International Journal of Thermofluids (Feb 2023)
Thermal performance of asphalt solar collector by improving tube and slab characteristics
Abstract
The urban heat island effect is observed when asphalt surface temperatures increase up to 70 °C throughout the summer, resulting in an increase in the temperature of the air above. As a consequence of the increased use of air conditioning, energy consumption increases in cities, and air quality deteriorates. Asphalt solar collectors are composed of buried tubes that carry a circulating fluid. Solar radiation causes the pavement's temperature to increase. Heat is transported from the pavement to the fluid, causing a drop in asphalt temperature and an increase in fluid temperature. What makes asphalt solar collectors so remarkable is their capability to generate energy from the rising fluid temperature. This work presents the first evaluation and comparison of the thermal performance of an asphalt solar collector using finned tube and conductive asphalt mixture techniques. A copper tube with a length of 500 mm was embedded in the middle of a 500 × 160 × 50 mm hot-mix asphalt slab. The sides and bottom of the test sections were insulated to prevent heat loss to the surrounding environment. Using one bare tube with reference asphalt mixture, two finned tubes with reference asphalt mixture and five bare tubes with different conductive asphalt mixtures, the thermal performance of the systems was examined. The models were heated by artificial solar radiation. Various materials, including quartzite aggregates, slag aggregates, silica sands, metallic waste powder, and steel wool fibres, were utilized as novel conductive asphalt mixture components. The experimental results showed that the efficiencies of the asphalt solar collector were 30.37, 33.33%, 30.69%, for bare, flat, and wire mesh extended surface tubes, respectively. The maximum efficiencies of the asphalt solar collector with quartzite combination and slag combination were 36.04%, and 36.49%, respectively. The thermal performance of the ASC is increased by 9.76%, and 1.1% by using flat and wire mesh extended surfaces, respectively, compared to that of the bare tube. Quartzite and slag samples enhance the thermal response of the asphalt solar collector up to 18.7%, and 20.18%, respectively. A significant thermal enhancement is achieved by utilizing industrial wastes as extended surfaces. However, asphalt solar collector application and the availability of cheap materials are the key factors in deciding the optimal enhancement technique.
