Numerical and experimental investigation on heat transfer enhancement by novel type vortex generator

In this study; thermal performance of a novel type conic vortex generator, NTCVG, in rectangular duct and the effects of configuration layout on heat transfer was studied experimentally and numerically as well. The thermal performance of vortex generators are highly dependent on their positions in the flow field. Therefore, the thermal performance of the NTCVG was investigated in terms of different attack angles (α), blade angles (β) and scale ratios (S) over a wide range of Reynolds numbers. Besides that, NTCVGs were positioned in a manner of in-line and staggered arrangement throughout the entire test region and experiments were carried out. The resulting longitudinal vortex flow structure, fluid velocity distributions as well as temperature distributions were visualized by numerical study. Numerical studies were carried out by using the software Fluent, ANSYS 2020 R2. Numerical studies were performed by taking experimental boundary conditions into account. In the first step, experiments were conducted to determine the thermal performance of NTCVG. As a result of the experiments, the optimum attack angle, blade angle and scale ratio, where the highest thermal enhancement factor, TEF, was reached, were detected to be as α=37.5°, β=30° and S=1:1, respectively. In this experimental stage, the highest TEF value of 1.316 was obtained at Re=5000. In the next phase of the experiment, experimental configuration layout studies were conducted in which NTCVGs, having in-line arrangement, were positioned in test region under longitudinal pitch ratios, the ratios of the longitudinal distances between two rows of NTCVGs to the channel height, PR=1.5, 2, 3 and 5 by keeping the optimum geometric parameters constant. TEF value was obtained to be reached a peak at PR=2 and the highest TEF value of 1.43 was attained at Re=5000. In the last step, NTCVGs were arranged in a staggered manner by keeping the optimum geometric parameter levels and the longitudinal pitch ratio of PR=2 constant. In the range of Re=5000-25000, in-line NTCVGs were detected to be more effective than staggered NTCVGs in terms of thermal performance, on the other hand, higher Darcy friction factor, f, values were obtained with staggered NTCVGs. As a result of the experiments, peak values of TEF=1.43 and 1.38 were achieved at Re=5000 for in-line and staggered arrays of NTCVGs, respectively.