Preparation method of composite phase change heat storage module for heat pump system

Abstract

The invention discloses a preparation method of a composite phase-change heat storage module for a heat pump system, which belongs to a phase-change material heat storage technology, and can meet the requirements of the heat pump system in multiple working conditions such as low-temperature heating, medium-temperature hot water supply and high-temperature refrigeration through the multi-stage phase-change characteristic of a compounded composite phase-change material. The heat storage capacity is effectively improved compared with a traditional single phase change material, meanwhile, the heat conductivity coefficient of the module is remarkably improved through the multi-stage honeycomb heat conduction structure, the heat storage utilization rate of the phase change material is ensured, the heat response time is effectively shortened, and powerful support is provided for efficient operation of a heat pump system.

Description

TECHNICAL FIELD

[0001] The present application relates to a phase change material heat storage technology, more particularly, the present application mainly relates to a preparation method of a composite phase change heat storage module for a heat pump system. BACKGROUND

[0002] As a high-efficiency energy utilization technology, heat pump systems achieve heating, cooling or hot water supply by utilizing low-grade heat energy, and are widely used in residential, commercial and industrial fields. However, traditional heat pump systems face various challenges in actual operation, especially in the case of load fluctuation, drastic changes in ambient temperature or intermittent operation, the problems of energy efficiency decline and system stability deficiency are particularly prominent. For example, in low temperature environment (below-10℃), the heating efficiency of air source heat pump decreases significantly, and the COP (coefficient of performance) may decrease to below 2.0; while in high temperature environment (above 35℃), the cooling performance is limited, and the system operation may appear overheating or frequent start-stop. In addition, the imbalance between heat supply and demand of heat pump system during start-up or switching operating conditions often leads to energy waste or unstable equipment operation, affecting the service life and user experience. Phase change heat storage technology is considered as an effective solution to improve the performance of heat pump systems due to its high heat storage density and nearly constant temperature heat release characteristics. Phase change materials (PCMs) can store or release a large amount of latent heat through phase change (such as solid-liquid or solid-solid phase change) at a specific temperature, thereby smoothing the heat load fluctuation of heat pump systems, improving energy efficiency and enhancing stability. However, existing phase change heat storage modules mostly use single phase change materials such as paraffin or fatty acid, which have a single phase change temperature (usually at a single temperature point such as 50℃), and the heat storage capacity is limited, which is difficult to adapt to the needs of heat pump systems in a wide temperature range (30-80℃) or complex operating conditions. Moreover, the optimization design of the heat conduction enhancement structure of the phase change material in use does not fully consider the actual operating conditions of the heat pump system, resulting in mismatch between heat conduction efficiency and system integration, and the heat response time is still relatively long. Therefore, it is necessary to research and improve the structure and preparation method of the phase change material heat storage module in view of the energy efficiency and stability requirements of the heat pump system under complex operating conditions. SUMMARY

[0003] One of the purposes of the present application is to provide a preparation method of a composite phase change heat storage module for a heat pump system in order to solve the technical problems of energy waste caused by imbalance between heat supply and demand of heat pump system in the prior art, limited heat storage capacity of single phase change material, and long heat response time caused by design defects of heat conduction structure.

[0004] To solve the above technical problems, the present application adopts the following technical scheme: The preparation method of a composite phase change heat storage module for a heat pump system provided by the present application comprises the following steps: Step A, preparing component A, 90-110 parts by weight of C18-C20 straight chain alkanes are mixed with 4-6 parts by weight of sodium hydroxide, stirred uniformly, and the obtained product is washed with deionized water and dried to obtain a modified alkane-based material, i.e. component A; preparing component B, 40-60 parts by weight of palmitic acid are mixed with 18-22 parts by weight of methanol and 0.1-1 part by weight of sulfuric acid catalyst, stirred uniformly, and the obtained product is purified by distillation and dried to obtain methyl palmitate, i.e. component B; preparing component C, 5-6 parts by weight of sodium chloride are mixed with 22-26 parts by weight of polyethylene glycol, stirred uniformly, and dried to obtain an inorganic salt-organic eutectic material, i.e. component C.

