Exergy Analysis of Processing Humidified Air in a Humidification-Dehumidification Desalination System

摘要

Based on earlier reported experimental data, this article concentrated on the evaluation of flow exergies for air and water in the humidification process. Total input and output exergies to the system were broken down into sub-components and analyzed. The former was separated into three exergy parts: air heating, water heating and pumping. The latter was separated into chemical and thermal output exergies. Calculating individual exergy incoming and outgoing flows, the exergy transfer of the process have been studied. The effect of flow rates and temperatures of air and water entering the humidification chamber -which actually represent the main parameters affecting the process- were investigated. The results obtained indicate that the exergy efficiency of the process was found to increase with increasing inlet water temperature and with decreasing inlet air temperature and water flow rate as well due to excessive exergy penalty exhausted in water pumping. Finally it has been noted, that there is an optimum value of air flow rate (V_a~·), for certain water flow rate (V_w~·), at which the exergy efficiency of the process is maximum. Varying air flow rate at two different water flow rates and regarding the volumetric flow rates of air and water as ratio between the gas carrying liquid, and the liquid sprayed, it was found that the best range of (V_a~· /V_w~·) was 10-15 v/v in both cases.