Mathematical modeling, simulation and optimization of solar thermal powered Encontech engine for desalination

Abstract

This paper investigates a solar driven external combustion and regenerative engine, which can be used for desalination of seawater by using gaseous working fluids. The effect of operating and design parameters on engine performance for different suction (Pc) and discharge (Ph) pumping pressures, hot (Th) and cold (Tc) space temperatures, regenerator effectiveness (εR), displacer full stroke length (X0) and dead volume of hot (Xho) and cold (Xc0) spaces is studied in detail. Optimization of pumping discharge pressure based on energy and exergy performance for six different working fluids is simulated. The energetic and exergetic analysis is performed at steady state conditions for the proposed thermodynamic cycle. Predominantly, mass and energy balance equations are applied to optimize the effect of different operating (Th,Tc,Pc,Ph) and design (εR,Xh0,Xc0,X0) parameters on the output work and efficiencies. An open source SCILAB code is utilized to solve the derived equations for pressure, volume, temperature, mass, and heat loads. The simulation results provide profiles for energy efficiency, exergy efficiency, and optimization based on selected design and operating parameters. Obtained results show that for each charging pressure and hot space temperature, there is a different optimum discharge pressure and optimum hot temperature based on exergetic and energetic efficiency values. Besides, the net hydraulic work-output rises with the increase in the charged mass and displacer full stroke length. Simulation and thermodynamic analysis of proposed engine can be useful to design and select the optimum pumping heads for an accessible heat source and sink temperatures used for desalination to reduce the electricity consumption.