[0005] Step B, components A, B and C are mixed in a mass ratio of 3-5:2-4:1-3, heated to above 90°C, then stirred uniformly, and then nano-silicon oxide, carboxylated multi-walled carbon nanotubes and polyacrylamide are sequentially added thereto, and the mixture is continuously stirred and mixed, and used as a phase change material; the nano-silicon oxide, carboxylated multi-walled carbon nanotubes and polyacrylamide account for 0.5%-1.5%, 0.2%-0.4% and 0.1%-0.3% of the total weight of the mixture of components A, B and C, respectively.

[0006] Step C, preparing a heat-conducting reinforcing structure, expanded graphite powder, epoxy resin and silane coupling agent are mixed, 3D printed into a multi-stage honeycomb structure, and then vacuum annealed to obtain a heat-conducting reinforcing structure; the epoxy resin and silane coupling agent account for 4%-6% and 0.3%-0.6% of the total weight of the expanded graphite powder, respectively.

[0007] Step D, the liquid phase change material is filled into the heat-conducting reinforcing structure in the multi-stage honeycomb structure under vacuum; and a phase change heat storage module is obtained.

[0008] As a preferred further technical solution, the method further comprises: encapsulating the phase change heat storage module in a metal shell, and pre-coating polytetrafluoroethylene and zirconia ceramic layers on the inner wall of the metal shell; and then installing two heat exchange interfaces on the metal shell.

[0009] A further technical solution is that the multi-stage honeycomb structure comprises primary pores, secondary pores and tertiary pores, the ratio of the pore size to the wall thickness of the primary pores is greater than that of the secondary pores, and the ratio of the pore size to the wall thickness of the secondary pores is greater than that of the tertiary pores.

[0010] Further, the first level of pores has a pore size of 0.4 mm, and the number of the first level of pores accounts for 55-65% of the total number of pores; the second level of pores has a pore size of 0.2 mm, and the number of the second level of pores accounts for 20-30% of the total number of pores; and the third level of pores has a pore size of 0.1 mm, and the number of the second level of pores accounts for 5-15% of the total number of pores.

[0011] Further, the first level of pores, the second level of pores and the third level of pores have an inclination angle of 25-35 degrees with respect to a horizontal line or a straight line perpendicular to the horizontal line.

[0012] Further, the inner surface of the heat exchange interface is coated with an alumina-graphene composite coating.

[0013] Compared with the prior art, one of the beneficial effects of the present application is that, by virtue of the multi-stage phase change characteristics of the composite phase change material, the heat pump system can meet the requirements of low-temperature heating, medium-temperature hot water supply and high-temperature refrigeration, and the heat storage capacity of the composite phase change material is effectively improved compared with the conventional single phase change material, and the multi-stage honeycomb heat conduction structure significantly improves the heat conduction coefficient of the module, ensuring the utilization rate of the heat storage of the phase change material and effectively shortening the heat response time, thereby providing strong support for the efficient operation of the heat pump system. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 FIG. 1 is a structural diagram of a composite phase change heat storage module according to an embodiment of the present application.

[0015] Figure 2 FIG. 5 is a DSC curve of a composite phase change material according to an embodiment of the present application.

[0016] Figure 3 FIG. 8 is a heat flow simulation diagram of a heat exchange interface according to an embodiment of the present application.

[0017] Figure 4 FIG. 11 is an energy efficiency comparison diagram of a composite phase change heat storage module in a heat pump system according to an embodiment of the present application.

[0018] Figure 5 FIG. 14 is a heat conduction efficiency test result of a heat conduction enhancement structure according to an embodiment of the present application.

