, then much thinner heat exchange elements and channels may be used practically. When a fan is used, the noise produced by the fan when generating high pressures is the main limiting factor in most use scenarios. Advanced fan designs such as multiple impellers with air flow straightening means between them, or counter rotating impellers, can be used to improve the pressure to noise ratio and thereby open the door to changes in the heat exchanger. Such variations of the device are also encompassed within the scope of this invention.

[0078] When the heat exchange elements (3) are staggered as described, the center of the air stream is suddenly and periodically brought close to a solid heat exchange element as it flows down the length of the device. This allows the heat to be conducted into or removed from the center much more effectively. The frequency with which the walls should be staggered is a question that can be approximately answered by simulation and experimentation.

[0079] A higher staggering frequency tends to increase efficiency and heat flux but makes the device longer, due to the spacing needed between slices, unless very thin heat exchange elements are used, and more complex to manufacture. 6 to 23 segments is a practical range for most purposes of concern.

[0080] According to simulations, the increase in heat transfer coefficient for a given drag factor (the drag in these devices is primarily viscous drag, which increases with surface area) is in the range of a factor of 2 and may be even more. This is an extremely significant improvement which is very hard to obtain through any other means, and the magnitude of this has not apparently been understood or valued by others until now even by those authors of the prior art patents which, for other applications and with other materials and designs and purposes, used staggered heat exchange elements. There is no mention of the use of staggered elements in non-rotating exchangers for decentralized ventilation.

[0081] Using the available cross sectional area through which the air may flow through a pipe is also important. This is primarily a matter of tooling costs and ensuring adequate clearance to fit in the pipe these devices are normally used in. The exterior wall of the device benefits from being relatively thin. Both of these factors are improved by the use of polymer materials rather than ceramics, which are less prone to cracking and are more conformal.

[0082] The transfer of water vapor (mass transfer) is also improved by staggering and air channel thicknesses (starting from smallest nominal dimension) in this range.

[0083] The turbulence within the small region where the gas meets the solid can actually be helpful in reducing viscous drag and increasing heat flux rate, depending on conditions. The “stairstep effect” of additively manufactured devices thus may be helpful in reducing the impediment to airflow within the device, and also the surface roughness provided by the particles of zeolite or any similar material.

[0084] The first embodiment is expected to be manufactured primarily through additive manufacturing, but the approximate geometry is amenable to injection molding and extrusion as well.

[0085] The thickness of the heat exchange elements is reduced as much as practical while allowing adequate thermal mass. The conduction within the walls is improved when they are thinner.

[0086] The inventor has found that the use of polymer materials is viable and practical when the heat exchange elements are in this thickness range. There is no need to use ceramics or metals for their higher thermal conductivity within the volume of the heat exchange elements (3), in contrast to generally perceived assumption that higher thermal conductivity is important in this context.

[0087] The optimal heat exchange element thickness and air channel thickness depends largely on the air moving device employed. This is usually a fan, however centrifugal versus axial fan makes a difference, and pistons, bellows, roots blowers, convel blowers, spring loaded fans (for rapid direction reversal) or other devices may be viable and would imply thinner heat exchange elements (3) and / or air channels.

[0088] Prior art devices use much thicker walls and thicker air channels, and no staggering of the internal heat exchange elements, leading to far inferior heat transfer efficiencies. They also suffer from internal conduction in the axial direction, which is detrimental to efficiency. The first embodiment as shown and described can sustain much higher flow rates at practical pressure drops, and at higher efficiencies, as indicated by the contents of table 1. This has significant implications for the economics of machines which employ this type of heat exchanger.

[0089] The inventor has found with some testing that this device also impedes the propagation of sound energy through the device noticeably better than a conventional prior art device, due to the different geometry and materials used. The sound energy on the exterior side of a wall is not generally welcome on the interior side of a building, so the sound attenuation through such devices is a useful feature.

[0090] The method of manufacturing the device will be apparent to a person skilled in the art. The devices that were tested were made using common Filament Deposition Manufacturing additive manufacturing techniques, with suitably small nozzles and gcode generation methods. Selective Laser Sintering is also suitable.

[0091] The PLA material also is a renewable resource, made through biological processes, and can be composted under suitable conditions.

[0092] The addition of alumina powder, iron, steel, copper, aluminum, or another powder with high volumetric heat capacity to the polymer would allow the solid fraction to be smaller for a given thermal mass, and thus the number of air channels to be more numerous, and thus further improve the relationship between the heat transfer efficiency, pressure drop or drag coefficient of the device, and fan reversal time, and thus make for a more performant energy recovery ventilator, all else being kept constant. The use of apollonian packing, in which a size distribution of powders is used to progressively fill voids and reduce the polymer content while increasing fluidity of the material during processing is a good approach. Similar to how it is used in so called high performance concrete to reduce the quantity of cement and water but retain adequate fluidity.

[0093] The inventor has found that the addition of a small element in between the heat exchange elements (3) to cause the air in the center of the channel to trade places with the air near the heat exchange elements is useful, however this actually ultimately resembles simply using a larger number of thinner slices and thus a higher frequency of staggering of the heat exchange elements (thinner slices). It is not, as prior art discusses in the context of rotating heat exchangers, for the purpose of inducing turbulence. Such an object in the flow path does not lead to the production of significant turbulence at the channel sizes and flow velocities of concern here (0.3-2.2 m / s and channels less than approximately 1.8 mm wide).

[0094] The inventor has in fact tested a device very similar to the first embodiment with a test apparatus to measure thermal efficiency and flow rates. The data collected from testing indicates that the performance figures indicated by Table 1 are correct.

[0095] The inventor has found that the ventilation warranted per room generally exceed the ability of decentralized energy recovery and heat recovery ventilators on the market which use a reversing fan, and this is due primarily to the limitations imposed by the heat exchangers, which unduly impede airflow and suffer from inadequate heat exchange efficiency to justify their cost in most contexts, combined with the limits of fan technology.Exemplary Second Embodiment

[0096] The second embodiment is the same general shape and design as the first, but the solid material is alumina or a similar material, and the thickness of the heat exchange elements, air channels and number of segments it is constructed from may be adjusted to adapt it to the new material. Alumina has an even higher volumetric heat capacity, 3.45 joules per degree per cubic centimeter, vs 2.25 for PLA. Thus, the heat capacity of the second embodiment is much larger, and this is useful in some contexts.

[0097] The collars extending upwards from each segment (5) may be retained or omitted if their production seems cumbersome.

[0098] Alternately, the heat exchange elements can be made thinner and the spiral density increased, to further reduce the impediment to airflow, while still allowing adequate thermal mass / heat storage capability. A device made of alumina of the same thermal mass as a device made from PLA may have approximately an 8% lower drag coefficient.

[0099] Zeolite or any other similar material may be bonded to the surface of the internal heat exchange elements to aid water vapor transfer, with e.g. the use of adhesive.

[0100] Alumina has a far higher thermal conductivity than polymer materials such as PLA, and while this may appear to be desirable at first blush, it provides minimal benefit because of the thinness of the heat exchange elements to begin with, and this can be detrimental if the heat exchange element staggering is not employed, or if the stacks are allowed to be in very good thermal contact for any reason.

[0101] This is because heat may be conducted axially down the length of the device, reducing the grade of the heat. It is fundamental and will be recognized by someone skilled in the art that axial conduction along the length of a regenerative heat exchanger tends to reduce system efficiency, this applies to many systems which use regenerative heat exchangers, even unrelated to building ventilation air. Table 2 indicates a calculated value to show approximately the magnitude of this effect in this context, and that it is significant.

[0102] Thus, the staggering of the internal heat exchange walls provides two useful effects. One, it improves transfer of heat energy from the air to the solid material, secondly, it impedes heat flow axially along the device.Exemplary Third Embodiment

[0103] The third embodiment is a non-rotating device for use in a pipe for decentralized energy recovery ventilation, and uses slices which have hexagonal, square or rectangular air channels, parallel, slanted or helical. The internal heat exchange elements are arranged so that again they split the air stream lengthwise. This can be accomplished by either making the slices identical and rotating each second one slightly while assembling them, or by making them slightly different from each other. The material may be Alumina, polylactic acid, or another material. The staggering leads to the splitting of the air stream in half lengthwise, increasing heat flux from air to solid and also preventing axial conduction between slices.

[0104] Although prior art reference U.S. Pat. No. 3,965,695A indicates such hexagonal channels which are also staggered, they imply the use of random staggering, the exclusive use of metals, and it is a rotating thermal wheel type device with a very different application. The size of the effect does not appear to be understood, and no mention is made of the drag to heat flux ratio improvement. The staggering is not in that case for the purpose of increasing heat flux but to prevent axial conduction. If polymers are used in the heat exchange elements, axial conduction is negligible anyway.

