Bernoulli heat pump with laminar refrigerant flow

Abstract

In a modified Bernoulli heat pump, the intake section of the Venturi tube is structured so that the flow of refrigerant is essentially laminar as it flows from the intake section through most of the middle (narrow) section. Additionally, a second two-phase component is added to the flowing gaseous refrigerant. A portion of the two-phase component evaporates and reaches a supersaturated state, which is maintained in the middle section by the laminar flow, increasing heat absorption.

Description

[Technical field]

[0001] The present invention is directed generally to heat pumps, and more particularly to heat pumps based on the Bernoulli effect. [Background technology]

[0002] Heat pumps - i.e. cooling or heating systems - based on the Bernoulli effect are known, hereafter referred to as Bernoulli heat pumps. Unlike conventional heat pumps using a two-phase refrigerant, the refrigerant in a state-of-the-art Bernoulli heat pump remains in the gas phase throughout. Typically, such systems include a so-called Venturi tube, which mainly consists of three sections in series: an intake section formed as a narrowing conduit, an intermediate section formed as a capillary tube, and an exhaust section formed as an expanding conduit. A blower causes the refrigerant to flow through the Venturi tube, and the speed of the refrigerant while flowing through the capillary tube increases significantly. Due to this increased speed of the refrigerant passing through the intermediate section, its temperature decreases due to the endothermic aspect of the Bernoulli effect, and it is able to take heat from any medium surrounding the tube (called the heat source or cooled medium). After the refrigerant leaves the exhaust section, its temperature can be higher than it was before it entered the intake section, due to the heat dissipated from the heat source. This latter heat is generally dissipated into some medium acting as a heat sink.

[0003] The main advantages of Bernoulli heat pumps over conventional heat pumps are that they are relatively simple in construction, and therefore relatively inexpensive, and relatively energy efficient. However, current technology Bernoulli heat pumps suffer from a significant drawback in that the achievable temperature difference between the heat source (the medium to be cooled) and the heat sink (which is generally the warmer medium) is relatively small, typically around 10° C. or less. Summary of the Invention

[0004] The object of the present invention is to provide an improved Bernoulli heat pump which makes it possible to achieve a larger temperature difference between the warm and cold media whilst maintaining or even improving the energy efficiency of the system, thus overcoming the drawbacks of the prior art systems mentioned above.

[0005] Thus, a novel feature of embodiments of the present invention is that the inlet is structured or the interior surface is shaped such that as the refrigerant flows from the inlet to the majority of the middle (narrow) section, the flow is essentially laminar, i.e., there are relatively small local perturbations in the overall average velocity, thus minimizing turbulence, preferably even at high Reynolds numbers. This results in reduced impedance to the flow and reduced energy load on the blower to aspirate the refrigerant, which advantageously results in inherent energy efficiency and higher flow rates, which can result in greater temperature reduction.

[0006] Another novel feature of embodiments of the present invention is the addition of a second two-phase component to the flowing gaseous refrigerant. This component is in the liquid phase (e.g., as droplets) while entering the intake, and then, due to the aerodynamic aspects of the Bernoulli effect, a portion of the liquid component evaporates within the flowing gaseous component as it accelerates through the converging intake as the gas pressure decreases. Furthermore, this evaporation can generally result in a condition known as supersaturation, where a relatively large amount of vapor is retained by the gaseous component, so that the size of the evaporated liquid portion is substantial. Because such evaporation is an endothermic process, the endothermic aspects of the Bernoulli effect discussed above extract more heat from the resulting mixture in addition to the heat directly extracted, thus advantageously promoting the overall temperature reduction of the refrigerant.

[0007] Moreover, in some embodiments, the vaporized two-phase components can advantageously cooperate with the previously mentioned novel feature of laminar flow, as follows: Due to laminar flow, a supersaturated condition can persist while the refrigerant flows through the middle of the Venturi tube, thus increasing the overall heat absorption from the heat source, further reducing the temperature of the latter.

[0008] Specifically, a Bernoulli heat pump for transferring heat from a heat source to a heat sink is disclosed, the Bernoulli heat pump comprising: a Venturi tube including a converging intake section, a narrow middle section, and a diverging exhaust section all interconnected coaxially and in series about a longitudinal axis of the Venturi tube, the middle section being in thermal communication with a heat source; A refrigerant; a blower disposed at a discharge end of the exhaust section and operative to force a refrigerant through the venturi; Here, the intake section, and preferably its inner surface, is configured to force the refrigerant into the intermediate section in a laminar flow.

[0009] Preferably, the shape of the inner surface can be derived from a plane flow model using potential flow theory.

[0010] In some embodiments, the inner surface of the intake has a shape formed by revolving a plane curve around the longitudinal axis of the Venturi tube, the plane curve being defined in Cartesian coordinates with an abscissa parallel to the longitudinal axis and a distance cπ therefrom by a function y=c(π-θ), where c is a parameter, y is the value along the ordinate of an arbitrary point on the plane curve, and θ is the angle between the abscissa and a radial vector from the origin of the Cartesian coordinates to the arbitrary point on the plane curve.

