JPS58195786A - Heat accumulating apparatus of latent heat type - Google Patents

Abstract

PURPOSE:To prevent the interfacial temperature from decreasing, and to improve a heat transferring characteristic, by mixing metallic powder or metallic short fiber having thermal conductivity in a heat-accumulating material, in a solar heat or the like heat accumulating apparatus for supplying hot-water or for heating rooms utilizing a latent heat accumulating material and a phase transition heat-transferring medium. CONSTITUTION:Metallic powder or metallic short fiber 6, having heat conductivity, that is a phase transition heat-transferring medium 3 such as Al, of which specific gravity is larger than that of a latent heat accumulating material 2 or of heat accumulating material 2 in the vicinity of a phase transition point, is filled in a heat accumulating part B. At the time when the heat is accumulated, the heat from outside is first absorbed by the metallic powder interpositioned in the solid phase 100 of a heat accumulating material, and heats the heat-transferring medium 3. The heat-transferring medium 3 is repeatedly evaporated and is condensed, passing through the interpositioned space in the solid phase 100, and melts a heat-accumulating material 100 down to accumulate heat in it. At the time when the heat is radiated, the condensed liquid of heat-transferring medium 3 is deposited on the metallic powder 6 and is settled down. Accordingly, the condensed liquid 3 in the vicinity of an interface C is prevented from remaining, so that the heat dissipating speed can be increased. In such a manner, the interfacial temperature is prevented from lowering, and a heat transferring characteristic can be improved in the titled apparatus.

Description

[Detailed Description of the Invention] The present invention stores thermal energy such as solar heat, and
This relates to heat storage devices used for heating, etc.

In recent years, research has been actively conducted on the use of inorganic and organic water salts as latent heat storage materials from the viewpoint of effective use of energy such as unstable solar heat and late-night electricity, and high-density storage. However,
In practical use, there were many problems unique to heat storage materials that needed to be resolved (supercooling, phase separation, low thermal conductivity of the solid phase, etc.).

As a conventional heat storage device, there is one shown in FIG. This makes the heat storage material 2 almost insoluble in the heat storage material and the density of the liquid phase of the heat storage material in the closed device 1 which includes a vapor space A, a space for a solid phase and a space B for a liquid phase. The heat transfer medium 3 having the same or higher density is directly contacted, and the heat transfer medium vapor that has received heat from the heat storage material and evaporated into the vapor space A is condensed in the closed device to form a condensate liquid. It is designed to be returned to the heat storage material. This method is
This is an excellent product that improves the problems inherent to the heat storage material mentioned above. However, since the heat transfer medium condensate that has condensed and dripped in the intermediate heat radiator receives heat while settling in the heat storage material melt and becomes a gas, the heat transfer medium is mostly concentrated in the upper part of the heat storage material, that is, between the heat storage material and the vapor space. It will be located at the interface. Then, a portion of the heat transfer medium evaporates into the vapor space, causing a temperature drop at the interface, and a solid phase of the heat storage material precipitates and adheres to the interface, inhibiting the evaporation of the heat transfer medium.

Therefore, the current situation is to improve the heat dissipation characteristics by using a pump, compressor, etc. to smooth the convection of the heat transfer medium and prevent the heat storage material from sticking at the interface. In any case, the heat storage material melt scatters and adheres to the walls of the space heater tube, and the heat storage material melt solidifies there, causing a reduction in heat dissipation characteristics.

In order to avoid this, it is necessary to increase the distance between the interface and the intermediate heat radiator, and as a result, dead space increases and the advantage of using the heat storage material (high heat storage density storage) is lost. In addition, when indirect heat exchange is performed in the heat storage material, only the temperature difference between the heat storage material melt and the radiator tube wall determines the rate, and the solid phase of the heat storage material adheres and grows on the tube wall. Due to the low thermal conductivity, the heat dissipation properties deteriorate rapidly.

An object of the present invention is to provide a heat storage device that prevents a temperature drop at the interface and significantly improves the heat transfer characteristics associated with the solid phase adhesion of the heat storage material to the radiator tube wall.

In order to achieve the above object, the present invention includes a latent heat type heat storage material in a heat storage tank, which is almost incompatible with the heat storage material and changes from liquid to gas when heat is absorbed, and from gas to liquid when heat is released. and enclosing a heat transfer medium whose condensed liquid has a specific gravity at least higher than the specific gravity near the phase transition point of the heat storage material, and thermally conductive metal powder or short metal fibers, leaving a space above; Both Nos. 1 and 7 are permanently provided with a radiator through which a heat exchange medium passes through the space.

In addition, when performing indirect heat exchange with the heat storage material melt using an inorganic or organic water salt as a latent heat type heat storage material, the wall surface of the radiator and the thermally conductive metal powder or In this method, a water-repellent film is formed on the surface of short metal fibers, a fluorinated hydrocarbon is used as the heat transfer medium, and aluminum is used as the thermally conductive metal powder/fiber.

With the above configuration, the input/output speed of the heat exchanger during heat storage/radiation can be significantly improved.

An embodiment of the present invention will be described below with reference to FIG. Inside the heat storage tank container 1, a hydrated salt type heat storage material (melt liquid is 2, solid phase is 100), for example, sodium acetate.
Water salt (for hot water supply: melting point 58℃, specific gravity (solid) 1. a,
ay/cJ (liquid) 1.28)/CJ) and as the heat transfer medium 3, for example, Freon-113 (boiling point 47.6°C,
Specific gravity: 26° C. 1.57 p, kJ), Afi powder (100 mesh) is enclosed as thermally conductive metal powder 6. The space A1 is filled with a heat storage material filling part B. Heat radiators 4 and 6 are provided in the space A1 and the heat storage material filling part B, respectively, and these are used in a connected manner. In addition, in Figure 2, the first
Items that are the same as those in the figures are indicated by the same numbers. In addition, the heat sink 5
The water repellent treatment of , and the metal powder 6 was carried out by applying a silicone water repellent (medylhydrodiene polysiloxane) or by heating and curing after immersion.

