JPS5845494A - Method of heat exchange in latent heat type heat accumulating tank - Google Patents

Abstract

PURPOSE:To effect heat exchange with an external material efficiently by a method wherein the heat of a heat accumulating material is transmitted to an antifreezing liquid through an operating liquid and the heat exchange is effected by the antifreezing liquid. CONSTITUTION:The vapor of the operating liquid becomes bubbles 8 and ascends through the heat accumulating material 2 while the molten heat accumulating material 2 is mixed and the temperature distribution thereof is unified. The vapor of the operating liquid arrives at the antifreezing liquid and gives the heat thereof to the antifreezing liquid 4 or the heat transmitting surface of a heat exchanger thereby being condensed and liquidized. The specific gravity of the liquidized operating liquid 3 is larger than the sames of the antifreezing liquid and the heat accumulating material 2, therefore, it sinks through these materials. Thus, the heat of the heat accumulating material is transmitted to the antifreezing liquid 4 effectively by the evaporation-condensation cycle of the operating liquid 3 and, further, the heat exchange is effected in the antifreezing liquid 4 (liquid) by the heat exchanger, therefore, a very efficient heat exchange system may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves adding a small amount of working fluid and antifreeze that are non-reactive and immiscible with the heat storage material to a part of the latent heat type heat storage tank, and then evaporating the working fluid.
The present invention relates to a method of transferring latent heat of a heat storage material to an antifreeze liquid by utilizing a condensation cycle, and efficiently exchanging heat with the outside using a heat exchanger provided in the antifreeze liquid.

FIG. 1 is an example of a conventional heat storage tank. The structure mainly includes a heat storage tank 100, a heat storage material 110, and a heat exchanger 120. In FIG. 1, when cold water flows into the heat exchanger 120, it absorbs latent heat from the heat storage material and flows out as hot water. However, one of the problems with such a latent heat type heat storage tank is as follows.

In other words, inorganic salts, organic substances, or paraffin are used as heat storage materials that utilize latent heat, but in any case, one of the problems is that heat transfer in the solid phase is poor, so it is difficult to store heat at a constant temperature in a short period of time. This means that it cannot be taken out. In other words, in the molten state, the temperature in the heat storage material is kept uniform due to convection, but once it begins to solidify, the temperature of the heat storage material near the heat exchanger drops rapidly due to poor heat transfer in the solid. This is because the rate at which heat is taken from the heat transfer surface of the heat exchanger is faster than the rate at which heat is transferred from the heat storage material in the portion away from the heat transfer surface. This is because if heat is not transferred, the only way to replenish the heat is by reducing the temperature of the heat storage material near the heat transfer surface. In other words, in the close vicinity of the heat transfer surface, the heat storage material releases its latent heat and solidifies. When solidified, thermal conductivity is poor, making it difficult to transfer heat from the molten heat storage material near the solidified heat storage material to the heat transfer surface. Therefore, the heat storage material is in a solid phase near the heat transfer surface, and remains in a liquid phase at a distance. Therefore, it takes a long time to effectively utilize the latent heat of the liquid phase.

In actual use, various measures have been taken to prevent the above phenomenon from occurring. For example, by adding fins to heat transfer tubes to shorten the distance between the heat transfer surfaces, or by increasing the heat exchange area. Although methods such as constructing a heat storage tank using the cylinder as one block have been carried out, the above problem has not been substantially solved.

The present invention solves the above problems and provides a method for efficiently exchanging heat.

FIG. 2 shows an example of a latent heat type heat storage tank that performs heat exchange by the method of the present invention. In Fig. 2, a heat storage tank IK heat storage material 2, a working fluid 3 whose specific gravity is larger than the specific gravity of the heat storage material in the molten state, and an antifreeze liquid 4 whose specific gravity is smaller than the specific gravity of the heat storage material in the bath molten state (at least it does not solidify when heat is extracted from the heat storage material) It is further comprised of a heat exchanger 6 for extracting heat to the outside. 6°7 is a pipe for extracting heat. Here, the heat storage material 2 working fluid and antifreeze are non-reactive and immiscible with each other.

When the heat storage material is in a molten state, the working fluid in the tank is in the liquid phase.
The heat storage material and the antifreeze are in equilibrium as a gas phase with the vapor pressure of the working fluid equal to the temperature of the antifreeze. □In order to facilitate evaporation and condensation of the working fluid in the gas phase, it is preferable to exclude non-condensable gases. Further, it is preferable that the vapor pressure of the antifreeze liquid is low. Now, when a low-temperature heat medium flows into the pipe 6 and exchanges heat with the antifreeze, the temperature of the antifreeze drops. Then, the working fluid vapor rises further in the lower part of the heat storage tank to compensate for the temperature drop. Since this is done continuously, there is no effective temperature drop of the antifreeze fluid. That is, the working fluid vapor becomes bubbles 8 and rises in the heat storage material, stirring the molten heat storage material and making its temperature distribution uniform. The working liquid vapor reaches the antifreeze liquid, gives heat to the antifreeze liquid or the heat transfer surface of the heat exchanger, and condenses into liquid. The liquefied working fluid has a higher specific gravity than the antifreeze fluid and the heat storage material, so it settles in them.

