Enhancing efficiency of water transportation to RO plants using solar concentrators

Abstract

Minimising the pressure losses of a fluid flowing through a pipe, as a result of surface friction, is crucial in designing and increasing the efficiency of a system using pipes. One way to achieve minimal pressure losses is by heating the fluid being transported. By heating the fluid, both the viscosity and the density of the fluid decreases, consequently decreasing pressure losses. Many types of technologies exist in order to heat up the working fluid. One such technologies include the use of solar concentrator technologies. The main aim of the research was to investigate the applicability of solar concentrators in the heating of water using solar energy in the reverse osmosis station located in Pembroke. The type of solar concentrator as well as a thorough market research was necessary to evaluate the ideal conditions the system should operate at the RO station. To validate a relationship between the temperature of the working fluid and the pressure losses induced, a preliminary study was conducted on the current setup utilised at the Pembroke RO station, via means of analytical calculations, 2D and 3D computational fluid dynamics (CFD) simulations. The overall performance of the solar concentrator was computed. Analytical calculations serve to compute the necessary parameters and serve as validation for the CFD results. By using 2D CFD modelling, an initial assessment involving the heat transfer through the parabolic trough piping was conducted. The parameters of the working fluid as well as the performance of the setup was analysed. Utilising 2D modelling allowed the study of the ideal length of the required parabolic trough piping, as 2D simulations utilise less computational power than 3D simulations. When using 3D modelling, the creation and generation of the ideal mesh was an essential task, despite the level of complexity required. Therefore, an in-depth mesh design process was presented. The mesh designed was thoroughly analysed for both the thermal and velocity boundary layers to be captured. The results obtained analytically and computationally were analysed and compared with each other. The ideal length and geometric concentration ratio were chosen based on the output temperature of the fluid. Due to a significant change in both density and viscosity of the water, a significant decrease in pressure loss was evident. Furthermore, by integrating the use of parabolic troughs in the current setup, a significant overall increase in efficiency was evident through calculations and simulations.