[0011] In some embodiments, the refrigerant includes a gas component and a mixed two-phase component, and the heat pump is configured such that the two-phase component is predominantly in a liquid phase while entering the intake section and predominantly in a gas phase while entering the intermediate section.

[0012] In some embodiments, a portion of the two-phase component that is in the gas phase when it enters the intermediate section supersaturates the gas component while in the intermediate section. Typically, the degree of supersaturation is at least 20%.

[0013] In some embodiments, the two-phase component comprises at least two different two-phase fluids.

[0014] In some embodiments, the upstream end of the intake section and the downstream side of the blower are in fluid communication with the surrounding atmosphere, the gas component is atmospheric air, and the Venturi further includes one or more nozzles disposed in the intake section and operative to spray the two-phase fluid into the air flowing therethrough.

[0015] In some of these embodiments, the heat pump is configured to supply two-phase fluid at an adjustable rate to one or more of the nozzles.

[0016] In some of these embodiments, the two-phase component comprises water; in some of these embodiments, the two-phase component comprises a non-aqueous fluid.

[0017] In some of the latter embodiments, the heat pump is configured to be able to recirculate the non-aqueous fluid to any of the nozzles, and preferably includes means for extracting the non-aqueous fluid from the refrigerant exiting the exhaust, and means for flushing the extracted non-aqueous fluid with water.

[0018] In some embodiments, the heat pump further includes a refrigerant flow path from the blower to the intake. In some of these embodiments, the flow path includes a condenser in thermal communication with the heat sink. In some of these embodiments, the amount of the gas component and the amount of the two-phase component are constant. [Brief description of the drawings]

[0019] The invention is herein described, by way of example only, with reference to the accompanying drawings. [Figure 1] FIG. 1 is a schematic diagram of a cross-sectional view of an example embodiment of a heat pump according to the present invention having an open-air configuration. [Figure 2A] FIG. 2 is a geometric diagram illustrating an example of a flow model from which the geometry of a portion of the heat pump of FIG. 1 may be derived. [Figure 2B] FIG. 2 is a geometric diagram illustrating an example of a flow model from which the geometry of a portion of the heat pump of FIG. 1 may be derived. [Figure 2C] 2 is a geometric diagram illustrating curves for defining the shape of a portion of the heat pump of FIG. 1 in some embodiments. [Figure 2D] 2C shows the mathematical derivation of the curves of FIG. 2C from the flow model of FIG. 2A. [Diagram 3] FIG. 2 is a schematic diagram in cross-section of another example embodiment of a heat pump according to the present invention having an open configuration. [Figure 4] FIG. 2 is a schematic diagram in cross-section of an exemplary embodiment of a heat pump according to the present invention having a closed loop configuration. [Diagram 5] FIG. 2 is a schematic diagram in cross-section of another exemplary embodiment of a heat pump according to the present invention having an open configuration, allowing recirculation of two-phase fluid in the refrigerant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Similar to prior art heat pumps, embodiments of the present invention mainly include three parts in series, namely, an intake part formed as a converging duct, an intermediate part formed as a capillary tube, and an exhaust part formed as a branching duct, all configured to allow a refrigerant that is mostly gaseous to flow through. Preferably, by a blower downstream of the exhaust part, the refrigerant flows through the Venturi tube, whereby its speed greatly increases while flowing through the intermediate part. Since the refrigerant flowing through the intermediate part thus increases its speed, its temperature drops due to the endothermic Bernoulli effect, thereby being able to absorb heat from any medium (referred to as the medium to be cooled or heat source) in thermal contact with the intermediate part. After the refrigerant exits the exhaust part, its temperature may become higher than the temperature before entering the intake part due to the heat dissipated from the heat source. This latter heat is generally dissipated to some medium that functions as a heat sink.

[0021] However, different from prior art Bernoulli heat pumps, the refrigerant in embodiments of the present invention flows into the intermediate part of the Venturi tube and at least a part of it is made to flow in a laminar flow. Laminar flow is defined herein as a situation where local perturbations in the speed of the refrigerant are substantially smaller than the overall average speed (v’ << V), thus minimizing turbulent flow. Generally, in such a flow, for a refrigerant with a large Reynolds number such as air, the Reynolds stress is less than 20 - 30 kg / ms 2 less.

[0022] As a result, the impedance to the flow decreases, and thus the energy load of the blower that sucks the refrigerant also decreases - which advantageously results in inherent energy efficiency and high flow velocity, and as a result, a greater temperature drop. In some embodiments, the laminar flow of the refrigerant can be achieved by appropriately shaping the inner surface of the intake part. Such a shape can be derived from a model of planar laminar flow of two interacting fluid flows using potential flow theory, as further illustrated by exemplary models below. Next, specific examples of the shape thus derived will be described.

