JPS58176291A - Thermal energy storage material composition - Google Patents

Abstract

PURPOSE:A thermal energy storage material compsn. suitable for a thermal energy storage material used for a heating apparatus utilizing solar heat and free from phase separation for a long period of time, which is obtd. by compounding sodium acetate trihydrate with one compd. selected from potassium formate, calcium formate, calcium nitrate, etc. CONSTITUTION:Sodium acetate trihydrate is compounded with at least one compd. selected from the group of ammonium formate, potassium formate, copper formate, manganese formate, calcium formate, calcium nitrate, calcium acetate and calcium halide to prepare the purpose thermal energy storage material compsn. It is adequate to add about 0.1-10wt%, based on the total amount of the compsn., said compd. The obtd. compsn. is free from phase separation due to crystallization or precipitation of an anhydrous acetate even if an energy storage/discharge cycle is repeated for a long period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the performance of sodium acetate trihydrate used as a compound.

Sodium acetate trihydrate has a melting point of 58°C and a heat of fusion of 60 cal/Ps per unit weight and 87c per unit volume, and is a compound that is expected to be put to practical use as a heat storage material that utilizes solar heat. be.

However, when the heat cycle of melting heat storage and solidification heat release is repeated over a long period of time, crystals of sodium acetate anhydride gradually precipitate in the system. The production of anhydrous salt itself does not interfere with the heat cycle, but when it gradually increases in large quantities and begins to precipitate and accumulate at the bottom of the system, a so-called phase separation phenomenon occurs, making efficient heat extraction impossible. is necessary.

As a countermeasure against this problem, methods such as adding a gelling agent to sodium acetate pentahydrate or encapsulating sodium acetate hexahydrate have been proposed, but their effects are not necessarily sufficient.

However, as a result of extensive research in order to solve this problem, the present inventors found that ammonium formate, potassium formate, copper formate, manganese formate, calcium formate, calcium nitrate, calcium acetate, and calcium halides were added to sodium acetate filtrate. A heat storage material composition containing at least one compound selected from the group allows efficient heat exchange without precipitation of sodium acetate anhydride or phase separation due to precipitation even after repeated heat storage-radiation heat cycles over a long period of time. In addition, the addition of the above compound slightly lowers the freezing point of sodium acetate hexahydrate, so even if a relatively inexpensive heat collector is used, it is possible to efficiently obtain a predetermined amount of heat. Having discovered that it can produce remarkable effects, the time has come to complete the present invention.

The compounds used in the present invention can be either anhydrous, hydrated, or anhydrous. Among these, calcium 10genide includes calcium chloride, calcium bromide, calcium iodide, and the like. As calcium chloride, any anhydrous salt, monohydrate salt, dihydrate salt, tetrahydrate salt, hexahydrate salt, etc. can be used. The compounds of the present invention may be used alone or in combination with 21 or more (Ao) Particularly preferred compounds include calcium formate and calcium nitrate tetrahydrate.

In addition to such compounds, for example, thallium formate, chromium formate, thallium formate, geranyl formate, cesium formate, thallium formate, nickel formate, etc. have a considerable effect on preventing phase separation, but are of little practical use in terms of toxicity.

The compounding amount of the compound is selected from the range of 0.1 to 10% by weight, preferably 0.5 to 2.0% by weight based on the entire composition. If the width is less than 0.1 weight, the effect will be poor, while if it is more than 10 weight, the amount of heat storage will decrease.

When preparing the heat storage material composition, it is also possible to use small amounts of other arbitrary components such as other heat storage materials and heat storage aids.

The heat storage material composition obtained in this way is suitably used for heating in a solar system that utilizes solar heat, and can perform a stable heat cycle over a long period of time.

Next, the heat storage material of the present invention will be explained in more detail by giving examples.

Example 1 Sodium acetate hexahydrate 49. SP and calcium formate 0
．． A mixture of 5 F (freezing point: 56°C) was placed in a large test tube and heated to 80°C to form a homogeneous solution. Furthermore, liquid paraffin 5- was added to prevent moisture evaporation.

After 2 hours, this composition □ was cooled at a rate of 0.25 T/*, and when it reached 50°C, a small amount of core crystals were added to solidify it. Thereafter, the temperature was raised to 80° C. again and maintained at this temperature for 2 hours, then cooling was started and the same operation was performed. This heat cycle was repeated 500 times, but no phase separation was observed. As a control example, when the use of calcium formate was omitted, phase separation was observed after 20 heat cycles, and anhydrous sodium acetate crystals accounted for the noise in the composition.

Examples 2 to 9 The same experiments as in Example 1 were conducted using the compounds shown in the table. The results are shown in the table.

Claims (1)

[Claims] A heat storage material made by blending sodium acetate trihydrate with at least one compound selected from the group of ammonium formate, potassium formate, copper formate, manganese formate, calcium formate, calcium nitrate, calcium acetate, and calcium chloride. Composition.