Optimized MCP thermal storage system and its assembly process

Abstract

Optimized PCM thermal storage system and its assembly method The invention relates to a thermal storage system (TSS) using a phase change material (PCM) comprising an enclosure intended to contain a PCM and a heat exchanger with a heat transfer fluid arranged at least partially in the enclosure in contact with the PCM, the heat exchanger comprising a bundle of parallel tubes intended to receive a heat transfer fluid, each tube comprising on its surface at least one helical fin wound helically along a longitudinal axis along which the tube extends, characterized in that the system comprises plates each comprising for each tube an opening through which a tube is arranged, and in that the diameter of the openings is less than the diameter of the helical fin. The present invention relates to a PCM thermal storage system provided with a heat transfer fluid exchanger and its assembly method.The field of the invention concerns Thermal Storage Systems (TSS) using Phase Change Materials (PCMs); and more particularly, the integration of a heat exchanger with optimized geometry. Figure for abstract: Fig.3.

Description

Title of the invention: Optimized MCP thermal storage system and its assembly method Technical field

[0001] The present invention relates to a MCP thermal storage system equipped with a heat transfer fluid exchanger and its assembly method.

[0002] The field of the invention relates to Thermal Storage Systems (TSS) using Phase Change Materials (PCMs); and more particularly, the integration of a heat exchanger with optimized geometry.

[0003] The invention will find its application in particular in urban or rural electrical and heat networks. The invention may also find applications in the development of electrical and thermal “smartgrid” networks, as well as in the interactions between these networks.

[0004] The invention will find its application in particular in urban, rural or industrial heating and / or cooling networks as well as in the storage of solar energy. The invention may also find applications in housing, off-grid thermal transport (trucks, boats, etc.) or in the thermal management of on-board (electric batteries) or stationary systems. The invention could be implemented according to a first application in the substations of heating networks, which present a significant challenge of compactness and offer significant potential replication (several tens of thousands of substations in France). According to a second application, the invention could be implemented for the storage of thermal energy from steam by the latent heat of the PCM. STATE OF THE ART

[0005] Heat networks consist of at least one heat source (thermal power station, thermal solar panels, geothermal source, etc.), a fluid network allowing the transport of calories to users via a heat transfer fluid and possibly a return network. Each calorie delivery station corresponds to a heat exchanger allowing the thermal transfer from the primary circuit (network connected to the heat source) to a secondary circuit; this second circuit is the property of the subscriber and is crossed by hot water (<100°C). This exchanger is the delivery point of the thermal energy, the assembly of exchanger, meter, and the different sets of valves is called: a substation.

[0006] The load of a heat network is very fluctuating, on average over the year the production units operate at 25% of their capacity, in general, the consumption peaks are 3 to 4 times greater than the average annual load. These Peaks (morning, evening) represent approximately 30% of the thermal consumption of a typical heating day. Backup (and emergency) generators are generally thermal power plants using heavy fuel oil, natural gas or coal, which are polluting and not always cheap. The use of a thermal storage system that would store calories while demand is low and reinject them into the network during consumption peaks could overcome this problem.

[0007] Thermal storage can be achieved by storage by enthalpy of change of state. In this case, storage is achieved via the phase change of a phase-change material. It is the enthalpy of phase change, most often during the solid / liquid state change, which is stored. This energy, which is for example absorbed during melting and released during solidification, results from the establishment, or rupture, of interatomic or intermolecular bonds. Commonly, the charging of the storage system is accompanied by the melting of the storage material, while the discharging is achieved by the solidification of said material. The material must be judiciously chosen according to the target temperature of the storage system, so that its melting temperature is within the operating temperature range.

[0008] The amount of thermal energy stored during the phase change is expressed with the following relationship: AQ=m*h M: Mass [kg] h: Mass enthalpy of solid-liquid phase change [kJ / kg]

[0009] One of the major advantages of this technology is that the phase change can be done at constant pressure and temperature. Therefore, the discharge of the stored energy is done at constant temperature.

[0010] The phase change enthalpy is relatively large compared to the sensible energy variation of a material. For example, the energy stored in the melting of a block of paraffin (change from 34 to 36°C for Rubitherm® RT35HC) is equivalent to the energy stored in this same quantity of paraffin if it is heated by 120°C.

[0011] Therefore, storage systems with a Phase Change Material (PCM) are interesting because the quantity of energy stored per unit volume is greater than that obtained by a sensitive system (better volume density of stored energy). As a result, the storage and material volumes are reduced, which reduces the price of the system, and limits thermal losses which are proportional to the external surface of the tank.

[0012] Thermal storage has recently developed around thermodynamic solar power plants in order to compensate for the intermittency of solar resources. Today, the The theme of thermal storage also concerns housing, urban heating networks and industry.

