Performance Analysis of Flat Plate and Evacuated Tube Collectors

Abstract

This study gives a thermal analysis on the effect of operating parameters on the performance of solar water heating systems with two distinct collector configurations; flat plate and heat pipe evacuated tube collectors. The thermal analysis of these two systems was conducted based on the account of variation in weather conditions of Adama and volume flow rate, using T*SOL® Simulation software, to study the impact of these operating conditions on the system efficiency, system solar fraction, storage tank outlet temperature, collector outlet temperature, energy accumulated and collected in the tank and collector. This is done to compare the performance of these two systems with each other, based on thermal analysis in order to provide the necessary information required to select the most appropriate solar collector and its operating conditions. The results showed that for a fluid circulating at 120 l/h, the highest monthly solar fraction of FPC and ETC systems were 80% and 64.6%, respectively, around November with a total solar irradiation of 191 kWh/month. For both systems, the hourly tank outlet temperature peaked in November to 87 °C and 71.2 °C for ETC and FPC, respectively. For a typical day in April, the maximum tank outlet temperature becomes 74 and 62.5 °C. Regarding the flow rate, simulation of the systems is done for three flow rates (80, 120 and 160 l/h). The results also showed that for a typical day in April, the hourly maximum tank inlet-outlet temperature difference was obtained for both ETC and FPC at 12:00 PM at a flow rate of 160 l/h, where the corresponding maximum tank outlet temperature becomes 74 and 62.5 °C. At this volume flow rate, a solar water heating system efficiency of 59% and 50%, and also a system solar fraction of 82% and 68.1% could be achieved for a SWH system employing ETC and FPC, respectively. Overall, ETC systems proved to be a more efficient system to satisfy the need of hot water.