Experimental assessment and optimization of design parameters of thermo-hydraulic performance of heat exchanger tube using hollow elliptical swirl generators

Present research work examines the experimental use of hollow elliptical swirl generators as a passive augmentation strategy to improve heat transfer and thermal performance in heat exchangers. Different geometrical parameters of hollow elliptical ring inserts, which include height ratio (HR = 0.45, 0.66, and 0.75), and number of inserts ( N = 4, 6, and 8) were placed inside test section under a range of Reynolds number ( Re ) from 3000 to 21,000. These inserts generate turbulence and increase the contact between fluid particles and heated walls, thereby enhance the heat transfer rate. According to the experimental results, when hollow elliptical inserts are inserted within the heat exchanger for HR = 0.75 and N = 8 at a Reynolds number of 3000, the maximum heat transfer increase is 4.2 times more than in a plain heat exchanger tube. However, increased turbulence caused a slight rise in friction factor. To make a balance between enhancement in both heat transfer and friction factor, thermal performance factor (TPF) has also calculated. Maximum TPF (1.22) was found for the shorter insert (HR = 0.45) at 3000 Re with 8 number of inserts compared to plain tube. Along with experimentation, Taguchi's approach has used for determination of optimal values of design parameters and their contribution in heat transfer, resistance factor, and thermal effectiveness of the heat exchanger tube using hollow elliptical swirl generators. The study finds that whereas height ratio contributes 84 % to the improvement of the friction factor, Reynolds number contributes 93 % and 88 % to the improvement of heat transfer and thermal performance, respectively. The results demonstrate how elliptical swirl generators can efficiently increase heat exchanger efficiency.