A hydrated salt phase separation inhibition system

Abstract

The invention discloses a hydrated salt phase separation suppression system, comprising: a heat storage device and a liquid medium layer composed of a liquid medium; the heat storage device comprises: a circulation pipe, an inner tank filled with a hydrated salt phase change material, and a jet nozzle arranged at the bottom of the inner tank; the melting point and density of the liquid medium are lower than those of the hydrated salt phase change material, and the boiling point is higher than the highest heat storage temperature of the heat storage device; the liquid medium layer covers the surface of the hydrated salt phase change material; the circulation pipe is connected to the jet nozzle; when the hydrated salt phase change material is in the heat release stage, and the temperature is between the freezing point temperature and the heat release starting temperature, the circulation pipe intermittently transports the liquid medium to the jet nozzle and then sprays it out, so as to form a forced turbulent dispersion effect in the hydrated salt phase change material. The invention effectively realizes the cyclic phase separation suppression of the hydrated salt phase change material without adding any additives.

Description

Technical Field

[0001] The invention relates to the technical field of phase change energy storage, and in particular to a hydrated salt phase separation inhibition system. Background Art

[0002] Phase change heat storage device is a device that uses phase change materials to absorb / release a large amount of latent heat during the melting / solidification process to store and utilize heat. The core is the stability and thermal performance parameters of phase change materials. The device has been widely used in power system peak regulation, solar energy utilization, aerospace, waste heat recovery, heating and air conditioning, and household appliance industries. Among the existing phase change energy storage materials, inorganic hydrated salts are an important type of phase change material. They have the advantages of wide range of use, large thermal conductivity, large phase change latent heat, low toxicity, and low price. Therefore, they have been used in phase change heat storage devices. However, during the application process, when the solid phase and liquid phase of the phase change material coexist, part of the solid phase is not completely dissolved in the liquid phase, but sinks to the bottom of the container to form a layer, and the phenomenon of "phase separation" occurs. This phenomenon seriously restricts its cycle life in the phase change heat storage device.

[0003] A large number of related studies have been carried out at home and abroad on the phase separation problem of hydrated salt phase change materials, and a variety of methods such as stirring method, thickener method, shallow dish container method, and additional water method have been proposed to inhibit the phase separation of phase change materials. Among the above-mentioned phase separation inhibition methods, the phase change heat storage device currently mainly uses the thickener method to inhibit the phase separation phenomenon of hydrated salts. However, experimental analysis and practical application show that the addition of thickeners to the matrix phase change energy storage material will lead to a decrease in the thermal conductivity of the matrix phase change energy storage material and a decrease in the heat storage rate, and as the addition ratio increases, the heat storage density of the matrix heat storage material also decreases. After a certain period of use, the thickener in the matrix material will fail under repeated temperature shocks, thereby losing the effect of phase separation inhibition, and ultimately leading to the failure of the entire heat storage device. Therefore, it is necessary to improve the existing heat storage device to extend the cycle life of the material while ensuring that the structure and heat capacity of the matrix phase change energy storage material are not destroyed. Summary of the invention

[0004] The purpose of the present invention is to improve the existing heat storage device and extend the cycle service life of the material without destroying the structure and heat capacity of the matrix phase change energy storage material.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a hydrated salt phase separation inhibition system, comprising: a heat storage device and a liquid medium layer composed of a liquid medium; the heat storage device comprises: a circulation pipe, an inner tank filled with a hydrated salt phase change material, and a jet nozzle arranged at the bottom of the inner tank; the melting point and density of the liquid medium are lower than those of the hydrated salt phase change material, and the boiling point is higher than the maximum heat storage temperature of the heat storage device; the liquid medium layer covers the surface of the hydrated salt phase change material; the circulation pipe is connected to the jet nozzle; when the hydrated salt phase change material is in the heat release stage and the temperature is between the freezing point temperature and the heat release starting temperature, the circulation pipe intermittently transports the liquid medium to the jet nozzle and then sprays it out to form a forced turbulence dispersion effect in the hydrated salt phase change material.