[0013] In particular, shell-and-tube exchanger technology is known. A shell in which a fluid circulates is traversed by a bundle of tubes in which another fluid flows. The two fluids exchange energy by conduction through the thickness of the tubes. In the case of thermal storage, this technology is adapted, there is no longer an exchange between two fluids in motion, but between a heat transfer fluid which circulates in the tubes and a PCM which is fixed in the shell (apart from the movements of natural convection in the liquid phase). During charging, the heat transfer fluid reaches a temperature higher than the melting temperature of the PCM and gives up energy to it, which causes it to melt; during discharge, the heat transfer fluid enters at a temperature lower than the solidification temperature of the PCM and recovers the previously stored energy, which causes the PCM to solidify.

[0014] Conventionally, the tubes are surrounded by circular fins increasing the heat exchange surface or by larger inserts.

[0015] However, in these shell-tube systems the conductivity remains low due to the MCP and the distances between the tubes generating dead zones, i.e. zones far from the fins. Indeed, the maximum diameter of the fins remains small, of the order of 55 mm, which leads to the use of many finned tubes in a latent heat storage, to diffuse the heat within the MCP. This disadvantage considerably increases the final cost of the latent heat storage. In addition, the large number of assemblies of the finned tubes on the upper and lower collector plates (often carried out by welding or expanding) generates an additional constraint on the cost of the system.Finally, the very low flow rate of the heat transfer fluid in the tubes, given the low partial flow rate of the heat transfer fluid circulating in each tube, implies a reduction in heat exchanges which requires the use of solutions such as the addition of internal hydraulic inserts in the tubes, which leads to a significant additional cost resulting from the purchase and assembly of these inserts (which can be carried out by brazing, crimping) in the finned tubes.

[0016] In addition, the mechanical stresses generated by the volume expansion of the MCP during its fusion of the solid-liquid MCPs can be particularly strong; if the fusion of the MCP begins at the bottom of the reservoir and a layer remains entirely solid above due to the dead zones, the rise in pressure of the liquid pocket can cause the deformation of the fins, or even the rupture of the reservoir. With the inserts, some of these disadvantages are limited, however the presence of play between the fins and the inserts penalizes the heat transfer and their implementation remains complex by requiring a long and meticulous assembly leading to high costs.

[0017] There is therefore a need to propose a device allowing improved conductive and convective heat transfers while being easy to design and inexpensive. SUMMARY

[0018] To achieve this objective, according to one embodiment, a thermal storage system (TSS) using a phase change material (PCM) is provided, comprising an enclosure intended to contain a PCM and a heat exchanger with a heat transfer fluid arranged at least partially in the enclosure in contact with the PCM, the heat exchanger comprising a bundle of parallel tubes intended to receive a heat transfer fluid, each tube comprising on its surface at least one helical fin wound helically along a longitudinal axis along which the tube extends, characterized in that the system comprises plates each comprising for each tube an opening through which a tube is arranged, and in that the diameter of the openings is less than the maximum external diameter of the helical fin.

[0019] This SST considerably increases the heat exchange surface between the MCP and the heat transfer fluid circulating in the tubes. In addition, this arrangement makes it possible to insert at least a portion of the fins, at least their end inside the volume formed between the stacked plates and occupied by the MCP. In addition, the optimization of the arrangement between the plates and the helical fins which can advantageously be in optimum contact makes it possible to ensure improved thermal conductivity. The helical fins ensure the possibility of assembling the tubes in the openings of the plates by screwing.

[0020] This SST design allows the melting or solidification front following the SST use phase (charging or discharging) not to cross a volume occupied only by MCP, presenting low thermal conductivity.

[0021] The SST according to the invention has optimized heat exchange surfaces which are not limited in the type of materials. The SST is thus obtained using inexpensive industrial processes and means.

[0022] According to another aspect, the invention relates to a method of assembling an SST as described above comprising the following successive steps: - stacking the plates on top of each other by aligning the openings to form a cassette of plates, - inserting the tubes by screwing into the openings of the plates, - assembling the ends of the tubes to collectors, - placing in the enclosure of the heat exchanger.

[0023] Assembly is therefore very quick and easy. BRIEF DESCRIPTION OF THE FIGURES

[0024] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment of the latter which is illustrated by the following accompanying drawings in which:

[0025] [Fig.l] [Fig.l] represents a perspective view of a helical finned tube according to an embodiment used in the SST according to the invention.

[0026] [Fig.2A] [Fig.2A] represents a perspective view of a plate according to an embodiment used in the SST according to the invention.

[0027] [Fig.2B] [Fig.2B] represents a perspective view of a plate according to another embodiment used in the SST according to the invention in which the opening has a slot.

[0028] [Fig.3] [Fig.3] represents a sectional view of the assembly of a helical finned tube within a plate cassette formed here by two plates.

[0029] [Fig.4] [Fig.4] represents a sectional view of the assembly of a bundle of helical finned tubes, two of which are represented here within a plate cassette formed here by two plates.

[0030] [Fig.5] [Fig.5] represents a sectional view of an SST according to the state of the art comprising a bundle of tubes with horizontal fins.

