CN103017368A - Phase-change heat transfer type intermediate temperature heat reservoir as well as manufacturing and application thereof - Google Patents

Abstract

The invention discloses a phase-change heat storage type medium-temperature heat storage device and a medium-temperature solar air-conditioning system composed of the phase-change heat storage type medium-temperature heat storage device. The screen, heat storage accumulation layer and heat exchange tubes, multiple hoops are fixed horizontally on the inner wall of the lower part of the box, multiple screens are respectively placed on each hoop, and the heat storage accumulation layer is laid on each screen respectively , the heat storage accumulation layer is made of composite phase change heat storage material and sand, the heat exchange tube is arranged in the inner cavity of the upper part of the box body, the tube cavity of the heat exchange tube is isolated from the inside of the box body and is separated from the outside of the box body The medium-temperature heat storage device uses water and water vapor as its phase-change heat-transfer medium, and the phase-change heat-transfer medium evaporates or condenses directly on the surface of the granular composite phase-change heat storage material Realize phase change heat. The invention has the advantages of excellent heat exchange capacity, high utilization rate of solar heat, simple structure, easy manufacture and long service life.

Description

A phase-change heat type medium-temperature heat storage device and its manufacture and application

technical field

The invention relates to a solar energy utilization device, in particular to a phase-change heat type medium-temperature heat storage device and its manufacture and application, belonging to the field of energy technology.

Background technique

Solar energy is a clean, environmentally friendly, efficient and inexhaustible new energy. The market for solar heat utilization products is huge, so all countries regard the utilization of solar energy resources as an important part of sustainable development strategies. At present, among solar thermal utilization, the technology of solar water heater is relatively mature, but there are still some unsatisfactory places. For example, most of these water heaters can only provide low-temperature hot water below 80 degrees for daily life, but cannot provide high-temperature air or steam that the water temperature required by industry reaches more than one hundred degrees.

Solar air-conditioning system is a very promising field of solar heat utilization. At present, many model projects have been operated, and a large number of system patents have been proposed. In order to use solar energy for cooling in rainy days and at night, the solar air-conditioning system must have a complete heat storage and heat exchange system. The solar collector of the solar air-conditioning system can only heat the water to about 90°C, and then the hot water directly enters the lithium bromide absorption refrigerator, and the temperature of the heat source working fluid of the lithium bromide absorption refrigerator is at least 80°C, if you want to use The heat storage/heat release process of the heat storage device is used to provide hot water with a heat source working medium above 80°C for the lithium bromide absorption refrigerator, and the existing heat collectors or heat storage devices cannot complete this task. At present, although there have been many experimental researches, engineering technology developments and patents on solar heat storage technology at home and abroad, and there are various types of heat storage materials used, most of them focus on solar low-temperature hot water heat storage, and at 100°C to 200°C There are very few solar heat storage applications in the interval. In addition, the existing types of heat storage devices are roughly the same in terms of structure and heat storage and release principles: one method is to bury heat transfer pipes in dense heat storage materials, and absorb heat through heat conduction between the heat storage materials and the pipes. Heat/exothermic; the other is to seal the dense heat storage material in various pipes and containers, and the pipes and containers are immersed in the heat exchange working medium. The performance of these heat storage devices is directly related to the thermal conductivity of the heat storage material, because now the heat storage materials are almost all materials with low thermal conductivity. At present, the heat transfer performance of various heat storage heat exchangers is not high. For this type of heat storage, improving the thermal conductivity of heat storage materials is still a research focus. The general method is to fill heat storage materials into various metal foams or graphite materials to form a dense composite heat storage material. The research and patents of this kind of composite phase change heat storage materials are currently the mainstream of heat storage material technology patents.

In the existing phase-change heat accumulators, although the phase-change heat of the heat transfer medium in the heat accumulator is also used to transfer heat, all heat storage materials are still wrapped in sealed metal pipes or sealed metal containers. The sealed container is immersed in the heat transfer medium. When storing heat, the high-temperature heat source heats the heat transfer medium (liquid) to cause boiling in the pool, and the heat enters the heat storage material through the metal wall, and transfers heat inside through the overall heat conduction of the heat storage material. When releasing heat, the heat storage material is used as a heat source, and the heat is transferred to the heat transfer medium liquid through the metal wall through the heat conduction of the whole material, and the liquid evaporates and then transfers the heat to the cold source working medium. The heat conduction inside the heat storage material is still the main thermal resistance. In addition, the heat transfer surface of the heat storage material is only the wall surface area of the metal clad container. However, in this patent study, the phase-change heat transfer medium is directly in contact with the filling layer of granular heat storage materials. The huge surface area of all granular heat storage materials is the heat transfer surface, and the volume of a single heat storage material particle is very small. Thermal conduction resistance is almost negligible.

