Experimental and Numerical Study on the Effect of Teardrop Dimple/Protrusion Spacing on Flow Structure and Heat Transfer Characteristics

Abstract

In this study, the flow characteristics and heat transfer were analyzed in rectangular wind tunnel installed with the teardrop dimples and protrusions. The flow characteristics, spacing effect on the heat transfer enhancement, Turbulence Kinetic Energy (TKE) and thermal performance are the main objectives of this study under the constant Reynolds number 20,000. The projected diameter of dimple and protrusion was fixed with D=26.4 mm and the depth of dimples and protrusions was 5.28 mm (H=0.2D). The spacing between protrusion-to-protrusion and dimple-to-dimple was varied with four spacing cases i.e., S=1.125, 1.25, 1.5 and 2 D. The computational fluid dynamics (CFD) was applied for simulation results. In the experimental results, the temperature of protruded surface covering with Thermochromic Liquid Crystal sheet (TLCs) was measured and converted into heat transfer coefficient. The results show that the heat transfer enhancement for teardrop dimple cases is higher than that for protrusion for both experimental and simulation results. When the spacing is getting larger, the thermal performance values for teardrop dimple cases gradually decrease while the values for teardrop protrusion cases gradually increase.