[0031] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. DETAILED DESCRIPTION

[0032] Before beginning a detailed review of embodiments of the invention, optional features which may possibly be used in combination or alternatively are set out below: - According to one example, the plates 50 comprise reliefs 51 projecting above and / or below a plate plane 56 extending in a longitudinal direction of extension of the plates; - According to one example, the plates 50 are stacked on top of each other with the openings 52 aligned with each other to form a plate cassette and the reliefs 51 are configured to act as plate spacers allowing the plates 50 to be stacked on top of each other in contact while maintaining a space 59 between two juxtaposed plates 50; The invention makes it possible, thanks to the superposition of the plates in contact with each other, to maintain the stack by their reliefs without requiring additional means for fixing the plates to the tubes. Each plate rests on a lower plate by the reliefs. In addition, the reliefs increase the exchange surface of the plates and thus improve the heat transfer performance. The reliefs also allow, when they are produced with removal of material to allow the molten MCP to rise freely between the plates. According to one example, the plates 50 extend in the same oblique longitudinal direction, preferably perpendicular, to the longitudinal axis 3 of the tubes 1; Preferably, the plates 50 are parallel to each other. According to one example, the openings 52 comprise a slot 61 configured to allow the helical fin 2 of the tube 1 to pass into the opening 52 of the plate 50; According to one example, the slot 61 has a depth 62 at least equal to half the difference between the maximum external diameter 7 of the helical fin 2 and the diameter 57 of the opening 52; According to one example, the slot 61 has a width 63 at least equal to the thickness 17 of the helical fin 2 with respect to the periphery of the opening 52; The presence of the slot makes it possible to facilitate the insertion of a tube into the plate and more preferably into the plates while advantageously having the tube centered in the opening. The thickness 17 of the fin advantageously corresponds to the thickness at the insertion radius; According to one example, the tubes 1 of the bundle of tubes comprise at least one end portion 5 by which the tube is introduced into the openings 52 of the plates 50 and which is devoid of a helical fin 2. Preferably, the tube comprises an end portion opposite the insertion end which is devoid of a fin; According to one example, the helical fin 2 has a maximum external diameter 7 decreasing towards its end arranged at an insertion end 4 of the tube 1 through which the tube 1 is introduced into the openings 52 of the plates 50; This arrangement makes it possible to reduce the diameter of the hole in the die-cast plates for the passage of the tube and thus promote the centering and wedging of the tube; According to one example, the diameter 57 of the openings 52 is at least equal to or greater than the external diameter 6 of the tubes 1. By external diameter of the tube is meant the external diameter of the tube itself without the fin; According to one example, the plate 50 has a thickness 60 less than or equal to the pitch 9 of the helical fin 2, preferably to the free height 16 between two successive bases of the helical fin 2; According to one example, the tubes (1) of the tube bundle comprise at an insertion end 4 of the tube 1 through which the tube 1 is introduced into the openings 52 of the plates 50, an imprint intended to cooperate with a driving tool for screwing the tubes into the openings 52 of the plates. 50 and configured to be removed after the tube 1 has been screwed into the plates 50; - According to one example, the plates 52 are perforated; advantageously, so as to allow better circulation of a fluid circulating around the exchanger. Preferably, the plates are perforated without removing material. This further increases the exchange surface area of ​​the plates.

[0033] For the remainder of the description, 'top' and 'bottom', or their derivatives, are understood to mean a quality of positioning relative to the SST or an element of the SST when the latter is installed functionally, the 'top' being oriented away from the ground and the 'bottom' being oriented towards the ground. The upper end is located at the top and the lower end is located at the bottom.

[0034] Vertical means that which is parallel to the direction of gravity given in particular by the plumb line and horizontal that which is perpendicular to the vertical. The top and the bottom being vertically opposed.

[0035] By horizontal we mean that which is perpendicular to the vertical.

[0036] Longitudinal axis means the axis parallel to the main direction of extension. Transverse means a direction perpendicular to a longitudinal direction. A transverse section is a section perpendicular to the longitudinal axis.

[0037] Thickness is generally measured in a direction perpendicular to the main plane of extension.

[0038] For the purposes of this disclosure, the expression "A and / or B" means (A), (B), or (A and B). For the purposes of this disclosure, the expression "A, B, and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0039] The SST 100 according to the invention comprises an enclosure 107 and an exchanger.

[0040] The enclosure 107 is conventionally of a cylindrical shape whose walls are formed of metallic material resistant to variations in pressure and temperature. For example, the enclosure 107 is made of structural carbon steel. The conventional grades for a pressure enclosure are P235GH, P265GH, P355GH. In the presence of a risk of oxidation or corrosion, austenitic stainless steels 304, 316 can be used. The enclosure can be made in a single piece, in two welded half-cylinders, or by superimposing shells.

[0041] The enclosure 107 is configured to receive an MCP.

[0042] The MCP is placed directly in the enclosure 107 and the exchanger plunges into said MCP.

