Performance of advanced corrugated-duct solar air collector compared with five conventional designs

Abstract

This paper presents the results of the experimental investigation and performance analysis of an advanced corrugated duct solar collector. The collector (air heater) is constructed of corrugated surfaces similar to those used for compact heat exchangers, with the air flowing normal to the corrugations. The collector is compared with five other conventional designs constructed and tested during the course of this work. The collectors are compared under the climatic conditions of Cairo (30°N), for the flow rate range of 0.01 to 0.1 kg/sm 2 and insolation of 650 to 950 W/m 2. The comparison revealed that the efficiency of the corrugated duct collector increases by a ratio of 15–43% over that of the next best conventional design (flow below flat absorber) and at double the efficiency of the base collector. Then, the corrugated duct collector was subjected to further investigation to evaluate the effects of the duct aspect ratio (duct depth to corrugation cycle length) on its performance. For the optimum duct aspect ratio of 0.61, the use of transparent rectangular slats, in the air gap, with aspect ratio of 2.0, enhances the efficiency by 34% compared with that of the same collector without slats. However, the pressure drop is within 20–80 Pa for the 5 m length of the collector. The new design is economically encouraging as the cost is almost the same, whereas the efficiency is enhanced by about 75% compared with the collector of flow below flat absorber. The performance charateristics of the corrugated duct collectors are given in the form of correlations with the reduced temperature, corrugation aspect ratio and mass flow rates.