[0023] Also, contrary to prior art Bernoulli heat pumps, the refrigerant in embodiments of the present invention is composed of at least two intermixed components, one component being a gas and one component being one or more two-phase fluids. The gas may be any fluid or combination of different fluids that maintains a gaseous state over the full range of temperatures and pressures encountered in the heat pump. As used herein, a two-phase fluid is one that can undergo a phase change - between liquid and gas - while flowing through the heat pump in response to changes in temperature and / or pressure of the refrigerant.

[0024] During operation, i.e., as the refrigerant flows through the Venturi tube due to the action of the blower, the two-phase components may first be mostly in the liquid phase (e.g., as droplets) while in the intake. Then, during acceleration through the converging intake, as the pressure of the gas decreases (due to the aerodynamic aspects of the Bernoulli effect), a significant portion of the liquid components may evaporate (i.e., transition to the gas phase) within the flowing gas component. Such evaporation is, in itself, an endothermic process, so that more heat is extracted from the resulting mixture in addition to the heat directly extracted by the endothermic aspects of the Bernoulli effect, thus advantageously enhancing the resulting overall temperature reduction. Furthermore, the evaporation of the two-phase components within the gas component may create a supersaturated condition such that a greater amount of the two-phase components can evaporate, thus further reducing the temperature of the refrigerant and increasing its heat absorption capacity. For example, if the gas is air and the two-phase component is water (as in many embodiments), the supersaturation may typically reach values ​​between 20% and 40% (i.e., relative humidity values ​​between 120% and 140%). Furthermore, due to the laminar flow of the refrigerant, in some embodiments, that supersaturation state may be maintained throughout most, if not all, of the intermediate portion of the Venturi tube, which may advantageously cause more heat from the heat source to be absorbed by the refrigerant (as described below). It will be appreciated that the combination of the novel presence of a two-phase component in the refrigerant and the novel arrangement of the laminar flow within the intermediate portion of the Venturi tube can energy-efficiently cool the heat source to temperatures significantly lower than those achievable with conventional Bernoulli heat pumps. The heat pump in some embodiments of the present invention can typically achieve a temperature difference between the heat source and the heat sink of 15°C.

[0025] As a further improvement, in some embodiments of the present invention, the two-phase component of the refrigerant may include two or more two-phase fluids having different boiling points and / or vapor pressures from each other. For example, one such fluid may be water and another may be ethanol or another organic liquid. These fluids may all be vaporized in the Venturi tube as described above. Since the partial vapor pressures of these fluids are additive, they may cooperate in absorbing more heat from the heat source, especially when both remain supersaturated in a laminar flow of the refrigerant.

[0026] A heat pump according to an embodiment of the present invention may be in one of two general configurations, the first being an open system and the second being a closed circuit system. An open system embodiment essentially consists of the Venturi tube described above, with a blower disposed at the downstream end of the exhaust section, and the front opening of the intake section and the exhaust side of the blower being substantially open to the surrounding atmosphere. Thus, the gaseous component of the refrigerant is ambient air, and the ambient atmosphere acts as a reservoir of the gaseous component as well as a heat sink. Preferably, one or more spray nozzles are disposed in the intake section adapted to spray the two-phase component of the refrigerant (e.g., water) in liquid phase into the air flowing therethrough. If the two-phase component fluid is water, it may be continuously replenished, but it is dissipated into the atmosphere as the refrigerant is discharged. If the two-phase component fluid is other than water, as in some embodiments, it is preferably extracted from the refrigerant as it is discharged from the Venturi tube and recirculated to be sprayed into the refrigerant in the intake section.

[0027] It should be noted that some prior art Bernoulli heat pumps (such as those disclosed in US8607579B2) include the injection of liquid into the flowing gas. However, it remains mostly liquid by design, where its role is simply to obtain a more effective heat exchange with the walls of the intermediate section of the Venturi tube, and not to increase the heat absorption capacity of the refrigerant by evaporation as is the case in the disclosed system. In such prior art heat pumps, even if some of the injected liquid vaporizes, due to the inherent turbulence, such vapor will condense on the surfaces of the intermediate section, and such condensation is exothermic, thus adding heat to the surfaces (and therefore to the heat source), reducing some of the cooling effect of evaporation.

[0028] In addition to the Venturi tube with the blower (as in the open system), an embodiment of the closed circuit system includes a relatively wide diameter conduit connecting the exhaust side of the blower with the front opening of the intake, and a condenser inserted in said conduit and in thermal contact with the heat sink (possibly via a heat exchanger). Thus, a closed flow path is formed. A binary refrigerant (including a gas component and a two-phase component having one or more two-phase fluids) is present in the flow path, and the blower is adapted and operable to continuously circulate it through the flow path. The gas component may be any gas (or mixture of gases), and the two-phase fluid may be one whose boiling point is within the range of temperatures and pressures that will be encountered in the flow path during operation. Typically, during operation, the two-phase components evaporate at the intake as described above, begin to condense as they pass through the exhaust due to the increase in pressure, and completely condense to liquid as they pass through the condenser due to the decrease in temperature caused by dissipating heat to the heat sink.

