THEORETICAL ANALYSIS OF A SOLAR AIR COLLECTOR WITH A RECTANGULAR AIR-DUCT PROFILE

Abstract

Any solar energy conversion system requires proper designing and sizing in order for it to be cost effective with respect to energy production under the prevailing climatic conditions and initial cost. Modelling and simulation have been considered as fast and cheap analytical tools for sizing of optimal solar energy systems for a given application prior to their construction. This work provides a theoretical analysis of a solar air heater (SAH) with a rectangular air duct profile and operated under natural airflow mode. The model was validated against experimental results measured outdoors on a prototype model. The validation results showed a good agreement between experimental and modelling results hence the model could be used for analytical analysis of this type of SAH system. The model was used to study the effects of various operating conditions and design parameters on the performance of SAH. The results show that increase of mass flow rate, solar insolation and collector area increases the efficiency of the SAH system. The optimal values of efficiency are obtained when the mass flow rate is greater than 0.01 kgs-1 and around mid-day when the insolation rate is greater than 1000 W/m2. It was also observed that the efficiency of the collector increases with increase in both the collector length and width and attains its optimum values of efficiency between 1.0 to 2.0 m for both length and width. In addition, better performances of the collector are obtained at low ambient temperatures and small channel depths.