Inorganic salt phase change material and preparation method therefor and use thereof

Abstract

The present application discloses an inorganic salt phase change material and a preparation method therefor and a use thereof. An inorganic salt phase change material composition comprises the following components: 89.0 wt.% to 92.5 wt.% of a hydrated inorganic salt A, 2.0 wt.% to 5.0 wt.% of a nucleating agent, 0.4 wt.% to 1.0 wt.% of a nucleation promoter, 0.2 wt.% to 2.7 wt.% of a thickener, and 1.5 wt.% to 5.0 wt.% of a thermally conductive filler. The nucleating agent is selected from at least one of a sodium salt, a strontium salt, and a metal oxide. The nucleation promoter is selected from at least one of non-metallic mineral materials.

Description

Inorganic salt phase change material, preparation method and application thereof

[0001] Related applications

[0002] The present application claims priority to the following Chinese patent application: Application No. 202411369732.8, filed on September 27, 2024, entitled "Inorganic salt phase change material, preparation method and application thereof", the entire contents of which are hereby incorporated by reference. TECHNICAL FIELD

[0003] The present application relates to the technical field of energy storage materials, in particular to an inorganic salt phase change material, a preparation method and application thereof. BACKGROUND

[0004] Phase change energy storage is a technology that uses the phase change (solid-liquid, gas-liquid) of materials to store energy. In the process of heating, both sensible heat storage and latent heat storage are involved, and in the process of latent heat storage, the temperature of the material is almost constant. Compared with water that only uses sensible heat storage, phase change materials have higher heat storage capacity, so the phase change energy storage technology is introduced into the heat pump system, and a phase change energy storage unit suitable for heat pumps is designed. The energy storage density of the phase change material can reach twice that of water (10℃~65℃), and the volume of the energy storage unit using the phase change material can be reduced to 50% of that of the energy storage unit using water for heat storage. Phase change materials have very high application advantages in heat pump systems.

[0005] In the energy storage process, the phase change material absorbs heat from the heat source; in the heat release process, the low-temperature domestic water flow passes through the high-power heat exchanger to exchange heat with the phase change material, realizing instant hot water. In the frequent energy storage process and heat release process of the phase change material, the phase change material repeatedly melts and crystallizes, which can easily cause the enthalpy value of the phase change material to decay, and further cause the enthalpy value of the phase change material to decay. SUMMARY

[0006] The present application provides an inorganic salt phase change material, a preparation method and application thereof, which can solve the problem of enthalpy value decay of the phase change material in the frequent melting-crystallization process.

[0007] In a first aspect, the present application provides an inorganic salt phase change material composition, which comprises the following components:

[0008] Inorganic hydrated salt A 89.0wt.%~92.5wt.%, nucleating agent 2.0wt.%~5.0wt.%, nucleating agent 0.4wt.%~1.0wt.%, thickening agent 0.2wt.%~2.7wt.%, thermal conductive filler 1.5wt.~5.0wt.%;

[0009] The nucleating agent is selected from at least one of sodium salt, strontium salt, metal oxide, and the auxiliary nucleating agent is selected from at least one of non-metallic mineral material.

[0010] In some embodiments, the composition comprises the following components: inorganic hydrated salt A 91.0 wt.%~92.5 wt.%, nucleating agent 2.5 wt.%~4.5 wt.%, auxiliary nucleating agent 0.5 wt.%~0.8 wt.%, thickening agent 0.8 wt.%~1.2 wt.%, and thermal conductive filler 2.0 wt.%~3.0 wt.% based on the total weight of the composition.

[0011] In some embodiments, the weight percentage of the inorganic hydrated salt A is f, the weight percentage of the nucleating agent is m, and the weight percentage of the auxiliary nucleating agent is n based on the total weight of the composition; the composition satisfies at least one of the following conditions:

[0012] (1) 20.56≤f / (m+n)≤23.13;

[0013] (2) 3.5≤m / n≤35.0.

[0014] In some embodiments, the inorganic hydrated salt A is selected from at least one of sodium acetate trihydrate, magnesium nitrate hexahydrate, potassium acetate monohydrate, sodium thiosulfate pentahydrate, sodium sulfate decahydrate, calcium nitrate tetrahydrate, and magnesium sulfate pentahydrate.

[0015] In some embodiments, the sodium salt of the nucleating agent is selected from at least one of disodium hydrogen phosphate dodecahydrate, sodium pyrophosphate, sodium carbonate, and disodium hydrogen phosphate heptahydrate; the strontium salt of the nucleating agent is selected from at least one of strontium chloride hexahydrate, strontium acetate, strontium carbonate, and strontium nitrate; and the metal oxide of the nucleating agent is selected from at least one of magnesium oxide, aluminum oxide, iron oxide, and magnetite.

[0016] In some embodiments, the non-metallic mineral material of the auxiliary nucleating agent is selected from at least one of mica, montmorillonite, quartz, expanded perlite, talc, calcite, and feldspar; the particle size Dv 50 satisfies 850μm≤Dv 50 ≤1500μm.

[0017] In some embodiments, the thickening agent is selected from at least one of cyclic dextrin, chitosan, xanthan gum, sodium carboxymethyl cellulose, and soluble starch.

[0018] In some embodiments, the thermal conductive filler is selected from at least one of metal foam, expanded graphite, boron nitride, and molybdenum disulfide.

[0019] In a second aspect, the present application provides a preparation method of the inorganic salt phase change material, comprising: mixing the components in the inorganic salt phase change material composition as described above.

[0020] In some embodiments, the mixing of the components in the inorganic salt phase change material composition comprises the following steps:

[0021] providing an inorganic hydrated salt A, heating the inorganic hydrated salt A to a preheating temperature which is greater than the melting point of the inorganic hydrated salt A, performing a preheating treatment to obtain molten inorganic hydrated salt A;

[0022] adding the nucleating agent to the molten inorganic hydrated salt A, performing an emulsification ultrasonic treatment to obtain a mixture A;

[0023] adding the nucleating agent and the heat-conducting filler to the mixture A, performing a blending treatment to obtain a mixture B;

[0024] adding the thickening agent to the mixture B, performing a thickening treatment to obtain a mixture C;

[0025] cooling and solidifying the mixture C to form the inorganic salt phase change material.

[0026] In some embodiments, the preheating treatment at least comprises: a time of 2h-3h, and a temperature range of 10℃-15℃ which is greater than the melting point of the inorganic hydrated salt A.