[0029] Figures 1 and 3 show in schematic cross-section an exemplary embodiment of a first general arrangement of a heat pump according to the invention, i.e. an open system. Figure 1 serves to explain some basic features of the invention, while Figure 3 shows in more detail the structure of a particular exemplary embodiment.

[0030] Central longitudinal axis (33) A circular shape with The Venturi tube, hereinafter, consists of an intermediate section formed as a capillary tube (10) connected at one end to an intake section (20) as described below and at the other end to an exhaust section (12). The latter is conical, although in other embodiments it may be of other flared shapes, its narrow end connected to the intermediate section (10) and having an inner diameter essentially equal to that of the intermediate section (10). The wide end of the exhaust section (12) is in fluid communication with the surrounding atmosphere, and coaxially disposed therein (or alternatively next to it) is a blower (14) which operates to draw air from the interior of the exhaust section and expel it to the atmosphere. The blower may also be generally disposed before the intake section, but this arrangement creates unwanted pressure and turbulence in the intake section and is therefore less desirable.

[0031] The intake section (20) primarily comprises a converging conduit (24) whose inner surface has a special shape, as described below, with the narrow ends of the conduits joined to a middle section, and their inner diameters being essentially equal. Optionally, the intake section (20) includes a short open cylindrical forward segment (22) joined to the wide end of the converging conduit (24). The wide end or forward segment (22) of the conduit (24) is in fluid communication with the surrounding atmosphere. As a novel feature, the shape of the inner surface of the converging conduit (24) is generally designed to cause the incoming air to flow laminarly into the middle section. Such shapes can be obtained analytically by devising a planar laminar flow model of two converging streams of fluid, writing equations characterizing the flows based on potential flow theory, solving them to obtain the boundary between the streams (which is usually a planar curve), and rotating the resulting curve (also called a "profile curve" or "profile") about an axis that coincides with the central axis (33) of the converging conduits (24) or the central axis of a Venturi tube (33) to form the desired shape.

[0032] A particular example of such a curve is illustrated in FIG. 2C as curve (31), which is shown in terms of Cartesian coordinates x (along the abscissa) and y (along the ordinate), with point O as the origin. Curve (31) is preferably defined by the function y=c(π-θ), where c represents a design parameter and θ is the angle between the abscissa and the radius vector r from the origin O to any point on the curve. This function may be derived, for example, from a planar model of the confluence between an incoming parallel flow of fluid and an outgoing flow of a similar fluid from a point source (described below with respect to FIG. 2A), by writing equations of the potential of the flowing fluid and solving them for so-called stagnation lines, which represent the boundary between the two flowing streams (described below with respect to FIG. 2D). As can be seen in FIG. 2C, the curve has a value of y=0 (where x=-c) at point A, a value of y=πc / 2 (where x=0) at point B, and a value of about 2.46c (where x=3c) at point E (point H on the abscissa). The curve could extend further beyond point E, but was chosen to end there for practical functional and design considerations. In either case, the horizontal dotted line y=πc represents the asymptote of the curve (31), which is parallel to the abscissa. The shape of the inner surface of the second segment (converging conduit) (24) of the intake section (20) (FIG. 1) is formed by rotating the curve (31) around the asymptote and aligning the asymptote with the longitudinal axis of the intake section (20). Consequently, in the exemplary embodiment, the inner radius of the second segment (24) is πc at point A, i.e., at its wide end (and therefore also the inner radius of the anterior segment (22)), it is πc-πc / 2=πc / 2 at point B, and it is approximately 0.68c at point E, i.e., at its narrow end (and therefore also the inner radius of the intermediate portion (10)).

[0033] 2A and 2B generally illustrate examples of flow models that may serve to derive a profile curve for rotationally defining the shape of the converging conduit (24). FIG. 2A relates to the derivation of the curve described above. It illustrates the confluence of a first stream (70) arriving as a parallel uniform stream from the left and a second stream emerging from a source orifice (71). The fluids of both streams are assumed to have very low Reynolds numbers, and therefore all flows are laminar. The first stream is seen to continue to the right along a separate path, as represented by line (72), while the second stream is seen to separate, turn, and continue to flow further to the right, as represented by line (73). The boundary between the two streams is represented by curve (74). An appropriate segment of line (74) can serve as a profile curve to define the shape of the converging conduit (24) by rotating it as described above.

[0034] As another example of a laminar flow model that may be used to derive a profile curve for a converging conduit (24), FIG. 2B further illustrates the confluence of a first stream (70) arriving as a parallel flow from the left and a second stream emerging from a source orifice (75) and flowing into a sink orifice (76), all with laminar flow. Representative streamlines (77) of the first stream and representative streamlines (78) of the second stream are shown. The boundary between the two streams is represented by a curve (79) (which in this case closes on itself). Again, an appropriate segment of the line (79) can serve as a profile curve to define the shape of the converging conduit (24) by rotating it as described above.

