JPH0118115B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the composition of an absorbent used in an absorption type air conditioner or water heater.

Conventionally, when water is used as a heat transfer medium, lithium bromide is generally used as an absorbent, and in actual operation it is used as an aqueous solution of lithium bromide.
The concentration of lithium bromide in the aqueous solution was approximately 62% by weight, and it was difficult to increase the concentration beyond that. This is because the crystallization temperature of a 62% by weight aqueous solution of lithium bromide is approximately 40°C, and if the crystallization temperature is increased by increasing the concentration higher than this, the This is because lithium bromide crystallizes, causing problems such as equipment malfunction. And as usual
When using a 62% by weight aqueous lithium bromide solution and using water as the heat transfer medium, the temperature in the evaporator during cooling will be approximately 5-7℃ and the vapor pressure will be 6mmHg.
Therefore, it was necessary to maintain the temperature within the absorber at approximately 40°C so that the vapor pressure would be approximately 6 mmHg. If you try to keep the temperature inside the absorber at around 40℃, it is difficult to remove the heat generated by absorption with air cooling, so a water cooling system must be used for cooling, which requires a cooling tower and requires equipment maintenance. The drawback was that it was difficult to manage. In addition, it is impossible to use outside air as a heat source for heating or hot water supply.
For example, it requires a high-temperature heat source such as a hot spring or high-temperature wastewater, and has the disadvantage of being limited to specific areas.

More specifically, in general, the temperature inside the absorber is
It is said that if the temperature is set to around 45°C, air cooling is possible, and heat pump heating using outside air as the heat source, which was difficult at 40°C, is also possible. concentration of
It is necessary to increase the absorption capacity by setting the content to about 65% by weight. However, as mentioned above, increasing the concentration increases the crystallization temperature, and in an aqueous solution containing only lithium bromide, cooling by air cooling,
It was virtually impossible to use outside air as a heat source for heating or hot water supply.

On the other hand, it has been proposed to add zinc bromide to lithium bromide to lower the crystallization temperature of the aqueous solution of the mixture compared to that of the lithium bromide aqueous solution, but in reality, crystallization only occurs at a maximum of about 18°C. It had the disadvantage that it could not lower the temperature and could not be applied to air conditioning in warm regions, or to heating or hot water supply in cold regions using outside air as a heat source.

In view of the above circumstances, it is an object of the present invention to have an absorption capacity similar to that of lithium bromide, and a crystallization temperature of an aqueous solution that is approximately 10°C higher than the crystallization temperature of an approximately 62% by weight aqueous lithium bromide solution. We provide an absorbent that can lower the temperature by as much as 30℃ or more if necessary, and can be used under air cooling of absorbers during air conditioning or for use in absorbers in a wide range of regions, regardless of whether it is warm or cold. Significant miniaturization of water cooling equipment, and
Its purpose is to enable heat pumps that use outside air as a heat source for heating and hot water supply.

The characteristic composition of the absorbent according to the present invention is that the dry weight ratio of zinc chloride to lithium bromide is 10% or more.
By using this aqueous solution of a mixture of lithium bromide and zinc chloride as an absorbent in absorption type air conditioners and water heaters, it is possible to reduce the amount of lithium bromide from the conventional 62% by weight. The crystallization temperature can be lowered by about 10 to 33 degrees Celsius compared to an aqueous solution.In other words, the solute concentration can be increased and the temperature of the absorber can be raised, making it possible to use air cooling or water cooling equipment for cooling. It has become much more compact and has become practical for heating and hot water supply using outside air as a heat source.

To explain further, it is known that when lithium bromide is used as an absorbent, the absorption capacity does not decrease even if a hygroscopic inorganic substance is mixed into it.
It is generally recognized that an aqueous solution of the mixture will have a higher crystallization temperature than an aqueous solution of lithium bromide alone. However, when the present inventors tried various experiments using lithium bromide as a base and mixed various hygroscopic inorganic substances into it, only zinc chloride mixed in a specific proportion was found to be 62% by weight. We have newly learned that the crystallization temperature is sufficiently lower than that of an aqueous solution of lithium bromide, and the results of an experiment to confirm this are shown below.

[Experiment 1] A large number of samples were prepared by mixing various amounts of zinc chloride into an aqueous solution of lithium bromide with a concentration of 65 _% . %aq.LiBr+Zncl ₂ ×100wt%) and crystallization temperature, the results shown in FIG. 1 were obtained.

From the results shown in Figure 1, we calculated the correlation between the dry weight ratio of zinc chloride to lithium bromide (=Zncl ₂ /LiBr x 100wt%) and the crystallization temperature.
The results shown in FIG. 3 were obtained.

From this experimental result, when zinc chloride is added in a dry weight ratio of 10% to 200% to lithium bromide,
It can be seen that the crystallization temperature decreases by 10°C or more, and when 15% to 130% is added, the crystallization temperature decreases by 20°C or more. This fact indicates that air cooling, heating using outside air as a heat source, hot water supply, etc. are possible.

[Experiment 2] A mixture of lithium bromide and zinc chloride in an approximately equal weight was prepared, and the relationship between vapor pressure and temperature was determined for each mixture with various aqueous solution concentrations (wt%). Upon investigation, the second
The results shown in the figure were obtained.

From the results of this experiment, it was found that when the concentration of the mixture of lithium bromide and zinc chloride was set to 78% by weight, for example, no crystallization occurred even at a vapor pressure of 6 mmHg, and the aqueous solution temperature at that time reached approximately 55°C. This shows that the temperature of the absorber can be raised to 45°C or higher, which is a temperature that allows air cooling, heating using outside air as a heat source, and hot water supply.

[Experiment 3] A comparative experiment was conducted to examine the effect of the dry weight ratio of zinc chloride to lithium bromide on the crystallization temperature and the effect of the dry weight ratio of zinc bromide to lithium bromide on the crystallization temperature. The results shown in the figure were obtained.

From this experimental result, the conventionally proposed addition of zinc bromide reduces the crystallization temperature by only about 18°C at most, but in the case of the present invention, it is possible to reduce the crystallization temperature by a wide range of about 40°C. There was a significant difference in performance.

The absorbent of the present invention can be used in various absorption type air conditioners, such as those exclusively for cooling or heating, those for both cooling and heating, or those incorporating hot water supply equipment.
It can also be used for water heaters.

[Brief explanation of drawings]

FIG. 1 is a graph showing the results of an experiment in which the correlation between the amount of zinc chloride added to an aqueous lithium bromide solution and the crystallization temperature of an aqueous solution of the mixture was investigated. FIG. 2 is a graph showing the results of an experiment in which the correlation between the change in concentration of an aqueous solution of a quantitative mixture of lithium bromide and zinc chloride, and the vapor pressure and temperature of the aqueous solution was investigated. Figure 3 shows
2 is a graph showing the results of calculating the correlation between the dry weight ratio of zinc chloride to lithium bromide and the crystallization temperature based on the experimental results shown in FIG. 1. Figure 4 is a graph showing the results of an experiment comparing how the crystallization temperature of a mixed aqueous solution of lithium bromide and additives decreases when zinc chloride is added and when zinc bromide is added. be.

Claims (1)

[Claims] 1. An absorbent for air conditioners or water heaters, characterized in that zinc chloride is added in a dry weight ratio of 10% to 200% relative to lithium bromide.