Investigation on heat and mass transfer characteristics for a zeolite-coated heat exchanger using comparatively low-temperature energy: Heating humidification mode and cooling dehumidification mode

Desiccant-based hybrid air-conditioning technologies are currently being developed to reduce energy consumption and enhance the effectiveness of indoor thermal environmental control in buildings. The purpose of this study is to propose a compact desiccant-based outdoor air-conditioning system that directly uses heated desorption and cooled adsorption with comparatively low-temperature energy, and to propose a mathematical model for the system by investigating the heat and mass transfer characteristics of a zeolite-coated heat exchanger (ZCHE). To study the heat and mass transfer characteristics of the ZCHE, the moisture removal capacity and the moisture removal regeneration were measured at various heat source temperatures and water flow rates using an experimental model. The measured values were adopted as boundary condition for mathematical model. The results show that the air-conditioning performance of the ZCHE is strongly dependent on the water temperature under constant air conditions. The humidification capacity of the ZCHE was measured 25.0 g at 5 kW heat capacity and the humidification capacity was measured 10.2 g at 0.6 kW cooling capacity. The relative errors of mass transfer coefficient and heat transfer coefficient are ±3.6% and ±3.8%, respectively. Moreover, the proposed mathematical model fitted well with measured values.