[0035] An example of a mathematical derivation of the above-shown function for profile curve (31) using the flow model of FIG. 2A and potential flow theory is shown in FIG. 2D. Note that this particular mathematical derivation is not binding and other derivations leading to such functions using the same model and theory are possible. Similar derivations may be used to obtain other profile curves from other flow models, e.g., the model of FIG. 2B.

[0036] In other embodiments, the inner surface of the conduit (24) may have other shapes that result in laminar flow of refrigerant through the intermediate portion, all within the scope of the present invention. Additionally, in some embodiments, such laminar flow may also be provided by other means, such as suitably shaped aerodynamic fins or other elements suitably positioned within the first and / or second portions, all within the scope of the present invention.

[0037] Surrounding and in thermal contact with the intermediate section (10) and preferably also part of the intake section (e.g. between points D and F in FIG. 1) is a heat exchanger (16). The latter is in turn in thermal contact with a heat source, which may be a solid or a fluid in a suitable container or conduit. In the embodiment of FIG. 3, the heat source is a fluid that may flow through a conduit (54) that surrounds the heat exchanger (16). The fluid may circulate through the conduit (54) to or from any space (not shown) that may be required for cooling or heat extraction, for example through openings (55) and (56). In other embodiments, the heat exchanger (16) may be directly immersed in the space that needs to be cooled or from which heat needs to be extracted.

[0038] During operation, atmospheric air (30), which mainly serves as the gaseous component of the refrigerant, flows into the intake section (20) (by the action of the blower (14)), where it accelerates while flowing in a stratified manner, and continues to flow, thus passing through the intermediate section (10), before slowing down and flowing through the exhaust section (12) and the blower (14) back to the atmosphere. While the air accelerates through the intake section (20), both its pressure and temperature become reduced, reaching respective minima when it reaches the intermediate section (10). While flowing in thermal contact with the heat exchanger (16) (within the intermediate section, and optionally within a part of the intake section), it absorbs heat from a heat source through the heat exchanger (16) (schematically indicated by arrows (34)). This reduces the temperature of the heat source and increases the temperature of the air. Then, while the air slows down through the exhaust section, its pressure and temperature return to normal and may become higher than the atmosphere (due to the absorbed heat) before it finally mixes with the atmosphere, thereby dissipating the absorbed heat. Due to the laminar flow, the flow velocity through the middle section (10) is much higher for a given force of the blower (14) than if the flow were turbulent (as in prior art Bernoulli heat pumps), and therefore the temperature of the flowing air is much lower, allowing a correspondingly lower heat source and a correspondingly higher rate of heat absorption therefrom.

[0039] Disposed within the intake section (20) (e.g., on the wall of the forward segment (22) as in the embodiment of FIG. 1, or near the end of the conduit (24) as in the embodiment of FIG. 3) are one or more spray nozzles (26) operative to spray a liquid two-phase refrigerant component (32), preferably water, into the flowing air (30). As shown in FIG. 3, the two-phase component can be supplied to the nozzles (26) through a supply pipe (27), where the supply rate can be regulated by a control valve (28).

[0040] In operation, the liquid component (32) is dispersed in the air (30) (possibly as droplets or a mist) and when this mixture is subjected to a reduction in pressure (as described above), a substantial portion of the fluid evaporates within the air sufficiently to become supersaturated. The state of supersaturation can be maintained throughout the intermediate section (10) by laminar flow. It is noted that, as an advantageous feature of the invention, the endothermic effect of the evaporation of the fluid combines with the endothermic Bernoulli effect of the acceleration of the bulk refrigerant to reduce the temperature of the bulk refrigerant significantly beyond that achievable by the Bernoulli effect alone. It is noted that the effect is enhanced by supersaturation since a greater proportion of the two-phase component can be evaporated in this manner.

[0041] While flowing through the heat exchanger (16), the thus cooled refrigerant absorbs heat from the heat source through the heat exchanger, as explained above. However, the rate of heat absorption is increased by the presence of the two-phase component, due to the decrease in the temperature of the refrigerant, as mentioned above. In addition, the decrease in the temperature of the refrigerant also makes it possible to achieve a greater degree of temperature reduction in the heat source (the medium to be cooled). It should be noted that since the temperature of the refrigerant increases (due to heat absorption), but the two-phase component remains in the gaseous state, the effect of supersaturation maintained throughout the intermediate portion (10) due to the laminar flow as described above may contribute to a further increase in the rate of heat absorption by the refrigerant.

[0042] Optionally, the spray rate of the (liquid) two-phase component can be increased beyond the rate at which it would evaporate and become supersaturated at the beginning of the intermediate section, so that some of it remains dispersed in the refrigerant as a liquid mist. As the refrigerant flows through the intermediate section (10) and absorbs heat from the heat exchanger (16), its temperature increases slightly and gradually. As a result, some of the mist can evaporate, thereby further contributing to heat absorption and keeping the temperature of the refrigerant relatively low.

