Performance optimization of solar humidification-dehumidification desalination process using Pinch technology

This paper presents a method of performance optimization of solar humidification-dehumidification desalination (HDD) process using Pinch technology. Pinch technology is used in the humidification process to determine the maximum possible saturated air temperature and the temperature of water rejected from the unit, and then in dehumidification process to determine the temperature of water leaving from heat exchanger. From pinch chart, all the thermal energy rejected, supplied and recovered are determined easily. Both the optimum mass flow rate ratio of water to dry air and maximum thermal energy recovery rate is obtained by adjusting mass flow rate ratio of water to dry air. The curve of optimum mass flow rate ratio of water to dry air at a different spraying water temperature is acquired by changing spraying water temperature follow the above steps. The analysis method using Pinch technology in HDD process proves a very simple, visual and efficient. From Pinch technology analysis, there exits an optimum mass flow rate ratio of water to dry air if given the temperature of spraying water and cooling water. The energy recovery rate can reach 0.67 at the optimum mass flows rate ratio when the spraying water temperature is 80 degrees C and cooling water temperature is 30 degrees C. The optimum mass flows rate ratio of water to dry air decreases with cooling water temperature declines when the spraying water temperature remains unchanged. If the minimum temperature difference at pinch points are 1 degrees C, the energy recovery rate could reach 0.75.