Optimal slope angle selection of an evacuated tube collector for domestic solar water heating

Abstract

A pressurized system utilizing evacuated tube collectors with internal heat pipes was investigated for the production of hot service-water for domestic use during all seasons in Pretoria, South Africa. The investigation focused on the prediction of seasonal hourly performance trends and the maximum thermal performance at the static optimal slope angle. This study was accomplished by developing the system’s theoretical performance model which was solved numerically using Engineering Equation Solver (EES). Results show the thermal performance trend changes during the seasons depending on the slope angle. Optimal performance parameters that influence the collector overall performance, depending on the water consumption of the occupants, were obtained and presented. The maximum performance in the summer was achieved at a slope angle of 25° and in winter the maximum performance was shown to exist at an angle of 40°. In a 20 receiver tube collector system, maximum performance was in September, reaching an outlet temperature of 103.98 °C and useful heat rate of 1 919.85 W.