[0027] In some embodiments, the emulsification ultrasonic treatment at least comprises an emulsification treatment and an ultrasonic treatment, wherein the emulsification treatment has a stirring speed of 5000r / min-8000r / min and a time of 10min-20min, and the ultrasonic treatment has an ultrasonic frequency of 40kHz-60kHz and a time of 20min-40min.

[0028] In some embodiments, the blending treatment at least comprises: a vacuum degree of -0.15Mpa--0.3Mpa, a stirring speed of 60r / min-90 / min, and a time of 2h-3h.

[0029] In some embodiments, the thickening treatment at least comprises: adding the thickening agent to the mixture B in several times, and a stirring speed of 20r / min-40r / min and a time of 1.5h-2h, and the weight of the thickening agent added each time is 0.2%-2.0% of the total weight of the thickening agent.

[0030] In a third aspect, the present application provides an inorganic salt phase change material, wherein the inorganic salt phase change material is prepared by the preparation method as described above.

[0031] In a fourth aspect, the present application provides a heat pump system, comprising an energy storage unit, wherein the energy storage unit comprises:

[0032] a main housing having an energy storage cavity inside;

[0033] a heat exchange pipe arranged in the energy storage cavity; and

[0034] a phase change layer comprising the inorganic salt phase change material as described above, the phase change layer being filled in the energy storage cavity and coated on the outer surface of the heat exchange pipe to exchange heat with the heat exchange medium in the heat exchange pipe.

[0035] The inorganic salt phase change material, the preparation method and the application thereof according to the embodiments of the present application can provide nucleation sites for the crystallization of the inorganic hydrated salt A by adding a nucleating agent and selecting the content of each component in the inorganic salt phase change material composition in a suitable range, and the nucleating agent is selected from at least one of non-metallic mineral materials, which can form a covering film on the surface of the inorganic salt phase change material to reduce the phase change enthalpy attenuation of the inorganic hydrated salt due to water evaporation in the repeated working process. In the crystallization process of the inorganic hydrated salt A, in addition to the nucleating agent promoting the formation of crystal nucleus, the nucleating agent can also promote the growth of crystal form, so as to improve the enthalpy attenuation of the inorganic salt phase change material and prolong the service life of the inorganic salt phase change material. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0037] FIG. 1 is a flowchart of a preparation method of an inorganic salt phase change material according to an embodiment of the present application;

[0038] FIG. 2 is a schematic diagram of a perspective structure of an energy storage unit according to an embodiment of the present application;

[0039] FIG. 3 is a schematic diagram of a perspective structure of a heat exchange structure according to an embodiment of the present application;

[0040] FIG. 4 is a schematic diagram of a perspective structure of a plurality of heat exchange pipes connected with a plurality of heat conduction fins according to an embodiment of the present application;

[0041] FIG. 5 is a schematic diagram of a perspective structure of a plurality of groups of adapter pipes according to an embodiment of the present application;

[0042] Fig. 6 is a structural schematic diagram of a heat pump system according to an embodiment of the present application. 10, heat pump system; 100a, phase change layer; 100, energy storage unit; 110, main housing; 20, heat exchange structure; 200, heat exchange pipe; 215, heat storage pipe; 216, heat release pipe; 212, heat conduction fin; 22, inlet main pipe; 23, outlet main pipe; 24, inlet header; 25, outlet header; 2101, switching main pipe; 2102, switching branch pipe; 300, heat source; 310, outlet end; 320, inlet end; 400, heating unit; 500, switching valve; 510, first switching valve; 520, second switching valve; 610, municipal water source; 620, domestic water pipe. DETAILED DESCRIPTION

[0043] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as exactly that endpoint. Any values that fall within the range of values along with the upper and lower limits on the range of values are also considered as being encompassed. For values that are less than or greater than a stated range, or that are greater than or less than a stated value, this is intended to "include" the value that is greater than or less than the stated range or value, as well as to "include" the stated range or value itself.

[0044] It should be noted that in various aspects of the present application, the present application only describes once for the same component in various aspects and does not repeat the description, and those skilled in the art should not understand it as a limitation of the present application.

[0045] In the present application, unless otherwise stated, the room temperature or normal temperature means 25±2℃.

[0046] As described above, the present application provides an inorganic salt phase change material composition, and the inorganic salt phase change material composition can be used to prepare an inorganic salt phase change material, and the inorganic salt phase change material can be used in a heat pump system to store and release heat.

[0047] The inorganic salt phase change material composition comprises the following components:

[0048] The inorganic hydrated salt A is 89.0wt.%-92.5wt.%, the nucleating agent is 2.0wt.%-5.0wt.%, the nucleating aid is 0.4wt.%-1.0wt.%, the thickening agent is 0.2wt.%-2.7wt.%, and the heat-conducting filler is 1.5wt.-5.0wt.%.

[0049] The nucleating agent is selected from at least one of sodium salt, strontium salt and metal oxide, and the nucleating aid is selected from at least one of non-metallic mineral materials.

[0050] In the present application, the inorganic hydrated salt A is the main component of the inorganic salt phase change material that undergoes phase change, so that the inorganic salt phase change material has a suitable phase change temperature and a suitable heat enthalpy value. The nucleating agent is used to provide nucleation sites for the inorganic hydrated salt A, so that the inorganic salt phase change material can repeatedly melt-crystallize. The thickening agent can improve the overall viscosity of the inorganic salt phase change material, so as to inhibit the phase separation of the inorganic salt phase change material, and make the inorganic salt phase change material have good stability in the frequent phase change process. The inorganic hydrated salt A has relatively poor thermal conductivity, so the inorganic salt phase change material also includes a thermal conductive filler. The thermal conductive filler has good thermal conductivity and is used to improve the overall thermal conductivity of the inorganic salt phase change material to efficiently transfer heat.

