Phase change heat storage device and heating and ventilation system

Abstract

The invention relates to the technical field of energy, in particular to a phase change heat storage device and a heating and ventilation system.The phase change heat storage device comprises a sealed shell, a plurality of independent heat storage units arranged in the shell, a main heat exchange flow channel penetrating through the heat storage units, a fluid inlet and a fluid outlet, the heating and ventilation system comprises a phase change heat storage device heat pump unit, a double-circulation pipeline and a user side heat exchanger. The multiple independent heat storage units are directly coupled with the penetrating main heat exchange flow channel, so that heat transfer fluid can rapidly flow through the units for heat charging or heat release, the heat energy transfer path is remarkably shortened, the problem of heat lag of a traditional single heat storage structure is solved, and the system can adjust the energy supply rate in real time according to the load requirement.

Description

Technical Field

[0001] The present invention relates to the field of energy technology, and in particular to a phase-change heat storage device and a heating and ventilation system. Background Art

[0002] The application of phase change heat storage technology in HVAC systems has been widely studied. Most existing technologies use a single phase change material encapsulated in a fixed-structure heat storage device, and connect it to the heat pump unit or the user end through traditional heat exchange pipelines. Such systems usually rely on direct energy supply from the heat pump unit, or perform heat storage and release operations under a simple time control strategy to achieve partial load regulation or peak-valley arbitrage functions of electricity prices.

[0003] Existing technologies have a significant problem of insufficient dynamic response capabilities in actual operation. Due to the inherent thermal hysteresis characteristics of phase change materials and the overly simplified coupling control strategy between the heat storage device, the heat pump unit and the user end, the system is often unable to quickly adjust the energy supply mode when responding to sudden load changes or complex electricity price policies, resulting in reduced energy efficiency or fluctuations in user comfort. For example, if the heat release rate of the heat storage device is insufficient during peak power hours, the system needs to urgently start the high-power heat pump unit to supplement heat, which not only increases operating costs, but may also reduce the life of the equipment due to frequent start-up and shutdown. In addition, the modularity of traditional heat storage devices is low, making it difficult to flexibly expand capacity according to building load requirements, further limiting the adaptability of the system.

[0004] Therefore, to address the above-mentioned problem of insufficient dynamic response capability, the present invention proposes a phase change heat storage device and HVAC system. By optimizing the structure of the heat storage unit, introducing a dual-circulation dynamic switching pipeline and an intelligent predictive control algorithm, efficient charging and discharging heat response and flexible capacity expansion are achieved, thereby improving the energy efficiency and economy of the system. Summary of the Invention

[0005] In order to overcome the problem of insufficient dynamic response capability in the prior art, the present invention proposes a phase change heat storage device and a HVAC system.

[0006] The technical solution of the present invention is: a phase change heat storage device and a HVAC system, comprising:

[0007] A sealed shell, used to encapsulate the phase change material and withstand working pressure;

[0008] Multiple independent heat storage units are arranged in the shell, each heat storage unit contains phase change material and enhanced heat transfer structure for efficient storage and release of heat energy;

[0009] A main heat exchange channel running through the heat storage unit for circulating heat transfer fluid;

[0010] The fluid inlet and fluid outlet communicated with the main heat exchange channel are used to connect to an external heat source or a heat exchange circuit at the user end.

[0011] Preferably, the phase change material is a composite organic paraffin or an inorganic hydrated salt, the phase change temperature of which is adjusted to a temperature within the range of 15-60°C by adjusting the material composition ratio, and the latent heat value is ≥180kJ / kg. The composite organic paraffin comprises a mixture of a paraffin matrix and nano-alumina particles, with a mass ratio of 3-8%, which is used to inhibit phase separation during the phase change process. The inorganic hydrated salt is modified sodium acetate trihydrate, with 1-5% of a nucleating agent and 2-10% of a thickener added. The phase change material is encapsulated in a sealed capsule made of high-density polyethylene or aluminum-plastic composite film, with a capsule wall thickness of 0.5-2mm and a compressive strength ≥0.3MPa.

[0012] Preferably, the enhanced heat transfer structure includes a metal fin array or a graphene thermal conductive grid, wherein the metal fin array is made of copper, the fin spacing is 5-15mm, the height is 20-50mm, the thickness is 0.5-2mm, and the surface is anodized; the graphene thermal conductive grid is formed by composite pressing of multi-layer graphene sheets and epoxy resin, the grid aperture is 1-5mm, and it is filled with phase change material to form a three-dimensional heat conduction path; the contact area between the heat transfer structure and the phase change material accounts for ≥60%, and it is fixed to the support frame inside the shell by welding or snapping.

