THEORETICAL COMPARISON OF THE THERMAL POWER OF FLAT-PLATE SOLAR COLLECTORS WITH SERPENTINE FLOW VERSUS PARALLEL FLOW

摘要

A complete theoretical model that describes the collector efficiency factor F’ of serpentine flow flat-plate solar collectors as a function of the tube geometry has been developed and compared with experimental results. The essential parts of the model are described in this paper. Based on this model, the serpentine flow geometry is compared with the fin-and tube geometry with regard to thermal performance. The material content of absorber plate and tubing is taken into account. The results of the calculations indicate that for identical conditions (material content, overall heat loss coefficient U_L, mass flow per tube, fluid inlet temperature), the serpentine-flow arrangement is superior to parallel flow. The difference decreases with increasing mass flow rate. For typical collectors (length x width = 2 x 1.2 m²) at a mean fluid temperature of 50 °C and at a mass-flow rate of 40 kg/h per tube, the thermal power of the serpentineflow collector is 2.6 % higher than that of the parallel-flow collector.