Thermal and thermohydraulic performance evaluation of a novel type double pass packed bed solar air heater under external recycle using an analytical and RSM (response surface methodology) combined approach

In the present study, an analytical and RSM (response surface methodology) combined approach has been applied to investigate the thermal and thermohydraulic performances of a novel type double pass packed bed solar air heater under external recycle with wire mesh screen as a packed bed material. An analytical model describing the various temperatures and heat transfer characteristics of such a double pass packed bed solar air heater under external recycle has been developed and employed to study the effects of mass flow rate, recycle ratio and varying channel depth between the top (upper and lower) glass covers for a fixed 95% porosity of the packed material on its thermal and thermohydraulic performances. The analytical model employs an iterative solution procedure to solve the governing energy balance equations describing the complex heat and mass transfer involved. Furthermore, RSM is then applied for developing mathematical models based on simulation results obtained from analytical study. The effect of parameters and their interactions on the responses are studied using RSM. The results obtained from RSM revealed that proposed mathematical model is significant and good agreement is achieved with reasonable accuracy. (C) 2014 Elsevier Ltd. All rights reserved.