[0043] The enclosure 107 contains at least one MCP. Mixtures of MCPs may be used. In the remainder of the description, the reference to an MCP is not limiting. Different MCPs may be used, in particular MCPs with solid / solid transition or preferably MCPs with solid / liquid transition. The invention is suitable for a wide range of applications. variety of PCMs and therefore a wide range of storage temperatures. The two main categories of PCMs that can be used are organic (paraffins, fatty alcohols, fatty acids, sugar alcohols, etc.) and inorganic (salt hydrates, metal alloys, etc.). It is preferred to target a material that does not oxidize and does not oxidize the metal structure of the exchanger or enclosure 107, that has a good specific enthalpy of phase change and that is not toxic. Preferably, the PCM will have a good heat capacity and the highest possible thermal conductivity. According to one possibility, the enclosure 107 comprises above the PCM 105 gas 104.

[0044] The MCP is a two-phase material, preferably solid and liquid, whose transition between these two phases stores or releases energy. Preferably, the transition from a first phase to a second phase will require heat which is therefore stored in the MCP in its second phase. Conversely, the transition from the second phase to the first phase is exothermic and releases the stored heat.

[0045] The exchanger 107 according to the invention is a heat energy exchanger using a heat transfer fluid. The exchanger 107 is configured to receive a heat transfer fluid 103 and advantageously allow its circulation.

[0046] The exchanger 107 comprises tubes 1, preferably called a tube bundle, and plates 50. The tubes are configured to receive the heat transfer fluid 103.

[0047] The plates 50 comprise openings 52 for tubes 1 through which the tubes 1 are arranged.

[0048] The heat transfer fluid is conventionally water, or steam, or any other fluid having heat transfer properties can be used, for example a thermal oil such as polychlorinated biphenyl (therminol®) or a mixture of isomers of (di)benzyltoluene (Jarytherm®).

[0049] The tubes 1 are connected to a fluid circuit of heat transfer fluid. A first end of the tubes 1 constitutes the inlet of the heat transfer fluid while the other end constitutes the outlet of the heat transfer fluid. The direction of circulation of the fluid is not unique, the fluid can, depending on whether it is charging or discharging, circulate in one direction or the other. In the following description, the case considered is a charge. The description is made for heat storage at positive temperature, it should be noted that it is also valid for cold storage with a PCM which can then be water. In this case, the mechanical stresses are greater during the solidification of the water, due to its higher density in the liquid state than in the solid state, unlike the majority of PCMs used for latent heat storage at positive temperatures.

[0050] The hydraulic connection of the tubes 1 can be made via manifolds, a plate tubular, a water box, a conical divergent,... In [Fig.l] an upper collector 101 and a lower collector 102 are shown.

[0051] The system may comprise a plurality of exchangers arranged in an enclosure 107.

[0052] When the SST operates to store thermal energy, the exchanger brings heat into the enclosure, there is a heat exchange from the heat transfer fluid to the MCP through the exchanger. This heat will allow the transformation of the MCP from the first phase to the second phase which will then store the heat from the heat transfer fluid. When the device operates to restore thermal energy, the exchanger cools the MCP, there is a heat exchange from the MCP to the heat transfer fluid through the exchanger, which allows the passage from the second phase to the first phase. This transformation is exothermic. The heat released is recovered by the heat transfer fluid.

[0053] The tubes 1 of the exchanger are advantageously arranged in a bundle of tubes. The tubes 1 are arranged parallel to each other. According to one possibility, the tubes are arranged vertically and preferably, the enclosure 107 extends in a main vertical direction.

[0054] The remainder of the description is made with reference to a single tube, but applies to all the tubes of the exchanger.

[0055] Each tube 1 extends along a longitudinal axis 3. Each tube 1 comprises on its surface 11, corresponding to the external surface of the tube, a helical fin 2. The helical fin 2 is a fin which is wound helically on the surface 11 of the tube 1 along the longitudinal axis of the tube 1. Preferably, each tube 1 comprises a helical fin 2. According to another possibility, each tube 1 comprises several helical fins arranged in continuity or discontinuity.

[0056] The helical shape of the fin 2 contributes to facilitating the convection movements of the MCP 105 in the enclosure 107 and in particular around the tubes 1. More precisely, the helical fin facilitates the formation on its surface of a continuous channel of liquid MCP allowing it to rise and extend freely at the free surface, thus limiting the risk of exerting significant mechanical stress on the exchanger during the volume expansion of the MCP. In addition, the helical shape of the radial fin facilitates the manufacture of the finned tubes.

[0057] The helical fin 2 can be either extruded, or crimped in a groove, or welded, at high frequency or laser for example, to the external surface 11 of the tube 1 following a helicoid.

[0058] The tubes 1 are advantageously cylindrical. For example, the tubes 1 have a diameter 6 generally between 17.2mm (DN10) and 60.3mm (DN50), the most common diameter being 33.7mm (DN25).

[0059] For example, the helical fins 2 have a maximum external diameter 7 of 56 mm. The maximum external diameter 7 of the helical fin 2 corresponds to the sum of the diameter of the tube 6 and the height of the fin 12 of the helical fin 2.

