Question

Given the choice between pure water and a NaCl-water solution as the thermal energy storage medium in medium temperature (40°F, 4.4°C) refrigeration applications, what are the pros and cons of each material?

Answer 1

Thermal energy storage (TES) is a key component of large successful thermal systems. A typical TES should allow for the minimum reasonable thermal energy losses and the corresponding energy savings, while permitting the highest efficiency of stored thermal energy.

There are three kinds of TES systems

1) sensible hear storage

It is based on storing thermal energy by heating or cooling a liquid or solid storage medium (here comes our water and NaCl-water solution)

2) Latent heat storage using PCMS

3)Thermo chemical storage (TCS)

Pure water and NaCl-water solution for TES medium for refrigerating applications pros and cons:

The high heat capacity of water makes it best TES medium.

Water medium is cheap in cost but large water storage tanks is needed.

The major differences are the obvious higher temperatures attainable in the molten salt state and when the salt solidifies (freezes) it contracts versus expanding like water. Thus, molten salt freezing in a pipe would not burst the pipe as water would.

molten salt has the benefits of high volume specific thermal capacity, is readily available and is relatively cheap but it has the drawback of a high freezing temperature (120-220^oC). This means that special care must be taken to ensure that the salt does not freeze (solidifies). Routine freeze protection operation increases maintenance and operational costs.

So ,each material has its own advantage and disadvantages for refrigerating applications.