Feasibility and optimization structure analysis on heat pump assisted desiccant cooling systems under dynamic conditions

Abstract

Heat-pump assisted hybrid desiccant cooling (HPDC) systems are generally placed with the evaporators located downstream of the desiccant wheel (HPDC-D) to deal with the adsorption of heat and control indoor temperature; positioning the evaporator upstream of the desiccant wheel (HPDC-U) can improve dehumidification performance. In this study, HPDC systems are established based on an analytic solution-validated desiccant wheel model, and the effect of the system configuration on the indoor temperature and humidity control is quantitatively analyzed in dynamic conditions. The proposed dimensionless parameters clarify the thermal performance of the dehumidification and regeneration processes. The simulation results propose an optimized HPDC-SE system with dual separate evaporators, and its energy consumption is compared. Finally, the feasibility of combining the HPDC system with a heat recovery plate is discussed. Due to the thermal imbalance between the condensing heat required for regeneration and the supply air cooling capacity required for the indoor sensible load, the HPDC-U system could not continuously control the indoor temperature below the control range in dynamic conditions, and the HPDC-D system could not continuously control the indoor humidity. The analysis of the dimensionless parameters shows that the thermal economy of the desiccant wheel decreases with the increase in the process inlet air humidity. The proposed HPDC-SE system can improve the indoor environment control effect and reduce the electricity consumption by 5%, 4.6%, and 11.7% compared to the HPDC-U system, respectively. The heat recovery plate has a low overall utilization and heat recovery rate for HPDC-U and HPDCSE systems, and affects the indoor humidity control of the HPDC-D system. Therefore, the heat recovery plate is not suitable for HPDC systems.