[0006] Optionally, the liquid medium is liquid paraffin or silicone oil.

[0007] Optionally, the hydrated salt phase change material is sodium sulfate decahydrate.

[0008] Optionally, the heat storage device further comprises: a jet pump provided on the circulation pipe and used for pumping the liquid medium.

[0009] Optionally, the heat storage device further comprises: a temperature sensor disposed on the inner tank and used to monitor the temperature change of the hydrated salt phase change material.

[0010] Optionally, the heat storage device further comprises: a heat exchange coil for storing / releasing heat from the hydrated salt phase change material, wherein the heat exchange coil is buried in the hydrated salt phase change material.

[0011] Optionally, the heat storage device further includes: a thermal insulation layer, which is wrapped around the outside of the inner tank and is made of polyurethane or rock wool.

[0012] Optionally, a vent hole communicating with the atmosphere is provided on the wall of the inner container.

[0013] Optionally, the number of the jet nozzles is 3-12.

[0014] Optionally, a corrosion-resistant layer is sprayed on the surface of the inner liner.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] (1) By adopting the intermittent jet method, the present invention effectively solves the phase separation problem of liquid hydrated salt phase change material by only using a jet pump and a jet nozzle without using any additives or changing the properties of the matrix phase change material;

[0017] (2) Based on the jet disturbance mechanism, the present invention can not only evenly disperse the precipitated granular phase change material, but also enhance the heat release process of the hydrated salt phase change material. This process has an obvious jet disturbance enhanced heat transfer effect, thus improving the heat release efficiency of the heat storage device.

[0018] (3) The present invention uses a liquid medium with a melting point lower than that of the corresponding phase change material and a boiling point higher than the heat storage termination temperature as a jet pump to spray the turbulent medium, and uses an internal circulation spraying method to avoid the use of an external gas source or liquid source. At the same time, the liquid medium used does not react with the hydrated salt phase change material, so it can also protect the phase change material from contact with the air and extend the service life of the hydrated phase change material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the hydrated salt phase separation inhibition system of the present invention.

[0020] Figure 2 A top view of the jet nozzle arrangement at the bottom of the inner tank (4 nozzles).

[0021] 1-hydrated salt phase change material, 2-inner tank, 3-heat exchange coil, 4-insulation layer, 5-outer shell, 6-liquid medium, 7-heat exchange medium inlet, 8-heat exchange medium outlet, 9-vent, 10-temperature sensor, 11-jet pump, 12-solenoid valve, 13-circulation pipe, 14-check valve, 15-jet nozzle, 16-control system. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0023] like Figure 1 As shown, it is a schematic diagram of the structure of the hydrated salt phase separation suppression system of the present invention. The hydrated salt phase separation suppression system of the present invention comprises: a heat storage device and a liquid medium layer composed of a liquid medium 6. The melting point of the liquid medium 6 is much lower than the melting point of the hydrated salt phase change material 1, the boiling point is much higher than the maximum heat storage temperature of the heat storage device, the density is less than the density of the hydrated salt phase change material 1, and it is immersed / covered on the hydrated salt phase change material 1. The heat storage device comprises: a circulation pipe 13, an inner tank 2 filled with a hydrated salt phase change material 1, and a jet nozzle 15 arranged at the bottom of the inner tank 2. The circulation pipe 13 is connected to the jet nozzle 15. When the hydrated salt phase change material 1 is at a temperature from the freezing point to the exothermic starting temperature, the circulation pipe 13 transports the liquid medium 6 to the jet nozzle 15 and then sprays it out to form a forced turbulence in the hydrated salt phase change material 1, uniformly disperse the granular hydrated salt phase change material 1 precipitated at the bottom of the inner tank 2, and suppress the phase separation phenomenon of the hydrated salt phase change material 1.

