Experimental study on frost formation on cold surfaces with different inclination angles under forced convection conditions

Abstract

This study investigates how factors like inlet wet air temperature, relative humidity, cold surface temperature, and wet air velocity affect frosting on cold surfaces of various angles under forced convection. Using frost layer thickness and quality as the primary evaluation indicators, a single-variable method is employed to study various operating conditions on a horizontal cold surface (0°). For cold surfaces with different inclination angles (0°, 45°, 90°, 135°, and 180°), an orthogonal experimental approach is further adopted to delve into the frost layer growth process on these surfaces in detail. The results indicate that, under certain operating conditions, frost thickness and quality on a horizontal cold surface increase with higher relative humidity, higher inlet wet air temperature, lower cold surface temperature, and faster wet air velocity. As the inclination angle of the cold surface increases, both frost thickness and quality first increase and then decrease, reaching their maximum values at an inclination angle of 90° and their minimum values at an inclination angle of 180°. Additionally, as the inclination angle continues to increase, the frost layer transforms from a smooth surface to one with more needle-like frost branches, which is particularly evident at an inclination angle of 180°.