Investigations on thermal performance characteristics of wire screen packed bed solar air heater

• Thermal performance of wire screen packed bed solar air heater has been analysed.
• Governing equation has been solved by Finite difference algorithm.
• A computer programme is developed in C++ language to obtain the analytical results.
• The analytical and experimental results are compared reasonably well.

This paper presents the theoretical investigations of thermal performance characteristics of solar air heater having its duct packed with blackened wire screen matrices. The heat transfer equations for two dimensional fully developed fluid flow under quasi-steady state conditions have been developed in order to analyze the thermal efficiency and temperature rise and to study the effect of system and operating parameters. Finite difference solution algorithm has been developed for obtaining numerical solutions of the governing equations for energy transfer. A computer programme is developed in C++ language to estimate the temperature rise of the entering air for evaluation of thermal efficiency by solving the governing equations numerically using relevant correlations for heat transfer coefficient for packed bed systems. Results of temperature distributions and other performance parameters obtained from analysis have been compared with available experimental results. The percentage deviation between the experimental and the analytical values of the dimensionless air temperatures of air and thermal efficiency have been found to be in the range of 7.18 to -9.83 and 7.20 to -9.65 respectively. This establishes the validity of proposed analytical model for the investigation of thermal performance characteristics of packed bed solar air heaters.