JPS6040799B2 - Direct heat exchange type latent heat storage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a direct assisted heat exchange type latent heat type heat storage device.

Currently, the emergence of an excellent heat storage device is eagerly awaited for the purpose of economical management of thermal energy.

To date, many heat storage Chochin methods have been studied, including the Kakasumi type, which uses the temperature change itself of the material, the latent heat type, which uses the latent heat of fusion of the material, and the reaction type, which uses the heat of chemical change of the material. However, each has its advantages and disadvantages. It goes without saying that the main challenge in heat storage research is improving the performance of heat storage devices, but an even more important issue is their cost.
A heat storage device is a device whose purpose is to conserve resources and energy, so if the cost is too high, no matter how good the performance is, the purpose of its development will be lost. The present invention aims to significantly reduce costs in such a heat storage device.

In general, in heat storage for heating, cooling, and hot water supply, inorganic hydrated salts (inorganic salts with crystal water, such as sodium sulfate 1
0k salt, Na2S04, 1 plate 20, sodium thiosulfate pentahydrate, Na2S2Q, 20, etc.) have been considered to be promising candidates for heat storage materials.

FIGS. 1a and 1b show structural examples of conventional latent heat type heat storage devices using these heat storage materials, and FIG. 1a is called a capsule type, and FIG. 1b is called a shell-tube type. In the capsule-type heat storage device shown in FIG.
5 shows a large number of capsules filled and sealed with heat storage material. Also, the shell of FIG. 1b. In the tube-type heat exchanger, the oven 1 is a heat storage container, 12 is an inlet for the heat medium, 13 is an outlet thereof, 14 is a latent heat type heat storage material made of inorganic water salt, and 15 is a heat exchange tube for passing the heat medium. shows. In these latent heat type heat storage devices, the heat storage material 4 and the heat storage material 4 store and release heat by repeating melting and solidification. It is installed for the purpose of securing a heat exchange surface and protecting the molten heat storage material from flowing out together with the heat medium.

However, manufacturing and processing these capsules and heat exchange tubes requires an extremely large amount of expense, and in some cases, it is not unusual for the cost to exceed the cost of the thermal insulation material itself. In order to reduce costs, the heat storage device uses a direct heat exchange method, omitting capsules and heat exchange tubes, and has a simple structure and low cost.
In a latent heat type heat storage device in which a hot soot (liquid) that does not mix with the heat storage material is brought into direct contact with the heat storage village in the form of small droplets to perform heat exchange, the storage material consists of an inorganic hydrated salt and its saturated aqueous solution, and before the amount of the saturated aqueous solution stores thermal energy or after releasing thermal energy,
The heat storage material is characterized in that the moisture content is adjusted to be 8 to 1 volume percent of the entire heat storage material.

Hereinafter, the heat storage device of the present invention will be explained in more detail with reference to the drawings.

FIG. 2 shows the basic structure of the latent heat type heat storage device according to the present invention, in which 21 is a heat storage container, 22 is a heat medium inlet, 23 is an outlet thereof, 24 is a heat storage material made of a material suitable for heat storage, and 25 is a heat storage material. A heat medium (liquid) body having a specific gravity smaller than that of the heat storage material, "In the heat storage container 21, a heat medium storage space 25' communicating with the heat medium outlet 23 is formed above the filled heat storage village 24. ing.