[0019] Figure 6 FIG. 17 is a schematic diagram of a multi-stage honeycomb-shaped expanded graphite structure according to an embodiment of the present application. DETAILED DESCRIPTION

[0020] The purpose of the present application is to provide a composite phase change heat storage module for a heat pump system, aiming to solve the problems of single phase change temperature, low heat conduction efficiency, poor environmental adaptability and insufficient integration efficiency with the heat pump system by self-researching multi-stage phase change design of composite phase change material, fine optimization of hierarchical heat conduction enhancement structure, manufacturing improvement of high-performance packaging shell and intelligent integration of dynamically adaptive heat exchange interface. The present application realizes efficient heat energy storage and release, significantly improves the energy efficiency and stability of the heat pump system, and is suitable for various application scenarios such as air source heat pump, ground source heat pump and industrial heat pump, especially for complex working conditions with large load fluctuation or environmental temperature change (such as low temperature heating, high temperature refrigeration or intermittent operation). Through innovative material formula, structure design and intelligent control, the present application not only improves the system energy efficiency ratio (COP increases by 20-22%), but also enhances the operation stability (temperature fluctuation <0.8℃), and widens the application range of the module in severe environments such as extreme cold, high salt corrosion, etc., providing a breakthrough solution for efficient and reliable operation of heat pump technology.

[0021] Accordingly, the present application provides a composite phase change heat storage module for a heat pump system, which realizes efficient heat energy storage and release by innovative formula and performance optimization of self-researched composite phase change material, fine design of hierarchical heat conduction enhancement structure, fine manufacturing and process improvement of high-performance packaging shell, intelligent integration and adaptation mechanism of dynamically adaptive heat exchange interface, significantly improving the energy efficiency and stability of the heat pump system. This module is designed for air source heat pump, ground source heat pump and industrial heat pump, and is suitable for temperature range of 30-80℃, especially for complex working conditions with large load fluctuation or environmental temperature change. The following is a detailed description of the technical solution, which verifies the performance advantages in combination with the figure group. The structure of the composite phase change heat storage module is shown in Figure 1

[0022] In one embodiment of the present application, the preparation of the above-mentioned composite phase change material is disclosed. The composite phase change material is designed with multi-stage phase change temperature (40℃, 55℃, 70℃) to meet the multi-working condition requirements of the heat pump system in low temperature heating (30-50℃), medium temperature hot water supply (50-60℃) and high temperature refrigeration (60-80℃), and the heat storage efficiency and cycle stability are improved by functional additives and process optimization.

[0023] ​In this embodiment, the composite phase change material is prepared by mixing modified alkane-based phase change material (phase change temperature 40°C, latent heat 192 J / g), fatty acid ester-based phase change material (phase change temperature 55°C, latent heat 158 J / g) and inorganic salt-organic eutectic material (phase change temperature 70°C, latent heat 128 J / g) in a mass ratio of 4:3:2, supplemented with 1wt% of nano-silicon oxide, 0.3wt% of carboxylated multi-walled carbon nanotubes (MWCNT) and 0.2wt% of polyacrylamide (PAM) based on the total weight of the three components. The three main components are prepared as follows: Component A (modified alkane-based phase change material): 100 g of C18-C20 straight-chain alkane (purity 99.8%, Sigma-Aldrich, item number H2030) is reacted with 5 g of sodium hydroxide (analytical purity, Merck, item number 106498) at 60°C under nitrogen protection (flow rate 0.5 L / min, purity 99.999%, Air Liquide) for 2 hours, with a stirring speed of 500 rpm (magnetic stirrer, IKA C-MAG HS7, model 0004186700). The product is washed with 500 mL of deionized water (resistivity 18.2 MΩ·cm, Milli-Q Integral system) for 3 times, and vacuum dried at 50°C (0.01 MPa, Labconco FreeZone 6L dryer, model 7752030) for 12 hours, obtaining 44.4 g of modified alkane-based material. The modified alkane-based material is verified by gas chromatography-mass spectrometry (GC-MS, Agilent 7890B / 5977B) to have a hydroxylation rate >95%, a phase change temperature of 40°C±0.3°C and a latent heat of 200 J / g±2 J / g.

