Approximately 40% of the domestic building load is used for heating and cooling, and fossil fuels are commonly used to produce heat. To lower the proportion of fossil fuels, policy subsidies for the use of new and renewable energy facilities are being activated. Among them, solar thermal systems can contribute to reducing the heating load of buildings, including hot water supply and space heating. The production of thermal energy in this solar thermal system takes place in a collector, and the heat collection system is generally categorized into an air-type solar collector, which can heat only air, and a water-type solar collector, which can heat only water. In contrast, a solar air-water heater is a collector that can heat air and water simultaneously and can be applied to both hot water supply and space heating, occupying the same area. This system can also improve solar energy utilization by retrieving waste heat at the top of the absorber plate. In this system, the increase in thermal efficiency of the air side results in an improvement in the total efficiency of the collector as well as the air heating performance. Furthermore, the performance of the solar air-water heater is affected by air and water mass flow rates. Thus, in this study, a novel type of solar air-water heater with a triangle obstacle was fabricated, and the thermal performance of this system was experimentally evaluated using various air and water mass flow rates when air and water were heated simultaneously. We observed that a higher air and water mass flow rate can lead to higher thermal performance of the suggested system.

The solar air-water heater is a combined system of air-type and water-type collectors and a composite collector that can produce hot water and heated air in one system. Although it can maximize heat acquisition by transferring some of the heat lost from the absorbent plate and pipe toward the air duct, the heat acquisition is low due to the low heat capacity. To address this problem, several studies have been conducted using turbulent promoters in ducts. In this study, to improve the air-side heat transfer performance of the solar air-water heater, perforated fins on the bottom side of the absorption plate were arranged in various arrangements. Thereafter, computational fluid dynamics (CFD) was performed according to the flow conditions, and the heat transfer performance and pressure drop characteristics were analyzed. Results indicated that the heat transfer performance improved by at least 1.24 times to a maximum of 2.21 times, and that the pressure drop was in the range of 4.10 ~ 7.38 times, confirming the thermal hydraulic performance parameter (THPP). In the case of the performance coefficient, when perforated fins were attached side by side to the pipe, the highest performance coefficient was 1.18.