Experimental and Theoretical Investigations of Performance of Psychometric Humidification and Dehumidification Solar Water Desalination System Coupled with an Evacuated Tube Solar Collector

Abstract

There is an acute scarcity of potable water in many parts of the world, and especially in the Middle East region. Important advances have been made in solar desalination technology but their wide application is restricted by relatively high capital and running costs. Until recently, solar concentrator collectors have usually been employed to distill water in compact desalination systems. Currently, it is possible to replace these collectors by the more efficient evacuated tube collectors, which are now widely available on the market at a similar price.

This paper describes the results of experimental and theoretical investigations of the operation of a novel small scale solar water desalination technology using the psychometric humidification and dehumidification process coupled with a heat pipe evacuated tube solar collector with an aperture area of about 1.73 m². A number of experimental tests were carried out using a laboratory rig to investigate its water production capacity. Solar radiation (insolation) during a spring term in the Middle East region was simulated by an array of halogen floodlights. A synthetic brackish water solution was used for the tests and its total dissolved solids (TDS) and electrical conductivity were measured before and after the distillation process.

A mathematical model was developed to describe the system’s operation. A computer program using the Engineering Equation Solver software was written to solve the system of governing equations to perform the theoretical calculations of the humidification and dehumidification processes. The experimental and theoretical values for the total daily distillate output were found to be closely correlated. The test results demonstrate that the system produces about 11.50 kg/m².day of clean water with high desalination efficiency. Following the experimental calibration of the mathematical parameter model, it was demonstrated that the performance of the system could be improved to produce a considerably higher amount of fresh water. A water quality analysis showed that levels were well within the World Health Organization guidelines for drinking water. Further research is being performed to improve the performance of the installation.