[0105] Table 1 shows figures obtained by simulation, experimentation and estimates. The inventor believes them to be more or less reasonable estimates for the climate in Ottawa, Ontario or a similar region. As you can see, the first embodiment is capable of providing far greater total heat energy recovery than a prior art type device. The rightmost column indicates the calculated heat energy captured in the climate of Ottawa, Ontario, Canada (4700 heating degree days).TABLE 1Quantitative performance comparison, based on simulation and estimates.Ratioofthermalmasscycle(RegeneratorheatFlowReversalefficiency,latenttotransferrateperiodsensibleefficiencyRegeneratoraircoefficient(cfm)(s)(%)(%)typebatch)Notes14845209072First2.4.embodiment148453085.268.16First1.65embodiment14845309172.8Second2.9embodiment14820309374.4First3.7embodiment148582089.671.68First1.9close toembodimentmaximalairflow at3 mmH2O forfirstembodiment7820907560prior2.9artdevice78453068.454.72prior2.175impedesartairflowdevicetoo muchtoachievethis with<3 mmH2OheatAirAirrecoveredenergythermalWaterwaterthermalRecoveredairtotalsavedheatpower,content,content,power,powerpower,recoveredpertransfersensibleg / m3,g / m3,latent(sensible)latentpowerseasoncoefficient(W)indooroutdoors(W)(W)(W)(W)(kWh)148534.878.561.893204812307113827148534.878.561.89320456218674148534.878.561.89320487233720148237.728.561.891422211063271757148713.168.561.89412639295934493278237.728.561.8914217885263137678534.878.561.89320366175541ExpectedRecoveredefficiency,RecoveredpowerEfficiencywithoutTotalpowerafterafteraxialairBeforeAxialaxialaxialFlowlosspoweraxiallossconductionconduction(CFM)(%)(W)loss(W)lossloss2075237.7217814.7163.368.64568.4534.87365.813.4352.465.8Table 2 shows to a first degree of approximation, what kind of impact axial heat conduction has, based on hand calculations, on efficiency, on a conventional prior-art device made from alumina, of the same design assumed in Table 1.OperationThe first, second, and third embodiments are all used in a similar way. They are installed in a pipe or hole of some kind, usually circular in cross section. An air moving device is placed before or after the device, and provides air pressure to force air through the device.

[0107] The direction of this airflow is reversed periodically, depending on flow rate and desired efficiency and trade-offs such as the nature and degree of noise produced by the air moving device, and how acceptable it is. A suitable reversal time is in the range of 30 seconds, for the first embodiment, given air pressures of 3 mm H2O or less. It may be longer if lower pressures are used, or shorter if higher pressures are used.

[0108] The air moving device is usually a fan, and usually an axial fan or combination of one or more axial fans. The use of two or more fan or impellers with flow straighteners between them, or a set of counter rotating fans with fan blades that are mirror images of each other, for instance, has been proposed to provide a quieter but still economical and compact air moving device.

[0109] Flow switches and centrifugal fans can also be used, as well as positive displacement devices such as pistons and Roots blowers, and so-called convel blowers.

[0110] For fans in particular, the noise emitted by the air moving device generally increases seriously when it rotates faster. To produce higher flow and pressures, higher rotational speeds and thus noise levels are implied, all else being equal. Pressure increases roughly in accordance with the square of blade velocity, while noise power increases approximately in accordance with the eighth power.

[0111] This is one reason that it is important for the heat exchanger device to achieve a low pressure drop / impediment to airflow. Humans are very sensitive to noise in their building environments, and it has proven detrimental effects. It is a form of pollution which it is important to limit.

[0112] Thus, these embodiments and those with features of the type and range described provides a lower impediment to air flow i.e. lower drag coefficient(s), lower pressure drop for a given flow rate, and / or a higher efficiency, or improved relationship between these factors, when used suitably (mostly, with a suitable fan reversal time), compared with prior art heat exchangers in use for this purpose and similar purposes, such as in a vehicle.

[0113] Lower impedance to air flow gives benefits that are not always immediately obvious. The psychoacoustics of noise dictate that humans generally find noise sources that vary in volume, rather than consistent noise, to be more detrimental, for a given average sound power. By allowing the heat exchanger to impede airflow less, the fan becomes much quieter at a given flow rate, and thus short fan reversal times become acceptable because the user does not notice the noise even at peak level, and thus small thermal masses become acceptable.Ramifications and Scope

[0114] While the above description contains many specificities, these should not be construed as limitations on the scope, but rather as an exemplification of several embodiment(s) thereof. Many other variations are possible. For example:Different Colors, Sizes and Materials:

[0115] The color of the device is generally not important, however it may be any color. The overall dimensions such as width or diameter and length of the device may very much be different.

[0116] The first embodiment is made with a pipe of 150 mm inner diameter in mind, however clearly a different diameter pipe has important benefits, in particular in designing a machine with even higher air flow capability or even lower fan noise.

[0117] The use of a device with larger diameter is particularly important as a larger diameter is a very effective way to increase air flow. Diameters such as approximately 8 or 12 inches are very likely to be commercially valuable as pipes, fans and hole drilling tools for these sizes are common and cost effective. A diameter of 12 inches implies a cross sectional area of 4 times greater than 6 inches, so the air flow can be greatly increased without encountering complications from fan noise and heat exchange efficiency etc.

[0118] The length of the device may also be varied. There may be an optimal length for any given application, and a wide range is usually usable even if not optimal, in any given application.

[0119] Different materials may also be used, even if they are not high volumetric heat capacity materials. Materials such as mylar or polypropylene are usable, for instance, in particular if lower thermal masses are acceptable due to the type of air moving device, or if the heat exchanger is used in a rotating thermal wheel type device.Filled or Composite Material Ramification;

[0120] Any of the embodiments, or similar devices may be made of a combination of alumina powder or fibers or similar combined with a polymer or other material. This may allow the walls to be thinner while maintaining adequate thermal mass for a purpose, with little additional cost. This allows either larger air channels or more numerous air channels in the same cross section, reducing the impediment to air flow and / or improving efficiency by increasing the surface area available for heat transfer.

[0121] The use of apollonian packing i.e. using a suitable distribution of particle sizes, may for instance allow very high alumina content while maintaining adequate processability of the material (e.g. low viscosity in the fluid state). An alumina content, in the range of 80% or more by volume may be practical, thus giving the material the processing advantages of polymers but most of the volumetric heat capacity of alumina.

[0122] This is particularly useful for retrofit devices, which are used in place of prior art devices with minimal or no change to the rest of an already installed system. This is because the fan reversal time tends to be relatively long for devices currently installed, i.e. the amount of air flowing in either direction before fan reversal occurs is relatively large. Therefore, a higher thermal mass is particularly useful in such a context.Rotating Device Ramification:

[0123] This ramification is similar to the first embodiment, but with the addition of additional walls similar to internal supporting wall (4), of similar but different orientation. Any given one of these walls may extend fully or partially along the radius of the device, with additional arc sections to prevent air from going around the walls, which connect the walls oriented parallel to the radius of the device i.e. orthogonal to the axis of rotation. These additional walls are to guide airflow, preventing flow cross-wise within the device. They are parallel to the direction of air motion desired much like the internal supporting wall (4). They resemble spokes, but there is no need for higher density towards the center, so some spokes are omitted in that area, and a circular arc is used to prevent air from going around the spokes at their ends, mostly where the two axially stacked segments analogous to heat exchanger segment (5), meet.

[0124] This device may be used in a rotating heat exchanger similar to the common thermal wheel type devices, possibly inside a pipe such as an 8, 10 or 12 inch diameter pipe, to save space. It may be a larger diameter than the first embodiment, as well, have a hole in the center 6 for an axle to aid rotation, and may be shorter, and have thinner internal heat exchange elements, which are acceptable due to lower thermal mass demands. The reduced diameter of the device provided by staggering a large fraction, such as 70 percent or more, of the heat exchange surfaces, is useful here so that it may be of smaller diameter. The pipe has to be sealed around it's periphery and larger diameter pipes are less convenient, more expensive to install, and allow more noise through.

[0125] In a thermal wheel type regenerative heat exchanger, instead of reversing the air flow through the heat exchanger elements by reversing the fan, the entire heat exchanger is rotated, with air flowing in different directions in different sections of the physical heat exchanger element assembly, at any given moment.

[0126] The additional walls described above serve to prevent air from flowing sideways through the exchanger from one side to the other, which would lead to air being “short circuited” from the indoor side, back to the indoors, or from the outdoors back to the outdoors. The importance of such walls is well known in the art of thermal wheel type device design.

[0127] This thermal wheel approach has much shorter practical flow reversal time for each heat exchange element, which allows the total thermal inertia of the heat exchanger to be reduced, allowing heat flux rate to be increased for a given efficiency, and allowing the length of the device to be smaller.

[0128] It also allows for continuous airflow, which improves average air flow rates due to the elimination of fan acceleration periods, and makes fan noise less of a problem due to the way humans tend to perceive or be affected by noise which varies in volume with time.

[0129] It also allows for the use of centrifugal fans without any kind of flow switch, which may produce less noise for a given level of pressure and air flow. The low thermal inertia demands makes the use of polymers more practical, compared with alumina, which has a higher volumetric heat capacity, in the range of 3.45 joules per degree per cubic centimeter, vs 2.25 for PLA and 1.65 for polyethylene terephthalate.

[0130] As discussed elsewhere in this document, the inventor has found that in this context that there is no need to use the usual metals in the heat exchange elements, and it is often detrimental 6 due to axial conduction, even within the slices.

[0131] Prior art reference GB1567239A indicates they considered staggering some but not all of the heat exchange surfaces / elements in a rotating device, but not for decentralized ventilation systems. Prior art reference U.S. Pat. No. 3,965,695A discusses staggering of honeycomb shaped elements only made out of metallic material and not for decentralized ventilation systems. There is one company that commercially produces rotating thermal wheels with a polymer material as the solid heat storage structure, but not with a staggered-heat exchange elements design.

[0132] For the most part, the inventor has found the complexity and relatively large diameter of current prior art thermal wheel type machines is what prevents their use in a small dwelling such as a house or apartment, especially in a decentralized ventilation scheme, which implies a higher number of lower cost, lower capacity, and physically smaller devices, which warrant higher reliability without maintenance.Further Ramifications:

[0133] Devices with very small thermal mass may be used if a piston or other air moving device is used. Another example of an air moving device that may make use of a heat exchanger with very small mass is a fan with spring loaded impeller, so that it may reverse direction at high frequency with good efficiency and speed. These heat exchanger devices suitable for pairing with such an air moving device may have very small air channels and thin walls, obtaining similar internal heat exchange surface areas and thus similar viscous drag. Viscous drag is generally the dominant source of drag / impediment to air flow in these devices. If a piston is used, a much higher pressure drop is allowable, without excessive noise from the air moving device.