[0043] As the refrigerant flows through the exhaust (12) and thus expands, its temperature and pressure increase, the latter of which causes the two-phase components of the refrigerant to condense or liquefy (again as droplets or mist). Finally, as the exhausted air mixes with the atmosphere, any heat absorbed thereby from the heat source is dissipated by the atmosphere, thus acting as a heat sink, and at the same time, the liquid (water) dispersed in the exhausted air is effectively removed from the system.

[0044] Referring again to FIG. 3, an example improvement is shown, namely, an interjection in the exhaust path of the settling tank (50) (i.e., between the exhaust section (12) and the blower (14)). The interjection causes some of the liquid components dispersed in the refrigerant to settle before reaching the blower (14), thus helping to protect the blower from the accumulation of liquid that could cause corrosion or otherwise damage it. Settled liquid (51) can accumulate at the bottom of the settling tank (50) from which it can be periodically removed, for example, by a plug (52).

[0045] Referring now to FIG. 4, an exemplary embodiment of the second general arrangement of the present invention, i.e., a closed circuit Bernoulli heat pump system, is shown in a schematic cross-sectional view. The arrangement shares with the first arrangement a Venturi tube including an inlet section (20), an intermediate section (10), and an outlet section (12) in series, as well as a blower (14) and a heat exchanger (16). Additionally, in this exemplary embodiment, an optional conduit (54) is shown surrounding the heat exchanger, which conduit (54) is configured to allow a liquid to flow therethrough. All of these are similar in structure and function to their counterparts in the arrangements of FIGS. 1 and 3 described above. The spray nozzle ((26) in FIG. 1) is not included. However, this arrangement additionally includes a flow path connecting the wide end of the inlet section (20) to the wide end of the outlet section (12). This flow path consists of a duct (40), a condenser (44), and a duct (42) in series, thus forming a closed flow circuit. The circuit is permanently filled with a two-component refrigerant, including a gas component and a two-phase component (which may consist of one or more different two-phase fluids), all intermixed. During operation, the refrigerant (30) circulates constantly through the closed circuit. The condenser (44) is in thermal contact with a second heat exchanger (46), which functions to transfer heat (48) from the refrigerant through the condenser to a medium (not shown), which is in thermal contact with the heat exchanger (46) and acts as a heat sink. In the illustrated exemplary embodiment, the heat sink is ambient air, and the heat transfer is assisted by a fan (47). For example, in other embodiments, the heat sink medium can be a flowing liquid.

[0046] The refrigerant components in a closed circuit heat pump may consist of any suitable material, including, for example, air as the gas component and water as the two-phase component. The selection of a suitable material may depend on the particular application, external conditions, and functional requirements, such as the rate of heat loss or the range of temperatures of the heated and cooled media. The two-phase components preferably include one or more fluids with a relatively high vapor pressure (i.e., a relatively large proportion evaporates in the gas component under supersaturation). Examples of such fluids other than water are Freon, and various organic liquids such as ethanol.

[0047] The operation of the system of FIG. 4 is as follows: the refrigerant is circulated (35) through the entire circuit by the blower (14). When emerging from the condenser and flowing through the duct (42), the two-phase components are mostly in the liquid phase and may form droplets or mist dispersed in the gas. When accelerating through the intake section (20), the entire refrigerant is cooled by the Bernoulli effect, but the liquid evaporates due to the reduction in pressure, which causes further cooling, resulting in a temperature much lower than the heat source. The flow through the intake section and then through the intermediate section (10) is laminar due to the special shape of the intake section's inner surface (which shape may be similar to that in the system of FIG. 1, as explained above), so that the refrigerant remains supersaturated, i.e. there is no significant condensation. While flowing through the intake section and the far part of the intermediate section (for example between points D and F in FIG. 1), the refrigerant thus cooled absorbs heat from the heat source (not shown) via the heat exchanger (16) and further cools it.

[0048] Upon expanding through the exhaust (12), the refrigerant's pressure and temperature increase. After passing through the blower (14) and while flowing through the duct (40), the pressure is further increased by the action of the blower. As a result, the two-phase components begin to condense, which is an exothermic process, and thus the temperature increases further to a temperature significantly higher than the heat sink. While flowing through the condenser (44), the refrigerant transfers heat (48) to the heat sink (not shown) via the heat exchanger (46) and is therefore cooled. Eventually, more of the two-phase components condense or liquefy, and the cycle begins again as described above.

[0049] An open Bernoulli heat pump, such as in the embodiments illustrated in Figures 1 and 3, is relatively economical when the two-phase component is water, because the condensed water in the discharged refrigerant is dispersed into the atmosphere, but the water can be continuously replenished, i.e., new water can be supplied to the spray nozzles. However, as described above with respect to the closed circuit arrangement, it is sometimes advantageous to use a fluid other than water in the two-phase component, and continuous replenishment is usually uneconomical. Figure 5 is a schematic cross-sectional view of an exemplary embodiment of an open Bernoulli heat pump featuring such two-phase fluid recirculation, thus advantageously allowing the two-phase component to economically include any suitable fluid, as described above.

