공기식 태양광/열 집열기 내 공기 유동 조건과 반원 저항체 형상조건에 따른 열전달 성능 평가

Abstract

Today, our convenient lives are based on the abundant energy produced by various machines and fossil fuels. However, the exhaustion of fossil fuels is just around the corner, and the transition to renewable energy is taking place. Among them, photovoltaic(PV) power generation has improved costs from hundreds to thousands of times since 1970, compared with the underlying energy industry of all other resources. PV power generation emerges as a representative player for new and renewable energy, and its demand also tends to increase. However, in the existing PV modules, natural heat generated during the power generation process causes a rise in module temperature, which also lowers power generation efficiency. Research was conducted on photovoltaic/thermal(PV/T) collectors that use waste heat by using heat generated during power generation as heating and hot water while increasing power generation efficiency. The PV/T collector is divided into an air-type PV/T and a liquid-type PV/T collector depending on the type of heat fluid. Air-type PV/T collectors have a lower heat recovery rate than liquid-type collectors. Therefore, in this study, semicircular turbulence promoters were attached to the back of the PV cell to improve the heat recovery rate. Based on computational fluid dynamics, the heat-transfer performance and pressure drop were evaluated by changing the Reynolds number (Re) and semicircular turbulence promoter shape conditions. The turbulence promoter shape conditions include the relative height and relative pitch of the turbulence promoter. In addition, the increasing ratio, which means an increase in height of the turbulence promoter in the direction of flowing air, the length of the turbulence promoter, and the distance between the turbulence promoters were considered as design parameters. Consequently, the heat transfer performance increased with a decrease in relative height of turbulence promoter, while the pressure drop increased with an increase in relative height of turbulence promoter. Also, both the heat transfer performance and pressure drop show better performance as the increasing ratio of turbulence promoter decreased. The thermos-hydraulic performance parameter considering both the heat transfer performance and pressure drop presented the maximum value of 1.92 for the relative height of 0.02, increasing ratio of 1.