An enhanced heating system based on cascade heat storage device

Abstract

The present invention discloses an enhanced heating system based on a cascade heat storage device, belonging to the technical field of domestic heat supply systems. The system comprises a phase-change heat storage device and a water tank installed indoors, and a solar collector installed outdoors. The solar collector is connected to both ends of the heat charging pipe of the phase-change heat storage device via pipelines, and the water tank is connected to the heat discharge pipe of the phase-change heat storage device via pipelines. The heat charging pipe is approximately heart-shaped. The water tank is connected to a domestic water inlet and a heat user-side outlet. An auxiliary electric heating device is installed in the water tank. The enhanced heating system based on the cascade heat storage device exemplified in the present invention has a simple structure, high solar energy utilization, and can ensure efficient hot water supply in various weather conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of domestic water supply systems, and in particular to an enhanced heating system based on a cascade heat storage device. Background Art

[0002] Solar energy is humanity's earliest renewable energy source, boasting advantages such as widespread distribution, easy availability, renewability, and environmental friendliness. Currently, solar energy is most commonly used for solar power generation and solar water heating, and the technology is relatively mature. While solar water heating technology has many advantages, it cannot operate on cloudy days, at night, or rainy days due to a lack of sunlight. Therefore, it is necessary to store the heat generated by the sun and release it during periods of low sunlight to ensure that the system can provide hot water around the clock. Currently, most existing technologies use natural gas or heat pumps as heat sources, making it difficult to guarantee hot water supply in areas without natural gas supply or during inclement weather. Existing heat storage technologies include thermochemical heat storage, sensible heat storage, and phase change heat storage. Phase change heat storage has a heat storage density 5 to 10 times higher than sensible heat storage, or even higher. Phase change heat storage has been widely researched due to its advantages of constant temperature and high heat storage density.

[0003] Patent No. CN2851981Y discloses a solar water heater phase change heat storage device, which utilizes the property of storing or releasing a large amount of heat during the phase change process of crystals. It includes a phase change heat storage device filled with crystals, and a bracket installed on the outside of a circular cylinder to form a heat storage device. When the weather is clear, the water temperature in the solar water heater water tank continues to rise, causing the material in the phase change heat storage device to absorb heat and change from solid to liquid. When there is no sunlight, the material in the phase change heat storage device begins to change from liquid to solid, generating a large amount of heat, causing the water temperature in the water tank to rise, ensuring that hot water of a certain temperature is available for use. The disadvantages of the above-mentioned prior art are: (1) a single phase change heat storage material is used, and its heat storage and heat release performance is relatively weak compared to multi-stage phase change heat storage devices; (2) it can only charge or release heat separately, and cannot charge and release heat at the same time, which cannot meet the requirements of heat users for simultaneous charging and releasing heat; (3) due to the use of a phase change material with a single melting point, it is impossible to store and utilize heat energy according to quality.

[0004] Patent No. CN112414193B discloses a multi-stage phase-change heat storage device with built-in fins and a method for enhancing heat transfer. A heat transfer fluid flows through each phase-change heat storage unit through a heat transfer fluid channel. The fins are built into each phase-change heat storage unit on the phase-change material side and close to the outer wall of the heat transfer fluid channel. The disadvantages of the above-mentioned prior art are: (1) the heat exchange tube is located in the center, resulting in slow melting of the phase-change material at the bottom; (2) while the addition of fins enhances the performance of the heat storage device, it increases manufacturing costs and reduces the amount of phase-change material filled. Summary of the Invention

[0005] In order to address the deficiencies in the prior art described above, the present invention aims to provide an enhanced heating system based on a cascade heat storage device, which has a simple structure, high solar energy utilization rate, and can ensure efficient hot water supply under different weather conditions.

[0006] The technical solution adopted by the present invention to solve the technical problem is:

[0007] Provided is an enhanced heating system based on a cascade heat storage device, comprising a phase change heat storage device and a water tank disposed indoors, and a solar heat collector disposed outdoors, wherein the solar heat collector is connected to both ends of a heat charging pipe of the phase change heat storage device via pipelines, and the water tank is connected to the heat dissipation pipe of the phase change heat storage device via pipelines;

[0008] The heat-filling tube is approximately heart-shaped;

[0009] The water tank is connected with a domestic water inlet and a heat user side outlet, and an auxiliary electric heating device is provided in the water tank.

[0010] Furthermore, the phase change heat storage device is filled with a phase change material, and the phase change material is composed of three materials, namely lauric acid, Mg(NO3)2·6(H2O)NH4NO3 and paraffin.