It is found in the existing relevant solar heat collection and heat storage technology literature: the Chinese patent with the publication number CN201032291, the name is: a solar heat storage unit and an integral solar water heater composed of it, which is characterized in that it includes a vacuum heat collection tube and a heat storage The heat storage component is arranged in the vacuum heat collecting tube, and the heat storage component includes a closed tube, a water inlet pipe and a water outlet pipe. The heat storage medium is water, which belongs to a primary heat storage technology, but it is more representative. In similar patents, the heat storage material can be various phase change materials, such as paraffin, a mixture of paraffin and other materials, etc., such as Chinese patent publication number: CN201327216, the name of the invention is: composite energy solar phase change thermal storage heating device , which mainly contains solar heat collector tubes and phase change heat storage bodies, and is characterized in that the phase change heat storage bodies are placed in the solar heat collector tubes, the outlet branch pipes are placed in the phase change heat storage bodies, and the water inlet branch pipes are placed in the water outlet branch pipes. What it adopts is a paraffin low-temperature solid-liquid phase change material.

It is found in the existing relevant technical literature of solar air-conditioning system: Chinese patent number is 200620050140.0, patent name: solar air-conditioning system. The patent consists of two parts: a double-effect absorption refrigerator and a solar heat collection system, and the solar heat collection system is composed of a solar heat collector, a solar control group, and a pipeline. The solar heat collector is a parabolic panel fixed on a truss and The heat collecting tube arranged at the focal point of the parabolic surface communicates with the high temperature generator of the double-effect absorption refrigerator through the pipeline and the solar control group. This patent is a solar air-conditioning system that can provide higher temperature hot water even on cloudy days. Chinese patent number is 200920185550.X, patent name: solar air conditioning system. The solar air-conditioning system consists of two parts: heating and cooling. The heating provides heat source through the solar collector, and the solar collector directly provides hot water to the indoor radiator; The power supply is provided by the evaporative air conditioner, and the cooling is provided by the evaporative air conditioner. These two patents basically represent the current mainstream technology of solar air-conditioning systems, which are characterized by: the heat collector has a low heat collection temperature, directly provides hot water to the refrigerator, and has no heat storage or only a symbolic low-temperature heat storage device.

In addition, the authorized Chinese patent held by the applicant, the patent number ZL 200910311344.3, the name of the invention patent: vacuum tube casing combined dual-purpose solar heater, is a kind of CPC heat collecting plate and all glass vacuum heat collecting tube A medium-temperature solar collector composed of high thermal efficiency and stability, which can provide water vapor above 120°C throughout the year.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a phase-change heat storage medium-temperature heat storage device, which adopts a solid-liquid phase change material as an intermediate medium for heat storage, and uses the phase-change heat of the intermediate medium to transfer heat, thereby The effect of improving the heat exchange capacity of the heat storage device and prolonging the service life is achieved; the present invention also provides a medium-temperature solar air-conditioning system using the phase-change heat storage type medium-temperature heat storage device and a medium-temperature heat storage system composed of the phase-change heat storage type. A method for preparing a heat storage material for a heat storage device.

The present invention is achieved through the following technical solutions:

A phase-change heat storage medium-temperature heat storage device, which is a closed pressure-resistant container, including a box body, a plurality of hoops, screens, heat storage accumulation layers and heat exchange tubes, and the plurality of hoops are horizontally arranged fixed on the inner wall of the lower part of the box, the plurality of screens are respectively placed on each frame, and the heat storage accumulation layer is respectively laid on each screen, and the heat storage accumulation layer is made of composite phase change heat storage material Mixed with sand, the heat exchange tube is arranged in the inner cavity of the upper part of the box body, the tube cavity of the heat exchange tube is isolated from the inside of the box body and communicated with the outside of the box body, and a heat-conducting working medium flows therein.

The composite phase change heat storage material is granular, and it is composed of organic bentonite and polyethylene wax in a mass ratio of 2.2:1, or composed of organic bentonite and low-density polyethylene in a mass ratio of 2:1.

The phase-change heat-type medium-temperature heat storage device uses water and water vapor as its phase-change heat-transfer working fluid, and the phase-change heat-transfer medium directly evaporates or condenses on the surface of the granular composite phase-change heat storage material to achieve phase change Heat exchange; in the heat storage stage, the phase-change heat storage medium-temperature heat storage is an open flow system, and the water vapor provided by the heat collector flows into the phase-change heat storage medium-temperature heat storage, and is condensed and discharged through the heat storage stack layer. Heat, the latent heat of condensation of water vapor is absorbed and stored by the composite phase-change heat storage material; in the exothermic stage, close the inlet and outlet valves of the phase-change heat storage medium-temperature heat storage, and turn the original open phase-change heat storage The medium-temperature heat storage becomes a closed space, and the water attached to the surface of the composite phase-change heat storage material is heated into water vapor, and the water vapor rises to the surface of the heat exchange tube to condense, heating the heat-conducting working medium in the heat exchange tube, and the water vapor again It is condensed into water droplets and falls into the heat storage accumulation layer; thus, the heat transfer between the composite phase change heat storage material and the heat exchange tube is completed in a cycle.

