The effect of thermo-fluid properties of air on the solar collector system

Abstract

The changing behaviour of the flat plate collector upon varying the carrier fluid (air) properties was investigated with the help of energy and momentum conservation. The finite element analysis of a collector was carried out using pdex3 type equations. The white box modelling approach was considered to determine the velocity and temperature fields across the collector system. It was postulated that the temperature gradient for the carrier fluid at the viscous sublayer was negligibly small. The thermophysical properties, density and heat transfer coefficient, of the carrier fluid, are varied and their effect on the temperature and velocity fields was qualitatively examined. With the help of the proposed scheme, the solar collector efficiency was found to vary from 38.57 to 77.45%. The velocity of the fluid layer onto the surface of the collector plate increased from 1.12 to 1.43 m·s−1 as the heat transfer coefficient decreased from 30 to 19.73 W·m−2·K−1; however, it had a reverse effect for the fluid layer flowing past the glazing cover. The velocity of the carrier fluid increased from 0.0097 to 0.0852 m·s−1 at the boundary of the glazing cover, whereas it decreased by 22% at the vicinity of the copper plate. The numerical solution of energy equation slightly overestimated temperature of carrier fluid by 2.1%.

Keywords

• Finite element analysis
• Solar collector
• Temperature gradient
• Free convection
• Momentum
• Fluid properties