[0011] Furthermore, the heat charging tube is located below the heat releasing tube.

[0012] Furthermore, the liquid flow directions in the heat charging tube and the heat releasing tube are opposite.

[0013] Furthermore, the outlet end of the heat release pipe is connected to the upper part of the water tank through a pipeline, and the inlet end is connected to the lower part of the water tank through a pipeline;

[0014] The domestic water inlet is communicated with the lower part of the water tank, and the heat user side outlet is communicated with the upper part of the water tank.

[0015] Furthermore, a radiator is provided on the pipeline connecting the outlet of the heat charging pipe and the solar collector.

[0016] Furthermore, it also includes an air source heat pump connected to the water tank.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. In the enhanced heating system based on the cascade heat storage device of the present invention, the heat-charging tube adopts a tube with a nearly heart-shaped structure (hereinafter referred to as the heart-shaped tube). Compared with the circular tube, the liquid phase velocity of the phase change material is slightly higher under the condition that the power of the heat-releasing tube remains the same, and the heat storage rate of the heat-charging tube is higher.

[0019] 2. In the enhanced heating system based on the cascade heat storage device of the present invention, the heat exchange fluid in the heat-charging tube flows from the high-melting-point phase change material to the low-melting-point phase change material, and the heat exchange fluid in the heat-releasing tube flows from the low-melting-point phase change material to the high-melting-point phase change material, thereby avoiding the waste of high-grade heat and improving the utilization rate of low-grade heat;

[0020] 3. The enhanced heating system based on the cascade heat storage device of the present invention uses different pipes for the heat charging pipe and the heat dissipation pipe. Therefore, the heat storage and heat dissipation processes can be carried out simultaneously without affecting each other, which greatly improves the adaptability to actual conditions.

[0021] 4. In the enhanced heating system based on the cascade heat storage device of the present invention, the heat charging pipe is located below the heat releasing pipe. The heat charging pipe is placed in the lower middle part. Compared with placing the heat charging pipe in the upper middle part, this design strengthens the natural convection during the heat absorption and melting process of the phase change material, accelerates the melting speed of the phase change material, and improves the heat charging efficiency.

[0022] 5. In the enhanced heating system based on the cascade heat storage device of the present invention, the phase change material uses three materials connected in series or in parallel. The phase change temperatures of the phase change materials are arranged in series or in parallel in the direction of the flow of the heat pipe fluid from high to low. Studies have shown that the heat storage performance is better when the phase change heat storage units are connected in series.

[0023] 6. In the enhanced heating system based on the cascade heat storage device of the present invention, since the water tank is large, the water inside the water tank will be stratified due to different temperatures. The high-temperature domestic water is in the upper part of the water tank, and the low-temperature domestic water is in the bottom of the water tank. Therefore, the system sets the domestic water inlet at the bottom of the water tank, so that the low-temperature domestic water introduced into the water tank is directly injected into the bottom of the water tank. When the domestic water is taken out of the heat user side, it is drawn from the upper part of the water tank. This minimizes the mixing of the stratified domestic water in the water tank and improves the overall system efficiency.

[0024] 7. In the enhanced heating system based on the cascade heat storage device of the present invention, due to the influence of natural weather, the heat generated by the solar collector may sometimes not meet the heat demand of the heat user side. In this case, an auxiliary electric heating device and an air source heat pump can be used to auxiliary heat the domestic water;

[0025] 8. In the enhanced heating system based on the cascade heat storage device exemplified in the present invention, although the thermal efficiency of the air source heat pump is much higher than that of the auxiliary electric heating device, when the external environment is extremely cold, if the air source heat pump is used, the water generated by the compressed air during the heat generation process of the air source heat pump will not have time to be discharged from the air source heat pump, and will have frozen inside the air source heat pump, making the air source heat pump itself and the pipes transporting domestic water extremely vulnerable to damage. Therefore, in extremely cold weather, an auxiliary electric heating device should be used for auxiliary heating. This design increases the adaptability of the system to the environment;

[0026] 9. The enhanced heating system based on the cascade heat storage device of the present invention uses three phase change materials with different melting points. Therefore, it can use different heat sources as the outdoor temperature changes. When the outdoor temperature is high, the heat can be directly sent to the radiator for heating after flowing through the area with the lowest phase change temperature or the area with the lowest phase change temperature and the medium temperature area through the heat release pipe, thereby increasing energy utilization.