Another technical solution of the present invention is as follows:

A method for preparing a composite phase-change heat storage material for the phase-change heat-type medium-temperature heat storage device, which is characterized in that organic bentonite and polyethylene wax are prepared in a mass ratio of 2.2:1 and then put into an organic Stir while heating in the heating container of the stirring device, heat to 160°C and keep stirring at this temperature for 1 hour, so that all the dissolved polyethylene wax is absorbed by the organic bentonite, and finally a granular composite phase change storage with an average particle size of 3mm is obtained. hot material.

Another technical solution of the present invention is as follows:

A medium-temperature solar air-conditioning system composed of the phase-change heating type medium-temperature heat storage device, which includes a medium-temperature solar heat collector, a phase-change heat type medium-temperature heat storage device, a refrigerator, a return pump, a hot water pump, and a storage Water tank, the medium-temperature solar heat collector is a vacuum tube casing combined dual-purpose solar heater, the inlet of the medium-temperature solar heat collector is connected to the water storage tank through a return pump, and its outlet is connected to the water storage tank through a water vapor valve. The phase-change heat type medium-temperature heat storage is connected, the water storage tank is connected with the phase-change heat type medium-temperature heat storage through a water outlet valve, and the heat exchange of the phase-change heat type medium-temperature heat storage One end of the pipe is connected to the refrigerator through a hot water pump, and the other end is directly connected to the refrigerator.

Compared with the existing heat storage that conducts heat through dense heat storage materials, the heat transfer of the phase-change heat storage medium-temperature heat storage in the present invention is through the intermediate medium in the heat storage. The heat exchange principle is not the heat conduction of the heat storage material, but the heat is transferred through the phase change heat of the intermediate medium, so this patent is called a phase change heat type medium temperature heat storage device. Therefore, the phase-change heat type medium-temperature heat storage device described in the present invention can achieve the following beneficial effects:

(1) The phase change heat method not only has a high heat transfer coefficient, but also has a very large overall heat transfer area on the surface of the composite phase change heat storage material, which can achieve very high heat storage and heat release efficiency. The temperature difference between them can be ignored, and the heat transfer resistance between the two is 2 orders of magnitude lower than that of traditional heat-conducting heat storage materials, so the heat exchange capacity of the heat storage device of the present invention is very excellent.

(2) The heat storage material is a composite phase change material, which is placed in the heat storage in the state of porous particles. The thermal conductivity of the heat storage material has nothing to do with the heat storage/heat release characteristics. There is no special requirement for thermal conductivity.

(3) The polyethylene wax in the composite phase change heat storage material is adsorbed and sealed in the nano-intercalation of bentonite at the nanoscale, so there will be no overflow during the repeated phase change process, thus ensuring its long-term repeated sexual life.

(4) The heat exchange pipeline can be installed freely without any strengthening measures, and the placement and replacement of the heat storage accumulation layer is also very simple, so it has the advantages of simple structure and easy manufacture.

The medium-temperature solar air-conditioning system of the present invention is a combination of high-efficiency solar vacuum tube heat collection and granular medium-temperature composite solid-liquid phase change material heat storage/heat release and phase change heat storage heat exchanger for all-weather use. The running solar air conditioning system is characterized by:

(1) The medium-temperature solar collector is composed of CPC heat collector plate and ordinary full-vacuum glass heat collector tube, which can provide medium-temperature water vapor at about 120°C as a high-quality heat source working fluid.

(2) The steam working medium of the heat collector does not directly enter the refrigerator, but enters the heat storage device to release heat, condenses into water and then flows back to the heat collector to form a loop; while the working medium of the refrigerator passes through the heat exchange tube in the storage The heat is absorbed in the heat tank to form another circuit, so the two working fluids form a double circuit isolated in the heat storage, and the heat storage material and the heat exchange pipeline are respectively located in different phase-change heat storage medium-temperature heat storage. space without direct contact.

(3) The phase-change heat storage medium-temperature heat storage device matched with the medium-temperature solar air-conditioning refrigeration system can provide 120°C water vapor for solar air-conditioning during the day, and provide water vapor at about 110°C at night to heat the refrigerator Hot water is used to meet the operation needs of the refrigerator; the improvement of the heat transfer performance of the heat storage device can reduce the temperature of the working medium of the collector as much as possible, thereby greatly improving the solar heat utilization rate of the entire medium-temperature solar air-conditioning system.

Description of drawings

Fig. 1 is a schematic structural view of a phase-change heat storage medium-temperature heat storage device of the present invention.

