A simulation study on a water chiller complete with a desuperheater and a reversibly used water cooling tower (RUWCT) for service hot water generation

In sub-tropical regions, a standard water cooling tower may be reversibly used, as part of a desuperheater heat recovery system for service hot water heating, to extract free heat from ambient air in colder seasons when building cooling load is reduced. Part of chilled water is pumped into a RUWCT where it is heated by warmer ambient moist air. This paper presents a simulation study where a steady-state mathematical model for such a desuperheater heat recovery system complete with a RUWCT has been developed. Simulation results based on the specifications of an actual chiller plant have demonstrated that the model developed is stable and behaves as expected. With the model developed, the operating characteristics of the refrigeration system with a desuperheater and a RUWCT were studied. The required flow rate of chilled water to be pumped into the RUWCT was calculated in order to satisfy a certain heat load. The maximum heating capacity of the system under different operating conditions were also evaluated. The simulation results also indicated that the use of a RUWCT would achieve a higher energy efficiency than the use of electrical heating as backup heat provisions when building space cooling load is reduced.