[0027] 10. The enhanced heating system based on the cascade heat storage device in the example of the present invention can store the heat at the collector outlet separately according to the different qualities of the heat at the collector outlet, because the different solar irradiance will cause the temperature of the solar collector to change. In addition, according to the different uses of the heat users, the area and flow rate of the heat exchange fluid entering the heat release tube of the phase change heat storage device are adjusted to obtain water with a temperature that meets the needs of the heat users, thereby further improving energy utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0029] Figure 1 It is a schematic diagram of the structure of the present invention;

[0030] Figure 2 is a cross-sectional view of a phase change heat storage device;

[0031] Figure 3 This is a comparative analysis diagram of the heat storage and release rates of a heart-shaped heat-charging tube and a circular heat-charging tube with the same hydraulic radius under the flow conditions of the heat exchange fluid with the same mass flow rate.

[0032] In the figure: 1-phase change heat storage device, 2-water tank, 3-solar collector, 4-domestic water inlet, 5-heat user side outlet, 6-auxiliary electric heating device, 7-air source heat pump, 8-radiator, 9-heat charging pipe, 10-heat releasing pipe, 11-phase change material. DETAILED DESCRIPTION

[0033] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the invention are shown in the accompanying drawings.

[0034] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] like Figure 1-2As shown, this embodiment provides an enhanced heating system based on a cascade heat storage device, including a phase change heat storage device 1 and a water tank 2 installed indoors, and a solar thermal collector 3 installed outdoors. The solar thermal collector 3 is connected to both ends of the heat charging pipe 9 of the phase change heat storage device 1 via pipelines, and the water tank 2 is connected to the heat release pipe 10 of the phase change heat storage device 1 via pipelines. The high-temperature working fluid heated by the solar thermal collector 3 enters the heat charging pipe 9. In the phase change heat storage device 1, the high-temperature working fluid undergoes heat exchange with the phase change material 11 to become a low-temperature working fluid, which then flows back into the solar thermal collector 3 to be heated. The water in the water tank 2 enters the heat release pipe 10, undergoes heat exchange with the phase change material 11, and then the heated high-temperature domestic water is sent to the water tank 2 for storage. In addition, a radiator 8 is provided on the pipeline connecting the outlet of the heat charging pipe 9 to the solar thermal collector 3, which can be used to heat the room.

[0036] In this embodiment, the heat charging tube 9 is approximately heart-shaped, and the heat charging tube 9 is located above the heat releasing tube 10. Compared with the circular tube, the heart-shaped tube has a smaller entropy generation, the liquid phase rate of the phase change material 11 is faster, and the heat releasing tube can release higher power after the liquid phase rate is stable. The heat charging tube 9 is placed in the lower middle part. Compared with placing the heat charging tube 9 in the upper middle part, this design strengthens the natural convection during the heat absorption and melting process of the phase change material 11, accelerates the melting rate of the phase change material 11, and improves the heat charging efficiency. In addition, the flow direction of the liquid in the heat charging tube 9 is opposite to that in the heat releasing tube 10, so that when the domestic water flows through the heat exchange pipe, the temperature of the surrounding phase change material 11 gradually increases, so that the domestic water is gradually heated, reducing the amount of entropy generated in the process of heating domestic water and improving heat utilization. The heat charging pipe 9 and the heat releasing pipe 10 of the phase change heat storage device 1 are designed independently. Since the heat charging pipe 9 and the heat releasing pipe 10 use different pipes, the heat storage and heat releasing processes can be carried out simultaneously without affecting each other, which greatly improves the adaptability to actual conditions.

[0037] The time a household uses hot water for a single time is generally 10 to 30 minutes (such as showering). To make it more realistic, the heat storage and release rates of a single pair of hot and cold pipes were simulated when the phase change material was completely solidified (phase change material 15°C) and the phase change material was completely melted (phase change material 60°C) and the hot and cold pipes were working simultaneously for half an hour.

[0038] Figure 3 The heat storage and release rates for the heart-shaped and circular tubes, both in the fully melted and solidified states of the phase change material, are shown at the same mass flow rate and hydraulic radius. As can be seen from the figure, the heart-shaped tube has higher heat storage and release efficiencies than the circular tube.

[0039] The heat charging tube adopts a heart-shaped tube with a concave cross-section at the upper end. During the simultaneous charging and discharging process, the amount of solid phase change material sandwiched between the heat charging tube and the heat discharging tube is reduced, thereby improving the stability of the domestic water temperature at the heat discharging pipe outlet of the phase change material heat storage device, thereby reducing the fluctuation of the domestic water temperature at the outlet of the phase change material heat storage device.