Fig. 2 is a structural schematic diagram of the medium-temperature solar air-conditioning system of the present invention.

In the figure,

1 Medium-temperature solar heat collector, 2 Phase-change heat type medium-temperature heat storage, 3 Refrigerator, 4 Return water pump, 5 Hot water pump, 6 Water storage tank, 7 Cabinet, 8 Water vapor inlet, 9 Water vapor valve, 10 Outlet Water outlet, 11 water outlet valve, 12 heat exchange tube, 13 heat exchange tube support frame, 14 ring frame, 15 screen mesh, 16 heat storage accumulation layer, 17 insulation material, 18 safety valve, 19 pressure gauge, 20 temperature sensor, 21 drain Shuikou, 22 air inflation ports, 23 inflation valves.

Detailed ways

The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. This embodiment provides detailed implementation methods and specific operating procedures on the premise of the technical solutions of the present invention, but the protection scope of the present invention is not limited to the following implementations example.

Please refer to Fig. 1, the illustrated phase-change heat type medium-temperature heat storage device 2 is a closed pressure-resistant container made of stainless steel, including a box body 7, a plurality of hoops 14, a screen 15, a heat storage accumulation layer 16 and a heat exchange Tube 12.

In the present embodiment, the box body 7 is a stainless steel cylindrical container with a diameter of 1.2m, a total height of 1.5m, and a wall thickness of 3mm, and its outer periphery is wrapped with an insulating material 17; The water vapor valve 9 and the water vapor inlet 8, and the pressure gauge 19, the temperature sensor 20 and the safety valve 18 connected in sequence; the water outlet 21 is respectively arranged under the box body 7, and the water outlet valve 11 and the water outlet 10 connected in sequence; The outer wall of the casing 7 is also provided with an air intake valve 23 and an air charging port 22 connected in sequence, so that the inside of the casing 7 is filled with air with a pressure of 2 atmospheres to form a pressure environment. The plurality of hoops 14 are ring-shaped, and are respectively horizontally welded and fixed on the inner wall of the lower part of the box body 7 . The plurality of screens 15 are respectively placed on the frames 14, and the screens 15 are made of stainless steel plate and 200-mesh stainless steel wire mesh. The heat storage accumulation layer 16 is respectively laid on the screens 15. The heat storage accumulation layer 16 is a porous accumulation layer formed by mixing composite phase change heat storage materials and sand grains. Steam and water can pass through the wire mesh, while The heat storage material will not leak out; the heat storage accumulation layer 16 has a thickness of about 50mm, and the number of layers depends on the needs. The heat exchange tube 12 is arranged in the inner cavity of the upper part of the box body 7, and is suspended above the heat storage accumulation layer 16 by the heat exchange tube support frame 13 fixed on the inner wall of the box body 7; the tube of the heat exchange tube 12 The cavity is isolated from the inside of the box body 7 and communicated with the outside of the box body 7, in which the heat-conducting working fluid provided to the refrigerator flows; the shape, diameter and length of the pipeline of the heat exchange tube 12 can be set as required.

The composite phase change heat storage material is in granular form, its phase change temperature is 110°C, and there is no special requirement on its thermal conductivity. In this embodiment, the composite phase change heat storage material is composed of organic bentonite and polyethylene wax in a mass ratio of 2.2:1.

The phase-change heat-type medium-temperature heat storage device 2 uses water and water vapor as its phase-change heat-transfer working medium, and the phase-change heat-transfer medium directly evaporates or condenses on the surface of the granular composite phase-change heat storage material to realize phase change. Transformation heat; in the heat storage stage, the phase-change heat storage medium-temperature heat storage 2 is an open flow system, and the water vapor provided by the heat collector flows into the phase-change heat storage medium-temperature heat storage 2, and passes through the heat storage accumulation layer Condensation and heat release in 16, the condensation latent heat of water vapor is absorbed and stored by the composite phase change heat storage material; in the heat release stage, the inlet and outlet valves of the phase change heat type medium temperature heat storage 2 are closed, and the original open The phase-change heat storage medium-temperature heat storage device 2 becomes a closed space, and the water attached to the surface of the composite phase-change heat storage material is heated to water vapor, and the water vapor rises to the surface of the heat exchange tube 12 to condense, and the heat exchange tube is heated. 12, and the water vapor is condensed into water droplets again and falls into the heat storage accumulation layer 16; thus, the heat transfer between the composite phase change heat storage material and the heat exchange tube 12 is completed in a cycle.

Polyethylene waxes have different melting points and latent heat of phase change according to different manufacturers. The melting point is roughly between 95°C and 118°C, such as 113°C for Japan and 118°C for South Korea. The used polyethylene wax of this patent is provided by a domestic manufacturer, and Table 1 has listed the physical properties of its commodity polyethylene wax. The physical properties of polyethylene wax hardly changed after being combined with organic bentonite to form a composite phase change heat storage material.