[0024] Component B (fatty acid ester-based phase change material): 50 g of palmitic acid (purity 99.5%, Alfa Aesar, item number A12244) is reacted with 20 g of methanol (purity 99.9%, Fisher Scientific, item number A412-4) under the action of 0.5 g of sulfuric acid catalyst (98%, Sigma-Aldrich, item number 258105) at 65°C for 4 hours (500 mL three-necked flask, heating jacket power 300 W, IKA CM-HS 7). The product is purified by vacuum distillation (0.02 MPa, 80°C, rotary evaporator Büchi R-300, model 11R300252V), and vacuum dried at 50°C for 12 hours, obtaining 33.3 g of methyl palmitate. The infrared spectrum (FTIR, PerkinElmer Spectrum Two, model L160000A) confirms the characteristic peak of ester group (1735 cm⁻¹), a phase change temperature of 55°C±0.3°C and a latent heat of 160 J / g±2 J / g.

[0025] Component C (inorganic salt-organic co-crystal material): Sodium chloride 5.8 g (purity 99.9%, Merck, Cat. No. 106404) and polyethylene glycol 24 g (PEG-600, purity 99.5%, Dow Chemical, Cat. No. P5402) were selected in a 1:4 molar ratio, stirred at 80 °C for 1 hour (water bath, Julabo F12, Model 9 160 012) at 500 rpm. Cooled to room temperature, vacuum dried at 50 °C for 12 hours, and 22.2 g of co-crystal material was obtained. The co-crystal structure was verified by X-ray diffraction (XRD, Bruker D8 Advance, Model A25), phase transition temperature 70 °C ± 0.3 °C, latent heat 130 J / g ± 2 J / g.

[0026] Additives: Nano-silica 1 g (particle size 20 nm, purity 99.9%, Evonik Aerosil 200, Cat. No. 134698). Carboxylated multi-walled carbon nanotubes 0.3 g (MWCNT, thermal conductivity 200 W / (m-K), Nanocyl NC7000, Cat. No. NC7000). Polyacrylamide 0.2 g (PAM, molecular weight 500 kDa, BASF, Cat. No. PAM500).

[0027] In a 500 mL stainless steel autoclave (Parr Instrument 4560, pressure resistance 5 MPa, Model 4560), 44.4 g of component A, 33.3 g of component B, and 22.2 g of component C were added. Nitrogen protection was set (flow rate 0.8 L / min, pressure 0.1 MPa), and the temperature was raised to 90 °C (temperature raising rate 5 °C / min, temperature control accuracy ± 0.5 °C). Stirring was performed at 800 rpm for 4 hours (mechanical stirrer, Heidolph RZR 2052, Model 036300510). Nano-silica 1 g (1st hour), MWCNT 0.3 g (2nd hour), and PAM 0.2 g (3rd hour) were added in sequence. After stirring was completed, ultrasonic treatment (40 kHz, 200 W, Branson CPX5800H, Model CPX-952-818R, treatment time 30 minutes) was performed to eliminate bubbles and agglomeration.

[0028] Cooling to 50 °C (temperature lowering rate 3 °C / min), the mixture was injected into a thermally enhanced structure mold (mold temperature 40 °C ± 1 °C) through a high-pressure injection device (KraussMaffei CX 80, Model CX80-380, pressure 0.05 MPa, injection speed 50 mL / min). The mixture was cured at 40 °C for 24 hours (incubator, Memmert IN160, Model IN160-230V, humidity <20%RH). As Figure 2The DSC curve and phase change peak stability after 2000 cycles of the phase change material are shown, with latent heat decay <3%, confirming excellent heat storage performance and cycle reliability.

[0029] In Figure 2 , the multi-stage phase change temperature and heat storage capacity of the composite phase change material of the application are demonstrated. The curve shows three distinct phase change peaks at 40°C, 55°C and 70°C, corresponding to latent heat values of 192 J / g, 158 J / g and 128 J / g, respectively, verifying the excellent heat storage performance of the material in a wide temperature range of 30-80°C. The 40°C phase change peak is suitable for low-temperature heating conditions (30-50°C), the 55°C phase change peak is suitable for medium-temperature hot water supply (50-60°C), and the 70°C phase change peak is suitable for high-temperature refrigeration (60-80°C), meeting the multi-condition requirements of heat pump systems. After 2000 thermal cycle tests, the latent heat decay is <3%, and the phase change temperature drift is <0.3°C, indicating that the material has excellent cycle stability, providing key support for the energy efficiency improvement (COP improvement of 20-22%) of the module in the heat pump system.