[0060] According to a preferred embodiment, the tube 1 comprises at least one insertion end 4 through which the tube 1 is introduced into the openings 52 of the plates 50. Advantageously, the tube 1 comprises a portion 5 arranged at the insertion end 4 which is devoid of a fin. This portion is called the insertion end portion 5. The insertion end portion 5 is for example smooth. The insertion end portion 5 comprises only the tube 1 and its surface 11. The surface 11 of the tube 1 may be smooth or for example grooved to facilitate the attachment of the fins without being limiting. This insertion end portion 5 makes it easier to introduce the tube 1 into the openings 52 of the plate 50. According to a possibility not shown, the tube 1 comprises an end portion opposite the insertion end which is also devoid of a fin.This arrangement advantageously makes it easier to adapt the size of the tubes 1 to the dimensions of the enclosure 107 by allowing easier cutting of the tubes 1. The absence of fins at the ends of the tubes also allows them to be assembled to the tube collector plates or to the hydraulic collection or distribution manifolds.

[0061] According to a first embodiment, the helical fin 2 has a maximum external diameter 7 which is constant over the entire tube 1.

[0062] According to a second embodiment, the helical fin 2 has a diameter 7 advantageously decreasing in the direction of the end of the fin arranged opposite the insertion end 4 of the tube. Preferably, the tube 1 comprises a decreasing portion 8 in which the maximum external diameter 7 of the helical fin 2 decreases in the direction of the insertion end 4 of the tube. The maximum external diameter 7 of the helical fin 2 decreases as it approaches this insertion end 4 of the tube 1. This arrangement makes it possible to reduce the diameter 57 of the opening 52 in the plates 20 for the passage of the tube 1 and thus promote the centering and wedging of the tube 1.

[0063] By way of example, a tube 1 has a length before connection to the upper collector 100 and lower collector 102 of between 1m and 6m, possibly the insertion portion 5 represents from 15 mm to 50 mm, possibly the decrease portion represents from 20 mm to 50 mm.

[0064] The helical fin 2 is advantageously defined by its pitch 9, its height 12, advantageously the thickness of the helical fin 2 at its base 14 and the thickness of the helical fin 2 at its top 15, the thickness 17 of the helical fin at its insertion radius and possibly the length 13 of the helical fin 2 and possibly the height 16 separating two successive bases 14 of the helical fin 2 along a vertical axis, more precisely separating the upper base face from the lower face of the next base. The pitch 9 of the helical fin 2 is chosen as a function of the plates 50 and in particular the reliefs 51 described below. The pitch 9 is understood as the distance between 2 successive vertices of the helical fin 2 along a vertical axis. The height 12 of the fin is understood as the distance between the vertex 15 and the base 16 of the helical fin 2, corresponding to the surface 11 of the tube 1.

[0065] For example, pitch 9 is defined so as to have a number of fins / meter between 196 fins / meter and 473 fins / meter, that is to say that pitch 9 is between 20mm and 55mm, more precisely between 21mm and 51mm. The pitch 9 of the helical fin 2 is chosen so that the helical fin 2 is in contact with the plates 50 and advantageously ensures a plane contact 10 between a surface of the plate 50 and a surface of the helical fin 2. This plane contact 10 between the plate 50 and the helical fin 2 is optimized to allow thermal conduction between the heat transfer fluid 103 and the MCP 105 passing through the plates 50, the helical fin 2 and the tube 1. Preferably, this plane contact 10 is made over at least a portion of the fin height 12 corresponding to half the difference between the maximum external diameter 7 of the helical fin and the diameter 57 of the opening 52.This plane contact 10 advantageously presents at least 25% of the height 12 of the helical fin, preferably at least 50%.

[0066] The helical fin 2 can either have a decreasing thickness from its base 14 to its top 15, or have a constant thickness from its base 14 to its top 15.

[0067] According to a preferred possibility, notably illustrated in figures 3 and 4, the helical fin 2 and the plates 50 are configured so that the helical fin 2 comes into contact with the plate 50 alternately by the first face 54 and the second face 55 of the plate 50. This arrangement is notably made possible by the screwing of the tube 1 onto the plate 50. The tube 1 is in continuous contact with the plate 50 via the helical fin 2. It is not possible to have a clearance between the helical fin 2 and the plate 50 unlike what happens with the inserts on the tubes of the state of the art.

[0068] According to one possibility, the tube 1 comprises at its insertion end 4 an imprint, not shown in the figures, configured to cooperate with a driving tool for screwing the tube 1 into the openings 52 of the plates 50. For example, a grooved, hexagonal, or other imprint may be provided at the insertion end 4. Advantageously, this imprint is removed to allow adjustment of the tube 1 to the dimensions of the enclosure 107 and to facilitate assembly of the tube 1 at its ends to the upper collector 101 and to the lower collector 102.

[0069] Advantageously, all of the tubes 1 of a bundle of tubes of the SST 100 are identical. However, it may be provided that tubes 1 of the tube bundle are different in structure, dimensions, shape, etc.

[0070] The SST 100 according to the invention comprises plates 52 advantageously forming part of the exchanger in the sense that they participate in the heat exchange between the MCP 105 and the heat transfer fluid 103.

[0071] According to a preferred embodiment, the plates 50 are preferably arranged perpendicular to the tubes 1. Preferably, the tubes 1 are parallel to each other and the plates 50 are parallel to each other.