Further, 26 is a heat insulating material layer L, 271 is a guide plate, 28 is a pump, 29 is a heat source or heat load, and the heat medium 25 supplied by the pump 281 is dispersed as small droplets into the heat storage village 24 at the inlet 22. The porous body to be ejected, 3 indicates a seed crystal generator formed by leading the tip of the pipe from the heat storage container 2 to the outside through the heat insulating material layer 26.Thus, the inlet at the bottom of the heat storage container 21 The configuration in which the heat medium is ejected as small droplets at 22 constitutes a means for bringing the heat medium into direct contact with the heat storage material, and the heat medium storage space 25' formed in the upper part of the heat storage container 21 and the outlet 23 communicating therewith constitute a means for directly contacting the heat medium with the heat storage material. Since the specific gravity of the heat medium 25 is made smaller than that of the heat storage material 24, it constitutes a means for separating and extracting the heat medium 25 that has been in direct contact with it for heat exchange from the heat storage village 24. Heat medium 25 as heat storage material 2
Means for direct contact with the shame and the contacted heat medium 2S
The means for separating the heat storage material 24 from the heat storage material 24 is not limited to the illustrated example, and other configurations that can be expected to have the same effect can be adopted. Inorganic hydrated salt is used as the heat flux material 24, but since the heat medium 25 floats therein in the form of small droplets, it must not solidify as a whole during the heat storage/dissipation operation.

Therefore, by containing more than the stoichiometric ratio of water in the inorganic hydrated salt, the inorganic Inorganic hydrated salts prepared so that crystals and their saturated aqueous solutions coexist are used.There are many types of inorganic hydrated salts, and an appropriate inorganic hydrated salt can be selected and used. The amount of water that should be added to obtain the desired amount of water differs depending on the type of inorganic hydrated salt.If this water content is too small, it will be difficult for the heat medium to float; The latent heat of fusion per volume decreases.As a result of various studies, an example of the moisture content that is considered to be appropriate is shown in the table below. In the state after the heat storage material is released, the heat storage material contains 8 to 18 volume percent of the saturated aqueous solution and the remaining hydrated salt crystals based on the total amount, and the heat transfer medium becomes small pieces and rises in the heat storage material. It is possible to do so.

Furthermore, by coexisting an inorganic hydrated salt with an appropriate amount of a saturated aqueous solution, disadvantageous phenomena such as "overcooling" and "phase separation" observed in conventional methods can be significantly improved. Further, as the heat storage body, crystals of two or more types of inorganic hydrated salts and saturated aqueous solutions thereof can also be used.

The apparent melting point of such a heat storage body is important in relation to the use of thermal energy (cooling, heating, hot water supply, etc.), but it also depends on the type of inorganic hydrated salt, the water content, the mixing ratio of two or more salts, etc. By appropriately selecting it, its apparent melting point can be adjusted and it can be used in a wide range of applications.Table 1 On the other hand, the heat medium 25 is generally a material that does not interact with the heat storage village 24 through chemical reactions, melting, etc. In addition, a liquid having a specific gravity lower than that of the heat storage material, such as silicone oil, kerosene, light oil, petroleum paraffin, and coconut oil, is used.

In special cases, a gas such as air may also be used. Various studies have been conducted on the above liquid, and silicone oil having a viscosity of 5 to 20 centistokes at the operating temperature is optimal. Silicone oil is excellent in that it has a low surface tension, easily forms droplets, and does not form an emulsion with the thermal storage melt, making it easy to separate. However, silicone oil with a high viscosity is This is not suitable because the transport power by the pump 28 becomes excessive. In addition, silicone oil covers the top surface of the heat storage material to prevent fluctuations in the moisture content of the heat storage material, and also has the effect of reducing corrosion of other equipment, such as solar heat collectors and water heaters. When storing heat in the heat storage container having the above configuration, the heat medium 25 is fed to the heat source 29 by the pump 28, heated in the heat source 29, and then returned to the inlet 22 of the heat storage container for circulation.

Examples of the heat source 29 include solar heat, factory waste liquid, and nighttime electricity. The heat medium heated by the heat source 29 and sent to the heat storage container passes through the porous body 30, becomes droplets, and rises (floats) inside the cage heat body 24, and directly flows into the heat storage material 24. and returns to the upper heat medium storage space 25' in the cage heat container 21. If such an operation is continued, the temperature of the heat storage village 24 rises, and at the same time, the inorganic hydrated salt crystals contained therein melt, and the amount of heat corresponding to the latent heat of fusion is stored. On the other hand, when releasing heat from a heat storage device, the heat medium 25 is sent to a heat load 29 such as a heating fan coil, an absorption chiller, or an oil supply device.
5 is allowed to cool and then returned to the inlet 22 to reflux.