[0051] Because the inorganic hydrated salt A repeatedly melts and crystallizes in the frequent heat storage and heat release processes, the inorganic hydrated salt A itself undergoes multiple water desorption and adsorption. In the molten state, it is easy to evaporate water at high temperature, which means that the crystallization effect is reduced, and it is easy to cause the heat enthalpy value of the inorganic hydrated salt A to attenuate, and then the overall heat enthalpy value of the inorganic salt phase change material to attenuate. In the embodiments of the present application, by adding a nucleating agent and selecting the content of each component in the inorganic salt phase change material composition to meet the range of the present application, the nucleating agent is selected from at least one of non-metallic mineral materials. The non-metallic mineral material belongs to a kind of heterogeneous nucleating agent insoluble in water, which can provide nucleation sites for the crystallization of the inorganic hydrated salt A, and at the same time can form a covering film on the surface of the inorganic salt phase change material, reducing the phase change heat enthalpy attenuation of the inorganic hydrated salt due to water evaporation in the repeated working process. In the process of crystallization of the inorganic hydrated salt A, in addition to the nucleating agent promoting the formation of crystal nucleus, the nucleating agent also promotes the growth of crystal type, so as to improve the heat enthalpy attenuation of the inorganic salt phase change material and prolong the service life of the inorganic salt phase change material. When the weight percentage content of the inorganic hydrated salt A is less than the lower limit of 89.0wt.%, the content of the inorganic hydrated salt A is too low, which leads to a low energy storage density. When the weight percentage content of the inorganic hydrated salt A is higher than the upper limit of 92.5wt.%, the content of the inorganic hydrated salt A is too high, which increases the risk of water evaporation. When the weight percentage content of the nucleating agent is less than the lower limit of 0.01wt.%, the content of the nucleating agent is too small, which cannot promote the growth of crystal type, and the protective film on the surface is not dense enough to prevent water evaporation. When the weight percentage content of the nucleating agent is higher than the upper limit of 1.0wt.%, the content of the nucleating agent is too high, which is easy to cause blockage when the inorganic salt phase change material is filled in a small space, leading to the difficulty of filling the inorganic salt phase change material.

[0052] In some embodiments, the composition comprises, based on the total weight of the composition, 91.0 wt.% to 92.5 wt.% of the inorganic hydrated salt A, 2.5 wt.% to 4.5 wt.% of the nucleating agent, 0.5 wt.% to 0.8 wt.% of the nucleating aid, 0.8 wt.% to 1.2 wt.% of the thickening agent, and 2.0 wt.% to 3.0 wt.% of the heat-conducting filler, so that the enthalpy decay rate of the inorganic salt phase change material is lower.

[0053] In some embodiments, the weight percentage of the inorganic hydrated salt A is f, the weight percentage of the nucleating agent is m, and the weight percentage of the nucleating aid is n, based on the total weight of the composition, wherein 20.56≤f / (m+n)≤23.13, so that the enthalpy decay rate of the inorganic salt phase change material is lower, the supercooling degree is also lower, and the inorganic salt phase change material still has good heat storage capacity after repeated melting-crystallization.

[0054] In some embodiments, 3.5≤m / n≤35.0, so that the ratio of the nucleating agent to the nucleating aid is appropriate, the nucleating aid can better promote the formation of crystals and improve the crystal form, thereby improving the heat storage capacity of the inorganic salt phase change material and prolonging the service life of the inorganic salt phase change material.

[0055] In the embodiments of the present application, the components in the inorganic salt phase change material composition are used in combination, and the prepared inorganic salt phase change material can maintain a phase change temperature close to the melting point of the inorganic hydrated salt A, so that the inorganic hydrated salt A with a corresponding melting point can be selected according to the heat exchange temperature requirement of the heat pump system.

[0056] In some embodiments, the melting point Tm of the inorganic hydrated salt A satisfies the condition formula 50℃≤Tm≤65℃, and the inorganic hydrated salt A is selected from at least one of sodium acetate trihydrate, magnesium nitrate hexahydrate, and potassium acetate monohydrate.

[0057] In some embodiments, the melting point Tm of the inorganic hydrated salt A satisfies the condition formula 35℃<Tm≤50℃, and the inorganic hydrated salt A is selected from at least one of sodium thiosulfate pentahydrate, sodium sulfate decahydrate, calcium nitrate tetrahydrate, and magnesium sulfate pentahydrate.

[0058] In some embodiments, the sodium salt of the nucleating agent is selected from at least one of sodium phosphate dibasic dodecahydrate (Na2HPO4·12H2O), sodium pyrophosphate (Na4P2O7), sodium phosphate dibasic heptahydrate, and sodium carbonate; the strontium salt of the nucleating agent is selected from at least one of strontium chloride hexahydrate (SrCl2·6H2O), strontium acetate, strontium carbonate, and strontium nitrate; and the metal oxide of the nucleating agent is selected from at least one of magnesium oxide, aluminum oxide, iron oxide, and magnetite. The use of the above nucleating agents can provide crystal sites for the inorganic hydrated salt A, so that the inorganic salt phase change material can repeatedly melt-crystallize.

[0059] In some embodiments, the non-metallic mineral material of the nucleation aid is selected from at least one of mica, montmorillonite, quartz, expanded perlite, talc, calcite, feldspar. By selecting the above nucleation aid, a thin film can be formed on the surface of the phase change material during solidification, reducing water evaporation caused by long-term high temperature, and promoting the crystal growth of inorganic hydrated salt A after the formation of crystal nucleus, thereby further improving the enthalpy decay of the inorganic salt phase change material.

[0060] In some embodiments, the non-metallic mineral material of the nucleation aid is selected from at least one of mica, montmorillonite, quartz, expanded perlite, talc, calcite, feldspar. By selecting the above nucleation aid, a thin film can be formed on the surface of the phase change material during solidification, reducing water evaporation caused by long-term high temperature, and promoting the crystal growth of inorganic hydrated salt A after the formation of crystal nucleus, thereby further improving the enthalpy decay of the inorganic salt phase change material. 50 The nucleation aid satisfies 850 μm≤Dv 50 ≤1500 μm. In this particle size range, the nucleation aid can be uniformly dispersed in the inorganic salt phase change material, and the thickening agent can be used to stabilize the nucleation aid in the system to prevent sedimentation. At the same time, the excess nucleation aid forms a cavity-like film on the surface of the inorganic salt phase change material, which can prevent water evaporation and insulation.

[0061] In some embodiments, the thickening agent is selected from at least one of cyclic dextrin, chitosan, xanthan gum, sodium carboxymethyl cellulose, and soluble starch. The above-mentioned thickening agent has good swelling property and can improve the viscosity of the inorganic salt phase change material, thereby inhibiting the phase separation of the inorganic salt phase change material during the phase change process.

[0062] In some embodiments, the heat-conducting filler is selected from at least one of porous heat-conducting material (metal foam, expanded graphite) and sheet heat-conducting material (boron nitride, molybdenum disulfide). In the embodiments of the present application, the heat-conducting filler is insoluble, and exists in the inorganic salt phase change material in the form of insoluble particles. The particle size Dv 50 of the heat-conducting filler satisfies 300 μm≤Dv 50 ≤900 μm. In this particle size range, the components in the inorganic salt phase change material are uniformly dispersed and have good stability, preventing local sedimentation of the heat-conducting filler, and the heat-conducting filler can more uniformly and efficiently play a heat-conducting role.