[0134] The supporting walls (4) can be omitted through any of various means, or may be optional in some contexts. For example, the spiral can be made to have a wavy pattern superimposed on the spiral pathway, so that the heat exchange elements are self supporting. A wavy spiral could also be interleaved between a linear spiral shape, to make the heat exchange elements self supporting. They could be supported by means that are not evident in a cross sectional view, such as an element behind or between each slice. They can be strong and rigid enough to simply be self supporting to an adequate degree. The device could be mounted with the central axis vertical, so the spiral does not sag anyway. The walls could be vertical flat plates instead of a spiral or concentric circles. Multiple nested or interleaved spirals could be used. Two or more superimposed spirals, one clockwise and the other counterclockwise, could be used. The flat supporting walls can extend merely part way up the slice and still provide adequate support.

[0135] A spacer could be used between each segment, which also served to support the heat exchange elements against the force of gravity. This allows the use of plastic sheet or ribbon, which is very economical, in the formation of the spiral.

[0136] These supporting walls (4) or the larger scale geometrical features and shapes can mostly be readily changed, in too many ways to cover them all explicitly, without affecting performance or manufacturability. A person skilled in the art will readily see the equivalence for the purpose between a spiral pathway and parallel flat internal heat exchange elements, or multiple spirals, for instance.

[0137] Accordingly, the scope of the disclosure should be determined not by the embodiment(s) illustrated, but by the appended claims and their legal equivalents.Conclusion

[0138] Thus, the reader will see that at least one embodiment of the heat exchanger can allow for a higher flow of air and larger amounts of energy recovered per season or per second, with less noise from the fan or other air moving device, without prohibitively or any higher manufacturing costs than prior art devices. This directly implies that an energy or heat recovery ventilator with a higher return on investment can be built with this heat exchanger than with prior art heat exchangers.

[0139] There are also many other advantages such as higher sound attenuation and possibly lower cost of manufacture. It may also be used during periods of air conditioning to prevent the intrusion of heat and water vapor while allowing fresh air in. These properties all contribute to higher quality of life, reduced greenhouse gas emissions and fuel costs. This benefit can be delivered to a great number of people using buildings in both hot and cold climates, if applied during new construction or through retrofit of existing buildings, leading to a large total net improvement in environmental and human well being.

[0140] The device is not meant to be limited to the forms shown or described. The size and geometry and relative position of the heat exchange elements or overall device may be varied, and the color size and material may be different.

[0141] Accordingly, the scope of the disclosure should be determined not by the embodiment(s) illustrated, but by the appended claims and their legal equivalents.

[0142] While preferred embodiments of the present invention have been shown and described above, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It is not intended that the invention be limited by the specific examples provided within the specification. While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of the embodiments herein are not meant to be construed in a limiting sense. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Furthermore, it shall be understood that all aspects of the invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is therefore contemplated that the invention shall also cover any such alternatives, modifications, variations or equivalents. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Examples

exemplary first embodiment

[0069]The first embodiment could be made of Polylactic Acid (PLA), or any material with similar properties, and the internal heat exchange elements (3) may be coated with a layer of zeolite 3A powder, silica gel powder, or a similar material to adsorb and desorb water vapor. Polylactic Acid is both low cost, easy to process and has a high volumetric heat capacity among the common polymers.

[0070]The zeolite can be bonded to the PLA by coating the plastic with a mixture of solvent and adhesive, allowing the solvent to evaporate, and then applying the powdered zeolite, which sticks to the adhesive permanently. The total mass of zeolite that sticks to the surfaces can be controlled by adjusting the particle size. There are many other usable methods for coating a surface with powder which are also suitable. After various rounds of testing, the inventor was able to get about 54 grams of powder onto the prototypes of the first embodiment, which is a good quantity for the purpose.

[0071]The ...

exemplary second embodiment

[0096]The second embodiment is the same general shape and design as the first, but the solid material is alumina or a similar material, and the thickness of the heat exchange elements, air channels and number of segments it is constructed from may be adjusted to adapt it to the new material. Alumina has an even higher volumetric heat capacity, 3.45 joules per degree per cubic centimeter, vs 2.25 for PLA. Thus, the heat capacity of the second embodiment is much larger, and this is useful in some contexts.

[0097]The collars extending upwards from each segment (5) may be retained or omitted if their production seems cumbersome.

[0098]Alternately, the heat exchange elements can be made thinner and the spiral density increased, to further reduce the impediment to airflow, while still allowing adequate thermal mass / heat storage capability. A device made of alumina of the same thermal mass as a device made from PLA may have approximately an 8% lower drag coefficient.

[0099]Zeolite or any othe...

exemplary third embodiment

[0103]The third embodiment is a non-rotating device for use in a pipe for decentralized energy recovery ventilation, and uses slices which have hexagonal, square or rectangular air channels, parallel, slanted or helical. The internal heat exchange elements are arranged so that again they split the air stream lengthwise. This can be accomplished by either making the slices identical and rotating each second one slightly while assembling them, or by making them slightly different from each other. The material may be Alumina, polylactic acid, or another material. The staggering leads to the splitting of the air stream in half lengthwise, increasing heat flux from air to solid and also preventing axial conduction between slices.

[0104]Although prior art reference U.S. Pat. No. 3,965,695A indicates such hexagonal channels which are also staggered, they imply the use of random staggering, the exclusive use of metals, and it is a rotating thermal wheel type device with a very different appl...

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of provisional patent application Ser. No. 63 / 597,160 filed 2023 Nov. 8, by the present inventor(s), which is incorporated by reference in its entirety. The title of the provisional patent application is “Non-rotating regenerative heat exchanger for use in heat or energy recovery ventilation.”STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINT INVENTOR

[0002] There are no joint inventors involved in this patent application.

[0003] The disclosures the inventor has made on the subject have been after the inventor submitted the provisional patent application mentioned in this application.

[0004] These are limited disclosures made to other companies, without detail regarding dimensions or geometry of the article, while discussing their potential interest in licensing the the technology.TECHNICAL FIELD OF THE INVENTION

[0005] The embodiments described here relates primarily to a regenerative heat exchanger. More particularly, the invention relates to the transfer of heat energy between two volumes of building ventilation air to transfer heat energy and water vapor from one volume of air to another volume of air.BACKGROUND AND DISCUSSION ON PRIOR ART

[0006] Roughly 20% of all greenhouse gas emissions are a result of the energy expended on heating or cooling fresh air being brought into buildings. Bringing in clean air is the only practical way to control the levels of many types of indoor air pollutants such as carbon dioxide and volatile organic chemicals. Other habitable spaces such as vehicle cabins also benefit from outdoor air being brought in.

[0007] An energy recovery ventilator is known and designed to transfer heat energy from polluted, outgoing ventilation air to incoming, relatively clean, air. This greatly reduces the energy that is lost or expended to maintain adequate indoor air quality in a habitable volume, compared with straightforward transfer of air into or out of the volume with no heat or energy recovery.

[0008] A large fraction of buildings, residential or commercial, merely use a fan or the wind to blow or suck air in and expel it during winter, along with all its heat energy, to the outdoors. A similar but inverted situation arises with air conditioning in summer, where unwelcome heat and water vapor intrudes into the building when fresh air is brought in. These problems generally apply to other habitable indoor / inside spaces, such as vehicle cabins or recreational vehicles.

[0009] A decentralized / ductless / push-pull type energy recovery ventilator uses a reversible air moving device to move air through a regenerative heat exchanger, while periodically reversing airflow direction. Heat is stored from one volume of air in the solid structure of the heat exchanger and then released into the other air volume. Water vapor is similarly transferred. These ventilators are usually used in pairs, with one ventilator blowing air out of the dwelling while the other blows air in, to prevent any net changes in indoor air pressure that would lead to an egress or ingress of air through cracks etc. in the building envelope. However, both units operate in reverse direction in synchrony periodically.

[0010] The regenerator surface can be coated with a small amount of silica gel adsorbent or zeolite based material, like the common 3A molecular sieve material, lithium chloride, calcium chloride or another material which captures and releases water vapor effectively when exposed to higher / lower surrounding humidity.

[0011] All commercially produced regenerative heat exchangers that are currently available are produced form a cylindrical block of alumina with round, square or hexagonal channels. They suffer from poor airflow and poor efficiency of heat and water vapor transfer, generally making the machines they are used in uneconomical. Such machines generally have very long or infinite payoff periods i.e. periods before a return on investment is seen on heating costs. The fans also make more noise than is generally acceptable, to achieve the flow rates they do.

[0012] None of the commercially available devices used in decentralized push-pull type units allow effective water vapor transfer. They only transfer small amounts of water vapor between air streams due to condensation / deposition and evaporation / sublimation.

[0013] The use of regenerative heat exchangers in rotating thermal wheel type devices is well known in the art, and the heat exchange elements in them are usually made of corrugated metal, sometimes with adsorbents. In this type of device, the heat exchanger is rotated while air flows in one direction on one side of the exchanger and another direction on the other side. Thus, the fan does not need to reverse direction, but the heat exchange elements inside the heat exchanger still “see” periodic direction reversal. The demands placed on the performance and properties of these heat exchanger wheels are different in many ways from non-rotating devices, but the physics at a small scale are very similar. Far more effort in general has been put into the development of rotating devices.BRIEF SUMMARY OF THE INVENTION AND DIFFERENT EMBODIMENTS

[0014] The embodiments described herein relate to regenerative type heat exchangers that are designed to store heat in the solid structure of the device while it transfers heat and water vapor from one volume of air to another volume of air. The fluid, in this case air, passes by the internal elements used for heat exchange (e.g. walls) (3) in alternate directions at different times.

