Solar air pre-heater design, Vol. I

The cost of fuel direct and indirect, environmental aspects and the degrading of dryer material as a result of possible reactions with heating media are some discouraging parameters operative in conventional drying. The present work is targeted to effectively using solar drying technologies. Conventional solar air heaters used for heating air in general, exhibited low thermal efficiency, attributed to poor heat transfer rate from absorber plate to air flowing in a duct on the lower side of the absorber plate. Packing elements have been employed to pack the duct of solar air heaters with a view to enhance the thermal efficiency. However, in such systems the pumping power needed to overcome the friction losses could reduce the benefits of increased useful heat gain. Thus the design of packed bed solar air heaters with high heat transfer rates and low friction losses draws renewed interest.