At this time, some of it absorbs heat from the heat storage material and vaporizes again, and the vapor rises in the form of bubbles. The other part settles to the bottom of the heat storage tank and forms three pools of working fluid. This working fluid absorbs heat from the surroundings, vaporizes again, and rises in the form of bubbles to reach the heat exchanger. On the other hand, the low-temperature heat medium flowing in from the pipe receives heat in the heat exchanger, becomes a high-temperature heat medium, and flows out from the pipe 6. In this way, the heat of the heat storage material is effectively transferred to the antifreeze liquid through the evaporation-condensation cycle of the working fluid, and the heat exchanger performs heat exchange within the antifreeze liquid (liquid), resulting in a very efficient heat exchange system.

As you can see from the above explanation, the amount of working fluid only needs to be small enough to transfer heat in the evaporation-condensation cycle, and the amount of antifreeze is sufficient as long as it covers the heat exchanger. , the proportion of the entire heat storage tank can be small.

However, when storing heat, it is sufficient to heat the entire heat storage tank or heat it through a suitable heat exchanger, or the same as a normal heating method.The method of the present invention has the following advantages.

(1) Since heat exchange is performed in the liquid phase, there is no solid phase area with poor heat transfer around the heat transfer surface of the heat exchanger.
Heat exchange takes place easily and quickly. , ゛(2) As the vapor of the working fluid passes through the heat storage material in the form of bubbles, the heat storage material is stirred by the bubbles, and the temperature distribution of the heat storage material becomes uniform, causing solidification at certain specific points. doesn't go. Also, since the solidified heat is stirred, it becomes fine crystals and accumulates at the bottom of the heat storage tank. That is,
The heat storage material that has released latent heat gradually settles to the bottom. Therefore, the latent heat of the entire heat storage material can be effectively utilized.

(3) Even if the heat storage material solidifies, the hydraulic fluid and antifreeze do not solidify. In particular, path force due to vaporization of the working fluid; since it exists in the form of open cells in the solidified heat storage material, the vapor of the working fluid passing through this path utilizes not only the sensible heat of the antifreeze fluid but also the sensible heat of the heat storage material. can.

As described above, according to the method of the present invention, the amount of heat from the heat storage material can be extracted efficiently. An example will be described below.

Sodium acetate trihydrate (N a CH-C00・3H
20) with Freon R-113 as the hydraulic fluid. 7 silicone oil is filled as antifreeze, and non-condensable gases such as air are discharged. These are mutually incompatible and non-reactive. The density of sodium acetate trihydrate at the melting point of 68°C is 1.34. Freon R-11
31,48 and silicone oil 1.1. Therefore, in a completely stationary state, Freon R-113. The liquid phase is composed of the sodium acetate trihydrate solution and the antifreeze solution in this order.

A heat exchanger is then installed inside the antifreeze. Therefore, heat exchange takes place in the liquid, making it very efficient.

When cold water is flowed through the heat exchanger with heat stored in the heat storage material, heat is exchanged with the antifreeze liquid on the heat transfer surface, and the temperature of the antifreeze liquid decreases. The vapor of Freon R-113 condenses when it comes into contact with the antifreeze, gives its heat to the antifreeze, and becomes a condensed liquid that drips. Since the liquid density of Freon R-113 is higher than other liquids,
It settles in the heat storage material. As it sinks, it absorbs heat from the sodium acetate and some of it evaporates, while some of it settles and reaches the bottom.
This absorbs heat and evaporates again. During this evaporation process, the working fluid becomes bubbles and rises in the heat storage material, so that the entire heat storage material is mixed and stirred. On the other hand, the sodium acetate trihydrate solution emits latent heat to Freon R-113 and solidifies. During this process, as explained above, the heat storage material is vigorously agitated by the bubbles of the working fluid, so it does not solidify from a specific part, but instead becomes a form in which fine crystals of thorium acetate are dispersed in the solution.

Since the density of the fine crystals of sodium acetate trihydrate is greater than the density of the solution, they settle and are successively deposited on the bottom of the heat storage tank. Therefore, the heat storage material solution and the antifreeze are in contact with each other in liquid phase, and heat exchange can be easily performed using the working fluid as a medium. In this way, the latent heat of sodium acetate trihydrate can be fully utilized.

Even after the sodium acetate is completely solidified, a path is formed through which the working fluid vapor passes during the solidification process, so that the sensible heat after assimilation can also be effectively utilized through this path.

As described above, according to the heat exchange method of the present invention, it is possible to extract latent heat and sensible heat from the latent heat type heat storage material very easily. Therefore, when the method of the present invention is applied to a latent heat type heat storage tank, a small and simple heat storage tank can be obtained. can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a conventional heat storage tank, and FIG. 2 is a cross-sectional view of a heat storage tank that does not explain the present invention in detail. 1... Heat storage tank, 2... Heat storage material, 3...
...Hydraulic fluid, 4...Fuichi fluid 1.5...
·Heat exchanger. Agent Tomina, patent attorney Toshio Nakao, and one other person Figure 1

Claims (1)

[Claims] A heat storage tank using a latent heat type heat storage material includes at least a heat storage material, a working fluid having a specific gravity larger than the specific gravity of the heat storage material in a molten state, and an antifreeze liquid having a specific gravity smaller than the specific gravity of the heat storage material in a molten state. A latent heat type heat storage heat exchange method in which heat from a heat storage material is transferred to an antifreeze liquid using the working fluid, and heat exchange is performed using the antifreeze liquid.