Heat transfer enhancement from a small rectangular channel with different surface protrusions by a turbulent cross flow jet

• Heat transfer enhancement is numerically studied for a small rectangular duct.
• The nozzle position and Reynolds number affects heat transfer rate significantly.
• Pumping power increases with duct and nozzle Reynolds number.
• Triangular protrusions are better heat transfer augmenter.

In the present study, thermo-hydrodynamic performance of a small rectangular channel with different protruded surfaces is investigated numerically in a three–dimensional computational domain. An air jet impinging normal to the main flow is considered to enhance heat transfer rate. Conservation equations for mass, momentum and energy are solved using finite volume method with SST k−ω turbulence model. Three different protrusion shapes have been tested: rectangular, trapezoidal and triangular, respectively. The duct and nozzle Reynolds numbers are varied in the range of 17,831 ≤ ReDh,duct ≤ 53,490 and 5,136 ≤ ReDh,nz ≤ 11,980, respectively. Also, three different nozzle positions (X/Dh,duct = 8.717, 11.597 and 14.258) along the axial direction of rectangular duct have been considered to choose the best location for heat transfer enhancement. A higher heat transfer enhancement rate is observed at the nozzle position 2 (X/Dh,duct = 11.597) as compared to the other positions considered in this study. Flow recirculation in inter-protrusion spaces has also been discussed. In this hybrid cooling strategy, the pumping power requirement with protrusions is observed to be higher than that of without protrusions. The heat transfer enhancement rate with triangular protrusions is found to be more as compared to other protrusion shapes.