[0024] Please continue reading Figure 1The heat storage device includes: an inner tank 2, a heat exchange coil 3, an insulation layer 4, an outer shell 5, a liquid medium 6, a heat exchange medium inlet 7, a heat exchange medium outlet 8, a vent 9, a temperature sensor 10, a jet pump 11, a solenoid valve 12, a circulation pipe 13, a check valve 14, a jet nozzle 15 and a control system 16.

[0025] In some embodiments, the inner liner 2 can be made of a metal material resistant to hydrated salt corrosion or a steel material sprayed with a corrosion-resistant layer.

[0026] The heat exchange coil 3 is fixed in the heat storage device and buried in the hydrated salt phase change material 1. It is a metal pipe resistant to hydrated salt corrosion or a steel pipe sprayed with a corrosion-resistant layer. The function of the heat exchange coil 3 is to pass the heating / cooling medium inside to achieve heat storage / release of the hydrated salt phase change material 1. The heating / cooling medium enters from the heat exchange medium inlet 7 and leaves from the heat exchange medium outlet 8.

[0027] The heat-insulating layer 4 of the heat storage device is located between the inner liner 2 and the outer shell 5 and can be made of polyurethane or rock wool materials, and mainly plays a role of heat preservation.

[0028] There is no reaction between the liquid medium 6 and the hydrated salt phase change material 1, and the melting point temperature and the freezing point temperature of the hydrated salt phase change material 1 are the same. According to the properties of the hydrated salt phase change material 1, the liquid medium 6 can be a medium such as liquid paraffin or silicone oil. After the liquid medium 6 is sprayed out from the bottom of the inner tank 2, the low-density liquid medium 6 can float again and cover the surface of the hydrated salt phase change material 1 to form a circulation loop. This method avoids the use of external gas and liquid sources, and reduces the use cost of the heat storage device. At the same time, the liquid medium 6 protects the hydrated salt phase change material 1 from contact with the air, thereby extending the service life of the hydrated salt phase change material 1.

[0029] The vent hole 9 is provided on the wall of the inner container 2, and its function is to communicate with the atmosphere to ensure that the device is in a normal pressure state.

[0030] The temperature sensor 10 is used to monitor the temperature change of the hydrated salt phase change material 1 during the heating and cooling process.

[0031] The circulation pipe 13 of the present invention is provided with a corresponding electromagnetic valve 12 and a check valve 14; the check valve 14 is used to prevent the backflow of the liquid medium 6 or the liquid hydrated salt phase change material 1 after the jet pump 11 stops operating.

[0032] The number of the jet nozzles 15 can be set to 3-12 according to the size of the device, and the jet intensity and jet direction can be adjusted, such as Figure 2The jet power of the jet nozzle 15 comes from the jet pump 11. In some embodiments, the forced turbulence formed by the jet nozzle 15 can also disturb the liquid hydrated salt phase change material 1, accelerate the heat transfer rate of the hydrated salt phase change material 1, and improve the heat release efficiency of the heat storage device.

[0033] The control system 16 of the present invention adopts an intermittent injection control mode, and controls the intermittent opening and closing of the jet pump 11 and the electromagnetic valve 12 under the set program conditions by sensing the temperature signal transmitted by the temperature sensor 10. The intermittent jet control mode is a constant temperature and timing control. In a specific temperature range, that is, from the freezing point temperature of the hydrated salt phase change material 1 to the exothermic starting point temperature, the control system 16 timingly and intermittently opens the jet pump 11 and the electromagnetic valve 12, thereby effectively realizing the disturbance of the liquid hydrated salt phase change material 1.

