JPS6230183A - Mixed liquid heat storage agent - Google Patents

Abstract

PURPOSE:To provide the titled heat-accumulating agent available at a low cost, having high solubility and composed of a mixture of a halide forming a dihydrate at normal temperature and a halide forming a hexahydrate at normal temperature. CONSTITUTION:The objective heat-accumulating agent can be produced by mixing (A) a halide forming a dihydrate at about normal temperature (e.g. LiCl, BaCl2, LiBr, BaBr2, etc.) and (B) a halide forming a hexahydrate at about normal temperature (e.g. MgCl2, CaCl2, NiCl2, CoCl2, MgBr2, CaBr2, NiBr2, CoBr2, etc.). The molar ratio of the dihydrate to the sum of dihydrate and hexahydrate is preferably 0.55-0.9.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a liquid heat storage agent, and particularly to a mixed liquid heat storage agent composed of halogen compounds of hexahydrate and dihydrate, which have a solubility of W6 and are inexpensive. .

[Background of the invention]

Heat storage agents are mainly materials with large specific heat, that is, sensible heat (solids,
There are two main types: those that use liquids) and those that utilize latent heat due to phase change of melting or vaporization.

The former uses water as a typical example, as well as concrete blocks,
Rocks, etc. are used, but the heat storage capacity (heat storage amount per heat storage agent)
Since the temperature is small, a large amount of heat storage agent is required.

The latter can be further divided into two types: those that utilize latent heat of fusion and those that utilize latent heat of vaporization. The former has calcium chloride as a main ingredient, but since it is a solid, it is inconvenient to handle, and there is a problem of supercooling, which causes a large difference between the melting start temperature and the solidification start temperature. (Citation: Japanese Unexamined Patent Publication No. 53
-70990 Publication) There are few examples of devices that utilize latent heat of vaporization, and there is only an aqueous solution of lithium bromide when an absorption refrigerator is converted into a heat storage type. This method uses a liquid heat storage agent,
By heating the liquid heat storage agent to evaporate the moisture and concentrating the heat storage agent, heat is converted into a concentration difference and stored.
It utilizes the latent heat of condensation generated when water vapor is absorbed into a thick heat storage agent. This method uses the latent heat of condensation of water (6 to 7 times the latent heat of solidification), so it has a large heat storage capacity, and it also has the advantage of being able to freely change the generated temperature by utilizing the concentration difference (
The solidification temperature is constant, but the water vapor absorption temperature varies depending on the atmospheric pressure and concentration). However, since lithium bromide aqueous solution is much more expensive than calcium chloride and the like, it has been considered unsuitable for heat storage requiring a large capacity heat storage agent.

On the other hand, inexpensive liquid heat storage agents such as magnesium chloride and calcium chloride are conceivable, but their solubility is low and they are not suitable for the latent heat of vaporization method that utilizes concentration differences.

The absorbent used in absorption refrigerators is also air-cooled.
In order to further increase the solubility, research into mixed absorbents in which other absorbents are mixed is also being accelerated.

For example, LiBr-LiCQ system, Liar-C,H
602 series, LiBr-Li5CN series (frozen, voQ56
, Nn646. p.

11), but the mixing ratio has not been optimized.

In addition, as a mixed heat storage agent, KCQ-LiCQ series and AgCQ2-KCQ are used to adjust the melting point of molten salt using latent heat of fusion.
(Industrial Materials Vol. 126 & 9, p. 44) [Object of the Invention] The object of the present invention is to provide a mixed liquid heat storage agent that is inexpensive and has high solubility by appropriately mixing halogen compounds. It's about doing.

[Summary of the invention]

The inventors investigated various substances that can be used as liquid heat storage agents and found that halides that form hydrates are inexpensive and have relatively high solubility. Further studies on halides revealed that bromide and chloride are especially advantageous in terms of solubility, cost, and safety.

This is because absorption refrigerators have traditionally used aqueous solutions of lithium bromide and lithium chloride.

As a result of further investigation, the inventors obtained the following new idea. That is, the solubility of most halides is (
1) Those with crystallization water are larger at room temperature (for example, KCQ and NaCQ without crystallization water are larger than Mac with hexahydrate salt)
The solubility is lower than that of Q larger, (e.g. Lie (1 than LiBr
has high solubility> (4) The solubility of the substance in units of L is insufficient as a liquid heat storage agent.

As a result of various studies on how to improve solubility, the inventors discovered that the solubility of halides with water of crystallization is greatly influenced by the number of water molecules hydrated with it, and that hydration is influenced by coexisting ions. (In other words, other halides coexisting) confirmed through experiments that the solubility can be improved by mixing halides.

Furthermore, we focused on the halides to be mixed: (1) dihydrate has higher solubility but is more expensive, and (2) hexahydrate has lower solubility than dihydrate but is cheaper. Hexahydrate salt was selected.

That is, 1. The gist of the present invention is to provide a highly soluble and inexpensive mixed liquid heat storage agent by appropriately mixing an inexpensive hexahydrate and a relatively highly soluble dihydrate halide. .

Chlorides such as LiCQ, BaCQ2, and LiBr are typical examples of chlorides that form dihydrates at room temperature and are subject to the present invention.

There are bromides such as BaBr2, and typical ones that turn into hexahydrate salts at room temperature include MgCQ, CaCQ2. N1C
Chlorides such as uztCoCQ, AgBr2. CaBr
, ,' NiBr, , CoBr.

There are bromides such as

[Embodiments of the invention]

The present invention will be explained in detail below using examples.