[0050] The exemplary embodiment illustrated in FIG. 5 is similar to the embodiment of FIG. 3 in that it includes an open venturi tube, an inlet section (20) (with converging conduits (24) shaped for laminar flow), a narrow middle section (10), and an exhaust cone (12), followed by a settling tank (50) and a blower (14). This embodiment also includes a heat exchanger (16) in thermal contact with the middle section (10), optionally surrounded by a conduit (54) for the flow of the heat source medium. However, the embodiment of FIG. 5 includes a fluid extraction box (60) located downstream of the blower (14), whereas in other embodiments the fluid extraction box (60) may be located upstream of the blower, for example, at the top of the settling tank (50). The fluid extraction box (60) may be filled with a porous material through which the exhaust refrigerant flows and which acts to absorb or adsorb at least a portion of the liquid phase fluid dispersed in the refrigerant during such flow. This material may be, for example, activated carbon. The fluid extraction box (60) is preferably provided with shutters (67) and (68) at the inlet and outlet windows, respectively. Fluidly connected to the fluid extraction box (60) are a flush supply pipe (61) whose other end is connected to a mains water supply via a valve (63) and a flush drain pipe (62) whose other end is fluidly connected to the bottom of the settling tank (50) where the liquid two-phase fluid (51) may accumulate. A liquid supply pipe (64) connects between the bottom of the settling tank (50) and one or more spray nozzles (16) of the intake section (20) via a flow control valve (65). The fluid in the pool (51) is typically a mixture of water and one or more other two-phase fluids (described further below).

[0051] The heat pump of FIG. 5 basically operates similarly to the embodiment of FIG. 3 described above, whereby air mixed with two-phase fluid flows through the entire Venturi tube, but (as a novel feature) it is discharged through the fluid extraction box (60). As a further novel feature, the two-phase liquid sprayed into the flowing gas is continuously fed from a pool of liquid (51) at the bottom of the settling tank (50) through a liquid supply pipe (64) to the nozzle (16). When the air pressure is already lower than that of the atmosphere, the nozzle (16) is preferably placed near the narrow end of the converging conduit (24), so that the fluid is forced to flow from the pool (51) out of the nozzle (16) by the pressure difference. The speed of this flow can be regulated by a control valve (65). As the discharge refrigerant flows through the top of the settling tank (50), some of the liquefied two-phase fluid dispersed therein may settle to the bottom of the tank and join the pool (51). As the exhaust refrigerant continues to flow through the fluid extraction box (60), most of the remaining non-aqueous portion of the liquefied fluid dispersed therein is absorbed or adsorbed by the porous material (e.g., activated carbon) and thus can be extracted from the exhaust refrigerant.

[0052] Over time, extracted fluid may accumulate in the fluid extraction box (60). It may therefore be necessary from time to time to flush the accumulated fluid from the fluid extraction box and return it to the pool (51). This process may be carried out as follows: temporarily stopping the operation of the heat pump (by stopping the blower (14)), temporarily closing the shutters (67) and (68) which are normally in the open position (e.g. flipped up) (as shown diagrammatically in the drawings), and opening the valve (63) so that water flows from the mains, through the supply pipe (61), the fluid extraction box (60) and the flush drain pipe (62) into the pool (51). During this process, the running water dissolves the fluid absorbed or adsorbed by the material in the fluid extraction box and flushes it into the pool. At the end of the process, normal operation of the heat pump may be resumed. In this way, it will be appreciated that most of the non-aqueous part of the two-phase component of the refrigerant is recirculated and only the small amount lost to the atmosphere needs to be replenished. In contrast, it is noted that the most aqueous portion of the two-phase components is not recycled but is replenished by flushing water during the process described above.

[0053] In the exemplary embodiment of FIG. 5, as described above, the two-phase component of the refrigerant consists of two parts: water and a non-aqueous fluid. Water is required in this embodiment to flush the extracted non-aqueous fluid. In other embodiments, other means for extracting and recirculating the non-aqueous fluid may be used, such that no additional fluid is required. In such embodiments that are within the scope of the present invention, a single non-aqueous body fluid may serve as the two-phase component of the refrigerant (as is the case in a closed-circuit heat pump, such as that described with respect to FIG. 4). However, as described above, in any arrangement of a heat pump, it may generally be advantageous to use two or more different fluids as the two-phase component. This is due to the fact that their partial vapor pressures are additive (even in supersaturated conditions) when they evaporate within the gas component. Thus, each of them can independently contribute to the heat absorption of the refrigerant while flowing through the middle part of the Venturi tube, and thus they can enable a greater overall cooling effect.

[0054] The numerical examples in the above description are merely examples and may be varied in a design optimization process. It is also understood that in various embodiments of the invention, two or more of its aspects may be combined into an optimized design. Moreover, it is understood that the above description is intended to serve as an example only, and that many other embodiments are possible within the scope of the invention as defined by the appended claims.