[0040] In addition, the phase change material 11 of this embodiment is made of three materials connected in series, and the phase change material 11 is lauric acid, Mg(NO3)2.6(H2O)NH4NO3 and paraffin.

[0041] In addition, the outlet end of the heat release pipe 10 is connected to the top of the water tank 2 through a pipeline, and the inlet end is connected to the bottom of the water tank 2 through a pipeline; the domestic water inlet 4 is connected to the bottom of the water tank 2, and the heat user-side outlet 5 is connected to the top of the water tank 2. Since the water tank 2 used is relatively large, the water inside the water tank 2 will produce stratification due to different temperatures, with high-temperature domestic water at the top of the water tank 2 and low-temperature domestic water at the bottom of the water tank 2. Therefore, the system sets the domestic water inlet 4 at the bottom of the water tank 2, so that the low-temperature domestic water introduced into the water tank 2 is directly injected into the bottom of the water tank 2, while the domestic water for heating on the heat user side is drawn from the top of the water tank 2. This minimizes the mixing of stratified domestic water in the water tank 2 and improves the overall system efficiency.

[0042] In this embodiment, the water tank 2 is further provided with an auxiliary electric heating device 6, and the water tank 2 is also connected to an air source heat pump 7. If the heat generated by the solar collector 3 is insufficient to heat the domestic water to the temperature required by the heat user due to reasons such as cloudy weather or nighttime, the auxiliary electric heating device 6 or the air source heat pump 7 can be used to auxiliary heat the domestic water in the water tank 2. Finally, when the domestic water in the water tank 2 meets the heat user's demand, the high-temperature domestic water is discharged through the heat user-side outlet 5, thereby achieving the purpose of meeting the user's domestic hot water demand. Although the air source heat pump 7 has a much higher thermal efficiency than the auxiliary electric heating device 6, when the external environment is extremely cold, if the air source heat pump 7 is used, the water generated by the compressed air during the heat generation process of the air source heat pump 7 will not have time to be discharged from the air source heat pump 7 and will have already frozen inside the air source heat pump 7, making the air source heat pump 7 itself and the pipes that transport the domestic water extremely vulnerable to damage. Therefore, the auxiliary electric heating device 6 should be used for auxiliary heating in extremely cold weather. This design increases the adaptability of the system to the environment while minimizing power consumption, thereby saving costs.

[0043] Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also includes other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, the above-mentioned features can be replaced with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An enhanced heating system based on a cascade heat storage device, characterized in that: The invention comprises a phase-change heat storage device (1) and a water tank (2) arranged indoors, and a solar heat collector (3) arranged outdoors, wherein the solar heat collector (3) is respectively connected to both ends of a heat charging pipe (9) of the phase-change heat storage device (1) through pipelines, and the water tank (2) is respectively connected to a heat releasing pipe (10) of the phase-change heat storage device (1) through pipelines. The heat-filling tube (9) is approximately heart-shaped; The water tank (2) is connected to a domestic water inlet (4) and a heat user-side outlet (5), and an auxiliary electric heating device (6) is provided in the water tank (2).

2. The enhanced heating system based on the cascade heat storage device according to claim 1, characterized in that: The phase change heat storage device (1) is filled with a phase change material (11), and the phase change material (11) is composed of three materials, namely lauric acid, Mg(NO3)2·6(H2O)NH4NO3 and paraffin.

3. The enhanced heating system based on the cascade heat storage device according to claim 1, characterized in that: The heat charging pipe (9) is located below the heat releasing pipe (10).

4. The enhanced heating system based on the cascade heat storage device according to claim 1, characterized in that: The liquid flow directions in the heat charging tube (9) and the heat releasing tube (10) are opposite.

5. The enhanced heating system based on the cascade heat storage device according to claim 1, characterized in that: The outlet end of the heat release pipe (10) is connected to the upper part of the water tank (2) through a pipeline, and the inlet end is connected to the lower part of the water tank (2) through a pipeline; The domestic water inlet (4) is in communication with the lower portion of the water tank (2), and the heat user-side outlet (5) is in communication with the upper portion of the water tank (2).

6. The enhanced heating system based on the cascade heat storage device according to claim 1, characterized in that: A radiator (8) is provided on a pipeline connecting the outlet of the heat charging pipe (9) and the solar heat collector (3).

7. The enhanced heating system based on the cascade heat storage device according to claim 1, characterized in that: It also includes an air source heat pump (7) in communication with the water tank (2).

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