Heat loss characteristics study of a trapezoidal cavity absorber with and without plate for a linear Fresnel reflector solar concentrator system

The numerical and experimental studies are conducted to analyze the heat loss in the cavity absorbers of linear Fresnel reflecting solar concentrator (LFRSC). The cavity is trapezoidal shape in cross section, which is placed at focus of the concentrator, has multiple tubes and water is used as the working fluid. The upper surface of the cavity has two models; with copper plate, above which absorber tubes are placed together and without copper plate i.e. absorber tubes alone without copper plate underneath. In both the models, the heat loss coefficient of projected absorber surfaces is analyzed with and without black chrome coating. For the numerical simulation of the trapezoidal cavity absorber, ANSYS FLUENT 12.0 version is used to develop the two dimensional model with non-Boussinesq numerical approximation. For the experimental study, two cavity absorbers are designed for operating in conjunction with a LFRSC experimental set up for the area of 4.0 m2. The overall heat loss coefficients are also estimated analytically by cavity correlations. The trend of variation of estimated heat loss coefficient by both methods is similar to experimental values. Also, estimated values by numerical study are very close to analytical and experimental values and the numerical model can be used for further analysis.