Dimensionless correlation of mass transfer on a frosted flat plate with thickness,mass,heat flux measurements

Abstract

The aim of the study is to investigate frosting on the horizontal flat plate which has uniform air velocity distribution upstream. While the air temperature is 21.9 °C, the relative humidity is 80% and the air velocity is 0.7 m/s; frost is formed on the flat plate at surface temperatures of −15.1, −11.2, −7.1 °C, then under these conditions frost thickness, frost mass are measured. Continuous heat flux measurements under frosting which is very rare in literature are performed, too. Considering only the initial part of the frosting process at high plate temperature first an increase in heat flux then a continuous decrease is observed. A new dimensionless mass transfer correlation that does not require frost surface temperature and additionally includes dimensionless plate length is presented. The mass transfer correlation is based on dimensionless numbers of Reynolds, Fourier, specific humidity, dimensionless temperature, and dimensionless plate length which are derived from air temperature, air velocity, air relative humidity, plate temperature, plate length, plate width, and time information. In obtaining the correlation, frost mass measurements from previous researchers were added to the presented experimental results to develop a correlation valid over a wide range. As a result of the broad data set, the ranges at which the correlation is valid; air velocity of 0.7–2.5 m/s, air temperature of 5–22 °C, plate temperature of −5 to −25 °C, air relative humidity of 50%–83.73% and plate length of 85.6–300 mm. Nondimensionalizing the plate length has increased the prediction capability of the correlation.