Experimental study of thermal performance improvement of a solar air flat plate collector through the use of obstacles: Application for the drying of'yellow onion'

In the solar air flat plate collector, the insufficiency of the thermal exc hange between the fluid and the absorber obliges the user to enhance their optimization. This low thermal exchange does not allow these systems to obt ain their best performance or the best thermal efficiency. In our experimen tal study, which consists of a solar energy simulation, we have sought to i mprove the efficiency-temperature rise couple of the flat plate solar colle ctor by considering several types of obstacles disposed in rows in the dyna mic air vein of the collector. Thus, we have proceeded to the application o f the best two systems (WDL1 and TL) for drying an agricultural product (Ye llow Onion). By comparing with the collector without obstacles (WO), the th ermal transfers and, consequently, the output temperature (T-OC) and the co llector efficiency (eta) are clearly improved. The drying times obtained wi th the proposed systems are very interesting. The heat quantities obtained in the case of WDL1 are very important compared with the collector WO. Howe ver, the entry to the drying cupboard of this high temperature (T-OC) in th e vicinity of the solar midday must be limited to the maximal value demande d by the considered product. Copyright (C) 1999 John Wiley & Sons, Ltd.