Numerical study of thermo-hydraulic characteristics for forced convective flow through wavy channel at different Prandtl
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Numerical study of thermo‑hydraulic characteristics for forced convective flow through wavy channel at different Prandtl numbers Sumit Kumar Mehta1 · Sukumar Pati1 Received: 25 October 2019 / Accepted: 4 February 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The present work numerically investigates the thermo-fluidic and entropy generation characteristics for laminar forced convective flow through wavy channel at different Prandtl number (Pr). Results are presented for the following range of parameters: Reynolds number 5 ≤ Re ≤ 200 , Prandtl number 0.72 ≤ Pr ≤ 100 , dimensionless amplitude 0.3 ≤ 𝛼 ≤ 0.7 and dimensionless wavelength 0.5 ≤ 𝜆 ≤ 1.5 . It is observed that with increase in Pr, the thickness of the thermal boundary layer at trough region decreases slowly for smaller Re, whereas at higher Re, the rate of decrement is higher. The average Nusselt number increases with Pr for all amplitude, wavelength and Reynolds number. The relative heat transfer enhancement compared to equivalent plane channel is presented in terms of enhancement ratio (ER), and it shows a non-monotonic variation of ER with Pr at lower Re and a monotonic one at higher Re. The combined alteration of rate of heat transfer and pressure drop as compared to plane channel is enumerated by performance factor (PF), and the variation of PF with Pr shows nonmonotonic behaviour at lower Re and monotonic one at higher Re. The variation of PF shows non-monotonic variation with Re for higher Pr and for smaller wavelength, whereas it monotonically decreases for all Pr at higher wavelength. Thermal entropy generation contribution is higher over the viscous one for all the cases considered. The local thermal entropy generation distribution varies with Re, Pr and geometrical configuration of the channel. For smaller amplitude (α = 0.3), the total entropy generation is minimum in the considered range of Re and Pr. Keywords Wavy channel · Prandtl number · Nusselt number · Entropy generation · Bejan number List of symbols A Amplitude (m) Be Bejan number (–) Cp Specific heat (J kg−1 K−1) ER Enhancement ratio (–) k Thermal conductivity (Wm−1 K−1) L Inlet half height (m) N ′′′ Dimensionless local entropy generation (–) N Dimensionless total entropy generation (–) Nu Nusselt number (–) Nu Average Nusselt number (–) PF Performance factor (–) Pr Prandtl number (–) Re Reynolds number (–) * Sumit Kumar Mehta [email protected] 1
Sukumar Pati [email protected]; [email protected]
s Wavy profile (m) S′′′ Local entropy generation rate (W K−1 m3) T Temperature (K) u, v x and y-velocity component (m s−1) U, V Dimensionless x and y velocity (–) X, Y Dimensionless coordinate (–) Greek symbols 𝛼 Dimensionless amplitude (–) ρ Density (kg m−3) µ Dynamic viscosity (kg m−1 s−1) θ Dimensionless temperature (–) 𝛷 Irreversibility distribution ratio (–) Subscript avg Average e End in Inlet s Start w Wall
Department of Mechanical Engineering, National Institute of Technology Silchar, Silchar 788010, India
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