Study of a Heat Pump for Simultaneous Cooling and Desalination

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Access to freshwater and energy resource management are two of the major concerns of the next decades. The global warming indicator, the decrease of rainfalls and the growing energy demand for cooling are correlated in the most populated agglomerations of the world. For industrial and social purposes, it seems vital to develop energy efficient systems for cooling and desalination. A heat pump can produce energy for space cooling and heat for desalination. Among the different desalination systems available, membrane distillation seems the most suitable solution to the condensing temperature level of a standard heat pump.This article presents the development of a model of heat pump for simultaneous cooling and desalination by air-gap membrane distillation. The model was first developed using EES software and validated with experimental results from our laboratory and from the literature. The desalination unit was then optimised by numerical means in terms of dimensions and operating conditions using a bi-dimensional model with Matlab. A coupled system with a heat pump was finally simulated. The objective is to estimate the freshwater production depending on the cooling loads of a refrigerator placed in a building submitted to the conditions given by a weather data file in the Trnsys environment. The energy consumptions are compared to those of a standard reverse osmosis plant producing the same amount of freshwater associated to a chiller of same cooling capacity as the heat pump. The results show that the heat pump for simultaneous cooling and desalination offers interesting perspectives.