The investigation of relation between radiative and convective heat transfer coefficients at the ceiling in a cooled ceiling room

Abstract

In this study, the relation between radiative and convective heat transfer coefficient at the ceiling is determined for a cooled ceiling room of which floor surface is isolated. Firstly, convective heat transfer is simulated numerically neglecting the radiative heat transfer at the surfaces ( ε w = ε c = 0) for different room dimensions (3 × 3 × 3, 4 × 3 × 4 and 6 × 3 × 4 m) and thermal conditions ( T c = 0–25 °C, T w = 28–36 °C). Then, radiative heat transfer is calculated theoretically for different surface emissivities ( ε w = ε c = 0.7, 0.8 and 0.9). Numerical data are compared with the results of correlations based on experimental data given in literature. New correlations for convective and radiative heat transfer coefficients at the ceiling are found in the current study. The ratio of radiative heat transfer coefficients to convective heat transfer coefficients ( h cr/ h cc) is determined. It was seen that the ratios range from 0.7 to 2.3 depending on the temperature difference. The ratios increase as the temperature differences increase. Therefore, a new correlation between the coefficients is developed depending on temperature difference at the ceiling.