[0013] Preferably, the heat storage unit uses modular packaging, the standard capacity of a single heat storage unit is 5-20kWh, the shape is a cube with a side length of 200-500mm, and the units are combined by detachable connectors, including quick clamp connectors and flange bolts. The temperature range of the connectors is -20-100℃. The modular combination supports parallel or series topology. When in parallel, the fluid is uniformly distributed through the collecting pipe. When in series, U-shaped elbows are used to connect adjacent units. The module housing is provided with a standardized interface, which is compatible with the piping systems of different manufacturers.

[0014] Preferably, the inner wall of the shell is covered with a corrosion-resistant nano-coating made of polytetrafluoroethylene with a thickness of 50-200 μm, which can withstand corrosion from fluids with a pH value of 3-11. A pressure balancing valve is provided on the top of the shell, and the valve body opening pressure is 0.1-0.3 MPa, which is used to release the gas generated by the volume change of the phase change material. The shell has an embedded temperature sensor array, which includes at least 6 PT100 platinum resistance probes evenly distributed in the gaps between the heat storage units, with a measurement accuracy of ±0.5°C. The signal is transmitted to an external controller via RS485 or wirelessly. A shock-proof bracket is provided at the bottom of the shell, and the bracket is made of Q235 carbon steel coated with a rubber shock-absorbing layer, with a load-bearing capacity of ≥500 kg.

[0015] Preferably, a HVAC system comprises:

[0016] Phase change thermal storage device;

[0017] Heat pump unit, used to provide heat source or cold source, and work in conjunction with phase change thermal storage device;

[0018] Double circulation pipeline, connecting the main heat exchange flow channel of the heat pump unit and the phase change heat storage device;

[0019] The user-end heat exchanger is used to provide heating or cooling to the indoor space, and selects direct energy supply from the heat storage device or the heat pump unit through a switching valve.

[0020] Preferably, the dual-circulation pipeline includes a first circulation and a second circulation, wherein the first circulation connects the outlet of the heat pump unit and the inlet of the heat storage device, and is used to transport the high-temperature heat transfer fluid to the heat storage device to store heat energy in the charging mode; the second circulation connects the outlet of the heat storage device and the inlet of the user-end heat exchanger, and is used to transport the heat energy released by the heat storage device to the user-end in the heat release mode. The two circulations realize mode conversion through a three-way switching valve. The inner diameter of the pipeline is 25-50mm, and it is covered with a 30mm thick polyurethane insulation layer. The heat loss rate is ≤5%. The first circulation and the second circulation can operate independently or synchronously, and the flow distribution of each branch is controlled by a flow regulating valve.

[0021] Preferably, the system further comprises an intelligent controller, which controls the start and stop and power distribution of the heat pump unit and the heat storage device based on electricity price signals, user load forecasts and temperature feedback.

[0022] Preferably, the user-end heat exchanger is a radiant floor or a fan coil unit, wherein the radiant floor uses PEX-A pipes embedded in the concrete layer, the pipe spacing is 100-200mm, the water supply temperature is 35-45℃, and the fan coil unit air volume is 500-1500m 3 / h, the outlet water temperature is 7-12℃ during cooling, the heat exchanger switches between heating and cooling modes via a three-way valve, the valve body has a pressure resistance of 1.6MPa and a leakage rate of ≤0.1%. In heating mode, the system directly provides hot water from the thermal storage device or heat pump unit. In cooling mode, the cold water generated by the heat pump unit first flows through the thermal storage device for pre-cooling before being delivered to the fan coil unit.

[0023] Preferably, the hardware core of the intelligent controller is an ARM Cortex-M7 processor with a built-in load forecasting algorithm and optimization control module. The controller collects data from the temperature sensor array in real time, and combines the time-of-use electricity price information to preferentially start the heat pump unit to charge the heat storage device during off-peak hours, and switch to the heat storage device for separate energy supply during peak hours. When the user-end temperature deviates from the set value by ±1°C, the PID algorithm is triggered to adjust the power of the heat pump unit or the switching valve opening. The adjustment cycle is adjustable from 10 to 60 seconds. The controller is equipped with a 7-inch touch screen and supports manual mode to override the automatic strategy.

