Forced convection heat transfer and flow characteristics in laminar to turbulent transition region in rectangular channel

Experimental investigations are performed on the forced convection heat transfer and friction characteristics in laminar to turbulent transition region in a vertical heated rectangular channel. The experiment is designed for analyzing the effect of Prandtl number on the heat transfer and friction characteristics in the transition region. Seven groups of experiments are carried out within the range of Reynolds number from 1000 to 2 × 104, and the Prandtl number in each group is 2.10, 2.34, 2.51, 2.69, 2.93, 3.18, and 3.45, respectively. The results show that the lower and the upper critical Reynolds number of transition region increase with the decrease of Prandtl number. However, the friction factors increase with increasing Prandtl number for a fixed Reynolds number in the transition region. In addition, the comparisons between present experimental data and classical correlations indicate that none of the existing correlations could be extended to predict the present friction and heat transfer characteristics in the transition region of the heated channel. Based on the experimental data, the empirical correlations for the calculation of friction factor and heat transfer coefficient in the rectangular channel in the flow transition region of forced circulation have been developed.

► Experiments were performed at a rectangular channel.
► Inlet and outlet fluid temperature are keeps constant with the increasing Reynolds number.
► The Prandtl number significantly influenced the thermal-hydraulics in transition region.
► New correlations for heat transfer and friction factor in transition region were developed.