Abstract
Co-relations of friction factor and Nusselt number for plain tubes have been widely developed, but less analysis has been done for tubes with wavy surfaces. This paper uses the Computational Fluid Dynamics (CFD) tool for the analysis of heat transfer and pressure drop in wavy-walled tubes, which can be utilized as a heating element for fluids. An investigation was done for the effect of Reynolds number (Re) and wavy-walled tube geometry on friction factor and Nusselt number of laminar and turbulent flow inside wavy-walled tubes. The numerical results and experimental comparison indicate that heat transfer and pressure drop for water are significantly affected by wavy-walled tube parameters and flow Reynolds number. These wavy-walled tubes are capable of increasing the heat transfer to or from a fluid by an order of magnitude but at an expense of higher pumping power. This ratio was found to remain at the minimum at a wave factor of 0.83 for 34 < Re < 3500 and maximum at a wave factor of 0.15 for 200 < Re < 17,000. New correlations of friction factor and Nusselt number based on wavy-walled tube parameters are proposed in this paper, which can serve as design equations for predicting the friction factor and heat transfer in wavy-walled tubes under a laminar and turbulent regime with less than 10% error. The quantitative simulation results match the experimental results with less than 15% error. The qualitative comparison with the experiments indicates that the simulations are well capable of accurately predicting the circulation zones within the bulgy part of the tubes.
Highlights
Heat transfer can be significantly improved by augmenting the heat transfer area as shown by Takeishi and Beate et al [1,2]
Reynolds number to betoused for simulations hashas been selected in in such a way that of Reynolds number be used for simulations been selected such a way thatthree threevalues valuesofofthe
The simulations for heat transfer and pressure drop in wavy-walled tubes under laminar as well as turbulent flow regime for high Prandtl number fluid was carried out using software Ansys Fluent
Summary
Heat transfer can be significantly improved by augmenting the heat transfer area as shown by Takeishi and Beate et al [1,2]. This augmentation can be done axially to form a tube having a diameter varying sinusoidally, forming a wavy-walled tube. Several studies have been conducted on the nature of flow through the tubes with variable cross-sections. Hatami et al [3] studied the heat transfer of a nanofluid in similar variable cross-section tubes like a venturi and a wavy tube. The rate of heat transfer in laminar flows can be augmented by utilizing such alternatives, which includes using low Prandtl number (Pr) fluids like liquid sodium as shown by Mehdi et al [4], using nanofluids as shown by
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