[0030] Manufacture of heat conduction enhancement structure: Select expanded graphite powder (particle size 50 μm, thermal conductivity 400 W / (m·K), purity 99.5%, Qingdao Graphite Co., item number EG-50), mix with 5wt% epoxy resin (viscosity 500 mPa·s, Hexion Epon 828, item number 828-100), add 0.5wt% silane coupling agent (KH-550, Shin-Etsu, item number KBM-903) to enhance adhesion.

[0031] As Figure 6 shown, multi-stage honeycomb structure design: primary pores (pore size 0.4 mm, wall thickness 0.1 mm, volume fraction 60%), secondary pores (0.2 mm, wall thickness 0.05 mm, volume fraction 25%), tertiary pores (0.1 mm, volume fraction 10%), total porosity 85%. Honeycomb inclination angle 30°±5° (optimization software: Ansys Fluent 2023 R1). Surface coated with 50 nm nano-graphite layer (CVD equipment: Aixtron Black Magic, model BM Pro). Embedded 0.1 mm graphite fiber mesh (tensile strength 500 MPa, Toray T300, item number T300-3000) and 0.05 mm carbon fiber mesh (shear strength 200 MPa, Hexcel IM7, item number IM7-GP).

[0032] The honeycomb structure was formed using a high-precision 3D printer (Stratasys J850, model J850 Pro, printing resolution 0.03 mm, printing speed 50 mm / s), printing temperature 200℃±2℃, layer thickness 0.02 mm. Annealing in a 170℃ vacuum furnace (0.01 MPa, Carbolite Gero HTK-8, model HTK-8-GR / 30) for 4 hours to eliminate internal stress. Plasma treatment (120 W, argon flow rate 10 sccm, 6 minutes, Diener Nano, model Nano-PCCE) to enhance surface hydrophilicity, contact angle reduced to 30°±5°. Vacuum infusion (0.03 MPa, 50℃, Kurt J. Lesker PVD 75, model PVD75) to fill the liquid composite phase change material described above, infusion time 30 minutes, filling rate >97%. As shown in Figure 5 , compared with the multi-stage honeycomb and single-pore structure, the thermal response time is shortened by 75% and the thermal conductivity is increased by 250%.

[0033] In Figure 5 a、 Figure 5 b, the performance difference between the multi-stage honeycomb expanded graphite structure of the present application and the traditional single-pore structure in thermal response time (from 30℃ to 70℃) and thermal conductivity is shown. The thermal response time of the multi-stage honeycomb structure of the present application (containing primary pores 0.4 mm, secondary pores 0.2 mm, tertiary pores 0.1 mm, porosity 85%) is only 25 seconds, which is shortened by 75% compared with the traditional single-pore structure (100 seconds); the thermal conductivity reaches 7 W / (m·K), which is increased by 250% compared with the traditional structure (2 W / (m·K)). These improvements benefit from the synergistic effect of multi-scale pore design, 30° tilt angle optimization and nanographite coating (50 nm), which significantly improves the thermal conduction efficiency and phase change material filling rate (>97%). The 75% shortening effect and 250% improvement effect are marked in the figure, which directly reflects the innovation and superiority of the heat conduction enhancement structure of the present application, and provides key support for the rapid thermal response and energy efficiency improvement of the composite phase change heat storage module in the heat pump system.