[0024] Beneficial effects of the present invention:

[0025] 1. Multiple independent heat storage units are directly coupled with the main heat exchange channel, allowing the heat transfer fluid to flow quickly through each unit to charge or release heat, significantly shortening the heat energy transfer path and overcoming the thermal lag problem of traditional single heat storage structures. The system can adjust the energy supply rate in real time according to load demand.

[0026] 2. The modular thermal storage unit design allows for dynamic adaptation to building load requirements of varying sizes by increasing or decreasing the number of units or adjusting the series / parallel topology, addressing the difficulty in scalability of traditional fixed-capacity thermal storage devices.

[0027] 3. The combined structure of the sealed shell and independent units avoids the stress impact of the volume expansion of the phase change material during repeated phase changes on the overall device. At the same time, the through-hole design of the main heat exchange flow channel ensures uniform fluid distribution and reduces the risk of local overheating or heat accumulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 What is shown is a schematic diagram of the system framework of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0030] The present invention provides an embodiment: a phase change heat storage device, comprising:

[0031] A sealed shell, used to encapsulate the phase change material and withstand working pressure;

[0032] Multiple independent heat storage units are arranged in the shell, each heat storage unit contains phase change material and enhanced heat transfer structure for efficient storage and release of heat energy;

[0033] A main heat exchange channel running through the heat storage unit for circulating heat transfer fluid;

[0034] The fluid inlet and fluid outlet communicated with the main heat exchange channel are used to connect to an external heat source or a heat exchange circuit at the user end.

[0035] Furthermore, the heat transfer fluid enters the main heat exchange channel through the fluid inlet, exchanges heat with the phase change material when flowing through multiple independent heat storage units. In the heat charging mode, the phase change material absorbs heat to undergo phase change and store energy. In the heat release mode, the phase change material releases heat and undergoes phase change to supply energy. Finally, the heat transfer fluid is output to the external system through the fluid outlet.

[0036] The present invention shortens the heat transfer path by running the main heat exchange channel through each independent heat storage unit, so that the fluid can efficiently exchange heat with all units at the same time, thereby improving the overall thermal response speed. At the same time, the modular independent heat storage unit design allows for flexible adjustment of the number of units or connection methods according to needs, thereby achieving elastic expansion of the system capacity. The combination of the sealed shell and the unitized structure not only ensures the packaging reliability of the phase change material, but also avoids the local heat accumulation problem common in traditional integral heat storage devices through the diversion design, making the temperature distribution more uniform and the system operation more stable.

[0037] The phase change material is a composite organic paraffin or an inorganic hydrated salt, the phase change temperature of which is adjusted within the range of 15-60°C by adjusting the material composition ratio, and the latent heat value is ≥180kJ / kg. The composite organic paraffin comprises a mixture of a paraffin matrix and nano-alumina particles, with a mass ratio of 3-8%, which is used to inhibit phase separation during the phase change process. The inorganic hydrated salt is modified sodium acetate trihydrate, with 1-5% of a nucleating agent and 2-10% of a thickener added. The phase change material is encapsulated in a sealed capsule made of high-density polyethylene or aluminum-plastic composite film, with a capsule wall thickness of 0.5-2mm and a compressive strength of ≥0.3MPa.

[0038] The enhanced heat transfer structure includes a metal fin array or a graphene thermal conductive grid, wherein the metal fin array is made of copper, the fin spacing is 5-15mm, the height is 20-50mm, the thickness is 0.5-2mm, and the surface is anodized. The graphene thermal conductive grid is made of a composite pressing of multi-layer graphene sheets and epoxy resin, the grid aperture is 1-5mm, and it is filled with phase change material to form a three-dimensional heat conduction path. The contact area between the heat transfer structure and the phase change material accounts for ≥60%, and it is fixed to the support frame inside the shell by welding or snapping.

[0039] The heat storage unit uses modular packaging. The standard capacity of a single heat storage unit is 5-20kWh. It has a cubic shape with a side length of 200-500mm. The units are connected by detachable connectors, including quick clamp connectors and flange bolts. The connectors have a temperature resistance range of -20-100°C. The modular combination supports parallel or series topology. When in parallel, the fluid is uniformly distributed through the collecting pipe. When in series, U-shaped elbows are used to connect adjacent units. The module housing is provided with standardized interfaces, which are compatible with the piping systems of different manufacturers.