Table 1 Physical properties of polyethylene wax

The physical properties of organic bentonite also vary greatly with different manufacturers, but it has little effect on the heat storage performance of the composite phase change heat storage material itself. The general physical properties of organic bentonite produced by a certain manufacturer are given below: specific heat 0.78KJ/(KgK), thermal conductivity 0.83W/(mK), density 2g/cm3, apparent viscosity 24mPas, montmorillonite content ≥ 95%, white Degree 88, expansion multiple 23, hardness 2.8, particle size/mesh 400 mesh, shape white fine powder, pH value 6-7.

When organic bentonite and polyethylene wax are mixed, the melting point, freezing point and latent heat of phase change of the composite phase change heat storage material hardly change. The test found that after repeated heating and condensation for 3 times, the mass overflow rate of the composite phase change heat storage material (the ratio of the mass of the phase change material after heating/cooling to the mass of the phase change material before heating/cooling) was about 3%. After repeated heating and cooling, the mass overflow rate is almost zero, which shows the excellent reusability of the composite phase change heat storage material.

The preparation method of the above-mentioned composite phase-change heat storage material is as follows: prepare organic bentonite and polyethylene wax according to a mass ratio of 2.2:1, put them into a heating container with a stirring device and stir while heating, and keep the temperature after heating to 160°C. The temperature was stirred for 1 hour, so that all the dissolved polyethylene wax was absorbed by the organic bentonite, and finally a granular composite phase change heat storage material with an average particle diameter of 3mm was obtained. A small amount of large-grained materials can be gently crushed with a wooden hammer. The heating temperature and material mixing ratio have a great influence on the apparent performance of the composite phase change heat storage material, so great attention must be paid.

The heat storage material needs to have a certain water storage capacity and at the same time ensure air permeability. Since organic bentonite is a hydrophobic material, the surface of the composite phase change heat storage material is hydrophobic. In order to increase the water storage and air permeability of the composite phase change heat storage material, mix the composite phase change heat storage material with a small amount of fine sand, put it into the heating container again while stirring while heating, and keep stirring at this temperature for 1 hour after heating to 160°C hours, most of the fine sand will adhere to the surface of the composite phase change heat storage material particles to form a hydrophilic surface structure, thereby preparing the heat storage accumulation layer 16. The heat storage accumulation layer 16 obtained after the experimental measurement has a stacking porosity of about 40%.

The composite phase-change heat storage material can also be composed of organic bentonite and low-density polyethylene in a mass ratio of 2:1, and its preparation method is similar to the above-mentioned method.

The working principle of the phase-change heat storage medium-temperature heat storage device 2 is as follows: during the day, the temperature of the water vapor provided by the heat collector (about 120°C) is higher than the phase change temperature (about 110°C) of the composite phase-change heat storage material A part of the water vapor condenses and releases heat outside the heat exchange tube 12, thereby heating the hot water for cooling flowing through the pipe, and the hot water circulates in the refrigerator; in addition, most of the water vapor condenses and releases heat inside the heat storage accumulation layer 16. Heat, latent heat of condensation of water vapor is absorbed by the composite phase change heat storage material, and the composite phase change heat storage material changes from a solid phase to a liquid phase. And at night, close each inlet and outlet valves of the phase-change heat storage type medium-temperature heat storage device 2, and the original open phase-change heat type medium-temperature heat storage device 2 becomes a closed space, and now the heat exchange tube 12 still circulates The flowing hot water for refrigeration continuously absorbs heat from the condensation process of the water vapor in the phase-change heat storage type medium-temperature heat storage device 2, and the water vapor in the phase-change heat storage type medium-temperature heat storage device 2 is continuously condensed into water droplets. As the mass of water vapor decreases, the steam pressure and temperature in the phase-change heat storage type medium-temperature heat storage device 2 will gradually drop below the phase change temperature (110°C) of the composite phase-change heat storage material; after that, the composite phase-change heat storage material begins to The phase change releases heat (from liquid to solid), and the water attached to the surface of the granular composite phase change heat storage material is heated to water vapor. water (the temperature increases from 85°C to 90°C), and the water vapor is condensed again into water droplets and falls into the heat storage accumulation layer 16, and so on, completing the heat transfer between the composite phase change heat storage material and the heat exchange tube 12. This heat transfer mechanism is very similar to that of a heat pipe. The phase-change heat-type medium-temperature heat storage device 2 utilizes the heat exchange characteristics of heat pipes to achieve very high heat storage and heat release efficiency. The heat conduction and heat transfer mode of the material is 1 to 2 orders of magnitude lower. At the same time, the granular composite phase-change heat storage material is filled with water and water vapor, and the phase-change heat process is simultaneously carried out everywhere in the heat storage accumulation layer 16. The effective heat transfer area on the surface of the particles is very large, making the phase-change heat storage medium temperature The heat transfer capability of the heat exchanger 2 is very excellent, the temperature difference between the composite phase change heat storage material and the heat exchange tube 12 is almost negligible, and the temperature difference inside the particles of the composite phase change heat storage material is also almost negligible.