[0034] Fabrication of the encapsulation shell and heat exchange interface: 316L stainless steel (thickness 2 mm, size 300 mm x 200 mm x 50 mm, temperature resistance -40°C to 180°C, pressure resistance 3.5 MPa, Outokumpu, item number 316L-2B) was used. The inner part was coated with a 0.15 mm silicone sealing layer (Dow Corning 732, item number 732-Clear, temperature resistance -60°C to 250°C), and the outer part was coated with a 50 pm polytetrafluoroethylene (PTFE, DuPont Teflon, item number Teflon-AF) + 20 pm zirconia ceramic layer (YSZ, Praxair, item number YSZ-123). The heat exchange interface was a double-layer spiral pipe, with the outer layer (copper, C11000, 12 mm in diameter, 1.2 mm thick, Wieland, item number Cu-DHP) used for high-temperature working conditions (> 60°C) and the inner layer (8 mm in diameter, 1.2 mm thick) used for low-temperature working conditions (< 50°C). The surface was coated with a 100 nm aluminum oxide-graphene composite coating (thermal conductivity 450 W / (m·K), CVD, Aixtron Black Magic, model BM Pro). As shown in Figure 3 , the heat flow simulation showed an efficiency of 92% and a temperature difference of <1°C, with a variable working condition efficiency improvement of 15%.

[0035] In Figure 3 , the heat exchange efficiency of the double-layer spiral pipe heat exchange interface (outer layer 12 mm, inner layer 8 mm, copper, 100 nm aluminum oxide-graphene coating) and the heat pump system was demonstrated. In the figure, the composite phase change heat storage module is connected to the heat pump system heat exchanger through the double-layer spiral pipes on both sides (red and dark red circles), and the heat flow is input from the left side (70°C) to the right side (69°C) with a temperature difference controlled within 1°C, and the heat exchange efficiency is above 92%. The color gradient represents the heat flow density distribution, and the central area has uniform heat flow, verifying the effectiveness of the dynamic adaptation mechanism (servo motor adjusts the spacing 3-5 mm, fuzzy PID algorithm optimizes the flow rate 0.3-2.5 L / min). The outer pipe is suitable for high-temperature working conditions (> 60°C), and the inner pipe is suitable for low-temperature working conditions (< 50°C), and the AI model (prediction error < 5%) ensures a variable working condition efficiency improvement of 15%. This figure intuitively reflects the efficient heat energy transfer capability of the heat exchange interface by indicating the heat flow direction, efficiency data, and temperature difference, providing key support for the energy efficiency improvement (COP improvement 20-22%) and stability (temperature fluctuation <0.8°C) of the heat pump system.

[0036] The composite phase change material layer was assembled with the thermal conductivity enhancement structure and the encapsulation shell, and a hydraulic press (Wabash MPI, model Genesis G30H-15, pressure 0.1 MPa, pressing time 5 minutes) was used to ensure tight bonding. The heat exchange interface was connected to the heat pump system heat exchanger through a standard flange (DN25, PN16, fastening torque 50 Nm, tool: Craftsman Torque Wrench, model 912304). The control system communicated with the heat pump main control unit (Siemens S7-1200, model 6ES7214-1AG40-0XB0) through an RS485 interface (Modbus RTU protocol, transmission rate 9600 bps) to transmit temperature, flow and pressure data in real time. Figure 4 The COP improvement (heating 5.0, cooling 5.4, hot water 4.8) and stability data are shown.

[0037] In Figure 4 , the difference in energy efficiency ratio (COP) performance between the module of the present application and the conventional single phase change material module under heating (ambient temperature -10°C) and cooling (ambient temperature 35°C) working conditions is shown. In the heating working condition, the COP of the module of the present application reaches 5.0, which is 22% higher than that of the conventional module (COP 4.1); in the cooling working condition, the COP reaches 5.4, which is 20% higher than that of the conventional module (COP 4.5). This energy efficiency improvement is due to the synergistic effect of the multi-stage phase change characteristics of the composite phase change material (40°C, 55°C, 70°C, latent heat 192 J / g, 158 J / g, 128 J / g), the multi-stage honeycomb thermal conductivity structure (thermal conductivity 7 W / (m·K)) and the dynamically adaptive heat exchange interface (efficiency > 92%). The column chart in the figure directly reflects the advantages of the module of the present application in energy efficiency and stability (temperature fluctuation <0.8°C after 5000 hours of operation), which provides technical support for the efficient operation of the heat pump system under multiple working conditions.