[0040] The inner wall of the shell is covered with a corrosion-resistant nano-coating made of polytetrafluoroethylene with a thickness of 50-200 μm, which is resistant to corrosion from fluids with a pH value of 3-11. A pressure balancing valve is provided on the top of the shell, and the valve body opening pressure is 0.1-0.3 MPa, which is used to release the gas generated by the volume change of the phase change material. The shell has an embedded temperature sensor array, which includes at least 6 PT100 platinum resistance probes evenly distributed in the gaps between the thermal storage units, with a measurement accuracy of ±0.5°C. The signal is transmitted to an external controller via RS485 or wirelessly. The bottom of the shell is equipped with a shock-proof bracket, which is made of Q235 carbon steel coated with a rubber shock-absorbing layer and has a load-bearing capacity of ≥500 kg.

[0041] See also Figure 1 , further, a HVAC system, comprising:

[0042] Phase change thermal storage device;

[0043] Heat pump unit, used to provide heat source or cold source, and work in conjunction with phase change thermal storage device;

[0044] Double circulation pipeline, connecting the main heat exchange flow channel of the heat pump unit and the phase change heat storage device;

[0045] The user-end heat exchanger is used to provide heating or cooling to the indoor space, and selects direct energy supply from the heat storage device or the heat pump unit through a switching valve.

[0046] The dual-circulation pipeline includes a first circulation and a second circulation, wherein the first circulation connects the outlet of the heat pump unit and the inlet of the heat storage device, and is used to transport the high-temperature heat transfer fluid to the heat storage device to store heat energy in the heat charging mode; the second circulation connects the outlet of the heat storage device and the inlet of the user-end heat exchanger, and is used to transport the heat energy released by the heat storage device to the user-end in the heat release mode. The two circulations realize mode conversion through a three-way switching valve. The inner diameter of the pipeline is 25-50mm, and it is covered with a 30mm thick polyurethane insulation layer. The heat loss rate is ≤5%. The first circulation and the second circulation can operate independently or synchronously, and the flow distribution of each branch is controlled by a flow regulating valve.

[0047] Furthermore, during periods of low electricity prices, the heat pump unit starts and transfers heat energy to the phase change heat storage device through the first cycle of the dual-circulation pipeline for energy storage. The phase change material undergoes phase change after absorbing heat. During peak electricity consumption or heating demand periods, the system automatically switches to the second cycle, and the heat storage device releases the stored heat energy to heat the building space through the user-side heat exchanger. At this time, the switching valve cuts off the direct energy supply path of the heat pump unit.

[0048] The system also includes an intelligent controller, which controls the start and stop and power distribution of the heat pump unit and the heat storage device based on electricity price signals, user load forecasts and temperature feedback.

[0049] The hardware core of the intelligent controller is an ARM Cortex-M7 processor with a built-in load forecasting algorithm and optimization control module. The controller collects data from the temperature sensor array in real time and, combined with time-of-use electricity price information, prioritizes starting the heat pump unit to charge the thermal storage device during off-peak hours. During peak hours, it switches to the thermal storage device for independent power supply. When the user-end temperature deviates from the set value by ±1°C, the PID algorithm is triggered to adjust the power of the heat pump unit or the switching valve opening. The adjustment cycle is adjustable from 10 to 60 seconds. The controller is equipped with a 7-inch touch screen and supports manual mode to override the automatic strategy.

[0050] Furthermore, the intelligent controller uses the ARM Cortex-M7 processor to collect data from the temperature sensor array and the user-end temperature sensor in real time. At the same time, it combines the time-of-use electricity price information obtained through 4G / Wi-Fi networking, uses the LSTM neural network algorithm to predict the user load demand in the next 12 hours, and automatically controls the heat pump unit to operate at 80-100% of the rated power during the off-peak period (0:00-8:00). Through the first cycle, the high-temperature heat transfer fluid of 50-60°C is transported to the heat storage device for heat storage. At the same time, the model predictive control (MPC) algorithm optimizes the heat charging rate and temperature curve. During the peak period (8:00-22 :00) Intelligently cut off the power supply of the heat pump unit, switch to the heat storage device to supply energy separately through the second cycle, and transmit 40-50℃ heat energy to the user-end heat exchanger. When it is detected that the user-end temperature deviates from the set value by ±1℃, the PID control algorithm is immediately triggered, and the flow control valve opening is dynamically adjusted to stabilize the supply and return water temperature difference within the range of 5-10℃. If the temperature continues to be 2℃ lower than the set value for 10 minutes, the heat pump unit will be automatically started for auxiliary heating. The system automatically generates an energy efficiency report every day including heat storage efficiency (≥85%), power saving data and equipment status, and displays real-time operating parameters and abnormal alarms through a 7-inch touch screen.