[0063] The second aspect of the present application provides a preparation method of an inorganic salt phase change material, which comprises mixing the components in the inorganic salt phase change material composition as described above to prepare the inorganic salt phase change material.

[0064] In the embodiments of the present application, the mixing of the components in the inorganic salt phase change material composition comprises the following steps:

[0065] Step S110, providing inorganic hydrated salt A, heating the inorganic hydrated salt A to a preheating temperature which is greater than the melting point of the inorganic hydrated salt A, and performing preheating treatment to obtain molten inorganic hydrated salt A.

[0066] Step S120, adding a nucleating agent to the molten inorganic hydrated salt A, performing emulsification ultrasonic treatment, and obtaining a mixture A.

[0067] Step S130, adding a nucleating agent and a heat-conducting filler to the mixture A, performing blending treatment, and obtaining a mixture B.

[0068] Step S140, adding a thickening agent to the mixture B, performing thickening treatment, and obtaining a mixture C.

[0069] Step S150, cooling and solidifying the mixture C to form an inorganic salt phase change material.

[0070] In steps S120-S140, the temperature is maintained at the preheating temperature to keep the inorganic hydrated salt A in a molten state so that the inorganic hydrated salt A is uniformly dispersed with other components.

[0071] In step S110, the inorganic hydrated salt A can be directly provided, heated to the preheating temperature, and preheated to obtain the molten inorganic hydrated salt A. In other embodiments, the inorganic salt and deionized water can be mixed according to the molar ratio of the inorganic salt to water in the inorganic hydrated salt A, heated to the preheating temperature, and preheated to obtain the molten inorganic hydrated salt A, where the preheating temperature is greater than the melting point of the inorganic hydrated salt A.

[0072] In some embodiments, the preheating treatment at least includes a time of 2-3 hours and a preheating temperature range of 10-15°C greater than the melting point of the inorganic hydrated salt A. Under this preheating condition, the inorganic hydrated salt A can be fully and uniformly molten to fully and uniformly contact other components of the inorganic salt phase change material.

[0073] When the melting point Tm of the inorganic hydrated salt A satisfies the condition formula 50℃≤Tm≤65℃, the preheating temperature is 60-75°C and the time is 2-3 hours. When the melting point Tm of the inorganic hydrated salt A satisfies the condition formula 35℃<Tm≤50℃, the preheating temperature is 45-55°C and the time is 1.5-2.5 hours.

[0074] In some embodiments, the emulsification ultrasonic treatment at least comprises: a stirring speed of 5000 r / min to 8000 r / min, an ultrasonic frequency of 40 kHz to 60 kHz, and a time of 20 min to 40 min. Under the emulsification ultrasonic treatment conditions, the nucleating agent particles can be more fully and uniformly stirred and dispersed into the molten inorganic hydrated salt A. The emulsification ultrasonic treatment can comprise alternately performing emulsification treatment and ultrasonic treatment, and performing the emulsification treatment in an emulsification device. Each emulsification treatment has a stirring speed of 5000 r / min to 8000 r / min and a time of 10 min to 20 min. The ultrasonic treatment is performed in an ultrasonic device. Each ultrasonic treatment has an ultrasonic frequency of 40 kHz to 60 kHz and a time of 20 min to 40 min. The total time of the emulsification treatment and the ultrasonic treatment is 30 min to 60 min.

[0075] In some embodiments, the blending treatment at least comprises: mixing the mixture A, the auxiliary nucleating agent, and the heat-conducting filler in a vacuum environment, and the vacuum degree is -0.15 MPa to -0.3 MPa, the stirring speed is 60 r / min to 90 r / min, and the time is 2 h to 3 h. Under the blending treatment conditions, the auxiliary nucleating agent can fully contact the inorganic hydrated salt A, and at the same time, the vacuum environment can make the bubbles formed during the preparation process break quickly, avoiding too much gas in the mixture B which is not conducive to subsequent filling. Moreover, due to the existence of negative pressure, the porous heat-conducting filler has a porous structure, which can fully absorb the nucleating agent, the auxiliary nucleating agent, the inorganic hydrated salt A, and other components in the composition, and better bridge effect is formed between the heat-conducting fillers to better play the heat-conducting effect.

[0076] In some embodiments, the preparation method of the inorganic salt phase change material further comprises: after the auxiliary nucleating agent and the heat-conducting filler are respectively subjected to a crushing treatment, the auxiliary nucleating agent and the heat-conducting filler are added into the mixture A. The particle size Dv 50 of the auxiliary nucleating agent satisfies 850 μm≤Dv 50 ≤1500 μm, and the particle size Dv 50 of the heat-conducting filler satisfies 300 μm≤Dv 50 ≤900 μm, so that the auxiliary nucleating agent and the heat-conducting filler can be uniformly dispersed in the mixture A. The crushing treatment can use at least one of a ball mill and a high-speed crusher.

[0077] In some embodiments, the thickening treatment at least comprises: adding the thickening agent into the mixture B in multiple times, and the stirring speed is 20 r / min to 40 r / min, the time is 1.5 h to 2 h, and the weight of the thickening agent added each time is 0.2% to 2.0% of the total weight of the thickening agent. The method of adding the thickening agent in multiple times with a small amount facilitates the swelling and uniform dispersion of the thickening agent in the inorganic salt phase change material, so as to better improve the phase separation and prevent the agglomeration of the thickening agent caused by the large amount of addition of the thickening agent.

[0078] As shown in FIG. 2, the application also provides a thermal storage unit 100 for a heat pump system, the thermal storage unit 100 comprising a metal shell and a phase change layer, the metal shell having an internal heat storage space, and the phase change layer being filled in the heat storage space, the phase change layer comprising the inorganic salt phase change material as described above, and the inorganic salt phase change material being used to exchange heat with the material in the heat storage space to store energy through phase change.

[0079] The metal shell comprises a main shell and a heat exchange structure 20, as shown in FIG. 3 and FIG. 4, the heat exchange structure 20 comprising a plurality of heat-conducting fins 212, the plurality of heat-conducting fins 212 being arranged in the internal space of the main shell, and a part of the inorganic salt phase change material being filled in the gap between two adjacent heat-conducting fins 212, and another part of the inorganic salt phase change material being filled in the gap between the heat-conducting fins 212 and the inner wall surface of the main shell. The distance between the two adjacent heat-conducting fins 212 is L1, and the distance between the heat-conducting fins 212 and the inner wall surface of the main shell is L2, 1.3mm≤L1≤1.8mm, and 3mm≤L2≤6mm. In this range, the components of the molten inorganic salt phase change material can smoothly enter the metal shell, and uniformly enter the gap between the two adjacent heat-conducting fins 212 and the gap between the heat-conducting fins 212 and the main shell, thereby preventing the generation of bubbles.

