Abstract
The impacts of the double V-rings (DVR) in the heat exchanger duct (HED) on heat transfer and flow structures are numerically analyzed. The general configuration of the DVR is called “type I,” while the discrete DVR can be split into two structures, which are called “types II and III.” The influences of the DVR sizes, DVR types and flow directions on heat transfer rate, friction loss, and thermohydraulic performance are considered. The Reynolds numbers in the range around 100–2000 (laminar regime at the entrance condition) are selected for the present investigation. The numerical problem of the HED installed with the DVR is solved with the finite volume method (a commercial code). The flow structure, heat transfer mechanism, and performance analysis in the HED that fitted the DVR are reported. The flow and heat transfer profiles in the HED fitted with the DVR are an important knowledge to develop the thermohydraulic performance of compact heat exchangers. As the numerical results, it is seen that the heat transfer ability of the tested duct improves around 1.05–16.62 times upper than the smooth duct. Additionally, the greatest value of the thermal enhancement factor in the HED fitted with the DVR is seen to be around 4.17 at a/H = 0.025, b/H = 0.10, Re = 2000, and V-upstream direction for the type I.
Highlights
The active method has high efficiency to augment the heat transfer potentiality, the operation and energy cost may extremely enhance. e passive method is an installation of vortex generators or turbulators into the heat exchangers to change a general flow structure. e vortex flows and impinging flows are detected when the vortex generators in the heat exchanger systems are installed. e variations of the flow structures disturb thermal boundary layer on heat transfer region that is a key cause for the heat transfer improvement. ere are various kinds of the vortex generators such as rib, baffle, winglet, and conical ring. e vortex generator selection for the heating/cooling systems depends on the application of the heat exchangers
As the previous works [14,15,16,17,18,19], we found that the V-shaped baffle/rib gives high efficiency to augment heat transfer rate and thermal performance
The greatest thermal enhancement factor (TEF) in the heat exchanger duct (HED) inserted with the double V-rings (DVR) is found to be around 4.17, 4.13, and 4.04, for types I, II, and III, respectively
Summary
An important step for the numerical investigation is numerical validation. e numerical validation can help guarantee the reliance and accuracy of the numerical solution. e numerical validation of the present investigation can be divided into two topics: (1) smooth square channel validation and (2) grid independence. e comparisons of the Nusselt number and friction factor between the present results with the values from the correlations [21] are done for the smooth duct validation. E friction loss in the HED inserted with the V-Downstream of the type III DVR is found to be around 1.74–55.65, 2.05–64.82, 2.43–76.89, and 2.85–90.50 times upper than the smooth duct, respectively, for a/H 0.025, 0.05, 0.075, and 0.1.
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