ANALYSIS OF THE EFFECT OF SURFACE EMISSIVITY AND TEMPERATURE ON RADIATION HEAT TRANSFER RATE IN METAL MATERIALS

Abstract

This study examines the characteristics of radiative heat transfer in metal specimens with different surface coatings. The experiment utilized two materials: an aluminum plate and an iron rod, each coated with either black or silver paint. Specimens were heated in an electric furnace at 80°C and 120°C (353 K and 393 K), and the resulting radiative heat flux from each surface was analyzed. Heat flux was calculated using the heat flux equation, and the influence of surface coating was assessed by comparing the radiation ratio between black and silver surfaces. The results indicate that radiative heat flux increases substantially with temperature for all specimens. Black-coated surfaces exhibited significantly higher heat flux values than silver-coated surfaces, attributable to their greater emissivity. At 393 K, the heat flux for the black-coated aluminum plate reached 848.89 W/m², whereas the silver-coated aluminum plate produced only 25.17 W/m². A comparable pattern was observed for the iron rod specimens. Radiation-ratio analysis shows that the heat flux from black surfaces can exceed that from silver surfaces by more than 30 times under identical conditions. These findings confirm that surface emissivity and temperature are critical factors influencing radiative heat transfer. The experimental results align with the fundamental theory of thermal radiation, showing that increased temperature and emissivity enhance radiative heat transfer.