[0051] Further, the LSTM neural network algorithm is explained:

[0052] The system continuously collects historical load data through IoT terminals, including parameters such as hourly heating / cooling power, indoor and outdoor temperature and humidity, and personnel activity patterns, and constructs a multidimensional training data set containing time series features. After data cleaning and normalization, the data is input into a three-layer LSTM network model. The model is iteratively trained using the Adam optimizer until the loss function converges. The resulting prediction model can capture the long-term dependencies of load changes, including nonlinear characteristics such as weekday / holiday patterns and the impact of sudden weather changes. During the actual operation phase, the controller updates the input data (current load, weather forecast, schedule, etc.) every 10 minutes, and uses a sliding window mechanism to input 72 consecutive hours of historical data and the predicted values ​​of external variables for the next 12 hours into the trained LSTM model, and finally outputs the time-based load demand curve.

[0053] Furthermore, the model predictive control (MPC) algorithm is described as follows:

[0054] Further, the PID control algorithm is explained:

[0055] When the user-end temperature sensor detects that the actual temperature deviates from the set value by ±1°C, the intelligent controller immediately starts the three-loop cascade PID control architecture - the outer loop temperature PID takes the temperature deviation as input (proportional coefficient Kp=0.8, integral time Ti=120s, differential time Td=30s) to calculate the target supply and return water temperature difference set value. The middle loop temperature difference PID outputs the target flow adjustment value based on the deviation between the actual difference measured by the supply and return water temperature sensor and the target temperature difference (proportional coefficient Kp=1.2, Ti=60s, Td=15s). The inner loop flow PID accurately adjusts the opening of the electric flow control valve through the feedback signal of the electromagnetic flowmeter to form a closed-loop control.

[0056] The user-side heat exchanger is a radiant floor or fan coil unit. The radiant floor uses PEX-A pipes embedded in the concrete layer, with a pipe spacing of 100-200mm, a water supply temperature of 35-45℃, and a fan coil unit air volume of 500-1500m 3 / h, the outlet water temperature is 7-12℃ during cooling, the heat exchanger switches between heating and cooling modes via a three-way valve, the valve body has a pressure resistance of 1.6MPa and a leakage rate of ≤0.1%. In heating mode, the system directly provides hot water from the thermal storage device or heat pump unit. In cooling mode, the cold water generated by the heat pump unit first flows through the thermal storage device for pre-cooling before being delivered to the fan coil unit.

[0057] Further, the workflow of the present invention is described, specifically:

[0058] The heat transfer fluid enters the main heat exchange channel through the fluid inlet, and when flowing through multiple independent heat storage units in the sealed shell, it exchanges heat with the composite organic paraffin or inorganic hydrated salt phase change material in the unit. When charging, the phase change material absorbs heat, melts to dissipate heat and store energy, and solidifies to release heat and supply energy when releasing heat. The metal fin array or graphene thermal conductive grid significantly enhances the heat transfer efficiency, and finally the fluid is output through the outlet.

[0059] During periods of low electricity prices, the heat pump unit starts and transfers heat energy to the phase change heat storage device for energy storage through the first cycle of the dual-circulation pipeline. The phase change material undergoes phase change after absorbing heat. During peak electricity consumption or heating demand periods, the system automatically switches to the second cycle. The heat storage device releases the stored heat energy and heats the building space through the user-side heat exchanger. At this time, the switching valve cuts off the direct energy supply path of the heat pump unit.

[0060] The intelligent controller uses an ARM Cortex-M7 processor to collect data from the temperature sensor array and user-end temperature sensors in real time. Combined with time-of-use electricity price information obtained through 4G / Wi-Fi networking, it uses an LSTM neural network algorithm to predict user load demand for the next 12 hours. During the off-peak hours (0:00-8:00), the heat pump unit is automatically controlled to operate at 80-100% of the rated power. Through the first cycle, a high-temperature heat transfer fluid at 50-60°C is transported to the thermal storage device for heat and energy storage. At the same time, a model predictive control (MPC) algorithm optimizes the charging rate and temperature curve.

