Study on performance of chemical heat storage system for direct steam generation

Abstract

A heat storage system that is used to generate steam directly by exploiting the dissolution phenomenon between CaBr2 and water was studied. The performance of the system in terms of the coefficient of performance (COP) or volumetric heat capacity (VHC) yielded maximal values for the amount of water supplied. The COP was 0.072 to 0.115 for steam pressures of 20–50 kPa at x = 7.5. VHC values recorded were 177.2 to 250.1 kJ/l for steam pressures of 20–50 kPa at x = 7.5. This calculation was validated by comparing the calculated value with the experimental result. The pressure settled at the equilibrium state for a very short duration at the heat release step, proving that the dissolution phenomenon involved a high mass transfer rate and was able to transform the heat of dissolution into enthalpy of steam. The amount of steam generated in the experiment conformed very well to the calculations, thus validating the calculation method.