Simulation study of a solar collector with a selectively coated polymeric double walled absorber plate

A simulation model describing a solar collector containing a selectively coated, polymeric, double walled absorber plate with parallel fluid flow channels has been developed and validated utilizing experimental data from such a solar collector module. The simulation model contains a more refined radiative energy balance, which takes into consideration the fact that the glazing may not be totally opaque to long wavelength radiation, and is solved by applying numerical integration to the non-linear differential equations that describe the system. The validated simulation model was then utilized to perform parametric sensitivity studies on the system heat transfer coefficients, collector efficiency factor, outlet temperature of the heat exchange fluid and average daily efficiency with regard to (i) mass flow rate for the heat exchange fluid; (ii) type of glazing, viz., glass, polymer film and double walled polymeric plate; (iii) channel height of double walled structure used as the absorber plate; and (iv) effect of the air gap thickness between the absorber plate and the glazing on the overall heat transfer phenomena. The daily performance tests on the solar collector modules exhibited average daily efficiencies in the range of 50-60% and maximum outlet heat exchange fluid temperatures in excess of 60degreesC. Such corrosion resistant selectively coated absorber plates would be ideal for heating the feedstock for desalination of seawater in an evaporation-condensation process. The results of these analyzes are reported in detail. (C) 2002 Elsevier Science Ltd. All rights reserved.