[0061] When the user-end temperature is detected to deviate from the set value by ±1°C, the PID control algorithm is immediately triggered, and the flow control valve opening is dynamically adjusted to stabilize the supply and return water temperature difference within the range of 5-10°C. If the temperature continues to be 2°C lower than the set value for 10 minutes, the heat pump unit will be automatically started for auxiliary heating. The system automatically generates an energy efficiency report every day that includes heat storage efficiency (≥85%), power saving data and equipment status, and displays real-time operating parameters and abnormal alarms on a 7-inch touch screen.

[0062] In the charging mode, the first cycle transports the high-temperature heat transfer fluid generated by the heat pump unit to each heat storage unit through the inlet of the heat storage device, allowing the phase change material to store heat. In the heat release mode, it switches to the second cycle, and the thermal energy fluid released at the outlet of the heat storage device is transported to the user-end heat exchanger through a pipeline for heating. The three-way switching valve realizes rapid conversion between the two modes, and the precise control of the flow regulating valve ensures that the flow distribution error of each branch is controlled within ±5%.

[0063] Furthermore, the present invention provides an embodiment of a phase change thermal storage HVAC system for office buildings:

[0064] The system consists of 6 parallel heat storage units, each with a capacity of 15kWh. It uses composite organic paraffin phase change materials and copper fin arrays to enhance heat transfer. The heat pump unit has a rated power of 30kW and runs at 25kW for 4 hours during the off-peak period at night (22:00-6:00) to fully charge the heat storage device. During the day, the second cycle of the double-circulation pipeline is used to supply radiant floor heat to the 2,000-square-meter office area. Actual measurements show that the system can maintain an indoor temperature of 22±0.5℃ at an outdoor temperature of -5℃, saving 52% energy compared to traditional electric boiler systems, with an investment payback period of 3.8 years.

[0065] Furthermore, the present invention provides an embodiment for application in a hospital HVAC system:

[0066] The device consists of 12 detachable heat storage units, using sodium acetate trihydrate phase change material and graphene thermal conductive grid. The units are connected by quick clamp connectors. The system can flexibly configure 4-12 units according to the needs of each ward in the hospital. The heat pump unit and the heat storage device work together to achieve 24-hour stable heating through the intelligent controller. Monitoring data shows that even in high-requirement areas such as operating rooms, the temperature fluctuation does not exceed ±0.3℃, and the operating noise is reduced by 15 decibels, meeting the special environmental requirements of the hospital.

Claims

1. A phase change thermal storage device, characterized in that: Includes: A sealed shell, used to encapsulate the phase change material and withstand working pressure; Multiple independent heat storage units are arranged in the shell, each heat storage unit contains phase change material and enhanced heat transfer structure for efficient storage and release of heat energy; A main heat exchange channel running through the heat storage unit for circulating heat transfer fluid; The fluid inlet and fluid outlet communicated with the main heat exchange channel are used to connect to an external heat source or a heat exchange circuit at the user end.

2. A phase change thermal storage device according to claim 1, characterized in that: The phase change material is a composite organic paraffin or an inorganic hydrated salt, the phase change temperature of which is adjusted within the range of 15-60°C by adjusting the material composition ratio, and the latent heat value is ≥180kJ / kg. The composite organic paraffin comprises a mixture of a paraffin matrix and nano-alumina particles, with a mass ratio of 3-8%, which is used to inhibit phase separation during the phase change process. The inorganic hydrated salt is modified sodium acetate trihydrate, with 1-5% of a nucleating agent and 2-10% of a thickener added. The phase change material is encapsulated in a sealed capsule made of high-density polyethylene or aluminum-plastic composite film, with a capsule wall thickness of 0.5-2mm and a compressive strength of ≥0.3MPa.

3. The phase change thermal storage device according to claim 1, characterized in that: The enhanced heat transfer structure includes a metal fin array or a graphene thermal conductive grid, wherein the metal fin array is made of copper, the fin spacing is 5-15mm, the height is 20-50mm, the thickness is 0.5-2mm, and the surface is anodized. The graphene thermal conductive grid is made of a composite pressing of multi-layer graphene sheets and epoxy resin, the grid aperture is 1-5mm, and it is filled with phase change material to form a three-dimensional heat conduction path. The contact area between the heat transfer structure and the phase change material accounts for ≥60%, and it is fixed to the support frame inside the shell by welding or snapping.