[0080] Optionally, each heat-conducting fin 212 extends in the vertical direction, and the heat-conducting space extending in the vertical direction is formed between the two adjacent heat-conducting fins 212, the heat-conducting space being filled with the inorganic salt phase change material, and the main shell has a filling inlet, the filling inlet being in communication with the internal space of the main shell, and the inorganic salt phase change material entering the internal space of the main shell through the filling inlet. The filling inlet is located above the heat exchange pipe in the vertical direction, so as to facilitate the smooth filling of the inorganic salt phase change material in the heat-conducting space between the two adjacent heat-conducting fins 212.

[0081] The heat exchange structure 20 further comprises a plurality of heat exchange pipes 200, the heat exchange pipes 211 being capable of passing the flowing heat exchange medium, the heat-conducting fins 212 having heat-conducting holes, each heat exchange pipe 200 penetrating the heat-conducting holes of the plurality of heat-conducting fins 212, and the main shell and the heat exchange structure 20 defining the heat storage space. The inorganic salt phase change material is filled in the heat storage space and covers the outer surfaces of the heat exchange pipes 200 and the heat-conducting fins 212, so as to exchange heat with the heat exchange medium in the heat exchange pipes 200. The heat exchange pipes 200 are connected to the plurality of heat-conducting fins 212, and the heat exchange pipes 200 are also capable of exchanging heat with the inorganic salt phase change material through the heat-conducting fins 212, thereby increasing the heat exchange area and improving the heat exchange efficiency.

[0082] In some embodiments, the heat exchange structure 20 further comprises a plurality of inlet headers 22 and a plurality of outlet headers 23, each of the inlet headers 22 is in communication with the inlets of the plurality of heat exchange tubes 200, and the heat exchange medium in the plurality of heat exchange tubes 200 is input through the same inlet header 22, each of the outlet headers 23 is in communication with the outlets of the plurality of heat exchange tubes 200, and the heat exchange medium in the plurality of heat exchange tubes 200 is output through the same outlet header 23. In the vertical direction, the inlet headers 22 and the outlet headers 23 are located above the plurality of heat exchange tubes 200, and are installed on the main shell 10 to place the inlet headers 22 and the outlet headers 23 in a suitable position, which helps to shorten the length of the pipeline and save space.

[0083] Optionally, the heat exchange structure 20 further comprises a plurality of inlet headers 22 and a plurality of outlet headers 23, each of the inlet headers 22 is in communication with the inlets of the plurality of heat exchange tubes 200, and the heat exchange medium in the plurality of heat exchange tubes 200 is input through the same inlet header 22, each of the outlet headers 23 is in communication with the outlets of the plurality of heat exchange tubes 200, and the heat exchange medium in the plurality of heat exchange tubes 200 is output through the same outlet header 23. In the vertical direction, the inlet headers 22 and the outlet headers 23 are located above the plurality of heat exchange tubes 200, and are installed on the main shell 10 to place the inlet headers 22 and the outlet headers 23 in a suitable position, which helps to shorten the length of the pipeline and save space.

[0084] Optionally, as shown in FIG. 5, the heat exchange structure 20 further comprises a plurality of adapter pipe groups, each of the adapter pipe groups comprises an adapter main pipe 2101 and an adapter branch pipe 2102, the adapter branch pipe 2102 has a plurality of adapter ends, one end of the adapter main pipe 2101 is connected to one of the adapter ends of the adapter branch pipe 2102, and the adapter pipe groups include an inlet adapter pipe group 213 and an outlet adapter pipe group 214. The other end of the adapter main pipe 2101 of the inlet adapter pipe group 213 is connected to the inlet header 24, and the remaining adapter ends of the adapter branch pipe 2102 are connected to the inlets of the plurality of heat exchange tubes 200 one by one. The other end of the adapter main pipe 2101 of the outlet adapter pipe group 214 is connected to the outlet header 25, and the remaining adapter ends of the adapter branch pipe 2102 are connected to the outlets of the plurality of heat exchange tubes 200 one by one. In this way, the adapter main pipe 2101 extends around the outside of the plurality of heat exchange tubes 200, the pipeline is smooth, and the assembly is facilitated.

[0085] In some embodiments, the plurality of heat exchange pipes include the heat storage pipe 215 and the heat release pipe 216, the inlet section of the heat storage pipe 215 is in communication with the outlet end of the heat source, and the outlet section is in communication with the inlet end of the heat source, the inlet section of the heat release pipe 216 is in communication with the municipal water source, and the outlet section is in communication with the domestic water pipe, the heat exchange medium in the heat storage pipe 215 receives the heat of the heat source and transfers the heat to the inorganic salt phase change material for heat storage, and the inorganic salt phase change material transfers the heat to the water flow in the heat release pipe 216 to realize heat release. In order to reduce the loss of heat in the transmission process and improve the thermal efficiency of the heat exchange structure 20, the heat storage pipe 215 and the heat release pipe 216 are alternately arranged, and optionally, the number of the heat storage pipe 215 and the heat release pipe 216 is the same, and the plurality of heat storage pipes 215 and the plurality of heat release pipes 216 in the heat exchange structure 20 are periodically and periodically arranged along the preset direction. The preset direction can be vertical or horizontal. Periodic arrangement helps to realize uniform distribution and stable release of heat, and avoids the occurrence of local overheating or overcooling.

[0086] In some embodiments, the material of the heat exchange pipe 200 is at least one of copper, copper alloy, and stainless steel; or the material of the heat exchange pipe 200 is copper, the material of the inlet manifold 22, the outlet manifold 23, the inlet header 24, and the outlet header 25 is stainless steel; or the material of the heat storage pipe 215 and the adapter pipe group connected to the heat storage pipe 215 is aluminum, and the material of the heat release pipe 216 and the adapter pipe group connected to the heat release pipe 216 is stainless steel.

[0087] As shown in FIG. 6, the present application also provides a heat pump system 10, which can include a water heater 100, and the water heater 100 can be provided to include an energy storage unit 100 and a heat source unit 300, the heat source unit 300 is in communication with at least one heat exchange pipe 200 of the energy storage unit 100, and the inorganic salt phase change material of the energy storage unit 100 is used to obtain the heat provided by the heat source unit 300 to perform phase change energy storage.