[0072] According to the invention, the plates 50 comprise openings 52 for tubes 1. The openings 52 are produced with material removal, preferably by pre-cutting and then stamping. The openings 52 are configured to receive the tubes 1. Each opening 52 receives a tube 1. The opening 52 is of a shape complementary to that of the tube 1 and advantageously to that of the helical fin.

[0073] Advantageously, the opening 52 has a diameter 57 less than the maximum diameter 7 of the helical fin 2. Advantageously, the diameter 57 of the opening is greater than or equal to the diameter 6 of the tube 1. In this way, the tube 1 can be introduced into the opening 52 and the helical fin 2 is in contact with the opening 52 to advantageously allow insertion by screwing and preferably in contact between the helical fin 2 and the plate 50.

[0074] According to one possibility, each opening 52 comprises at least one slot 61 configured to allow the helical fin 2 of the tube 1 to pass into the opening of the plate 52 during its insertion.

[0075] The slot 61 advantageously extends from the periphery of the opening 52. For example, the slot 61 extends along a main component parallel to the radius of the opening 52. The slot 61 may be inclined relative to the radius of the opening 52.

[0076] The slot 61 is defined in particular by its depth 62 corresponding to the distance separating the base of the slot 61 at the periphery of the opening 52 and the top of the slot, opposite its base. The depth 62 of the slot 61 is advantageously configured to allow the helical fin 2 to pass and more precisely the depth 62 is at least equal to half the difference between the maximum external diameter 7 of the helical fin 2 and the diameter 57 of the opening 52. This arrangement makes it possible to have the longitudinal axis 3 of the tube 1 centered in the opening 52.

[0077] The slot 61 may be rectangular or triangular in shape as illustrated in [Fig.2B]. The slot 61 is advantageously of a shape complementary to that of the helical fin 2. If the helical fin has a constant thickness from its base 14 to its apex 15, the slot 61 will preferably be rectangular in shape, while if the helical fin 2 has a decreasing thickness from its base 14 to its apex 15, the slot 61 will preferably be triangular in shape. The slot 61 advantageously has a width at least equal to the thickness 17 of the helical fin at its insertion radius. The insertion radius of the helical fin 2 corresponds, preferably, to half the diameter 57 of the opening 52. This arrangement makes it easier to insert the tube 1 and the fin 2 into the opening 52 without offsetting the tube 1.

[0078] According to one possibility, the edges of the slot 61 can be offset, that is to say arranged at least partly on a different longitudinal plane of the plate. The two edges of the slot 61 can be offset in height so as to facilitate the insertion of the helical fin.

[0079] Preferably, the plate 50 has a thickness 60. The thickness 60 of the plate preferably at the level of the opening 52 is in line with the pitch 9 of the helical fin 2 and more preferably with the height 16 separating two successive bases 14 of the helical fin 2.

[0080] Preferably, the plates 50 have a shape corresponding to the shape of the interior of the enclosure 107. The plates 50 are configured to be advantageously stacked in the enclosure 107 of the SST 100. For example, the plates 50 are circular or hexagonal in shape. The plates 50 advantageously form a cassette of plates, i.e. a set of plates.

[0081] Each plate 50 extends along a plate plane 56 in a longitudinal direction, advantageously perpendicular to the longitudinal axis 3 of the tubes 1.

[0082] According to one embodiment, the plates 50 or at least some plates, for example one plate out of two alternating, comprise reliefs 51. By way of example, the reliefs 51 are formed by plastic deformation of the plates 50 forming so-called stamped plates 50.

[0083] Preferably, the reliefs 51 are configured to act as spacers for plates 50. Advantageously, in the SST 100 according to the invention, the plates 50 are stacked in contact with each other, preferably at least partially by their reliefs 51. A relief 51 may be in contact with another opposite relief 51 formed on a plate above or below it or in contact with the plate 50 itself.

[0084] The reliefs 51 allow the plates 50 to be superimposed in contact with each other. The plates 50 are stacked and rest on each other by contact zones 58. According to the invention, it is not necessary to provide means for fixing the plates 2 to the tubes 1 to ensure the superposition of the plates 2.

[0085] The reliefs 51 have a function of spacers for the plates 2. The reliefs make it possible to maintain a space between two juxtaposed plates 2. Indeed, the plates 2 are spaced from each other by at least the height of the reliefs 51 of a plate 50, or even the sum of the height of the reliefs of 2 successive plates 50 illustrating the spacing 59 between the plates.

[0086] Advantageously, the plates 50 comprise a first face 54 and a second opposite face 55. The reliefs 51 are preferably formed on at least one of the two faces 54-55 of the plates. It is thus understood that the reliefs protrude on at least one of the two faces 54-55. According to one possibility illustrated in Figures 3 and 4, the reliefs 51 protrude on the two faces 54 and 55. According to one possibility illustrated in particular in the figure, the plates 50 comprise reliefs 51 and advantageously flat portions spacing the reliefs.

