Performance analysis of optically semi-transparent material packed-bed solar air heater

Abstract

This paper deals with theoretical analysis of performance of solar air collector having its duct packed with optically semitransparent materials. The heat transfer equations for two dimensional fully developed fluid flows under quasi-steady state conditions have been developed in order to analyze the thermal, thermo-hydraulic and exergy performance and to study the effect of system and operating parameters. A computer programme is developed in c++ language to estimate the temperature rise of entering air for evaluation of performance by solving the governing equations numerically using relevant correlations for heat transfer coefficient for packed bed systems. Results of air temperature rise and thermal efficiency obtained from the analysis have been compared with available experimental results and results are found fairly in closed agreement. It has been found that there is considerable enhancement in thermal efficiency with packed bed collector. Effect of total bed depth on efficiency show that there is an upper limiting value of total bed depth beyond which the thermal efficiency begins to fall again and this type of characteristics behavior is observed at all mass flow rate. It is also noticed that there exists an optimal value of effective and exergy efficiencies for a given mass flow rate.

Keywords

• Solar energy,Optically semi-transparent packed bed; Solar air heater; Plane collector