Numerical optimization and convective thermal loss analysis of improved solar parabolic trough collector receiver system with one sided thermal insulation

Abstract

Two types of receiver systems currently employed in solar parabolic trough collector technology are evacuated annuli receivers and air filled annuli receivers. While former receiver find its way into high temperature grid-acquaintance solar parabolic trough collectors, latter are more inclined towards non-grid solar thermal applications like low temperature process heat. Evacuated receivers utilize vacuum filled annuli to stamp down the convection losses; this makes them substantially expensive―while prizing them with benchmark among receivers. Contrary, air filled annuli based receivers are relatively less expensive, but are subpar in thermal performance relative to evacuated receivers. This work deals with the air filled receiver system and would try to abridge the economy and efficiency between both types of system using computational fluid dynamics based numerical simulation approach. A heat blocking thermal insulator is jibed in the sun facing receiver annulus, which does not receive concentrated Sun’s radiation, and is simulated for the combined conduction and convective losses and also for better temperature distribution around the absorber. Consequently, its convective heat losses were investigated for varying wind speed and mass flow rate of heat transfer fluid and are compared with mainstream air filled annuli receivers. Simulation results are compared with experimentation in which wind velocity was in range of 0.43 – 4.99 m/s, glass envelop temperature decreased with increase in wind velocity which directly insinuates the decrease in convection losses around glass envelop. These comparative implications could be served as a point of reference par excellence to develop solar parabolic trough collector for small scale process heat applications in India.