During the heat storage and heat release process of the phase-change heat storage type medium-temperature heat storage device 2, the temperature of the water vapor in the phase-change heat type medium-temperature heat storage device 2 is different (the temperature of the water vapor during heat storage is about 120°C, The water vapor temperature is about 110°C when exothermic). The temperature of the hot water in the heat exchange tube 12 should be kept stable, so the flow rate of the water in the heat exchange tube 12 should be adjusted by adjusting the loop flow of the heat exchange tube 12 pipeline during the day and night, so as to ensure the same heat exchange power.

Fig. 2 is a structural schematic diagram of the medium-temperature solar air-conditioning system of the present invention. The medium-temperature solar air-conditioning system shown in the figure includes a medium-temperature solar heat collector 1 , a phase-change heat storage type medium-temperature heat storage 2 , a refrigerator 3 , a return water pump 4 , a hot water pump 5 and a water storage tank 6 . The inlet of the medium-temperature solar heat collector 1 is connected to the water storage tank 6 through a return pump 4, and its outlet is connected to the phase-change heat type medium-temperature heat storage 2 through a water vapor valve 9. The water tank 6 is connected to the phase-change heat storage type medium-temperature heat storage device 2 through the water outlet valve 11, and one end of the heat exchange tube 12 of the phase-change heat type medium-temperature heat storage device 2 is connected to the refrigerator 3 through the hot water pump 5 , and the other end is directly connected with the refrigerator 3.

Described medium-temperature solar heat collector 1 is a combined dual-purpose solar heater of a vacuum tube casing, which is an authorized Chinese patent (invention patent) held by the applicant. Name: Vacuum tube casing combined dual-purpose solar heater, patent number ZL 200910311344.3), is a medium-high temperature pressure-bearing collector composed of CPC collector plates and all-glass vacuum collector tubes. The heat collector 1 can provide water vapor above 120°C to the absorption air-conditioning refrigerator 3 during the day as a cooling heat source, and at the same time, the composite phase-change heat storage material in the phase-change heat storage medium-temperature heat storage 2 absorbs and stores excess heat At night, the phase-change heat storage medium-temperature heat storage device 2 can provide 110°C water vapor to the absorption air-conditioning refrigerator 3 as a cooling heat source. The size, volume, and quality of the composite phase-change heat storage material used for the phase-change heat storage medium-temperature heat storage device 2 are determined according to the power of the entire solar air-conditioning system. The overall system may include several parallel phase-change heat-type medium-temperature Heat storage 2.

The power of the refrigerator 3 in this embodiment is 7.5kW, and the efficiency is 0.75. Calculated according to the working time of medium-temperature solar collector 2 for 8 hours in the daytime and 8 hours in the evening, the output power of the corresponding medium-temperature solar collector 2 is greater than 20kW, of which 10kW is directly used for cooling during the day, and the phase-change heat storage type medium-temperature heat storage 2. Store the remaining heat energy for 8 hours of work at night. The heat storage capacity is greater than 384000kJ, and the quality of polyethylene wax required is about 1500kg.

The diameter of the phase-change heat storage type medium-temperature heat storage device 2 is 1.2m, the total height is 1.5m, and the number is 5 phase-change heat type medium-temperature heat storage devices 2 of the same size. 2Use 300kg of polyethylene wax, lay on 10 sieves respectively, and accumulate 30kg on each sieve. The composite phase change heat storage material is prepared with organic bentonite and polyethylene wax at a mass ratio of 2.2:1, the total mass is close to 5000kg, the particle size of the composite phase change heat storage material is about 3mm, and the void ratio of the heat storage accumulation layer 16 is maintained at About 30%-40%, in order to absorb moisture and transmit steam.

The heat exchange tubes 12 of the refrigerator 3 pass through each phase-change heat storage medium-temperature heat storage 2 in series. According to calculations, the heat exchange tubes 12 are copper tubes with an inner diameter of 12mm and a total length of 20m, that is, each phase-change heat storage type As long as the heat exchange tube 12 is 2m long in the medium-temperature heat storage device 2, a U-shaped tube is generally used. The head of the hot water pump 5 is 20m, and a 50W low-power water pump can meet the requirements.