[0015] Without wishing to be bound by theory, in one of the embodiments, the regenerative type exchangers are particularly suitable and meant for use in ductless / push-pull / decentralized energy- and heat-recovery ventilator devices, which are used to transfer heat energy from outgoing building ventilation air to incoming air, or vice versa. However, a person skilled in the art would understand that the exchangers can be used in any other ventilator systems.

[0016] In one of the embodiments, the exchangers have external walls (2), and internal heat exchange elements (3), which are staggered which are capable of dividing the air flowing lengthwise along the device i.e. along the direction of travel repeatedly as the air flows lengthwise (axially) along the device. However, the design can be varied as needed depending on the ventilator system, the type of facility it's being used in, and its eventual use.

[0017] Very little of the cross section of the inner region of the pipe which passes through a building wall, allowing access to clean outdoor air, and in which the exchanger is typically inserted, is not available for air flow and heat exchange. This is advantageous over prior art devices which have thick outer housings walls or collars or foam collars between the actual heat exchanger and the inner diameter of the pipe. This is because producing new devices of custom size is costly, the outer walls of ceramic devices need to be thick and strong enough to resist cracking, and the ceramic is very rigid, and thus large nominal clearances must be left to allow for out-of-roundness and other variations in pipe geometry, so that the heat exchanger will reliably fit in the pipe segments it encounters in the real world.

[0018] Through additive manufacturing, custom and optimized designs can be produced for a given application with low tooling and manageable production cost, especially from polymers, and powder-filled polymers such as steel, copper, or alumina filled polymers.

[0019] The “tuning” of the length, diameter, and internal feature dimensions, is dependent on the application, but the parameters used in the first embodiment are a good compromise for typical residential decentralized ventilation.

[0020] The first embodiment may integrate an adsorbent, for instance Zeolite 3A, Type A Silica gel, or any other similar material, into the surface of the walls, bonded to the polymer material, to adsorb water vapor from one volume of air and subsequently release the water vapor into the air volume which is passed through the device in the opposite direction. A person skilled in the art would know that many variations of this embodiment with other adsorbent materials are encompassed within this disclosure.

[0021] The second embodiment is the same general design as the first embodiment, but the structure is made from a different material, for instance Alumina or any other similar material, to increase thermal mass and allow larger volumes of air to be passed in each direction during operation, making its use as a retrofit device in ventilators with long fan reversal times more practical. Zeolite or another adsorbent may be bonded to the surface with adhesive or through other means, or simply allowed to cling to the surface through weak forces such as van der waals forces.

[0022] The third embodiment is made of a cellular structure with a stack of segments, each segment similar to a conventional prior art device but much shorter. Each segment is rotated about 90 degrees relative to the last in the stack, or is slightly different in design, or rotated about 180 degrees (the walls can be offset from center such that 180 degree relative rotation of each slice places them in a manner such that they are staggered, even if the slices are identical), so that the walls split the air streams lengthwise repeatedly as the air flows lengthwise down the device. Any other variation of rotation between 30 degrees to 210 degrees is encompassed within the scope of this invention. Again, adsorbent may be added to it in a manner similar to any of the other embodiments. This embodiment plugs into existing manufacturing methodologies well because each segment or “slice” in the stack is basically the same as a conventional device, but heat flux is improved and axial conduction losses are greatly reduced. Indeed, a crude example can probably be made just by cutting a conventional device into segments, rotating each segment suitably, and then taping them back together.

[0023] The various embodiments described in this document have the following advantages over prior art devices, specific to the embodiments indicated:

[0024] The exemplary first, second and third embodiments are capable of transferring heat between volumes of air with higher efficiency, for a given average air flow rate.

[0025] The first, second and third embodiments described impede air flow through the device to a lower degree for a given flow rate. That is, the pressure drop is lower for a given flow rate.

[0026] The first embodiment is low cost to manufacture and requires only small amounts of capital to start manufacturing of a given design i.e. has low tooling costs associated with its manufacture, and any changes.

[0027] The first, second and third embodiments exhibit higher sound attenuation from indoor side to outdoor side than prior art devices of equal internal surface area and mass due to staggering of the internal heat exchange elements, causing reflections and attenuation of the sound waves.

[0028] The first embodiment additionally attenuates sound to a higher degree than prior art devices of equal mass due to the damping effect of the polymer material it is made from being larger than that of ceramics or metals.

[0029] There are a few publications that discuss regenerative heat exchangers in general. U.S. Pat. No. 5,050,667A shows a typical assembled ductless energy recovery ventilator with heat exchanger in place. U.S. Pat. No. 3,367,406A describes the heat exchanger with very thin walls and narrow channels, but for a purpose quite different than the goal of the present invention. U.S. Pat. No. 3,369,592A describes generically the purpose of a rotating heat exchanger device and provides broadly the role and nature of the corrugated heat exchange elements in that context, without providing any specifics. U.S. Pat. No. 9,404,689B2 shows the staggering of some elements but not all of the heat exchange surface, and the device is rotating, specifically made only of metals, and not for decentralized ventilation. US20140033924A1 talks briefly about heat element staggering but only of lattice elements made of sintered material. Other element types are not considered, and the value is not recognized, and it is for a purpose different than the goal of the present invention. No mention of the drag to efficiency ratio is mentioned. U.S. Pat. No. 2,558,752A shows limited staggering of some sections of the heat exchange surface, but only of small regions. The invention briefly discusses the effect of the heat element staggering, but not quantitatively. U.S. Pat. No. 3,369,592A only briefly discusses the staggering effect. Moreover, the reynolds number that helps predict fluid flow patterns are a bit unclear and different from the goal of the present invention. U.S. Pat. No. 3,965,695 briefly discusses staggering of heat elements for the purpose of interrupting axial flow which is only limited to metals with only random offset, not to split the air stream in half or thirds. U.S. Pat. No. 5,580,370 discusses a typical total sorption wheel. WO2018233775A1 describes a push-pull type heat exchanger made only of metals and ceramic, and does not teach staggering, and EP3401610B1 discusses interruption of heat flow axially along their proposed device. DE102013020758 shows addition of adsorbent to the interior surface of channels. GB1567239A shows a brief staggering effect but only for some fraction of the heat exchange elements, and only for a rotating device, and mentions polymers only in passing.EMBODIMENTS

[0030] The present invention overcomes the various problems and deficiencies of the prior art.

[0031] In an embodiment of the invention, an article or a device is provided which is a regenerative heat exchanger for transferring heat between volumes of building ventilation in a 6 decentralized manner.

[0032] The article comprises a plurality of solid elements as means for heat exchange, past which air may flow (3). The article also comprises means to hold said solid elements in position relative to each other. The solid elements as means for heat exchange (3) are staggered, thereby splitting the air stream flowing along the device longitudinally, along the nominal axis of the air flow one or more times as it flows through the device, whereby said staggering leads to increased ratio of the amount of heat energy and or water vapor transferred between air volumes and the air pressure needed to cause a predetermined rate of air flow through said article. In an exemplary embodiment the air flow channels or gaps between said solid elements as means for heat exchange have less than 4.8 mm in the shortest dimension. A person skilled in the art would understand that other variations of this device are encompassed within the scope of the present disclosure.

[0033] In a further embodiment, the solid elements as means for heat exchange are in the form of flat plates, spiral walls, concentric circles, concentric squares, airfoil like elements, rods, or any structure of equivalent or nearly equivalent geometry for heat transfer purposes. The solid elements may be fixed and non-rotating.

[0034] In a further embodiment, the article further includes an adsorbent or other material as means to retain and release water vapor in the process of transferring it between air volumes, such as zeolite, silica gel, or calcium or lithium chloride. The solid elements may be fixed and non-rotating.

[0035] In a further embodiment, said solid elements as means for heat exchange are made primarily of polylactic acid or any other similar material that's coated with an adsorbent to aid the transfer of water vapor. The solid elements may be fixed and non-rotating.

[0036] In a further embodiment, said solid elements as means for heat exchange are made primarily of a material of high volumetric heat capacity, such as alumina, polylactic acid, another plastic, iron, or some combination thereof, and which is fixed and non-rotating. Any other material with similar volumetric heat capacity as the ones noted above are also encompassed within the scope of this invention.

[0037] In a further embodiment, said solid elements as means for heat exchange are solid walls around air channels of hexagonal, square, round, triangular, or any other shape equivalent for the purpose of heat transfer, and which is fixed and non-rotating.

[0038] In a further embodiment, said solid elements as means for heat exchange are solid walls around air channels of hexagonal, square, round, triangular, or any other shape equivalent for the purpose of heat transfer, which is used in a rotating thermal wheel type configuration rather than non-rotating, in which more than 80 percent, of the active surface area of said elements as means of heat exchange are staggered relative to surfaces encountered by the most previous single set of elements upstream.

[0039] In a further embodiment, said solid elements as means for heat exchange are solid walls around air channels of hexagonal, square, round, triangular, or any other shape equivalent or nearly equivalent for the purpose of heat transfer, which is used in a rotating thermal wheel type configuration rather than non-rotating, and wherein said elements as means for heat exchange consist partly or primarily of a polymer or any other similar material fit for the intended purpose.

[0040] In a further embodiment, the solid material of which it is primarily constructed may be made primarily of any suitable material for heat storage and release, which in an exemplary embodiment may be a thermoplastic such as polyethylene terephthalate or polypropylene, and which may be combined with alumina or any other suitable material that fits the intended purpose.