[0038] As described in the above embodiments of the present application, the present application matches the multi-working condition requirements of the heat pump system in low-temperature heating, medium-temperature hot water supply and high-temperature refrigeration, etc. by the multi-stage phase change characteristics (40℃, 55℃, 70℃, latent heat value 192J / g, 158J / g, 128J / g) of the composite phase change material, and the heat storage capacity is increased by 20-30% compared with the traditional single phase change material (such as paraffin, latent heat about 150J / g). The multi-stage honeycomb heat conduction structure improves the thermal conductivity to 7 W / (m·K), and the thermal response time is shortened by 75% (25 seconds vs 100 seconds), ensuring fast heat energy transfer. The dynamically adaptive heat exchange interface realizes heat exchange efficiency >92%, and reduces heat loss by 15%. The comprehensive effect makes the coefficient of performance (COP) of the heat pump system reach 5.0 in the heating condition (environmental temperature -10℃), which is increased by 22% compared with the traditional module (COP 4.1); the COP reaches 5.4 in the refrigeration condition (environmental temperature 35℃), which is increased by 20% compared with the traditional module (COP 4.5); and the COP reaches 4.8 in the hot water supply condition (inlet water temperature 55℃), which is increased by 18%.

[0039] The self-developed composite phase change material significantly improves the cycle stability through the PAM micro-crosslinking network and nano-silicon oxide stabilizer, and the latent heat attenuation is <3% and the phase change temperature drift is <0.3℃ after 2000 times of thermal cycle (30-80℃), ensuring consistent long-term operation performance. The high-performance packaging shell adopts 316L stainless steel and multi-layer protective coating, and can withstand -40℃ to 180℃, 3.5 MPa pressure, 1200 hours of environmental test without deformation, corrosion resistance is increased by 25% (ASTM G31, pH=3, mass loss <0.003 mg / cm²), and 800 hours of salt spray test (ISO 9227) without coating peeling. The dynamically adaptive heat exchange interface controls the temperature difference to be <1℃ through the fuzzy PID algorithm and AI model control, and the temperature fluctuation is <0.8℃ after 5000 hours of continuous operation, and the system stability is increased by 30%. Figure 4 The stability test data (fluctuation <0.8℃) of the module prove the reliable operation ability of the module in complex working conditions.

[0040] The multi-stage phase change temperature design (30-80℃) makes the module adapt to low-temperature heating (30-50℃), medium-temperature hot water supply (50-60℃) and high-temperature refrigeration (60-80℃), covering various application scenarios such as air source heat pump, ground source heat pump and industrial heat pump. The multi-stage heat conduction structure has a compressive strength of 12 MPa, meeting the vibration environment requirements (IEC 60068-2-6); the corrosion-resistant shell adapts to extremely cold regions (-40℃), coastal high-salt environments and industrial high-temperature scenarios (180℃), and has no performance degradation after 800 hours of salt spray test. The module performs well in the heating condition at -10℃, the refrigeration condition at 35℃ and the hot water supply condition at 55℃, Figure 4 which demonstrates the superiority of its environmental adaptability and multi-working condition performance, providing flexibility for the application of heat pump systems in diversified scenarios.

[0041] The composite phase change heat storage module prepared by the application adopts environmentally friendly materials (316L stainless steel and recyclable phase change materials), and uses nitrogen protection (flow rate 0.8 L / min) in the production process to reduce emissions. Energy efficiency is improved (COP is improved by 20-22%), which significantly reduces the energy consumption of the heat pump system, saves 25% of the electric energy in the heating season, and reduces the operation cost of the user by 20%. High cycle stability (latent heat attenuation <3% after 2000 cycles) and durability (service life >10 years) reduce the replacement frequency and reduce the whole life cycle cost. Figure 4 The energy efficiency data of Figure 2 The cycle stability data of indirectly verify the economic benefits and environmental friendly characteristics of the module.