After the installation and commissioning of the overall system is completed, air is charged into the phase-change heat storage type medium-temperature heat storage device 2 through the air charging port 22 and the air intake valve 23 to make the phase-change heat type medium-temperature heat storage device 2 and the medium-temperature solar heat collector 1. The pressure of the pipeline reaches 2 atmospheres to ensure that the water is heated to about 120 degrees in the medium-temperature solar collector 1. After boiling and evaporating into water vapor, it enters the phase-change heat storage type medium-temperature heat storage 2, because the temperature of the water vapor must be Higher than the phase change temperature (110°C) of the composite phase change heat storage material, the water vapor can finally condense into supercooled water and flow back to the water storage tank 6, and then be pumped into the medium temperature solar collector 1 by the return water pump 4 to complete the cycle; otherwise, if The water vapor temperature is lower than the phase change temperature of the composite phase change heat storage material, and the water vapor will flow back into the water storage tank 6 and the return water pump 4, thereby causing the return water pump 4 to be blocked. In order to avoid this situation, the actual placement of composite phase change heat storage materials should be more than the calculated value.

The working process of the medium temperature solar air conditioning system is as follows:

During the heat storage stage of the phase-change heat storage type medium-temperature heat storage device 2 during the day, the return water pump 4 is turned on to supply water to the medium-temperature solar heat collector 1, and the solar radiation energy is absorbed by the medium-temperature solar heat collector 1 to heat the flow in the pipe of the medium-temperature solar heat collector 1 The supercooled water finally evaporates into water vapor at the outlet of the medium-temperature solar heat collector 1, and provides water vapor at about 2 atmospheres and 120°C to the phase-change heat storage type medium-temperature heat storage 2. Then start the water supply circulation system of the refrigerator 3, adjust the flow rate of the hot water pump 5, and ensure that the water supply temperature of the refrigerator 3 is between 90°C and 95°C. The water vapor from the medium-temperature solar heat collector 1 enters the phase-change heat type medium-temperature heat storage device 2 and then passes through the surface of the heat exchange tube 12 and the heat storage accumulation layer 16, and a part of the water vapor is heated with the flowing hot water in the heat exchange tube 12. Exchange, condensed on the surface of the heat exchange tube 12 to become saturated water dripping, most of the water vapor passes through the composite phase change heat storage material and exchanges heat with it, and condenses on the surface of the composite phase change heat storage material to become saturated water. In the lowermost heat storage accumulation layer 16 of the phase-change heat type medium-temperature heat storage device 2, the saturated water releases heat and becomes supercooled water, and the supercooled water is pumped back to the medium-temperature solar heat collector 1 by the return water pump 4 to complete the work of the heat collector. quality cycle. At the beginning of the process, the water supply flow rate of the return pump 4 is adjusted so that the steam temperature at the inlet of the phase-change heat storage medium-temperature heat storage 2 is slightly higher than the water saturation temperature corresponding to the internal pressure of the phase-change heat storage medium-temperature heat storage 2, that is, the water The steam should reach the level of dry steam, and the temperature of the water vapor during operation thereafter only needs to be higher than the phase change temperature of the composite phase change heat storage material.

During the heat release stage of the phase-change heat storage medium-temperature heat storage device 2 at night, the inlet and outlet valves of the phase-change heat storage medium-temperature heat storage device 2 are closed to form a closed space. Since the water supply cycle of the refrigerator 3 is still running, the working medium of the refrigerator still flows and absorbs heat in the heat exchange tube 12, so the remaining water vapor in the phase-change heat storage type medium-temperature heat storage 2 is continuously condensed on the surface of the heat exchange tube 12 Heat release, the mass of water vapor in the phase-change heat storage type medium-temperature heat storage device 2 decreases, the steam pressure drops, and the corresponding phase-change heat type medium-temperature heat storage device 2 also continuously drops in water vapor temperature. After the temperature drops below the phase transition temperature (110°C) of the composite phase change heat storage material, the composite phase change heat storage material begins to phase change and release heat, and the water adhering to its surface is heated to become water vapor at about 110°C. After the water vapor rises, it exchanges heat with the heat exchange tube 12, and then condenses into water droplets and falls into the heat storage accumulation layer 16. This cycle repeatedly realizes the heat transfer between the composite phase change heat storage material and the flowing water in the heat exchange tube 12. . At this time, since the temperature difference between the water vapor and the water supply temperature of the refrigerator 3 decreases, the heat transfer performance decreases. Therefore, in order to ensure that the water supply temperature of the refrigerator 3 is still around 90°C, it is necessary to manually adjust the water flow of the refrigerator 3 appropriately.

When the medium-temperature solar collector 1 is working during the day, the inlet and outlet valves of the phase-change heat storage type medium-temperature heat storage device 2 are opened, and the phase-change heat storage type medium-temperature heat storage device 2 and the heating tube of the medium-temperature solar heat collector 1 form a circulation flow path , the hot water flowing out of the phase-change heat type medium-temperature heat storage device 2 is pumped back to the medium-temperature solar heat collector 1 by the return water pump 4 . When the medium-temperature solar heat collector 1 is not working at night, close the inlet and outlet valves of the phase-change heat storage type medium-temperature heat storage device 2 to form a closed container.