[0087] The reliefs 51 can take very varied forms such as point projections or longitudinal reliefs extending from one edge to the other of a plate 2, for example ribs, or undulations as illustrated in Figures 3 and 4. The reliefs 51 can form a network following a recurring pattern alternating for example a relief 51 oriented towards the first face 54 of the plate 50, called upper relief, and a relief 51 oriented towards the second face 55 of the plate 50, called lower relief. Preferably, the ribs extend from one side to the other of the plate 2. The reliefs 51 extend in a main direction perpendicular to the plate plane 56 from which they extend. The reliefs 51 can be ribs of parallelepiped shape or of rounded shape.

[0088] Preferably, the reliefs 51 are configured to generate a contact zone 59 between two juxtaposed plates 50a and 50b. The contact zone 59 is advantageously a plane contact zone. For example, the stacking of the plates 50 allows some of their reliefs 51 to come into contact, for example the lower reliefs of a plate 50a from above are in contact with the upper reliefs of the plate 50b located below.

[0089] Advantageously, the reliefs 51 are formed by stamping the plate 50, they can also be obtained by other types of mechanical machining (modeling, stamping, Guérin process, or engraving for the smallest reliefs) or laser. Preferably, the reliefs 51 are formed by deformation of the plate 50 and not by adding material to the plate 50. The reliefs 51 and the plate 50 are integral. The reliefs 51 and the face 54 or 55 of the plate 50 form a monolithic part in order to optimize heat transfers.

[0090] The shape of the reliefs must be chosen to ensure a mechanical function and a thermal function. Mechanical, because the reliefs allow the plates 50 to rest on each other, thus ensuring their spacing 59 and advantageously maintaining the overall structure. Indeed, the reliefs 51 and therefore the spacing 59 generated by them must be compatible with the pitch 9 of the helical fin 2 of the tube 1. The plates 50 and the tubes 1 are in physical and thermal contact. The weight of the plates 50 thus rests both on the helical fins 2 and on themselves thanks to the reliefs 51. Thermal, because the reliefs 51 increase the exchange surface and improve the heat transfers in the direction orthogonal to the plates 50: in fact, the plates 50 being in contact with each other in the vertical direction, advantageously by the contact zones 59, they promote conductive heat transfers in this direction.

[0091] Furthermore, the plates 50 advantageously extend over the entire transverse surface of the enclosure 107, consequently there are no dead zones, that is to say zones distant from the plates 50, as may exist with finned tubes of the state of the art or with inserts of the state of the art.

[0092] The set of plates 50 forms a 3-dimensional structured plate cassette also called a matrixed plate cassette.

[0093] For example, the reliefs 51 have a minimum thickness of 8 mm and a maximum of 10 cm, more preferably between 2 and 5 cm. The thickness of the reliefs is to be readjusted according to the number of tubes per square meter and the desired power.

[0094] Plates 50 of different geometries can be stacked in the same exchanger. The plates 50 can be stacked on top of each other in different ways, for example with the ribs of one plate 50 parallel to the ribs of the plates 50 stacked on either side or with ribs of one plate 50 perpendicular to the ribs of the other plates 50 stacked on either side. According to a possibility not shown, the stack comprises plates 50 having a relief and flat plates without relief. The plates 50 having reliefs 51 have reliefs 51 extending from the two faces 54, 55 of the plate 50. Thus, the stack successively comprises a plate 50 with relief, then a flat plate then a plate 50 with relief... Advantageously, the plates 50 are stacked by gravity.

[0095] According to a preferred embodiment, the plates 50 are perforated and preferably without removal of material.

[0096] By way of example, the plates 50 comprise perforations. The plates 50 are advantageously perforated without removing material as illustrated in FIGS. 2A and 2B.

[0097] For example, the reliefs 51 are openwork.

[0098] According to one possibility, the holes are formed in the plate 50 mechanically by punching or shearing operations.

[0099] In Figures 3 and 4, the perforations or holes are not illustrated to simplify the drawings.

[0100] The plates 50 are preferably embossed, cut, or even made of expanded metal.

[0101] The perforations allow the passage of the liquid MCP: they do not block convective transfers and prevent the mechanical stresses generated by the volume expansion of the MCP during its change of state, by allowing the in place of fluid paths. Preferably, the perforations are made without removing material in order to optimize heat transfers by maximizing the exchange surface of the exchanger 3.

[0102] According to one possibility, the plates 50 are secured to the tubes 1 and / or to the helical fins 2, for example by stirring.

[0103] The invention also relates to a method of assembling the SST 100 described above. The method comprises a step of stacking the plates 50 on top of each other, advantageously in contact while maintaining a space between two juxtaposed plates 50 thanks to the reliefs 51. The plates 50 are stacked so that the openings 52 for tubes 1 are aligned. Preferably, the alignment of the openings 52 can be achieved using assembly guides, which are preferably metal bars of the same diameter as the tubes 1. The stacking is advantageously done by gravity. The plates 50 rest on each other. The tubes 1 are then introduced into the openings 52 of the plates 50. Advantageously, the tubes 1 are introduced into the openings 52 of the plates 50 by screwing the helical fin 2 onto the opening 52.