4. The phase change thermal storage device according to claim 1, characterized in that: The heat storage unit uses modular packaging. The standard capacity of a single heat storage unit is 5-20kWh. It has a cubic shape with a side length of 200-500mm. The units are connected by detachable connectors, including quick clamp connectors and flange bolts. The connectors have a temperature resistance range of -20-100°C. The modular combination supports parallel or series topology. When in parallel, the fluid is uniformly distributed through the collecting pipe. When in series, U-shaped elbows are used to connect adjacent units. The module housing is provided with standardized interfaces, which are compatible with the piping systems of different manufacturers.

5. The phase change thermal storage device according to claim 1, characterized in that: The inner wall of the shell is covered with a corrosion-resistant nano-coating made of polytetrafluoroethylene with a thickness of 50-200 μm, which is resistant to corrosion from fluids with a pH value of 3-11. A pressure balancing valve is provided on the top of the shell, and the valve body opening pressure is 0.1-0.3 MPa, which is used to release the gas generated by the volume change of the phase change material. The shell has an embedded temperature sensor array, which includes at least 6 PT100 platinum resistance probes evenly distributed in the gaps between the thermal storage units, with a measurement accuracy of ±0.5°C. The signal is transmitted to an external controller via RS485 or wirelessly. The bottom of the shell is equipped with a shock-proof bracket, which is made of Q235 carbon steel coated with a rubber shock-absorbing layer and has a load-bearing capacity of ≥500 kg.

6. A heating and ventilation system, using a phase change thermal storage device according to claims 1-5, characterized in that: Also includes: Heat pump unit, used to provide heat source or cold source, and work in conjunction with phase change thermal storage device; Double circulation pipeline, connecting the main heat exchange flow channel of the heat pump unit and the phase change heat storage device; The user-end heat exchanger is used to provide heating or cooling to the indoor space, and selects direct energy supply from the heat storage device or the heat pump unit through a switching valve.

7. A HVAC system according to claim 6, characterized in that: The dual-circulation pipeline includes a first circulation and a second circulation, wherein the first circulation connects the outlet of the heat pump unit and the inlet of the heat storage device, and is used to transport the high-temperature heat transfer fluid to the heat storage device to store heat energy in the heat charging mode; the second circulation connects the outlet of the heat storage device and the inlet of the user-end heat exchanger, and is used to transport the heat energy released by the heat storage device to the user-end in the heat release mode. The two circulations realize mode conversion through a three-way switching valve. The inner diameter of the pipeline is 25-50mm, and it is covered with a 30mm thick polyurethane insulation layer. The heat loss rate is ≤5%. The first circulation and the second circulation can operate independently or synchronously, and the flow distribution of each branch is controlled by a flow regulating valve.

8. The HVAC system according to claim 6, characterized in that: The system also includes an intelligent controller, which controls the start and stop and power distribution of the heat pump unit and the heat storage device based on electricity price signals, user load forecasts and temperature feedback.

9. The HVAC system according to claim 6, characterized in that: The user-side heat exchanger is a radiant floor or fan coil unit. The radiant floor uses PEX-A pipes embedded in the concrete layer, with a pipe spacing of 100-200mm, a water supply temperature of 35-45℃, and a fan coil unit air volume of 500-1500m 3 / h, the outlet water temperature is 7-12℃ during cooling, the heat exchanger switches between heating and cooling modes via a three-way valve, the valve body has a pressure resistance of 1.6MPa and a leakage rate of ≤0.1%. In heating mode, the system directly provides hot water from the thermal storage device or heat pump unit. In cooling mode, the cold water generated by the heat pump unit first flows through the thermal storage device for pre-cooling before being delivered to the fan coil unit.

10. The HVAC system according to claim 8, characterized in that: The hardware core of the intelligent controller is an ARM Cortex-M7 processor with a built-in load forecasting algorithm and optimization control module. The controller collects data from the temperature sensor array in real time and, combined with time-of-use electricity price information, prioritizes starting the heat pump unit to charge the thermal storage device during off-peak hours. During peak hours, it switches to the thermal storage device for independent power supply. When the user-end temperature deviates from the set value by ±1°C, the PID algorithm is triggered to adjust the power of the heat pump unit or the switching valve opening. The adjustment cycle is adjustable from 10 to 60 seconds. The controller is equipped with a 7-inch touch screen and supports manual mode to override the automatic strategy.

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