The heat medium 25 introduced from the inlet 22 exchanges heat while rising (floating) in the form of small droplets in the heat storage village 24, thereby cooling the heat storage material 24. As a result, the molten inorganic hydrated salt precipitates, and the corresponding latent heat of melting is imparted to the heating wire 25. As is clear from the above description, in the heat storage material 24, as the temperature of the heat storage material 24 changes, the ratio of the amounts of the inorganic hydrated salt crystals contained therein to the saturated aqueous solution that is the melt thereof changes greatly. do.

However, in order to prevent the entire heat storage material from solidifying in the process of heat storage and release, it is necessary to contain water in an amount higher than the stoichiometric ratio of the inorganic hydrated salt, so that even at a temperature below the melting point of the hydrated salt, an appropriate amount of saturated aqueous solution is produced. Since it is prepared in a state where it coexists with the crystals of the inorganic hydrated salt, direct contact between the two by dispersing the heat medium in the heat storage body will not be hindered. Next, the guide plate 27 will be explained.

This guide plate 27 is for suppressing the rapid rise and separation of the heat medium 25 in the heat storage material 24 and for maintaining sufficient contact time between the two to improve heat exchange performance. ,b
An example of its structure is shown below. The guide plate 27 in the same figure has a small hole 33 on one side of its flat plate part 32 that causes the heat medium to flow out and float in the form of small droplets, and around the small hole 33 to direct the flow of the heat medium (arrow) in an appropriate direction. It has a green plate 34 that supports the hydrated salt crystals 35 deposited on the flat plate part 32 so that they do not slip off. The flat plate part 32 has a small hole group 33
5 to 7 degrees from the horizontal with the side with the
The heat storage container 21 is joined to the edge plate 34 so as to be inclined at an angle of .
If such a guide plate 27 is not installed, inorganic hydrated salts will precipitate from the melt during the heat dissipation process of the heat storage device.
The hydrated salt crystals settle to the bottom of the container due to the difference in specific gravity, and when a large amount of hydrated salt crystals settle to the bottom of the container, it becomes difficult for the heat transfer medium to flow through the inlet 22, and a drift occurs, causing heat transfer. Sometimes the replacement is defective.

However, when the guide plate is installed, the hydrated salt crystals generated in the heat storage material are dispersed and supported, and all of them do not accumulate at the bottom of the vessel, improving heat exchange performance. The preferred distance between the guide plates is 5 to 10 spaces. Next, the seed crystal generator 31 will be explained.

This seed crystal generator 31 has a tubular container filled with an inorganic hydrated salt of the same type as the heat storage material, one end of which is opened in contact with the heat storage material 24 inside the heat storage container 21, and the pond end is insulated. It penetrates the material layer 26, is drawn out to the outside, and is sealed. If the temperature of the heat storage material is sufficiently raised and the inorganic hydrated salt in the heat storage village is completely melted, the next time you try to dissipate heat, slight supercooling will be observed due to the lack of crystal nuclei. Sometimes.
The hydrated salt in the seed crystal generator 31 is not heated, especially in the portion pulled out to the outside, so it can remain as a crystal without melting. Therefore, the crystals act as seed crystals during heat dissipation, allowing smooth solidification to proceed with little overcooling. As is clear from the detailed description above, the heat storage device of the present invention uses a direct contact heat exchange method, thereby eliminating the need for capsules and heat exchange tubes, which required a great deal of expense in conventional devices. This makes it possible to construct a heat storage device at an extremely low cost, and greatly contributes to the effective use of thermal energy. Examples of the present invention are shown below. [Example 1] A cylindrical heat storage device having the structure shown in FIG. 2 and having a heat storage container diameter of 3 mm and height of 80 mm was manufactured.