[0041] In a further embodiment, the article may further include small elements to encourage mixing of the air within the air channel as it flows, thereby improving the ratio of flow impediment or flow drag to heat exchange efficiency. Other modifications that may allow similar result of improving the ratio of flow impediment or drag to heat exchange efficiency are also intended within the scope of the invention.

[0042] The invention further describes an article or a device, which is a regenerative heat exchanger for transferring heat between volumes of building ventilation in a decentralized manner. The article may comprise internal solid walls or elements as means for heat exchange with interspersed air channels. The interspersed air channels may be less than 1 mm-4 mm in the shortest dimension, more preferably less than 1.7 mm in the shortest dimension. The article or device may further comprise means for holding such solid elements in position relative to each other, which may be the elements themselves, and which is fixed and non-rotating.

[0043] In a further embodiment, the internal solid walls or element of the article as means for heat exchange are of thickness less than 0.3 mm-0.9 mm in the shortest dimension, preferably 0.65 mm in the shortest dimension.

[0044] In a further embodiment, the article may be composed primarily of alumina. In a further embodiment, the article may be composed primarily of any suitable material, which may be a thermoplastic such as polylactic acid, polyethylene terephthalate or polypropylene, and which may be combined with alumina or other material.

[0045] In a further embodiment, the air channels are less than 0.5 mm to 1.9 mm, preferably 1.35 mm in the shortest nominal dimension. In a further embodiment, the article may be made primarily of any suitable material, which may be a thermoplastic such as polylactic acid, polyethylene terephthalate or polypropylene, and which may be combined with alumina or other material, and which is coated with zeolite or another adsorbent or other material such as calcium chloride, to aid the transfer of water vapor. A person skilled in the art would understand that other suitable article materials or coating materials could be used as replacements that fit the intended purpose.

[0046] In another embodiment, the article may also comprise air flow channels or gaps between said solid elements as means for heat exchange having less than 2 mm to 6 mm in the shortest dimension, preferably less than 4.8 mm in the shortest dimension.BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The above and other aspects, features and advantages of the invention will become more readily apparent from the following description of the accompanying drawings. However, a person skilled in the art would understand that these figures are merely for representative purposes only and other variations of the embodiments shown and described may be possible.

[0048] FIG. 1 shows an exemplary primary embodiment.

[0049] FIG. 2 shows a cross section of the exemplary primary embodiment. It consists of many sections or “segments”, stacked. The thickness of the heat exchange elements is not to scale.

[0050] FIG. 3 shows a close up of the cross sectional view, showing the way the internal heat exchange elements are staggered and spaced, dividing the air stream lengthwise as it traverses the length of the device.

[0051] FIG. 4 shows the front view of the exemplary first embodiment, showing thin walls and thin air channels. The number of spiral rotations, thickness, and air gap is not exact.REFERENCE NUMERALS

[0052] The various parts shown in the figures and described herein are referred to by means of reference numerals throughout the description.

[0053] Notch to allow the passage of wires past the device after inserting it into a pipe is referred to by reference numeral referred to by reference numeral 1.

[0054] External wall is referred to by reference numeral 2.

[0055] Internal heat exchange element is referred to by reference numeral 3.

[0056] Internal supporting wall is referred to by reference numeral 4.

[0057] Segment of the assembly is referred to by reference numeral 5.DETAILED DESCRIPTION OF THE INVENTION

[0058] The following description is of preferred embodiments by way of example only and without limitation to the combination of features necessary for carrying the invention into effect.

[0059] All terms are intended to be understood as they would be understood by a person skilled in the art. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosure pertains. The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0060] Although various features of the present disclosure can be described in the context of a single embodiment, the features can also be provided separately or in any suitable combination. Conversely, although the present disclosure can be described herein in the context of separate embodiments for clarity, the present disclosure can also be implemented in a single embodiment.

[0061] Reference in the specification to “some embodiments,”“an embodiment,”“one embodiment”, “alternate embodiment”, or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments, of the present disclosures.

[0062] In the design of decentralized energy recovery ventilators, the space the device consumes in the wall it is built into is at a premium. For this reason, the methods usually employed in rotating heat exchangers, such as increasing diameter and size of the heat exchanger, which reduces velocity in the channels thus improving the flow to pressure relationship for a given efficiency, become less viable.

[0063] Additionally, simplicity and low cost of each device becomes more important. Additionally, noise production of the machine becomes considerably more important. The so-called dead space, which is the volume of air that is contained in the heat exchanger and sometimes adjoining duct or other volumes, also becomes more important compared with centralized ventilation systems.

[0064] The staggering of the heat exchange elements (3) to split the air stream lengthwise in two nearly equal parts improves all of these factors, if all else is kept constant to whatever degree practical.

[0065] Splitting the air stream in three equal or nearly equal parts is also an improvement over not staggering them at all, but overall it is fundamentally usually more useful in the context of decentralized building ventilation to split the air streams in half and then adjust the other parameters of the exchanger to adapt it to a given application if higher heat flux or flows are warranted.

[0066] Although the description uses the terms first embodiment, second embodiment etc, no superiority or order of any embodiment over another is implied or intended by these terms.

[0067] The inventor believes that the reason these developments were not uncovered before is fundamentally a lack of exploration, which is an outgrowth of, the inventor believes cultural ideas about the priorities in business, the lack of realization that increased performance was practical, and the high cost of manufacturing devices of novel design through conventional means, and lack of knowledge about additive manufacturing both during prototyping and for use during final manufacture.

[0068] The progress the inventor has made is by employing significant knowledge of several unrelated fields to even understand progress is possible and that the devices developed could be worth the investment and economically viable to produce and sell, and considerable amounts of human and monetary capital and time to actually realize such progress. They are also interrelated and one will not realize the potential without undertaking the more nuts and bolts stages. Together, these undertakings, which led to this superior result are best described as, simply, exploratory activity. Some credit should also go to relatively recent developments in manufacturing and prototyping techniques opening new doors.Exemplary First Embodiment

[0069] The first embodiment could be made of Polylactic Acid (PLA), or any material with similar properties, and the internal heat exchange elements (3) may be coated with a layer of zeolite 3A powder, silica gel powder, or a similar material to adsorb and desorb water vapor. Polylactic Acid is both low cost, easy to process and has a high volumetric heat capacity among the common polymers.

[0070] The zeolite can be bonded to the PLA by coating the plastic with a mixture of solvent and adhesive, allowing the solvent to evaporate, and then applying the powdered zeolite, which sticks to the adhesive permanently. The total mass of zeolite that sticks to the surfaces can be controlled by adjusting the particle size. There are many other usable methods for coating a surface with powder which are also suitable. After various rounds of testing, the inventor was able to get about 54 grams of powder onto the prototypes of the first embodiment, which is a good quantity for the purpose.

[0071] The internal walls (3) to which heat is transferred into from the air, and subsequently out of to the air, may be a spiral shape, with a width of 0.25 mm and about 98 rotations of the spiral. The width of the air channel between heat exchange element surfaces may be 1.25 mm. It is functionally very similar to a stack of flat plates, for this purpose. The spiral path is just faster and easier to manufacture through additive manufacturing. Flat plates also work and are equivalent in terms of their heat transfer and drag or fluid flow related properties in almost every way. One exception is that the air exiting from the fan is usually rotating, i.e. exhibiting a twisting motion. When this interacts with a stack of plates, it leads to a non-uniform pressure on the intake side of the heat exchanger. This tends to push an excessive amount of air through some areas and not as much through others. Spirals and concentric circles avoid this concern. The supporting walls can be rotated relative to each other in each slice, to reduce this effect, as well, or minimized in size. A person skilled in the art would understand that the dimensions provided are merely exemplary and could be modified to fit the intended design and purpose.

[0072] Each set of internal walls in each section (3) similar to the individual slice / segment (5) in the finished, assembled, device, is rotated 180 degrees relative to the ones in adjacent slices. This causes the heat exchange elements to be “staggered” i.e. to split the air stream lengthwise, as indicated in FIG. 3. This is due to the spiral nature of the heat exchange elements, in this case, as a spiral rotated in this way will combine with a non-rotated spiral path such that the path of the second spiral lies in between the paths of the first. However it can be accomplished through other means if concentric circles or other designs are used.

[0073] As can be seen from the drawings, except for the supporting walls (4) and the outermost wall (2), the elements which serve as means of heat exchange do not have walls which are colinear or coplanar in most areas. That is, a large fraction of the wall surfaces used for heat exchange are staggered or offset from each other. Additionally, the heat exchange elements (3) split the air stream in half. If higher internal surface areas are desired, rather than splitting the air stream into thirds, the air channel width or other parameters may be changed while maintaining the approach of splitting the air stream in half. This halfing brings the under-tapped center of the air stream into contact with the heat exchange elements effectively.

[0074] There is a notch (1) at the top of the device to allow the passage of wires for a fan, sensors and valves etc. on the other side of the heat exchanger while it is installed in a pipe.

[0075] Inside the air channel, air flows down the length of the device. Heat is transferred into or out of the heat exchange elements (3) by various mechanisms, mostly conduction and radiation. The influence of convection is limited because the gas flow is mostly laminar due to channel geometry and gas velocity, which is usually in the range of 0.3 to 2.2 meters per second, but can deviate from this.

[0076] The inventor has found, through simulation and experimentation, that the primary impediment to heat flow from the bulk of the gas to the internal regions of the wall is within the gas stream itself. The center of the gas stream in each segment of the device, or in the whole of a prior art device, has a low rate of addition or loss of heat because the heat mostly diffuses through the gas sideways. When the channel is made thinner, this effect is reduced. However in the completed device, if the entire cross section is filled with channels and all else is held constant, the viscous drag also increases, and thus we are limited in how thin we can practically make the channel.