[0088] In some embodiments, as shown in FIG. 6, the plurality of heat exchange pipes 200 of the energy storage unit 100 includes a heat storage pipe 215 and a heat release pipe 216, the inlet section of the heat storage pipe 215 is in communication with the outlet end 310 of the heat source unit 300, and the outlet section is in communication with the inlet end 320 of the heat source unit 300, the inlet section of the heat release pipe 216 is in communication with the municipal water source 610, and the outlet section is in communication with the domestic water pipe 620, the energy storage unit 100 has a heat storage mode, a heat release mode and a mixed mode, specifically, in the heat storage mode, the high-temperature heat exchange medium of the heat source 300 enters the heat storage pipe 215 from the inlet section of the heat storage pipe 215, the inorganic salt phase change material absorbs the heat of the high-temperature heat exchange medium in the heat storage pipe 215 and stores the heat, and the high-temperature heat exchange medium becomes low-temperature heat exchange medium and returns to the inlet end 320 of the heat source 300 from the outlet section of the heat storage pipe 215; in the heat release mode, the low-temperature water flow supplied by the municipal water source 610 enters the heat release pipe 216 from the inlet section of the heat release pipe 216, the inorganic hydrated salt transfers heat to the low-temperature water flow in the heat release pipe 216, and the low-temperature water flow absorbs heat to become high-temperature water flow and flows out from the outlet section of the heat release pipe 216 for use by the user; in the mixed mode, the high-temperature heat exchange medium of the heat source 300 enters the heat storage pipe 215 from the inlet section of the heat storage pipe 215, at the same time, the low-temperature water flow supplied by the municipal water source 610 enters the heat release pipe 216 from the inlet section of the heat release pipe 216, the inorganic salt phase change material absorbs the heat of the high-temperature heat exchange medium in the heat storage pipe 215 and simultaneously transfers heat to the low-temperature water flow in the heat release pipe 216, and the low-temperature water flow absorbs heat to become high-temperature water flow or medium-temperature water flow and flows out from the outlet section of the heat release pipe 216 for use by the user.

[0089] The heat pump system 10 further includes a heating unit 400, a reversing valve 500 and connecting pipes in communication between various structures, the reversing valve 500 includes a first reversing valve 510, the first end of the first reversing valve 510 is in communication with the outlet end 310 of the heat source 300, the second end is in communication with the heating unit 400, and the third end is in communication with the heat exchange pipe 200 of the energy storage unit 100, by switching the flow path of the first reversing valve 510, the outlet end 310 of the heat source 300 is in communication with at least one of the heating unit 400 and the energy storage unit 100, to correspondingly provide high-temperature heat exchange medium to the heating unit 400 and the energy storage unit 100. The number of heating units 400 can be multiple, and the reversing valve 500 can further include a second reversing valve 520, which is arranged in the connecting pipe in communication between the second end of the first reversing valve 510 and the multiple heating units 400, by switching the flow path of the second reversing valve 520, the second end of the first reversing valve 510 is in communication with one or more of the multiple heating units 400, thereby making the heat source 300 in communication with one or more of the multiple heating units 400.

[0090] The following describes the preparation method of the inorganic salt phase change material in combination with examples and comparative examples. Those skilled in the art will understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application. In the following examples, unless otherwise specified, the various raw materials used are commercially available.

[0091] The performance test method of the inorganic salt phase change material in each embodiment and comparative example of the present application is as follows:

[0092] 1. Phase change temperature and supercooling degree test method

[0093] The phase change temperature adopts the step cooling curve method: 100 g of the phase change material is placed in a high borosilicate glass bottle, a K-type thermocouple is inserted into the middle of the phase change material, and then the phase change material is heated to 20°C above the melting point of the inorganic hydrated salt and stabilized for 30 min. Then, it is naturally cooled in an environment of 30°C below the melting point, and the temperature information of the phase change material over time is collected to obtain the temperature-time curve and the corresponding theoretical phase change temperature (T theory ) and actual phase change temperature (T actual ).

[0094] The difference between the theoretical phase change temperature (T theory ) and the actual phase change temperature (T actual ) is the supercooling degree (T sc ).

[0095] 2. Heat enthalpy value attenuation rate test method after 2000 cycles

[0096] The initial unit mass heat enthalpy value of the phase change material is measured by a DSC device.

[0097] The phase change material is loaded into a cycle test device,

[0098] The melting-crystallization cycle is performed according to the following steps:

[0099] (1) Initial temperature 0°C, stand for 5 min;

[0100] (2) Perform temperature rising treatment, temperature rising rate 5°C / min, stop temperature 80°C, stand for 5 min;

[0101] (3) Perform temperature lowering treatment, temperature lowering rate 5°C / min, end temperature 0°C, stand for 1 min.

[0102] Among them, the above steps (1)-(3) are the first melting-crystallization cycle, and then steps (2)-(3) are a melting-crystallization cycle. After the phase change material is subjected to 2000 melting-crystallization cycles, the unit mass heat enthalpy value of the phase change material after 2000 cycles is measured by a DSC device.

[0103] The calculation formula of the unit mass enthalpy decay rate is: H% = (1 - AH n / AH0) x 100%;

[0104] wherein, AH n is the unit mass enthalpy after the phase change material circulates n times, kJ / kg;

[0105] AH0is the initial unit mass enthalpy of the phase change material, kJ / kg.

[0106] 3. Energy storage density test method

[0107] The solid-state (p s ) and liquid-state density (p l ) of the phase change material are measured by using a density meter;

[0108] The solid-state specific heat capacity C ps and liquid-state specific heat capacity C pl of the phase change material are tested by using the MDSC method through a differential scanning calorimeter (DSC).

[0109] The initial unit mass enthalpy AH0of the phase change material is measured by using a differential scanning calorimeter (DSC).

[0110] The energy storage density AQ is calculated according to the following formula: AQ = p s x (T actual - 10) x C ps + (p s + p l ) / 2 x AH0+ p l× (65 - T actual ) x C pl .

[0111] Example 1

[0112] The present embodiment provides a preparation method of an inorganic hydrated phase change material, which comprises the following steps:

[0113] (1) Preheating treatment

[0114] According to the molar ratio of the inorganic salt sodium acetate (CH3COONa) to deionized water being 1:3, 55.47 g of the inorganic salt sodium acetate and 36.53 g of deionized water are weighed and uniformly mixed, and heated to a preheating temperature of 75°C to obtain molten CH3COONa·3H2O.

[0115] The weight percentage content of CH3COONa·3H2O is 92wt.% based on the total weight of the inorganic hydrated phase change material composition.