Heat storage village A (
A water content of 6% by weight and the remainder being anhydrous sodium carbonate) was added, and silicone oil was added to the top of the heat storage material until the thickness reached 7 arcs to serve as a heat medium. Ten guide boards with the shapes shown in Figure 3 a and b were installed. The heat medium was pumped out from the outlet 23 with an electric pump, heated using marrow heat while flowing back into the inlet 22, and the temperature at the inlet 22 was adjusted to 6°C. The temperature difference between the outlet and inlet of the silicone oil was measured, and the amount of thermal energy transferred from the heat medium to the heat storage material was calculated using the Japanese-Korean fever and flow velocity. The relationship between the determined heat content Q of the heat storage material and the average temperature T of the heat storage material is shown in FIG. Curve C in the figure is for heat storage material 1, and curve C2 is for comparison with heat storage material A and the same volume of water tested. The temperature at which Q rapidly increased (the apparent melting point of the thermal storage village) was approximately 33°C. When taking a temperature range of 1 and 0 above and below (total of 2 and 0) from this apparent melting point, the heat capacity of heat storage material A is about 3.7 times that of water. Increase the flow rate of silicone oil to 500
Assuming that the rate is constant at '/min, it took about 1.8 hours to reach point P2 from point P in Fig. 4, but if the guide board 27 was removed, the time required was about 3.5 hours. It was shown that the guide plate had a great effect on promoting heat exchange. 〔Example
2] The same apparatus as in Example 1 was filled with cage heating material B (moisture content: 43% by weight, remainder being anhydrous sodium acetate).

The temperature of the entire heat storage device was raised uniformly to 6g0 in advance to completely melt the inorganic hydrated salt in the heat storage material. next,
Silicone oil was pumped out using an electric pump and cooled by a water flow heat exchanger on the way to the inlet 22 to maintain the inlet temperature at 24°C. From the temperature difference, flow velocity, and specific heat at the outlet and inlet of the silicone oil, calculate the amount of thermal energy transferred from the bulk heat material B to the heat medium, and calculate the relationship between the heat capacity Q of the heat storage material and the average temperature T as shown in Figure 5. Shown below. The curve C3 corresponds to the heat storage material B, and the curve C4 corresponds to the same volume of water as the heat storage material B measured for comparison. The apparent melting point of Satatsumura B is 5
It was 70. From this temperature up and down 1oo○ (total 20 degrees
), the amount of heat storage in heat storage village B is approximately 4.5 times that of water.
It becomes 1 times. When the seed crystal generator was removed and tested, subcooling of about 8°C from the above-mentioned apparent melting point was observed. [Example 3] Using the same equipment as described above, heat storage material C (moisture content: 40.5
Weight percent, anhydrous sodium acetate 30.5 weight percent, sodium thiosulfate 30.5 weight percent).

Melting in this case occurred between 40 and 55° C., and although it did not exhibit a clear apparent melting point as described above, the heat content in this temperature range was observed to be 3.4 times higher than that of water.

[Brief explanation of the drawing]

Figures 1a and 1b are cross-sectional views of a conventional latent heat type heat storage device, Figure 2 is a sectional view of a direct heat exchange type heat storage device of the present invention, and Figures 3a,
b is a plan view and a sectional view of the guide plate, and FIGS. 4 and 5 are diagrams showing the test results. 21... Heat storage container, 22... Inlet, 2
3... Outlet, 24... Heat storage material, 25.
...Heat medium, 25'...Heat medium storage space. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A latent heat type heat storage device in which droplets of a heat medium (liquid) that does not mix with the heat storage material are brought into direct contact with the heat storage material to perform heat exchange, and the heat storage material is an inorganic hydrated salt and its saturated aqueous solution. , and the amount of water is adjusted so that the amount of the saturated aqueous solution is 8 to 18 percent by volume of the entire heat storage material before storing thermal energy or after releasing thermal energy. A direct heat exchange type latent heat storage device.