Experimental study of friction and heat transfer characteristics in narrow rectangular channel

This work presents an experimental investigation of the friction and heat transfer characteristics in a narrow rectangular channel. Nine groups of experiments are conducted and the fluid temperature difference between the inlet and outlet of the test section is kept constant in each experimental run. The results show that the friction factors in isothermal condition can be well correlated by the Leon correlation for the developed laminar and turbulent flow, and the Bhatti and Shah correlation for the laminar to turbulent transition region. In addition, the friction factors prediction correlations in non-isothermal condition are proposed based on the viscosity ratio method.The heat transfer characteristic is not affected by the change of temperature difference in laminar flow. However, as in the fully developed turbulent flow, the Prandtl number significantly influences the heat transfer characteristic. The heat transfer temperature difference between the wall and fluid increases with the increase of Reynolds number in the laminar flow, and decreases sharply as the flow enters the transition region. However, it does not present a significant variation in the fully developed turbulent flow regime. Based on the analysis of heat transfer temperature difference, a new correlation for calculating the Nusselt number in the turbulent flow regime of a rectangular channel is introduced and the agreement between experimental data and predicted values is satisfactory.

► The Nusselt number increases with the fluid temperature difference in turbulent flow.
► Heat transfer temperature difference increases with Re in laminar flow.
► Heat transfer temperature difference does not change significantly in turbulent flow.
► A correlation for heat transfer calculation in turbulent flow is introduced.