[0034] The working principle of the hydrated salt phase separation suppression system of the present invention is as follows:

[0035] During the heat storage period, the heating medium (which can be an electric boiler or solar energy to provide heat source) is fed into the heat exchange coil 3 through the heat exchange medium inlet 7, and transfers heat to the hydrated salt phase change material 1 in the heat storage device through its tube wall, so that it continuously absorbs heat and melts and the temperature rises. When the hydrated salt phase change material 1 in the heat storage device is completely melted and the temperature rises to the set value, the temperature sensor 10 will sense the corresponding temperature signal and transmit the signal value to the control system 16. The control system 16 automatically stops the circulation input of the heating medium according to the received signal and the set heating termination temperature parameter, and ends the entire heat storage process. During the entire heat storage period, the jet pump 11 and the corresponding solenoid valve 12 are never turned on.

[0036] During the heat release period, the heat storage device releases heat to the outside. At this time, the cooling medium enters the heat exchange coil 3 from the heat exchange medium inlet 7, and exchanges heat with the hydrated salt phase change material 1 through its tube wall. Since the temperature of the hydrated salt phase change material 1 is higher than the temperature of the cooling medium during this period, heat is continuously transferred from the hydrated salt phase change material 1 to the cooling medium, and the temperature of the cooling medium is increased to provide heat to the outside. When the temperature of the hydrated salt phase change material 1 in the heat storage device drops to the set value, the heat release process is completed, and the control system 16 will stop the circulation input of the cooling medium. In addition, after the hydrated salt phase change material 1 completes heat storage, it will undergo phase separation (precipitation at the bottom). Therefore, in the initial stage of heat release (during which the hydrated salt phase change material 1 is always in liquid state), the control system 16 intermittently opens the jet pump 11 and the electromagnetic valve 12 according to the set jet temperature zone (the temperature zone is the melting point temperature of the hydrated salt phase change material 1 - the heat release starting temperature), so as to form the internal circulation and turbulent flow movement of the liquid hydrated salt phase change material 1, thereby achieving the full suspension and uniform dispersion of the bottom hydrated salt phase change material 1 precipitation in the entire material area. Outside the jet temperature zone of the heat release process, the jet pump 11 and the electromagnetic valve 12 will always be in a closed state.

[0037] Example 1

[0038] Sodium sulfate decahydrate (Na2SO4·10H2O) is a typical hydrated salt phase change material 1, and its phase change temperature is 32°C, which is very suitable for use in floor heating, cooling pads and other products. However, Na2SO4·10H2O has obvious phase separation in application engineering. Therefore, this implementation case uses Na2SO4·10H2O as the hydrated salt phase change material 1 and liquid paraffin (C18) as the liquid medium 6, and the following implementation case is described.

[0039] First, according to the structural design drawing of the invention device, the device system is manufactured. After the system is manufactured, Na2SO4·10H2O is filled in the inner tank 2 of the heat storage device in the form of solid powder. After the filling of Na2SO4·10H2O is completed, the heat storage process is started through the control system 16, so that the heating medium (the temperature of the heating medium is 45°C) enters the heat exchange coil 3 to continuously transfer heat to Na2SO4·10H2O, and makes it absorb heat and melt. When Na2SO4·10H2O absorbs heat and melts completely, and the temperature reaches 40°C, the heating process is stopped. Then, liquid paraffin (C18, melting point 22°C) is immediately filled into the heat storage device, and the filling thickness is 30mm higher than the inlet of the circulation pipe 13. Finally, the heat release process is started by the control system 16, so that the cooling medium (cooling medium temperature is 25°C) enters the heat exchange coil 3 to cool the liquid Na2SO4·10H2O. From the beginning of cooling to before the Na2SO4·10H2O solidifies, the jet pump 11 and the solenoid valve 12 are opened intermittently at regular intervals to achieve internal circulation disturbance of the liquid Na2SO4·10H2O, evenly disperse the bottom phase separation precipitation and enhance convective heat transfer. The condition for opening the jet pump 11 and the solenoid valve 12 is that the hydrated salt phase change material 1 is in the cooling and heat release process, but the temperature is higher than the solidification point of the hydrated salt phase change material 1. In this case, the opening condition of the jet pump 11 and the solenoid valve 12 is the process of liquid Na2SO4·10H2O decreasing from 40°C to 33°C during the heat release process.