[0077] If a positive displacement air moving device such as a piston is used, then much thinner heat exchange elements and channels may be used practically. When a fan is used, the noise produced by the fan when generating high pressures is the main limiting factor in most use scenarios. Advanced fan designs such as multiple impellers with air flow straightening means between them, or counter rotating impellers, can be used to improve the pressure to noise ratio and thereby open the door to changes in the heat exchanger. Such variations of the device are also encompassed within the scope of this invention.

[0078] When the heat exchange elements (3) are staggered as described, the center of the air stream is suddenly and periodically brought close to a solid heat exchange element as it flows down the length of the device. This allows the heat to be conducted into or removed from the center much more effectively. The frequency with which the walls should be staggered is a question that can be approximately answered by simulation and experimentation.

[0079] A higher staggering frequency tends to increase efficiency and heat flux but makes the device longer, due to the spacing needed between slices, unless very thin heat exchange elements are used, and more complex to manufacture. 6 to 23 segments is a practical range for most purposes of concern.

[0080] According to simulations, the increase in heat transfer coefficient for a given drag factor (the drag in these devices is primarily viscous drag, which increases with surface area) is in the range of a factor of 2 and may be even more. This is an extremely significant improvement which is very hard to obtain through any other means, and the magnitude of this has not apparently been understood or valued by others until now even by those authors of the prior art patents which, for other applications and with other materials and designs and purposes, used staggered heat exchange elements. There is no mention of the use of staggered elements in non-rotating exchangers for decentralized ventilation.

[0081] Using the available cross sectional area through which the air may flow through a pipe is also important. This is primarily a matter of tooling costs and ensuring adequate clearance to fit in the pipe these devices are normally used in. The exterior wall of the device benefits from being relatively thin. Both of these factors are improved by the use of polymer materials rather than ceramics, which are less prone to cracking and are more conformal.

[0082] The transfer of water vapor (mass transfer) is also improved by staggering and air channel thicknesses (starting from smallest nominal dimension) in this range.

[0083] The turbulence within the small region where the gas meets the solid can actually be helpful in reducing viscous drag and increasing heat flux rate, depending on conditions. The “stairstep effect” of additively manufactured devices thus may be helpful in reducing the impediment to airflow within the device, and also the surface roughness provided by the particles of zeolite or any similar material.

[0084] The first embodiment is expected to be manufactured primarily through additive manufacturing, but the approximate geometry is amenable to injection molding and extrusion as well.

[0085] The thickness of the heat exchange elements is reduced as much as practical while allowing adequate thermal mass. The conduction within the walls is improved when they are thinner.

[0086] The inventor has found that the use of polymer materials is viable and practical when the heat exchange elements are in this thickness range. There is no need to use ceramics or metals for their higher thermal conductivity within the volume of the heat exchange elements (3), in contrast to generally perceived assumption that higher thermal conductivity is important in this context.

[0087] The optimal heat exchange element thickness and air channel thickness depends largely on the air moving device employed. This is usually a fan, however centrifugal versus axial fan makes a difference, and pistons, bellows, roots blowers, convel blowers, spring loaded fans (for rapid direction reversal) or other devices may be viable and would imply thinner heat exchange elements (3) and / or air channels.

[0088] Prior art devices use much thicker walls and thicker air channels, and no staggering of the internal heat exchange elements, leading to far inferior heat transfer efficiencies. They also suffer from internal conduction in the axial direction, which is detrimental to efficiency. The first embodiment as shown and described can sustain much higher flow rates at practical pressure drops, and at higher efficiencies, as indicated by the contents of table 1. This has significant implications for the economics of machines which employ this type of heat exchanger.

[0089] The inventor has found with some testing that this device also impedes the propagation of sound energy through the device noticeably better than a conventional prior art device, due to the different geometry and materials used. The sound energy on the exterior side of a wall is not generally welcome on the interior side of a building, so the sound attenuation through such devices is a useful feature.

[0090] The method of manufacturing the device will be apparent to a person skilled in the art. The devices that were tested were made using common Filament Deposition Manufacturing additive manufacturing techniques, with suitably small nozzles and gcode generation methods. Selective Laser Sintering is also suitable.

[0091] The PLA material also is a renewable resource, made through biological processes, and can be composted under suitable conditions.

[0092] The addition of alumina powder, iron, steel, copper, aluminum, or another powder with high volumetric heat capacity to the polymer would allow the solid fraction to be smaller for a given thermal mass, and thus the number of air channels to be more numerous, and thus further improve the relationship between the heat transfer efficiency, pressure drop or drag coefficient of the device, and fan reversal time, and thus make for a more performant energy recovery ventilator, all else being kept constant. The use of apollonian packing, in which a size distribution of powders is used to progressively fill voids and reduce the polymer content while increasing fluidity of the material during processing is a good approach. Similar to how it is used in so called high performance concrete to reduce the quantity of cement and water but retain adequate fluidity.

[0093] The inventor has found that the addition of a small element in between the heat exchange elements (3) to cause the air in the center of the channel to trade places with the air near the heat exchange elements is useful, however this actually ultimately resembles simply using a larger number of thinner slices and thus a higher frequency of staggering of the heat exchange elements (thinner slices). It is not, as prior art discusses in the context of rotating heat exchangers, for the purpose of inducing turbulence. Such an object in the flow path does not lead to the production of significant turbulence at the channel sizes and flow velocities of concern here (0.3-2.2 m / s and channels less than approximately 1.8 mm wide).

[0094] The inventor has in fact tested a device very similar to the first embodiment with a test apparatus to measure thermal efficiency and flow rates. The data collected from testing indicates that the performance figures indicated by Table 1 are correct.

[0095] The inventor has found that the ventilation warranted per room generally exceed the ability of decentralized energy recovery and heat recovery ventilators on the market which use a reversing fan, and this is due primarily to the limitations imposed by the heat exchangers, which unduly impede airflow and suffer from inadequate heat exchange efficiency to justify their cost in most contexts, combined with the limits of fan technology.Exemplary Second Embodiment

[0096] The second embodiment is the same general shape and design as the first, but the solid material is alumina or a similar material, and the thickness of the heat exchange elements, air channels and number of segments it is constructed from may be adjusted to adapt it to the new material. Alumina has an even higher volumetric heat capacity, 3.45 joules per degree per cubic centimeter, vs 2.25 for PLA. Thus, the heat capacity of the second embodiment is much larger, and this is useful in some contexts.

[0097] The collars extending upwards from each segment (5) may be retained or omitted if their production seems cumbersome.

[0098] Alternately, the heat exchange elements can be made thinner and the spiral density increased, to further reduce the impediment to airflow, while still allowing adequate thermal mass / heat storage capability. A device made of alumina of the same thermal mass as a device made from PLA may have approximately an 8% lower drag coefficient.

[0099] Zeolite or any other similar material may be bonded to the surface of the internal heat exchange elements to aid water vapor transfer, with e.g. the use of adhesive.

[0100] Alumina has a far higher thermal conductivity than polymer materials such as PLA, and while this may appear to be desirable at first blush, it provides minimal benefit because of the thinness of the heat exchange elements to begin with, and this can be detrimental if the heat exchange element staggering is not employed, or if the stacks are allowed to be in very good thermal contact for any reason.

[0101] This is because heat may be conducted axially down the length of the device, reducing the grade of the heat. It is fundamental and will be recognized by someone skilled in the art that axial conduction along the length of a regenerative heat exchanger tends to reduce system efficiency, this applies to many systems which use regenerative heat exchangers, even unrelated to building ventilation air. Table 2 indicates a calculated value to show approximately the magnitude of this effect in this context, and that it is significant.

[0102] Thus, the staggering of the internal heat exchange walls provides two useful effects. One, it improves transfer of heat energy from the air to the solid material, secondly, it impedes heat flow axially along the device.Exemplary Third Embodiment

[0103] The third embodiment is a non-rotating device for use in a pipe for decentralized energy recovery ventilation, and uses slices which have hexagonal, square or rectangular air channels, parallel, slanted or helical. The internal heat exchange elements are arranged so that again they split the air stream lengthwise. This can be accomplished by either making the slices identical and rotating each second one slightly while assembling them, or by making them slightly different from each other. The material may be Alumina, polylactic acid, or another material. The staggering leads to the splitting of the air stream in half lengthwise, increasing heat flux from air to solid and also preventing axial conduction between slices.

[0104] Although prior art reference U.S. Pat. No. 3,965,695A indicates such hexagonal channels which are also staggered, they imply the use of random staggering, the exclusive use of metals, and it is a rotating thermal wheel type device with a very different application. The size of the effect does not appear to be understood, and no mention is made of the drag to heat flux ratio improvement. The staggering is not in that case for the purpose of increasing heat flux but to prevent axial conduction. If polymers are used in the heat exchange elements, axial conduction is negligible anyway.