[0055] To the extent that the appended claims have been drafted without multiple dependencies, this is done solely to accommodate formal requirements in jurisdictions that do not permit such multiple dependencies. It should be noted that all possible combinations of features implied by making a claim multiple dependent are expressly contemplated and should be considered part of the present invention.

Claims

1. 1. A Bernoulli heat pump for transferring heat from a heat source to a heat sink via a refrigerant, said Bernoulli heat pump comprising: a Venturi tube including a converging inlet section having an inlet end and an outlet end, a narrow intermediate section, and a diverging exhaust section having an inlet end and an outlet end, all interconnected coaxially and in series about a longitudinal axis of the Venturi tube, the intermediate section being in thermal communication with the heat source; The refrigerant; a blower disposed near the outlet end of the exhaust section and operative to force the refrigerant through the venturi; Here, the intake section and the intermediate section are circular about the longitudinal axis, an inner surface of the intake section is configured to cause the refrigerant to flow into the intermediate section in a laminar flow, the inner surface has a shape that can be defined by rotating a plane curve about the longitudinal axis, the plane curve having a distance from the axis that monotonically and nonlinearly decreases from a maximum value near the inlet end to a minimum value near the outlet end, the rate of decrease being maximum near the inlet end and minimum near the outlet end, wherein the plane curve can be derived from a theoretical model of planar laminar flow of two converging streams, the plane curve being derived from a boundary between the two converging streams.

2. 2. The Bernoulli heat pump of claim 1, wherein in a theoretical model of laminar flow, a first of the two flows arrives as a parallel flow and a second of the two flows emerges from an opening of an assumed source.

3. 3. The Bernoulli heat pump of claim 1, wherein the plane curve is defined in terms of Cartesian coordinates of an abscissa parallel to the longitudinal axis and a distance cπ therefrom by a function y=c(π-θ), where c is a parameter, y is the value along the ordinate of an arbitrary point on the plane curve, and θ is the angle in radians between the abscissa and a radial vector from the origin of the Cartesian coordinates to the arbitrary point on the plane curve.

4. 4. The Bernoulli heat pump of claim 1, wherein the refrigerant comprises a mixture of a gas component and a two-phase component, and the Bernoulli heat pump is configured and operative to cause a majority of the two-phase component to be in liquid phase while entering the intake section, and such that the velocity of the refrigerant as it leaves the intake section is high enough to cause a majority of the two-phase component to be in gas phase while entering the intermediate section.

5. 5. The Bernoulli heat pump of claim 4, further configured and operative to supersaturate a gas component of the two-phase component that is in the gas phase upon entering the intermediate section while flowing through the intermediate section.

6. 6. The Bernoulli heat pump of claim 5, wherein the degree of supersaturation is at least 20%.

7. The Bernoulli heat pump of claim 4 , wherein the two-phase component comprises at least two different two-phase fluids.

8. 5. The Bernoulli heat pump of claim 4, wherein an upstream end of the intake section and a downstream side of the blower are in fluid communication with the surrounding atmosphere, the atmosphere acting as a heat sink, the gaseous component being atmospheric air, and the Venturi further comprising one or more nozzles disposed in the intake section and operative to spray a two-phase fluid into the air flowing therethrough.

9. The Bernoulli heat pump of claim 8 , wherein the two-phase component comprises water.

10. 10. The Bernoulli heat pump of claim 8 configured to supply two-phase fluid at an adjustable rate to one or more of the nozzles.

11. The Bernoulli heat pump of claim 8 , wherein the two-phase component comprises a non-aqueous fluid.

12. The Bernoulli heat pump of claim 11 configured to enable any of the non-aqueous fluids to be recirculated to any of the nozzles.

13. 13. The Bernoulli heat pump of claim 12, further comprising means for extracting said non-aqueous fluid from the refrigerant exiting the exhaust, and means for flushing the extracted non-aqueous fluid with water.

14. The Bernoulli heat pump of claim 4 , further comprising a refrigerant flow path from a blower to the intake portion.

15. The Bernoulli heat pump of claim 14 , wherein the refrigerant flow path includes a condenser in thermal communication with a heat sink.

16. 15. The Bernoulli heat pump of claim 14, wherein the amount of the gas component and the amount of the two-phase component are constant.

17. the extracting means includes a settling tank disposed in the refrigerant flow path downstream of the exhaust and configured to have a bottom for accumulating settled liquid; 14. The Bernoulli heat pump of claim 13, further comprising a liquid supply tube having one end fluidly connected to the bottom of the settling tank and an opposite end in direct or indirect fluid communication with any one of the nozzles.

18. a fluid extraction box disposed in the refrigerant flow path downstream of the settling tank or the blower, the fluid extraction box including a porous material operative to absorb or adsorb non-aqueous fluids from the refrigerant; 18. The Bernoulli heat pump of claim 17, further comprising: means for causing extracted non-aqueous fluid to flow from said fluid extraction box to said bottom of said settling tank.

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