Two-stage Air-dehumidification System for the Tropics – Assessment of Conceptual System Configurations

Abstract

Under tropical climate conditions, conventional air-conditioning systems consume a considerable amount of electricity in order to get rid of the high latent load (humidity) of the ambient air. This is due to the applied simultaneous dehumidification and cooling processes. Therefore, an idea of a separate handling of the latent and the sensible loads is investigated by applying series connected heat powered dehumidification and electricity powered cooling systems. A two-stage dehumidification system including a membrane-based heat and mass exchanger and an Evaporatively COoled Sorptive dehumidification system (ECOS system) is proposed to dehumidify the ambient air; the sensible load (cooling of dehumidified air) is handled by an efficient conventional cooling process operating at relatively high evaporation temperatures (14 െ 20 Ԩ). The aim of this study is to evaluate different conceptual system configurations and to find optimized systems for tropical climate conditions (air humidity and temperature are in the order of 20 g୴/kgୟ୧୰ and 32 Ԩ, respectively) by means of simulation calculations. The dehumidification capacity, the total specific removed enthalpy and the thermal coefficient of performance (COP) of the system are used as criteria for an assessment of the proposed concepts. The dehumidification system is mathematically modelled in MATLAB and linked with TRNSYS-17.1. Experimental data are used to validate the components models. Design and performance data of simulated air-dehumidification systems that are based on the concepts are presented. Results of the performance assessment show that using additional ambient air flow for the evaporative cooling process in the ECOS system can improve the dehumidification performance of the system and can reduce the cooling load of the cooling system significantly.