[0105] Table 1 shows figures obtained by simulation, experimentation and estimates. The inventor believes them to be more or less reasonable estimates for the climate in Ottawa, Ontario or a similar region. As you can see, the first embodiment is capable of providing far greater total heat energy recovery than a prior art type device. The rightmost column indicates the calculated heat energy captured in the climate of Ottawa, Ontario, Canada (4700 heating degree days).TABLE 1Quantitative performance comparison, based on simulation and estimates.Ratioofthermalmasscycle(RegeneratorheatFlowReversalefficiency,latenttotransferrateperiodsensibleefficiencyRegeneratoraircoefficient(cfm)(s)(%)(%)typebatch)Notes14845209072First2.4.embodiment148453085.268.16First1.65embodiment14845309172.8Second2.9embodiment14820309374.4First3.7embodiment148582089.671.68First1.9close toembodimentmaximalairflow at3 mmH2O forfirstembodiment7820907560prior2.9artdevice78453068.454.72prior2.175impedesartairflowdevicetoo muchtoachievethis with<3 mmH2OheatAirAirrecoveredenergythermalWaterwaterthermalRecoveredairtotalsavedheatpower,content,content,power,powerpower,recoveredpertransfersensibleg / m3,g / m3,latent(sensible)latentpowerseasoncoefficient(W)indooroutdoors(W)(W)(W)(W)(kWh)148534.878.561.893204812307113827148534.878.561.89320456218674148534.878.561.89320487233720148237.728.561.891422211063271757148713.168.561.89412639295934493278237.728.561.8914217885263137678534.878.561.89320366175541ExpectedRecoveredefficiency,RecoveredpowerEfficiencywithoutTotalpowerafterafteraxialairBeforeAxialaxialaxialFlowlosspoweraxiallossconductionconduction(CFM)(%)(W)loss(W)lossloss2075237.7217814.7163.368.64568.4534.87365.813.4352.465.8Table 2 shows to a first degree of approximation, what kind of impact axial heat conduction has, based on hand calculations, on efficiency, on a conventional prior-art device made from alumina, of the same design assumed in Table 1.OperationThe first, second, and third embodiments are all used in a similar way. They are installed in a pipe or hole of some kind, usually circular in cross section. An air moving device is placed before or after the device, and provides air pressure to force air through the device.

[0107] The direction of this airflow is reversed periodically, depending on flow rate and desired efficiency and trade-offs such as the nature and degree of noise produced by the air moving device, and how acceptable it is. A suitable reversal time is in the range of 30 seconds, for the first embodiment, given air pressures of 3 mm H2O or less. It may be longer if lower pressures are used, or shorter if higher pressures are used.

[0108] The air moving device is usually a fan, and usually an axial fan or combination of one or more axial fans. The use of two or more fan or impellers with flow straighteners between them, or a set of counter rotating fans with fan blades that are mirror images of each other, for instance, has been proposed to provide a quieter but still economical and compact air moving device.

[0109] Flow switches and centrifugal fans can also be used, as well as positive displacement devices such as pistons and Roots blowers, and so-called convel blowers.

[0110] For fans in particular, the noise emitted by the air moving device generally increases seriously when it rotates faster. To produce higher flow and pressures, higher rotational speeds and thus noise levels are implied, all else being equal. Pressure increases roughly in accordance with the square of blade velocity, while noise power increases approximately in accordance with the eighth power.

[0111] This is one reason that it is important for the heat exchanger device to achieve a low pressure drop / impediment to airflow. Humans are very sensitive to noise in their building environments, and it has proven detrimental effects. It is a form of pollution which it is important to limit.

[0112] Thus, these embodiments and those with features of the type and range described provides a lower impediment to air flow i.e. lower drag coefficient(s), lower pressure drop for a given flow rate, and / or a higher efficiency, or improved relationship between these factors, when used suitably (mostly, with a suitable fan reversal time), compared with prior art heat exchangers in use for this purpose and similar purposes, such as in a vehicle.

[0113] Lower impedance to air flow gives benefits that are not always immediately obvious. The psychoacoustics of noise dictate that humans generally find noise sources that vary in volume, rather than consistent noise, to be more detrimental, for a given average sound power. By allowing the heat exchanger to impede airflow less, the fan becomes much quieter at a given flow rate, and thus short fan reversal times become acceptable because the user does not notice the noise even at peak level, and thus small thermal masses become acceptable.Ramifications and Scope

[0114] While the above description contains many specificities, these should not be construed as limitations on the scope, but rather as an exemplification of several embodiment(s) thereof. Many other variations are possible. For example:Different Colors, Sizes and Materials:

[0115] The color of the device is generally not important, however it may be any color. The overall dimensions such as width or diameter and length of the device may very much be different.

[0116] The first embodiment is made with a pipe of 150 mm inner diameter in mind, however clearly a different diameter pipe has important benefits, in particular in designing a machine with even higher air flow capability or even lower fan noise.

[0117] The use of a device with larger diameter is particularly important as a larger diameter is a very effective way to increase air flow. Diameters such as approximately 8 or 12 inches are very likely to be commercially valuable as pipes, fans and hole drilling tools for these sizes are common and cost effective. A diameter of 12 inches implies a cross sectional area of 4 times greater than 6 inches, so the air flow can be greatly increased without encountering complications from fan noise and heat exchange efficiency etc.

[0118] The length of the device may also be varied. There may be an optimal length for any given application, and a wide range is usually usable even if not optimal, in any given application.

[0119] Different materials may also be used, even if they are not high volumetric heat capacity materials. Materials such as mylar or polypropylene are usable, for instance, in particular if lower thermal masses are acceptable due to the type of air moving device, or if the heat exchanger is used in a rotating thermal wheel type device.Filled or Composite Material Ramification;

[0120] Any of the embodiments, or similar devices may be made of a combination of alumina powder or fibers or similar combined with a polymer or other material. This may allow the walls to be thinner while maintaining adequate thermal mass for a purpose, with little additional cost. This allows either larger air channels or more numerous air channels in the same cross section, reducing the impediment to air flow and / or improving efficiency by increasing the surface area available for heat transfer.

[0121] The use of apollonian packing i.e. using a suitable distribution of particle sizes, may for instance allow very high alumina content while maintaining adequate processability of the material (e.g. low viscosity in the fluid state). An alumina content, in the range of 80% or more by volume may be practical, thus giving the material the processing advantages of polymers but most of the volumetric heat capacity of alumina.

[0122] This is particularly useful for retrofit devices, which are used in place of prior art devices with minimal or no change to the rest of an already installed system. This is because the fan reversal time tends to be relatively long for devices currently installed, i.e. the amount of air flowing in either direction before fan reversal occurs is relatively large. Therefore, a higher thermal mass is particularly useful in such a context.Rotating Device Ramification:

[0123] This ramification is similar to the first embodiment, but with the addition of additional walls similar to internal supporting wall (4), of similar but different orientation. Any given one of these walls may extend fully or partially along the radius of the device, with additional arc sections to prevent air from going around the walls, which connect the walls oriented parallel to the radius of the device i.e. orthogonal to the axis of rotation. These additional walls are to guide airflow, preventing flow cross-wise within the device. They are parallel to the direction of air motion desired much like the internal supporting wall (4). They resemble spokes, but there is no need for higher density towards the center, so some spokes are omitted in that area, and a circular arc is used to prevent air from going around the spokes at their ends, mostly where the two axially stacked segments analogous to heat exchanger segment (5), meet.

[0124] This device may be used in a rotating heat exchanger similar to the common thermal wheel type devices, possibly inside a pipe such as an 8, 10 or 12 inch diameter pipe, to save space. It may be a larger diameter than the first embodiment, as well, have a hole in the center 6 for an axle to aid rotation, and may be shorter, and have thinner internal heat exchange elements, which are acceptable due to lower thermal mass demands. The reduced diameter of the device provided by staggering a large fraction, such as 70 percent or more, of the heat exchange surfaces, is useful here so that it may be of smaller diameter. The pipe has to be sealed around it's periphery and larger diameter pipes are less convenient, more expensive to install, and allow more noise through.

[0125] In a thermal wheel type regenerative heat exchanger, instead of reversing the air flow through the heat exchanger elements by reversing the fan, the entire heat exchanger is rotated, with air flowing in different directions in different sections of the physical heat exchanger element assembly, at any given moment.

[0126] The additional walls described above serve to prevent air from flowing sideways through the exchanger from one side to the other, which would lead to air being “short circuited” from the indoor side, back to the indoors, or from the outdoors back to the outdoors. The importance of such walls is well known in the art of thermal wheel type device design.

[0127] This thermal wheel approach has much shorter practical flow reversal time for each heat exchange element, which allows the total thermal inertia of the heat exchanger to be reduced, allowing heat flux rate to be increased for a given efficiency, and allowing the length of the device to be smaller.

[0128] It also allows for continuous airflow, which improves average air flow rates due to the elimination of fan acceleration periods, and makes fan noise less of a problem due to the way humans tend to perceive or be affected by noise which varies in volume with time.

[0129] It also allows for the use of centrifugal fans without any kind of flow switch, which may produce less noise for a given level of pressure and air flow. The low thermal inertia demands makes the use of polymers more practical, compared with alumina, which has a higher volumetric heat capacity, in the range of 3.45 joules per degree per cubic centimeter, vs 2.25 for PLA and 1.65 for polyethylene terephthalate.

[0130] As discussed elsewhere in this document, the inventor has found that in this context that there is no need to use the usual metals in the heat exchange elements, and it is often detrimental 6 due to axial conduction, even within the slices.

[0131] Prior art reference GB1567239A indicates they considered staggering some but not all of the heat exchange surfaces / elements in a rotating device, but not for decentralized ventilation systems. Prior art reference U.S. Pat. No. 3,965,695A discusses staggering of honeycomb shaped elements only made out of metallic material and not for decentralized ventilation systems. There is one company that commercially produces rotating thermal wheels with a polymer material as the solid heat storage structure, but not with a staggered-heat exchange elements design.

[0132] For the most part, the inventor has found the complexity and relatively large diameter of current prior art thermal wheel type machines is what prevents their use in a small dwelling such as a house or apartment, especially in a decentralized ventilation scheme, which implies a higher number of lower cost, lower capacity, and physically smaller devices, which warrant higher reliability without maintenance.Further Ramifications:

[0133] Devices with very small thermal mass may be used if a piston or other air moving device is used. Another example of an air moving device that may make use of a heat exchanger with very small mass is a fan with spring loaded impeller, so that it may reverse direction at high frequency with good efficiency and speed. These heat exchanger devices suitable for pairing with such an air moving device may have very small air channels and thin walls, obtaining similar internal heat exchange surface areas and thus similar viscous drag. Viscous drag is generally the dominant source of drag / impediment to air flow in these devices. If a piston is used, a much higher pressure drop is allowable, without excessive noise from the air moving device.

