Volume 32: A Sustainable, Clean and Carbon-free Energy Future

Numerical investigation of thermal performance of swirl generator in a solar water heater Xingyu Feng, Nicholas J. Miles, Guozhen Li, Zheng Wang, Philip Hall

Abstract

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.

Keywords solar heat exchanger, 4-lobed swirl generator, twisted tape, decaying swirl flow, CFD Ansys fluent, field synergy principle