Abstract
This paper presents the results of a comprehensive numerical study to analyze conjugate, turbulent mixed convection heat transfer from a vertical channel with four heat sources, uniformly flush-mounted to one of the channel walls. The results are presented to study the effect of various parameters like thermal conductivity of wall material (k s), thermal conductivity of flush-mounted discrete heat source (k c), Reynolds number of fluid flow (Re s), modified Richardson number (Ri +) and aspect ratio (AR) of the channel. The standard k-ε turbulence model, modified by including buoyancy effects with physical boundary conditions, i.e. without wall functions, has been used for the analysis. Semi-staggered, non-uniform grids are used to discretise the two dimensional governing equations, using finite volume method. A correlation, encompassing a wide range of parameters, is developed for the non-dimensional maximum temperature (T *) using the asymptotic computational fluid dynamics (ACFD) technique.
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Abbreviations
- AR:
-
aspect ratio of the channel (H/S)
- Gr +s :
-
modified Grashof number, based on volumetric heat generation (β gS3ΔT ref/ν2)
- H :
-
height of the channel (m)
- H 1 :
-
height of the heat source (m)
- k :
-
turbulent kinetic energy (m2/s2)
- k c :
-
thermal conductivity of heat source (W/m K)
- k f :
-
thermal conductivity of fluid (W/m K)
- k * :
-
non-dimensional turbulent kinetic energy (k/(V ∞)2)
- k s :
-
thermal conductivity of channel wall (W/m K)
- p * :
-
non-dimensional pressure ( \({\overline{p}} \mathord{\left/ {\vphantom {{\overline{p}} {\rho V_{\infty}^{2}}}} \right. \kern-\nulldelimiterspace} {\rho V_{\infty}^{2}}\))
- \(\bar{p}\) :
-
time averaged pressure (N/m2)
- \({\dot{q}}^{\prime\prime\prime}\) :
-
rate of volumetric heat generation from heat source (W/m3)
- Re s :
-
Reynolds number based on S (V ∞ S/υ)
- Ri :
-
Richardson number (Gr/Re 2)
- Ri + :
-
modified Richardson number (Gr +s /Re 2s )
- S :
-
spacing between two channel walls or width of the square enclosure (m)
- T :
-
temperature at any point (K)
- T * :
-
non-dimensional temperature (T − T ∞/ΔT ref)
- T * C :
-
non-dimensional maximum temperature on the conducting wall
- T * C :
-
temperature on the conducting wall (K)
- T max :
-
maximum temperature (K)
- T *max :
-
maximum non-dimensional temperature
- T w :
-
wall temperature (K)
- T ∞ :
-
uniform inlet temperature (K)
- t * :
-
non-dimensional time (t v ∞/S)
- ΔT ref :
-
reference temperature difference ( \({\dot{q}}^{\prime\prime\prime} 4{H}_{1}\delta/{k}_{\rm f}\))
- \(\bar{u}\) :
-
time averaged x-component of velocity (m/s)
- u * :
-
non-dimensional horizontal velocity ( \({\overline{u}} \mathord{\left/ {\vphantom {{\overline{u}} {V_{\infty}}}} \right. \kern-\nulldelimiterspace} {V_{\infty}}\))
- \(\bar{v}\) :
-
time averaged y-component of velocity (m/s)
- v * :
-
non-dimensional vertical velocity ( \({\overline{v}} \mathord{\left/ {\vphantom {{\overline{v}} {V_{\infty}}}} \right. \kern-\nulldelimiterspace} {V_{\infty}}\))
- V ∞ :
-
uniform inlet velocity (m/s)
- x * :
-
non-dimensional horizontal coordinate (x/S)
- y * :
-
non-dimensional vertical coordinate (y/S)
- β:
-
coefficient of volume expansion (K−1)
- δ:
-
thickness of channel wall (m)
- ɛ:
-
dissipation rate of k (m2/s3)
- ɛ* :
-
non-dimensional dissipation rate (ɛ S/(V ∞)3)
- υ:
-
kinematic viscosity (m2/s)
- υ * t :
-
turbulent eddy viscosity (m2/s)
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Mathews, R.N., Balaji, C. & Sundararajan, T. Computation of conjugate heat transfer in the turbulent mixed convection regime in a vertical channel with multiple heat sources. Heat Mass Transfer 43, 1063–1074 (2007). https://doi.org/10.1007/s00231-006-0192-9
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DOI: https://doi.org/10.1007/s00231-006-0192-9