Investigation of flash evaporation in solar water desalination systems

Abstract

The research emphasis on studying water flash evaporation in vertical mounted constant cross section channel during its flow in the upward direction. In this study the heat addition rate to the flowing water is realized by power-controlled heat source capable to simulate heat extraction process from typical designed solar collector within specified time intervals and utilize this heat during water heating up and evaporation. The implemented flash evaporation technique is based on static depressurization of the upward flowing fluid in the test section. The mathematical model simulates the heat generation rate during hottest annual day based on Iraq climate. The test section diameter is 5 cm and its length is 2m. The model uses homogenous two-phase flow equations during flash evaporation process, since the rate of depressurization in the vertical mounted test section covers low range of upward water velocities. Steam generation rate in the test section exit is calculated based on accumulated steam quality of the upward flowing water starting from flash inception position till the test section exit. The effect of fluid mass flow rate and heat addition rate on distilled water production rate is discussed.