[0040] According to the above implementation case, the jet pump 11 and the solenoid valve 12 are always closed during the heat storage process, and are conditionally opened during the heat release process (the opening condition is that the temperature of the hydrated salt phase change material 1 is between the heat release start temperature and the freezing point temperature).

[0041] In summary, a hydrated salt phase separation inhibition system of the present invention adopts an intermittent jet method. Without adding any additives and without affecting the performance parameters of the matrix phase change material, it only uses a jet pump 11, a jet nozzle 15, a circulation pipe 13 and a solenoid valve 12 to effectively achieve the cyclic phase separation inhibition and dispersion recovery and heat transfer enhancement of the hydrated salt phase change material 1.

[0042] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A hydrated salt phase separation suppression system, characterized in that: include: A heat storage device and a liquid medium layer composed of a liquid medium (6); The heat storage device comprises: a circulation pipe (13), an inner container (2) filled with a hydrated salt phase change material (1), a control system (16), a temperature sensor (10), a jet pump (11), a solenoid valve (12), and a jet nozzle (15) arranged at the bottom of the inner container (2); The melting point and density of the liquid medium (6) are lower than those of the hydrated salt phase change material (1), and the boiling point is higher than the maximum heat storage temperature of the heat storage device; the liquid medium layer covers the surface of the hydrated salt phase change material (1); The circulation pipe (13) is connected to the jet nozzle (15); the jet direction of the jet nozzle (15) can be either horizontal or vertical; when the hydrated salt phase change material (1) is in the heat release stage and the temperature is between the solidification point temperature and the heat release starting temperature, the control system (16) adopts an intermittent injection control mode, and controls the intermittent opening and closing of the jet pump (11) and the electromagnetic valve (12) under set program conditions by sensing the temperature signal transmitted by the temperature sensor (10), so as to control the circulation pipe (13) to intermittently transport the liquid medium (6) to the jet nozzle (15) and then spray it out, so as to form a forced turbulence in the hydrated salt phase change material (1); the intermittent injection control mode is a constant temperature and timing control, and in a specific temperature range, the control system (16) opens the jet pump (11) and the electromagnetic valve (12) in a timed and intermittent manner.

2. The hydrated salt phase separation suppression system according to claim 1, characterized in that: The liquid medium (6) is liquid paraffin or silicone oil.

3. The hydrated salt phase separation suppression system according to claim 1, characterized in that: The hydrated salt phase change material (1) is sodium sulfate decahydrate.

4. The hydrated salt phase separation suppression system according to claim 1, characterized in that: The heat storage device further comprises: a temperature sensor (10) disposed on the inner container (2) and used for monitoring the temperature change of the hydrated salt phase change material (1).

5. The hydrated salt phase separation suppression system according to claim 1, characterized in that: The heat storage device further comprises: a heat exchange coil (3) for storing / releasing heat from the hydrated salt phase change material (1); the heat exchange coil (3) is buried in the hydrated salt phase change material (1).

6. The hydrated salt phase separation suppression system according to claim 1, characterized in that: The heat storage device further comprises: a heat-insulating layer (4), the heat-insulating layer (4) being wrapped around the outside of the inner liner (2) and being made of polyurethane or rock wool.

7. The hydrated salt phase separation suppression system according to claim 1, characterized in that: A vent hole (9) communicating with the atmosphere is provided on the wall of the inner container (2).

8. The hydrated salt phase separation suppression system according to claim 1, characterized in that: The number of the jet nozzles (15) is 3 to 12.

9. The hydrated salt phase separation suppression system according to claim 1, characterized in that: The surface of the inner container (2) is sprayed with a corrosion-resistant layer.

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