[0042] In addition to the above, it should be noted that the "one embodiment", "another embodiment", "embodiment" and the like mentioned in the specification refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment described in the general description of the application. The same expression appears in several places in the specification does not necessarily refer to the same embodiment. Further, when a specific feature, structure or characteristic is described in conjunction with any embodiment, it is claimed that the implementation of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of the application.

[0043] Although the application is described herein with reference to a number of illustrative embodiments of the application, it should be understood that various modifications and implementations can be devised by those skilled in the art which will fall within the principles of the application disclosed herein. More specifically, many variations and modifications of the subject combination arrangement, as well as the components thereof, and / or the arrangement itself, can be made within the scope and spirit of the application as disclosed in the above specification, figures and claims. In addition to variations and modifications of the combination arrangement, and / or the components thereof, other uses will also be apparent to those skilled in the art from the above disclosure.

Claims

1. A method for preparing a composite phase change heat storage module for a heat pump system, characterized in that The method comprises the following steps: Preparation of component A, 90-110 parts of C18-C20 straight-chain alkanes and 4-6 parts of sodium hydroxide are mixed together by weight, stirred uniformly, and the obtained product is washed with deionized water and dried to obtain a modified alkane-based material, i.e., component A; Preparation of component B, 40-60 parts of palmitic acid and 18-22 parts of methanol, 0.1-1 parts of sulfuric acid catalyst are mixed together by weight, stirred uniformly, and the obtained product is purified by distillation and dried to obtain methyl palmitate, i.e., component B; Preparation of component C, 5-6 parts of sodium chloride and 22-26 parts of polyethylene glycol are mixed together by weight, stirred uniformly, and dried to obtain an inorganic salt-organic eutectic material, i.e., component C; Components A, B, and C are mixed in a mass ratio of 3-5:2-4:1-3, heated to above 90°C, then stirred uniformly, and then nano-silicon oxide, carboxylated multi-walled carbon nanotubes, and polyacrylamide are sequentially added thereto, and the mixture is continuously stirred and mixed to obtain a phase change material; The nano-silicon oxide, carboxylated multi-walled carbon nanotubes, and polyacrylamide account for 0.5%-1.5%, 0.2%-0.4%, and 0.1%-0.3% of the total weight of the mixture of components A, B, and C, respectively; Preparation of a heat-conducting reinforcing structure, expanded graphite powder, epoxy resin, and silane coupling agent are mixed, 3D printed into a multi-level honeycomb structure, and then vacuum annealed to obtain a heat-conducting reinforcing structure; The epoxy resin and silane coupling agent account for 4%-6% and 0.3%-0.6% of the total weight of the expanded graphite powder, respectively; The liquid phase change material is injected into the heat-conducting reinforcing structure in a vacuum environment and filled in the multi-level honeycomb structure; A phase change heat storage module is obtained.

2. The method of claim 1, wherein The method further comprises packaging the phase change heat storage module in a metal shell, and pre-coating polytetrafluoroethylene and zirconia ceramic layers on the inner wall of the metal shell; Then two heat exchange interfaces are installed on the metal shell.

3. The method of claim 1 or 2, wherein the method further comprises: The multi-level honeycomb structure comprises primary pores, secondary pores, and tertiary pores, the pore diameter to wall thickness ratio of the primary pores is greater than that of the secondary pores, and the pore diameter to wall thickness ratio of the secondary pores is greater than that of the tertiary pores.

4. The method of claim 3, wherein the method further comprises: The pore diameter of the primary pores is 0.4 mm, and the number of primary pores accounts for 55%-65% of the total number of pores; the pore diameter of the secondary pores is 0.2 mm, and the number of secondary pores accounts for 20%-30% of the total number of pores; the pore diameter of the tertiary pores is 0.1 mm, and the number of secondary pores accounts for 5%-15% of the total number of pores.

5. The method of claim 4, wherein the method further comprises: The primary pores, secondary pores, and tertiary pores have an inclination angle of 25-35° with respect to a horizontal line or a straight line perpendicular to the horizontal line.

6. The method of claim 2, wherein the method further comprises: The inner surface of the heat exchange interface is coated with an aluminum oxide-graphene composite coating.

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