Surface modification of transversely twisted-turbulator using perforations and winglets: An extended study

Twisted-turbulators are effective passive techniques for enhancing the thermal performance of heat exchangers. Although numerous studies have been conducted on longitudinal forms, there are very scarce studies on transverse forms. In this study, particular attention is paid on the effects of perforation, winglet, and a combination of both, as modifications, on the performance of transversely twisted-turbulators (TTTs) through a rectangular channel. Firstly, experimental tests are performed on the TTTs with three different twist-angles of 0 degrees, 90 degrees, and 180 degrees for the Reynolds number range from 1643 to 4929. Then, numerical simulations are carried out on these models. It is found that the effects of perforations and winglets depend on the twist-angle of TTTs. In the case of 0 degrees TTTs, introducing both perforations and winglets leads to lower values of h and Delta p. The results show that the solid model is more effective in fluid dispersion towards the hot walls and generate stronger vortices inside the channel. Based on the experimental data, for the case of 0 degrees TTTs, the average reduction of h and Delta p between the solid model and other models are as follows, 9.8% and 16.4% for the perforated model, 16.2% and 16.9% for the winged model, and 23.6% and 41.8% for the combined model. However, in the cases of 90 degrees and 180 degrees TTTs, creating winglets enhances these parameters, leading to better overall performance. The highest overall performance indexes of 1.55, 1.66, and 1.65 are recorded for the solid 0 degrees TTT, winged 90 degrees TTT, and winged 180 degrees TTT models at the Reynolds number of 1643.

Automated summary

Twisted-turbulators are effective passive techniques for improving the thermal performance of heat exchangers, especially when considering varying twist angles and the effects of perforations and winglets. Experimental tests and numerical simulations show that different modifications have different effects on the performance of the transversely twisted-turbulators (TTTs), with solid models being more effective in fluid dispersion in certain cases. Overall, the addition of winglets improves the performance of TTTs with twist angles of 90 degrees and 180 degrees, while for 0 degrees TTTs, a combination of perforations and winglets leads to lower values of heat transfer coefficient and pressure drop.