HEAT TRANSFER AND PRESSURE LOSS CHARACTERIZATION IN A CHANNEL WITH DISCRETE FLUSH-MOUNTED AND PROTRUDING HEAT SOURCES

Abstract

This work deals with an experimental investigation of the convective heat transfer and pressure loss in a rectangular channel with discrete flush-mounted and protruding heat sources. Six protruding obstacle heights, which represent the range of the dimensionless protrusion of 0<h/H<0.805, are studied in this work. The temperatures on the heater surfaces and that of the fluid are collected, and data obtained at steady state are used to calculate the heat transfer coefficients, the Nusselt number, and the pressure loss coefficient. The results show that at lower Reynolds number, free convection cannot be neglected for cases where the discrete heat sources are flush-mounted on the channel floor. For cases of discrete protruding heat sources, heat transfer is dominated by forced convection and free convection can be ignored. The presence of the protruding heat sources distorts the flow in the channel, causing a substantial increase in heat transfer. Based on the experimental data, empirical correlations for the Nusselt number in terms of Reynolds number, and the dimensionless protruding height, are obtained for each heater by means of multiregression in the range Re=1,500 - 6,300 and h/H=0.151 - 0.805. The presence of the protruding heat sources increases the pressure loss dramatically. The results show that the pressure loss is dominated by the inertial effect. The results also quantify that the pressure loss coefficient, f, increases as the Reynolds number is decreased and /or h /H is increased. Based on the experimental data, an empirical relationship for the pressure loss coefficient in terms of Reynolds number and the dimensionless protruding height is obtained.