(Method for measuring solubility) Table 1 shows the type and temperature (near the saturation concentration of the main ingredient at a temperature of 0° C.) of the liquid heat storage agent (hexahydrate as the main ingredient, divalent salt additive) used.

Table 1 Put 300cc of the main ingredient into a 500Ω cylindrical glass container, and
Place the main ingredient in the container in a constant temperature water tank at 60-1100rC.
Stir at a rotational speed of p and keep the main ingredient uniformly at 0°C. Add a predetermined amount of additive to it and dissolve it, then add water and bring it to an equilibrium state while stirring thoroughly until a small amount of solid additive remains in the aqueous solution (solid-liquid equilibrium state). . Next, the additive (solid) remaining in the aqueous solution is filtered,
Measure the weight after drying. Subtract the residual amount from the added amount to obtain the net added amount to determine the total dissolved concentration. By changing the amount of additive added, the mixing ratio of the main ingredient and additive is changed, and the change in total concentration (solubility) at each mixing ratio is determined.

In the following examples, the mixing ratio is expressed as the addition rate X (weight ratio) defined by the following formula.

X=0 represents only the base agent, and x=1 represents only the additive.

<Example 1> Fig. 1 shows the relationship between the addition rate or the total concentration C when lithium bromide (additive for dihydrate) is mixed into an aqueous calcium chloride solution (main ingredient for hexahydrate). The total concentration of the mixed liquid heat storage agent has a peak (maximum solubility) near the addition rate of 0.75, and the solubility (total concentration) improves by mixing.

The total concentration (m solubility) of the mixed liquid heat storage agent exceeds the value of the higher solubility of the base agent and additive alone (in Figure 1, the concentration of lithium bromide aqueous solution alone (X = 1.○) is 59%). If the effective range is the range of the addition rate, it is X=0.6 to 0.
It is 9.

<Example 2> Fig. 2 shows the relationship between the addition rate X and the total concentration C when lithium bromide (dihydrate additive) is mixed into an aqueous calcium bromide solution (hexahydrate base ingredient). The total concentration of the mixed liquid heat storage agent has a peak (maximum solubility) near the addition rate of 0.55, and the solubility is improved by mixing.

The effective area is X=0.4 to 0.8.

<Example 3> Figure 3 shows the relationship between the addition rate or total concentration C when lithium chloride (additive for dihydrate) is mixed into an aqueous calcium chloride solution (main ingredient for hexahydrate). The total concentration of the mixed liquid heat storage agent has a peak (maximum solubility) near the addition rate o of 55, and the solubility is improved by mixing.

The effective area is X=0.3 to 0.8.

The optimum mixing ratio varies somewhat depending on the substance. Focusing on the fact that solubility is greatly affected by the number of water molecules hydrated in each substance, the results of these Examples were rearranged using the molar ratio Y defined by the following formula as the addition rate.

The results are shown in FIG.

(moles of dihydrate additive) Y=O represents only the base agent, and Y=1 represents only the additive.

As a result, the optimum value (peak) of the addition rate Y expressed in molar ratio
is around 0.75 regardless of the material, and the effective area is X=
It is about 0.55 to 0.9.

In this way, by expressing the addition rate as a molar ratio, it was discovered that regardless of the substance, the optimum mixing ratio is 0.75 and the effective range is Y=0.55 to 0.9.

This optimum addition rate (molar ratio) and effective area are common values for dihydrate and hexahydrate halides, considering that solubility is greatly influenced by the number of water molecules hydrated in the substance. , NiCQ, , CoBr, and BaBr have been confirmed to have similar values.

The basic idea of solubility improvement of the present invention is that "the solubility is improved by changing the affinity between a substance (ion) and water molecules during hydration using other coexisting ions."

In the present invention, from the viewpoints of solubility, water vapor absorption, stability, and safety of the liquid heat storage agent, an aqueous solution of a halogen compound is targeted, but the concept of the present invention is not limited thereto.

Furthermore, hydration refers to ``solvation,'' in which solute ions (molecules) are surrounded by solvent molecules in a solution and stabilized, when the solvent is water (included in solvation). Therefore, the present invention is not limited to aqueous solutions (hydration), but is also common to a wide range of other solutions that form solvation (for example, solutions that form complexes consisting of disposed bonds).

Further, although the present invention is directed to a liquid heat storage agent, it can be applied as is as an absorbent for current absorption refrigerators and heat pumps.

〔Effect of the invention〕

According to the present invention, a mixed liquid heat storage agent composed of a comparatively inexpensive internal water salt and a highly soluble double salt has high solubility and can be produced at low cost.

[Brief explanation of drawings]

Figures 1, 2, and 3 are characteristic diagrams of an example showing the relationship between the mixing ratio (weight ratio) and solubility of each substance when the winter substances of the present invention are mixed, and Figure 4 is a characteristic diagram of an example showing the relationship between the mixing ratio (weight ratio) and solubility of each substance when the winter substances of the present invention are mixed. It is a figure which shows the result of an Example showing the relationship between a common mixing ratio (molar ratio) and solubility of substances. X...Addition rate.

Claims (1)

[Scope of Claims] 1. A mixed liquid heat storage agent comprising a mixture of a halide that forms a dihydrate at around room temperature and a halide that forms a hexahydrate at around room temperature. 2. The mixed liquid heat storage agent according to claim 1, wherein at least one of the two halides is a bromide or a chloride. 3. In claim 1, the addition rate (molar ratio) of the dihydrate to the sum of the dihydrate and hexahydrate is 0.55 to 0.
A mixed liquid heat storage agent characterized by having a temperature of 9.