Flat sheet direct contact membrane distillation study to decrease the energy demand for solar desalination purposes

Abstract

One of the most important feature of any desalination technology is energy consumption of producing fresh water specially when its energy source is solar energy. To improve this, study of various input parameters and determination of their effects on energy consumption would be essential. In this paper, a one-dimensional model is used to investigate the effects of different operational and geometrical parameters on energy consumption of flat sheet direct contact membrane distillation (DCMD) for solar desalination purposes. It is assumed that the energy consumption of DCMD includes of electrical to drive electro pumps and thermal energy. In this regard, variation of each parameter is studied at different inlet bulk flow temperatures difference (TD). Results show that specific energy consumption (EC) of DCMD is improved by increasing inlet bulk flow temperature difference regardless of any parameter variations. Nevertheless, increasing of Inlet mass flow rate and decreasing inlet salinity are also enhanced specific energy consumption. For geometrical parameters, increasing length, width and channel height increase energy consumption while increasing membrane porosity and thickness do the opposite. It is also observed that the electrical energy incorporates a very small portion of whole energy consumption in most cases but when small channel width or height is selected it becomes significant. Since electrical energy is more expensive than thermal energy, careful channel geometry design must be done.