[0116] (2) Emulsification ultrasonic treatment

[0117] At 70°C, 4 g of nucleating agent disodium phosphate dodecahydrate was added into molten CH3COONa·3H2O, and emulsification treatment was performed in an emulsification device at a stirring speed of 6000 r / min for 15 min. Then ultrasonic treatment was performed in an ultrasonic device at an ultrasonic frequency of 55 kHz for 30 min, to obtain mixture A.

[0118] The weight percentage of disodium phosphate dodecahydrate was 4 wt.% based on the total weight of the inorganic hydrated phase change material composition.

[0119] (3) Blending treatment

[0120] At 70°C, 0.8 g of nucleating agent mica with a particle size Dv 50 of 1000 μm and 2.0 g of heat-conducting filler boron nitride with a particle size Dv 50 of 300 μm were added into mixture A, and uniform stirring was performed under the action of a vacuum stirrer. The blending treatment was performed at a vacuum degree of -0.3 MPa, a stirring speed of 80 r / min, and a time of 2.5 h, to obtain mixture B.

[0121] The weight percentage of mica was 0.8 wt.% and the weight percentage of boron nitride was 0.8 wt.% based on the total weight of the inorganic hydrated phase change material composition.

[0122] (4) Thickening treatment

[0123] At 70°C, 1.2 g of thickening agent sodium carboxymethyl cellulose was added into mixture B in three times, and thickening treatment was performed at a stirring speed of 30 r / min for 1.5 h, to obtain mixture C.

[0124] The weight percentage of sodium carboxymethyl cellulose was 1.2 wt.% based on the total weight of the inorganic hydrated phase change material composition.

[0125] (5) Cooling treatment

[0126] Mixture C was cooled to room temperature of 25°C, and mixture C was solidified to form the inorganic salt phase change material.

[0127] Examples 2 to 6, Examples 9 to 16, and Comparative Examples 1 to 4 were the same as Example 1, except that the contents of inorganic salt, deionized water, nucleating agent, nucleating agent aid, heat-conducting filler, and thickening agent were adjusted as shown in Table 1.

[0128] Example 7, except that the content of inorganic salt, deionized water, nucleating agent, nucleating agent aid, heat-conducting filler and thickening agent in each processing step is adjusted according to Table 1, and the preheating temperature of step (1) is 60°C, and the temperature of steps (2) to (4) is 55°C, and the rest is the same as Example 1.

[0129] Example 8, except that the content of inorganic salt, deionized water, nucleating agent, nucleating agent aid, heat-conducting filler and thickening agent in each processing step is adjusted according to Table 1, and the preheating temperature of step (1) is 55°C, and the temperature of steps (2) to (4) is 50°C, and the rest is the same as Example 1.

[0130] The preparation parameters and performance parameters of Examples 1 to 16 and Comparative Examples 1 to 4 are shown in Table 1.

[0131] As can be seen from Examples 1 to 16 and Comparative Examples 1 to 4 in Table 1 and Table 2, by adding water-insoluble nucleating agent aid to the inorganic salt phase change material composition, and selecting the components of the inorganic salt phase change material composition within a suitable range, the enthalpy value of the inorganic salt phase change material after 2000 cycles can still be maintained at a high level, the enthalpy value attenuation rate after 2000 cycles is ≤5%, and the supercooling degree and energy storage density are within a suitable range. The inorganic salt phase change material of the present application can be used in a heat pump system and has good heat storage performance.

[0132] As can be seen from Comparative Examples 1 to 2, when the weight percentage content of inorganic hydrated salt A is less than the lower limit of 89.0wt.%, the content of inorganic hydrated salt A is too low, resulting in a lower energy storage density of 10°C to 65°C, and when the weight percentage content of inorganic hydrated salt A is higher than the upper limit of 92.5wt.%, the content of inorganic hydrated salt A is too high, increasing the risk of water evaporation and easily causing phase separation. When the weight percentage content of nucleating agent aid is less than the lower limit of 0.4wt.%, the content of nucleating agent aid is too low, and the effect of promoting crystal growth is not achieved, and the protective film on the surface is not dense enough to prevent water evaporation, and the enthalpy value attenuation rate of the inorganic salt phase change material after 2000 cycles is deteriorated, and when the weight percentage content of nucleating agent aid is higher than the upper limit of 1.0wt.%, the content of nucleating agent aid is too high, and it is easy to cause blockage when filling the inorganic salt phase change material in a narrow space, resulting in difficulty in filling the inorganic salt phase change material.

[0133] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An inorganic salt phase change material composition, wherein, The composition comprises the following components: Inorganic hydrated salt A 89.0wt.%~92.5wt.%, nucleating agent 2.0wt.%~5.0wt.%, nucleating aid 0.4wt.%~1.0wt.%, thickening agent 0.2wt.%~2.7wt.%, heat-conducting filler 1.5wt.%~5.0wt.%; The nucleating agent is selected from at least one of sodium salt, strontium salt, metal oxide, and the nucleating aid is selected from at least one of non-metallic mineral material.

2. The composition of claim 1, wherein, The composition comprises the following components based on the total weight of the composition: Inorganic hydrated salt A 91.0wt.%~92.5wt.%, nucleating agent 2.5wt.%~4.5wt.%, nucleating aid 0.5wt.%~0.8wt.%, thickening agent 0.8wt.%~1.2wt.%, heat-conducting filler 2.0wt.%~3.0wt.%.

3. The composition of claim 1, wherein, The weight percentage content of the inorganic hydrated salt A is f, the weight percentage content of the nucleating agent is m, and the weight percentage content of the nucleating aid is n based on the total weight of the composition; the composition satisfies at least one of the following conditions: (1) 20.56≤f / (m+n)≤23.13; (2) 3.5≤m / n≤35.

0.

4. The composition of claim 1, wherein, The inorganic hydrated salt A is selected from at least one of sodium acetate trihydrate, magnesium nitrate hexahydrate, potassium acetate monohydrate, sodium thiosulfate pentahydrate, sodium sulfate decahydrate, calcium nitrate tetrahydrate, and magnesium sulfate pentahydrate.

5. The composition of claim 1, wherein, The sodium salt of the nucleating agent is selected from at least one of disodium hydrogen phosphate dodecahydrate, sodium pyrophosphate, sodium carbonate, and disodium hydrogen phosphate heptahydrate; The strontium salt of the nucleating agent is selected from at least one of strontium chloride hexahydrate, strontium acetate, strontium carbonate, and strontium nitrate; The metal oxide of the nucleating agent is selected from at least one of magnesium oxide, aluminum oxide, iron oxide, and magnetite.

