Experimental investigation of heat transfer enhancement and fluid flow characteristics in a protruded surface heat exchanger tube

• Effect of “Protruded surface” on heat transfer enhancement is presented.
• Significant improvement in thermal performance factor is observed.
• Correlations have been developed for Nu, f, and η.

This study emphasize on experimental work to enhance the heat transfer by some modification on the surface of the heat exchanger tube. The modification has been made by inserting some protruded shape sheet metal surface within the tube and the surface of sheet metal attached to the surface of the tube. The experiment has been done by using the parameter viz. stream wise spacing (x/d) = 10, 20, 30, 40, span wise spacing (y/d) = 10, 20, 30, 40 and Reynolds number in the range of 6000–35,000. The experimental results shows a significant enhancement in heat transfer rate and friction factor due to the presence of the protrusion on the heat exchanger tube over the conventional smooth heat exchanger tube. On the basis of experimental results and observations, it was found the enhancement of 3.43 times in heat transfer and 2.31 times enhancement in thermo hydraulic performance factor in the case of stream wise spacing of (x/d) = 10 and span wise spacing (y/d) = 10 respectively. The statistical correlations for Nusselt number, friction factor and thermo hydraulic performance factor as a function of flow and roughness parameters have been developed with the aid of experimental data collected for different set of roughness parameters. The deviation between predicted and experimental values for Nusselt number, friction factor and thermo hydraulic performance factor are of the order of ±10%, ±15%, and ±12% respectively.