Numerical investigation of thermal performance of swirl generator in a solar water heater

This paper presents a numerical investigation of the potential of a 4-lobed swirl generator for enhancing the thermal performance of an active Solar Water Heater (SWH). The hydro-thermal performance of the generator was thoroughly evaluated using the code ANSYS FLUENT 2021 R1, and the results were validated against available experimental data in the literature. The predicted results demonstrated that the proposed swirl generator was capable of giving a higher Performance Evaluation Criteria (PEC) compared to twisted tape as it enhanced the heat transfer at the expense of a much lower pressure loss than the twisted tapes. However, with only one swirl generator, the PEC value for the swirl generator was only slightly higher than 1 and the analysis with the field synergy principle revealed that the thermal enhancement produced only prevails for 30D to 40D downstream. To achieve optimal thermal enhancement in the SWH, strategic placement regimes were examined by regularly placing 2, 3 and 4 swirl generators, respectively, inside the SWH. Simulation results indicated that, with an optimal placement of the swirl generator, the heat transfer coefficient is increased by 9.9% with an extra pressure drop of 26.9% more than a plain circular tube. This increase in heat transfer coefficient can reduce the overall pumping time and, more importantly, can make the SWH more reliable in moderate weather.