[0134] The supporting walls (4) can be omitted through any of various means, or may be optional in some contexts. For example, the spiral can be made to have a wavy pattern superimposed on the spiral pathway, so that the heat exchange elements are self supporting. A wavy spiral could also be interleaved between a linear spiral shape, to make the heat exchange elements self supporting. They could be supported by means that are not evident in a cross sectional view, such as an element behind or between each slice. They can be strong and rigid enough to simply be self supporting to an adequate degree. The device could be mounted with the central axis vertical, so the spiral does not sag anyway. The walls could be vertical flat plates instead of a spiral or concentric circles. Multiple nested or interleaved spirals could be used. Two or more superimposed spirals, one clockwise and the other counterclockwise, could be used. The flat supporting walls can extend merely part way up the slice and still provide adequate support.

[0135] A spacer could be used between each segment, which also served to support the heat exchange elements against the force of gravity. This allows the use of plastic sheet or ribbon, which is very economical, in the formation of the spiral.

[0136] These supporting walls (4) or the larger scale geometrical features and shapes can mostly be readily changed, in too many ways to cover them all explicitly, without affecting performance or manufacturability. A person skilled in the art will readily see the equivalence for the purpose between a spiral pathway and parallel flat internal heat exchange elements, or multiple spirals, for instance.

[0137] Accordingly, the scope of the disclosure should be determined not by the embodiment(s) illustrated, but by the appended claims and their legal equivalents.Conclusion

[0138] Thus, the reader will see that at least one embodiment of the heat exchanger can allow for a higher flow of air and larger amounts of energy recovered per season or per second, with less noise from the fan or other air moving device, without prohibitively or any higher manufacturing costs than prior art devices. This directly implies that an energy or heat recovery ventilator with a higher return on investment can be built with this heat exchanger than with prior art heat exchangers.

[0139] There are also many other advantages such as higher sound attenuation and possibly lower cost of manufacture. It may also be used during periods of air conditioning to prevent the intrusion of heat and water vapor while allowing fresh air in. These properties all contribute to higher quality of life, reduced greenhouse gas emissions and fuel costs. This benefit can be delivered to a great number of people using buildings in both hot and cold climates, if applied during new construction or through retrofit of existing buildings, leading to a large total net improvement in environmental and human well being.

[0140] The device is not meant to be limited to the forms shown or described. The size and geometry and relative position of the heat exchange elements or overall device may be varied, and the color size and material may be different.

[0141] Accordingly, the scope of the disclosure should be determined not by the embodiment(s) illustrated, but by the appended claims and their legal equivalents.

[0142] While preferred embodiments of the present invention have been shown and described above, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It is not intended that the invention be limited by the specific examples provided within the specification. While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of the embodiments herein are not meant to be construed in a limiting sense. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Furthermore, it shall be understood that all aspects of the invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is therefore contemplated that the invention shall also cover any such alternatives, modifications, variations or equivalents. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Examples

exemplary first embodiment

[0069]The first embodiment could be made of Polylactic Acid (PLA), or any material with similar properties, and the internal heat exchange elements (3) may be coated with a layer of zeolite 3A powder, silica gel powder, or a similar material to adsorb and desorb water vapor. Polylactic Acid is both low cost, easy to process and has a high volumetric heat capacity among the common polymers.

[0070]The zeolite can be bonded to the PLA by coating the plastic with a mixture of solvent and adhesive, allowing the solvent to evaporate, and then applying the powdered zeolite, which sticks to the adhesive permanently. The total mass of zeolite that sticks to the surfaces can be controlled by adjusting the particle size. There are many other usable methods for coating a surface with powder which are also suitable. After various rounds of testing, the inventor was able to get about 54 grams of powder onto the prototypes of the first embodiment, which is a good quantity for the purpose.

[0071]The ...

exemplary second embodiment

[0096]The second embodiment is the same general shape and design as the first, but the solid material is alumina or a similar material, and the thickness of the heat exchange elements, air channels and number of segments it is constructed from may be adjusted to adapt it to the new material. Alumina has an even higher volumetric heat capacity, 3.45 joules per degree per cubic centimeter, vs 2.25 for PLA. Thus, the heat capacity of the second embodiment is much larger, and this is useful in some contexts.

[0097]The collars extending upwards from each segment (5) may be retained or omitted if their production seems cumbersome.

[0098]Alternately, the heat exchange elements can be made thinner and the spiral density increased, to further reduce the impediment to airflow, while still allowing adequate thermal mass / heat storage capability. A device made of alumina of the same thermal mass as a device made from PLA may have approximately an 8% lower drag coefficient.

[0099]Zeolite or any othe...

exemplary third embodiment

[0103]The third embodiment is a non-rotating device for use in a pipe for decentralized energy recovery ventilation, and uses slices which have hexagonal, square or rectangular air channels, parallel, slanted or helical. The internal heat exchange elements are arranged so that again they split the air stream lengthwise. This can be accomplished by either making the slices identical and rotating each second one slightly while assembling them, or by making them slightly different from each other. The material may be Alumina, polylactic acid, or another material. The staggering leads to the splitting of the air stream in half lengthwise, increasing heat flux from air to solid and also preventing axial conduction between slices.

[0104]Although prior art reference U.S. Pat. No. 3,965,695A indicates such hexagonal channels which are also staggered, they imply the use of random staggering, the exclusive use of metals, and it is a rotating thermal wheel type device with a very different appl...

Claims

1. An article, which is a regenerative heat exchanger for transferring heat between volumes of building ventilation in a decentralized manner, said article comprising:a. A plurality of solid elements as means for heat exchange, past which air may flow;b. Means to hold said elements in position relative to each other, wherein said elements as means for heat exchange are staggered, thereby splitting the air stream flowing along the device longitudinally, along the nominal axis of the air flow one or more times as it flows through the device, whereby said staggering leads to increased ratio of the amount of heat energy and or water vapor transferred between air volumes and the air pressure needed to cause a predetermined rate of air flow through said article; andc. With air flow channels or gaps between said solid elements as means for heat exchange having less than 4.8 mm in the shortest dimension.

2. The article of claim 1 wherein said elements as means for heat exchange are in the form of flat plates, spiral walls, concentric circles, concentric squares, airfoil like elements, rods, or any structure of equivalent or nearly equivalent geometry for heat transfer purposes, and which is fixed and non-rotating.

3. The article of claim 1 further including an adsorbent or other material as means to retain and release water vapor in the process of transferring it between air volumes, such as zeolite or calcium chloride and which is fixed and non-rotating.

4. The article of claim 1 wherein said elements as means for heat exchange are made primarily of polylactic acid coated with an adsorbent to aid the transfer of water vapor, and which is fixed and non-rotating.

5. The article of claim 1 wherein said elements as means for heat exchange are made primarily of a material of high volumetric heat capacity, such as alumina, polylactic acid, another plastic, iron, or some combination thereof, and which is fixed and non-rotating.

6. The article of claim 1 wherein said elements as means for heat exchange are solid walls around air channels of hexagonal, square, round, triangular, or any other shape equivalent for the purpose of heat transfer, and which is fixed and non-rotating.

7. The article of claim 1 wherein said elements as means for heat exchange are solid walls around air channels of hexagonal, square, round, triangular, or any other shape equivalent for the purpose of heat transfer, which is used in a rotating thermal wheel type configuration rather than non-rotating, in which more than 80 percent of the active surface area of said elements as means of heat exchange are staggered relative to surfaces encountered by the most previous single set of elements upstream.

8. The article of claim 1 wherein said elements as means for heat exchange are solid walls around air channels of hexagonal, square, round, triangular, or any other shape equivalent or nearly equivalent for the purpose of heat transfer, which is used in a rotating thermal wheel type configuration rather than non-rotating, and wherein said elements as means for heat exchange consist partly or primarily of a polymer material.

9. The article of claim 1 wherein said solid elements as means for heat exchange are made primarily of any suitable material for heat storage and release, which may be a thermoplastic such as polyethylene terephthalate or polypropylene, and which may be combined with alumina or other material.

10. The article of claim 1 further including small elements to encourage mixing of the air within the air channel as it flows, thereby improving the ratio of flow impediment / drag to heat exchange efficiency.

11. An article, which is a regenerative heat exchanger for transferring heat between volumes of building ventilation air in a decentralized manner, said article comprising:a. Internal solid walls or elements as means for heat exchange with interspersed air channels less than 1.7 mm in the shortest dimension, andb. means for holding such solid elements in position relative to each other, which may be the elements themselves, and which is fixed and non-rotating.

12. The article of claim 11 wherein said internal solid walls or elements as means for heat exchange are of thickness less than 0.65 mm in the shortest dimension.

13. The article of claim 11 which is composed primarily of alumina.

14. The article of claim 11 made primarily of any suitable material, which may be a thermoplastic such as polylactic acid, polyethylene terephthalate or polypropylene, and which may be combined with alumina or other material.

15. The article of claim 11 wherein the air channels are less than 1.35 mm in the shortest nominal dimension.

16. The article of claim 11 made primarily of any suitable material, which may be a thermoplastic such as polylactic acid, polyethylene terephthalate or polypropylene, and which may be combined with alumina or other material, and which is coated with zeolite or another adsorbent or other material such as calcium chloride, to aid the transfer of water vapor.

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