Experimental study of frost growth on a horizontal cold surface under forced convection

Frost formation on a horizontal copper surface under low air temperature and forced convection conditions is investigated experimentally. Both the frost crystals pattern and the frost layer thickness formed on the cold plate are compared under different experimental conditions. The environmental variables considered in this study include the ambient temperature ( T ∞ ), air relative humidity (φ), and velocity ( v ), as well as the cold surface temperature ( Tw ). The tested ranges are −5≤ T ∞ ≤5 °C, 50%≤ φ≤80%, 2.2≤ v ≤8.0 m/s, −16.8≤ T w ≤−25.5 °C. The experimental results show the cold surface temperature and the air relative humidity have obvious effects on the frost growth: the frost layer thickness increases strongly with the decreasing cold surface temperature and increasing air relative humidity. The air temperature and air velocity or Reynolds number are also important factors affecting the frost crystals’ growth and thickness. With the increase of the air temperature and velocity, the frost crystals become denser, and the frost layer thickness become thicker, but this trend becomes weaker under higher air temperature and velocity.