6. The composition of claim 1, wherein, The non-metallic mineral material of the nucleating aid is selected from at least one of mica, montmorillonite, quartz, expanded perlite, talc, calcite, and feldspar; The particle diameter Dv of the non-metallic mineral material of the co-nucleating agent 50 satisfies 850 μm ≤ Dv 50 ≤ 1500 μm.

7. The composition of claim 1, wherein, The thickening agent is selected from at least one of cyclic dextrin, chitosan, xanthan gum, sodium carboxymethyl cellulose, and soluble starch; The heat-conducting filler is selected from at least one of metal foam, expanded graphite, boron nitride, and molybdenum disulfide.

8. A method for producing an inorganic salt phase change material, wherein, comprising: mixing the components in the inorganic salt phase change material composition of any one of claims 1-7.

9. The production method according to claim 8, wherein mixing the components in the inorganic salt phase change material composition comprises the following steps: providing inorganic hydrated salt A, heating the inorganic hydrated salt A to a preheating temperature greater than the melting point of the inorganic hydrated salt A, performing preheating treatment to obtain molten inorganic hydrated salt A; adding the nucleating agent to the molten inorganic hydrated salt A, performing emulsification ultrasonic treatment to obtain mixture A; adding the nucleating aid and heat-conducting filler to the mixture A, performing blending treatment to obtain mixture B; adding the thickening agent to the mixture B, performing thickening treatment to obtain mixture C; Cooling and solidifying the mixture C to form the inorganic salt phase change material.

10. The preparation method of claim 9, wherein, the pre-heating process at least comprises: a time of 2-3 hours, and a pre-heating temperature of 10-15℃ higher than the melting point of the inorganic hydrated salt A; the emulsification ultrasonic treatment at least comprises an emulsification process and an ultrasonic treatment, the emulsification process at a stirring speed of 5000-8000r / min for 10-20min, and the ultrasonic treatment at an ultrasonic frequency of 40-60kHz for 20-40min; the blending process at least comprises: a vacuum degree of -0.15 to -0.3Mpa, a stirring speed of 60-90r / min, and a time of 2-3 hours; the thickening process at least comprises: adding the thickening agent into the mixture B in several times, and a stirring speed of 20-40r / min for 1.5-2 hours, and the weight of the thickening agent added each time is 0.2-2.0% of the total weight of the thickening agent.

11. An inorganic salt phase change material, wherein, The inorganic salt phase change material is prepared by the preparation method of any one of claims 8-10.

12. An energy storage unit, wherein, Comprise: a metal shell comprising a main shell and a heat exchange structure, the main shell having an energy storage cavity inside, and the heat exchange structure being arranged in the internal space of the main shell, and the main shell and the heat exchange structure defining a heat storage space; and a phase change layer comprising the inorganic salt phase change material of claim 11, the phase change layer being filled in the heat storage space and wrapped on the outer surface of the heat exchange structure to exchange heat with the heat exchange medium in the heat exchange structure.

13. The energy storage unit of claim 12, wherein, The heat exchange structure comprises: a plurality of heat-conducting fins, each of the heat-conducting fins having a heat-conducting hole; a plurality of heat exchange pipes, the heat exchange pipes being capable of passing through flowing heat exchange medium, and each of the heat exchange pipes penetrating the heat-conducting holes of a plurality of the heat-conducting fins; wherein each of the heat-conducting fins extends in the vertical direction, and adjacent two of the heat-conducting fins form a heat-conducting space extending in the vertical direction, and the heat-conducting space is filled with the inorganic salt phase change material; The main shell has a filling inlet, the filling inlet communicates with the internal space of the main shell, and the inorganic salt phase change material enters the internal space of the main shell through the filling inlet, and the filling inlet is located above the heat exchange pipes in the vertical direction.

14. The energy storage unit of claim 13, wherein, the heat exchange structure further comprises a plurality of inlet manifolds and a plurality of outlet manifolds; each of the inlet manifolds communicates with the inlets of a plurality of the heat exchange pipes; each of the outlet manifolds communicates with the outlets of a plurality of the heat exchange pipes; wherein in the vertical direction, the inlet manifolds and the outlet manifolds are both located above a plurality of the heat exchange pipes and are installed on the main shell (10).

15. The energy storage unit of claim 14, wherein, the heat exchange structure further comprises a plurality of inlet header pipes corresponding to a plurality of the inlet manifolds and a plurality of outlet header pipes corresponding to a plurality of the outlet manifolds; Each of the inlet headers is in communication with the inlets of a plurality of the heat exchange tubes through a corresponding inlet manifold; Each of the outlet headers is in communication with the outlets of a plurality of the heat exchange tubes through a corresponding outlet manifold; In the vertical direction, the inlet manifold and the outlet manifold are both above the plurality of the heat exchange tubes.

16. The energy storage unit of claim 15, wherein, The heat exchange structure further comprises a plurality of adapter pipe groups, each of the adapter pipe groups comprising an adapter main pipe and an adapter branch pipe, the adapter branch pipe having a plurality of adapter ends, one end of the adapter main pipe being connected to one of the adapter ends of the adapter branch pipe; The adapter pipe groups comprise inlet adapter pipe groups and outlet adapter pipe groups; The other end of the adapter main pipe of the inlet adapter pipe groups is connected to the inlet manifold, and the remaining adapter ends of the adapter branch pipe are connected to the inlets of the plurality of the heat exchange tubes one by one; The other end of the adapter main pipe of the outlet adapter pipe groups is connected to the outlet manifold, and the remaining adapter ends of the adapter branch pipe are connected to the outlets of the plurality of the heat exchange tubes one by one.

17. The energy storage unit of claim 16, wherein, The plurality of the heat exchange tubes comprise heat storage tubes and heat release tubes, the inlet section of the heat storage tube being in communication with the outlet end of the heat source unit, and the outlet section being in communication with the inlet end of the heat source, the inlet section of the heat release tube being in communication with the municipal water source, and the outlet section being in communication with the domestic water pipe; The heat exchange structure satisfies one of the following conditions: (1) The material of the heat exchange tube is at least one of copper, copper alloy, and stainless steel; (2) The material of the heat exchange tube is copper, and the materials of the inlet header, the outlet header, the inlet manifold, and the outlet manifold are stainless steel; (3) The material of the heat storage tube and the adapter pipe groups connected thereto is aluminum, and the material of the heat release tube and the adapter pipe groups connected thereto is stainless steel.

18. A heat pump system wherein, comprising: a heat source unit for providing heat; and The energy storage unit of any one of claims 12-17, the inorganic salt phase change material of the energy storage unit being used to obtain the heat provided by the heat source unit for phase change energy storage.

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