The medium-temperature solar air-conditioning and refrigeration system in this embodiment and the matching phase-change heat storage medium-temperature heat storage device 2 can provide 120°C water vapor for solar air-conditioning during the day, and 110°C water vapor for heating the refrigerator at night 3. Hot water is used to meet the operation needs of the refrigerator 3. The phase-change heat storage medium-temperature heat storage device 2 utilizes the huge heat transfer surface of the porous composite phase-change heat storage material and the heat pipe phase-change heat technology to achieve very high heat storage and heat release efficiency, and its composite phase-change heat storage The heat transfer resistance between the material and the heat exchange tube 12 is two orders of magnitude lower than that of the traditional heat conduction heat storage material, and the temperature difference between the composite phase change heat storage material and the heat exchange tube 12 can be ignored. The improvement of the performance of the phase-change heat storage type medium-temperature heat storage device 2 can reduce the working medium temperature of the medium-temperature solar heat collector 1 as much as possible, thereby greatly improving the solar heat utilization rate of the overall system.

Claims (7)

1. A phase-change heat storage type medium-temperature heat storage device, characterized in that: the medium-temperature heat storage device is a pressure-resistant container, which includes a box body, a plurality of hoops, screens, heat storage accumulation layers and heat exchange tube, the plurality of hoops are respectively horizontally fixed on the inner wall of the lower part of the box, the plurality of screens are respectively placed on each hoop, and the heat storage accumulation layer is respectively laid on each screen, the The heat storage accumulation layer is made of composite phase change heat storage material and sand. The heat exchange tube is arranged in the inner cavity of the upper part of the box. The lumen of the heat exchange tube is isolated from the inside of the box and is separated from the outside In communication, there is a heat-conducting working medium flowing therein. 2. The phase-change heat-type medium-temperature heat storage device according to claim 1, characterized in that: the composite phase-change heat storage material is granular, and it is composed of organic bentonite and polyethylene wax in a mass ratio of 2.2:1. Than composition. 3. The phase-change heat-type medium-temperature heat storage device according to claim 1, characterized in that: the composite phase-change heat storage material is granular, and it is composed of organic bentonite and low-density polyethylene at a ratio of 2:1. mass ratio composition. 4. The phase-change heat type medium temperature heat storage device according to claim 1, characterized in that: water and steam are used as the phase change heat transfer working medium in the phase change heat type medium temperature heat storage device, the The phase change heat transfer working medium directly evaporates or condenses on the surface of the granular composite phase change heat storage material to realize phase change heat; in the heat storage stage, the phase change heat type medium temperature heat storage is an open flow system, and the collector provides The water vapor flows into the phase-change heat storage medium-temperature heat storage device, and heat is released through condensation in the heat storage stack layer, and the condensation latent heat of water vapor is absorbed and stored by the composite phase-change heat storage material; in the heat release stage, the The inlet and outlet valves of the phase-change heat storage medium-temperature heat storage device turn the original open phase-change heat storage type medium-temperature heat storage device into a closed space, and the water attached to the surface of the composite phase change heat storage material is heated into water vapor. The water vapor rises to the surface of the heat exchange tube to condense, heats the heat-conducting working medium in the heat exchange tube, and the water vapor is condensed again into water droplets and falls into the heat storage accumulation layer; thus, the composite phase change heat storage material and heat exchange process are completed in a cycle. Heat transfer between heat pipes. 5. A method for preparing a composite phase-change heat storage material for a phase-change heat-type medium-temperature heat storage device according to claim 2, characterized in that: organic bentonite and polyethylene wax are prepared in a mass ratio of 2.2:1 Then put it into a heating container with a stirring device and stir while heating. After heating to 160°C, keep the temperature and stir for 1 hour, so that all the dissolved polyethylene wax is absorbed by the organic bentonite, and finally obtain granular particles with an average particle size of 3 mm. Composite phase change heat storage materials. 6. A medium-temperature solar air-conditioning system composed of the phase-change heat type medium-temperature heat storage device according to claim 1, characterized in that: the solar air-conditioning system includes a medium-temperature solar heat collector, a phase-change heat type medium-temperature Heat storage, refrigerator, return water pump, hot water pump and water storage tank, the inlet of the medium temperature solar collector is connected with the water storage tank through the return water pump, and its outlet is exchanged heat with the phase through the water vapor valve The water storage tank is connected to the phase-change heat storage type medium-temperature heat storage device through a water outlet valve, and one end of the heat exchange tube of the phase-change heat storage type medium-temperature heat storage device is connected to the The refrigerator is connected, and the other end is directly connected with the refrigerator. 7. The medium-temperature solar air-conditioning system according to claim 6, characterized in that: said medium-temperature solar heat collector is a combined dual-purpose solar heater of vacuum tube casing.

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