Note that the heat transfer medium 3 and metal powder 6 used in the above example
The amounts of these are approximately 2% and 0.1% of the heat storage material 2, respectively (weight ratio).

Next, the heat storage/radiation process will be explained. Heat storage material solid phase 10
Usually, there are nest-like voids inside the voids caused by volume changes during crystallization due to heat dissipation, and the heat transfer medium condensate 3 and metal powder 6 are interposed inside the voids. From this state, heat is supplied from an external or internal heater (not shown in the figure) to start storing heat. In this heat storage process, although the thermal conductivity of the heat storage material solid phase 10o alone is generally low, the presence of the metal powder 6 improves the thermal conductivity and quickly transfers heat to the heat transfer medium 3. The heat transfer medium 3 that has received heat passes through the gap and transfers heat to the heat storage material solid phase 100 while repeating evaporation and condensation. As a result, the supplied thermal energy is quickly stored, and the inside of the heat storage tank container 1 is filled with the heat storage material melt 2 and the saturated vapor of the heat transfer medium 3 made of gas and liquid. As a result of the experiment, the presence of the metal powder 6 made it possible to improve the heat input rate during heating by about three times.

Next, heat radiation is performed by flowing cold water into the radiators 4 and 6. Then, the heat transfer medium vapor 3 existing in the space A is cooled, and condenses and drips on the tube wall of the radiator 4. At that time, the cold water is heated by the latent heat of vaporization released. Then, the heat transfer medium condensate 3 that has returned to the heat storage material melt 2 adheres to the metal powder 6 around it and settles down. As a result, the heat transfer medium 3 no longer stagnates near the interface C, and the heat radiation rate increases significantly (approximately 60 times). The state is shown in Figure 3a and Figure 3S.
...Heat transfer medium condensate, ...Metal powder,
...Indicates a heat storage material crystal. ). Then, the heat transfer medium 3 receives heat again, becomes a gas, and evaporates into the space A. At this time, the heat storage material melt 2 is poured into the heat transfer medium 3 and is vigorously stirred. Subsequently, since the water is heated by indirect heat exchange in the heat storage material melt 2, the water repellent layer is formed on the tube wall of the radiator 6, so the heat storage material solid phase 1oO is It becomes difficult to adhere. Figure 3 shows the state where it has started to adhere. A heat transfer medium condensate 3 and a heat storage material solid phase 100 containing metal powder 6 adhere to the tube wall of the radiator 6 . The heat transfer medium condensate 3 and the metal powder 6 are close to each other, and as a result, the heat transfer coefficient of indirect heat exchange is significantly improved (approximately 30 to 6
0%).

During the above process, the metal powder behaves by adhering to the heat transfer medium in the heat storage material melt during heat storage and heat dissipation, and this greatly affects the wettability of the metal powder to the heat storage material or heat transfer medium. are doing. In general, thermally conductive metals have a higher specific gravity than heat storage materials and heat transfer media, so metal particles (10 mesh or less) settle at the bottom (AQ-=2.7f/crll)
5Cu-...-8,96f/cr/l.

ate). However, metal powder (1 was used in the example)
00 mesh) exhibits the above-mentioned characteristics due to its large area and wettability. In general, if the heat storage material is difficult to wet and the heat transfer medium is easy to wet, an annotation will occur around the heat transfer medium.In the case of AQ powder, it behaved well even with non-water repellent treated materials. If both are easily wetted, treat the metal powder used to make it water repellent, and use a heat storage material,
Alternatively, a medium (for example, liquid paraffin) that has a smaller specific gravity than the heat transfer medium and is compatible with the heat transfer medium may be used. Note that the same applies when metal fibers are used.

As described above, according to the heat storage device of the present invention, the speed of heat exchanger and heat output during heat storage and heat dissipation can be significantly improved, and the specific gravity of the heat transfer medium can be changed to thermally conductive metal powder or By increasing the appearance by attaching metal fibers, it is possible to provide versatility to the heat transfer medium.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional heat storage device, FIG. 2 is a cross-sectional view of a heat storage device according to an embodiment of the present invention, and FIG. 3 is a state diagram of the heat storage device according to the present invention during heat dissipation. Near the interface, b indicates the vicinity of the radiator in the heat storage material. 1... Heat storage tank container, 2... Heat storage material melt (however, the solid phase is indicated by 1oo), 3... Heat transfer medium, 4, 5... ...Radiator, 6...Thermally conductive metal powder or metal fiber, A...Space, B
-,... Heat storage material filling part, C... Interface Figure 1 #j25i Figure 113

Claims (3)

[Claims] (1) The latent heat type heat storage material inside the container is almost incompatible with the heat storage material, and it changes from liquid to gas when heat is absorbed, and from gas to liquid when heat is released, and the specific gravity of the condensed liquid is at least A heat transfer medium having a specific gravity greater than the specific gravity near the phase transition point of the heat storage material, and thermally conductive metal powder or short metal fibers are sealed in the container with a space left above, and at least the space is used for heat exchange. A latent heat type heat storage device equipped with a radiator through which a medium passes. (2) A radiator having a water-repellent film when an inorganic or organic hydrated salt is used as the latent heat type heat storage material, and Claim 1 using a thermally conductive metal powder or metal fiber. The latent heat type heat storage device described in . (3) The latent heat type heat storage device according to claim 1 or 2, wherein a fluorinated hydrocarbon is used as the heat transfer medium, the thermally conductive metal powder is used, or aluminum is used as the metal fiber.