[0104] Advantageously, the method then comprises connecting the ends of the tubes 1 to the heat transfer fluid network 103. The ends of the tubes 1 are connected respectively to the upper collector 101 and lower collector 102.

[0105] According to one possibility, before connecting the ends of the tubes to the heat transfer fluid network 103, the tubes 1 are brought to the dimensions of the enclosure and / or the imprint is removed and / or the insertion end portion 5 is removed.

[0106] Advantageously, the method then comprises the installation in the enclosure 107 of the heat exchanger formed of the tubes 1 with helical fins 2 and the plates 50 forming the plate cassette.

[0107] List of references 1. Tube 2. Fin 3. Longitudinal axis of the tube 4. Insertion end 5. End portion 6. External diameter of the tube 7. Maximum external diameter of the fin 8. Decay portion 9. Pitch of the helical fin 10. Contact surface between the plate and the helical fin 11. External surface of the tube 12. Height of the helical fin 13. Helical fin length 14. Base of the helical fin 15. Top of the helical fin 16. Height separating two successive bases of the helical fin 17. Thickness of the helical fin at the insertion radius 50. Plate 50 a. First plate 50 b. Second plate 51. Relief 52. Opening 54. First side 55. Second side 56. Plate plan 57. Diameter of the opening 58. Contact area between the plates 59. Spacing between plates 60. Plate thickness 61. Slit 62. Slot Depth 63. Slot width 100. SST 101. Upper collector 102. Lower manifold 103. Heat transfer fluid 104. Gas Sky 105. MCP 106. Longitudinal axis of the enclosure 107. Pregnant

Claims

Claims

1. Thermal storage system (TSS) using phase change material (PCM) comprising an enclosure (107) intended to contain a PCM (105) and a heat exchanger with heat transfer fluid arranged at least partially in the enclosure (107) in contact with the PCM (105), the heat exchanger comprising a bundle of parallel tubes (1) intended to receive a heat transfer fluid, each tube (1) comprising on its surface (11) at least one helical fin (2) wound helically along a longitudinal axis (3) along which the tube (1) extends, characterized in that the system comprises plates (50) each comprising for each tube (1) an opening (52) through which a tube (1) is arranged, and in that the diameter (57) of the openings (52) is less than the maximum external diameter (7) of the helical fin (2).

2. SST according to the preceding claim in which the helical fin (2) is, at least in part, in contact with at least one plate (50).

3. SST according to any one of the preceding claims in which the plates (50) comprise reliefs (51) projecting above and / or below a plate plane (56) extending in a longitudinal direction of extension of the plates.

4. SST according to the preceding claim in which the plates (50) are stacked on top of each other with the openings (52) aligned with each other to form a cassette of plates and the reliefs (51) are configured to act as plate spacers allowing the plates (50) to be stacked on top of each other in contact while maintaining between two juxtaposed plates (50) a space (59).

5. SST according to any one of the preceding claims in which the plates (50) extend in the same oblique longitudinal direction, preferably perpendicular, to the longitudinal axis (3) of the tubes (1).

6. SST according to any one of the preceding claims wherein the openings (52) comprise a slot (61) configured to allow the helical fin (2) of the tube (1) to pass into the opening (52) of the plate (50).

7. SST according to the preceding claim in which the slot (61) has a depth (62) at least equal to half the difference between the maximum external diameter (7) of the helical fin (2) and the diameter (57) of the opening (52).

8. SST according to any one of the two preceding claims in which the slot (61) has a width (63) at least equal to the thickness (17) of the helical fin (2) with respect to the periphery of the opening (52).

9. SST according to any one of the preceding claims in which the tubes (1) of the tube bundle comprise at least one end portion (5) through which the tube is introduced into the openings (52) of the plates (50) and which is devoid of a helical fin (2).

10. SST according to any one of the preceding claims in which the helical fin (2) has a maximum external diameter (7) decreasing towards its end arranged at an insertion end (4) of the tube (1) by which the tube (1) is introduced into the openings (52) of the plates (50).

11. SST according to any one of the preceding claims wherein the diameter (57) of the openings (52) is at least equal to or greater than the external diameter (6) of the tubes (1).

12. SST according to any one of the preceding claims in which the plate (50) has a thickness (60) less than or equal to the pitch (9) of the helical fin (2).

13. SST according to any one of the preceding claims wherein the tubes (1) of the tube bundle comprise at an insertion end (4) of the tube (1) by which the tube (1) is introduced into the openings (52) of the plates (50), an imprint intended to cooperate with a driving tool for screwing the tubes into the openings (52) of the plates (50) and configured to be removed after the tube (1) has been screwed into the plates (50).

14. SST according to any one of the preceding claims in which the plates (52) are perforated.

15. Method of assembling an SST according to any one of the preceding claims comprising the following successive steps: • stacking the plates (50) on top of each other by aligning the openings (52) to form a cassette of plates, • inserting by screwing the tubes (1) into the openings (52) of the plates (50) • assembling the ends of the tubes (1) to collectors (102, 103) placed in the enclosure (107) of the heat exchanger.

Images