Enhancing the Thermal Efficiency and Optimum Temperature of a Modified Evacuated Tube Solar Air Collector by using the Reflector

Abstract

The experimental investigation of the thermal efficiency of a retrofitted evacuated tube solar collector employing air as the working fluid, with and without a rectangular aluminum sheet reflector during the winter, considering both sunny day and hazed day climatic conditions occurred at Glocal University in Saharanpur, India, between 30 17' (latitude) North and 77 38' (longitude) East. The solar collector comprises vacuum tubes with directed inner tubes that are 22 mm in diameter and are put in a single-ended steel cuboid-shaped manifold. The inner steel tubes supply the input air into the vacuum tube. The heated air is generated in vacuum tubes, collected in the central header cylindrical manifold, and expelled through the exit pipe. With an aluminum sheet reflector fixed, the flow velocity, mass flow rate, and irradiance affect thermal efficiency and exit air temperature. In the case of a stainless-steel tube with a 22 mm diameter and a length of 1.27 meters, the maximum temperature difference between the outside air and the input air is 71.9 C, and the maximum temperature recorded is 96.9 C. A higher efficiency of 36.69% is attained with a suitable aluminum sheet reflector at an increased flow rate of 20.14 kg/h. In ETSCs that have been updated, there is an average rise in exit air temperature of 37.5%.