Retrofit of a liquid desiccant and evaporative cooling-assisted 100% outdoor air system for enhancing energy saving potential

Abstract

The objective of this research is to retrofit a liquid desiccant (LD) and indirect/direct evaporative cooling-assisted 100% outdoor air system (LD-IDECOAS) to enhance its operating energy saving potential. Two retrofit cases of existing LD-IDECOAS have been considered. The first case involves replacing the indirect and direct evaporative coolers with an M-cycle or a dew-point indirect evaporative cooler (i.e., Case 1), and the other one involves adding an enthalpy exchanger before the LD unit of the system in case 1 (i.e., Case 2). By conducting detailed energy simulations for each retrofit case, the improvements in operating energy saving and the coefficient of performance (COP) over the existing LD-IDECOAS were quantitatively evaluated. The results showed that case 1 might provide enhancement in cooling capacity and thermal COP; however, the heating energy consumption for regenerating the desiccant solution increased with the higher process airflow rate when compared to the existing LD-IDECOAS. It was also found that the cooling capacity, thermal COP, and primary COP could be improved by adding a membrane enthalpy exchanger, as done in case 2, without any significant increase in the heating energy consumption for regenerating the desiccant solution.