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Proceedings ArticleDOI

A Correlation for Nusselt Number Under Turbulent Mixed Convection Using Transient Heat Transfer Experiments

01 Jan 2010-pp 225-232

Abstract: This paper reports the results of an experimental investigation of transient, turbulent mixed convection in a vertical channel in which one of the walls is heated and the other is adiabatic. The goal is to simultaneously estimate the constants in a Nusselt number correlation whose form is assumed a priori by synergistically marrying the experimental results with repeated numerical calculations that assume guess values of the constants. The convective heat transfer coefficient “h” is replaced by the Nusselt number (Nu) which is then assumed to have a form Nu = a (1+RiD ) b ReD c where a, b and c are the constants to be evaluated. From the experimentally obtained temperature time history and the simulated temperature time history, based on some guess values of a, b, and c, one can define the objective function or the residue as the sum of the square of the difference between experimentally obtained and simulated temperatures. Using Bayesian inference driven by the Markov chain Monte Carlo method, one, more or all of the constants a, b and c are retrieved together with the uncertainty involved in these estimates. Additionally, the estimated parameters are compared with experimental benchmarks.Copyright © 2010 by ASME
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Journal ArticleDOI
Lokanath Mohanta1, Fan Bill Cheung1, Stephen M. Bajorek2, Kirk Tien2  +1 moreInstitutions (2)
Abstract: Heat transfer by mixed convection in a rod bundle occurs when convection is affected by both the buoyancy and inertial forces. Mixed convection can be assumed when the Richardson number ( Ri = Gr / Re 2 ) is on the order of unity, indicating that both forced and natural convection are important contributors to heat transfer. In the present study, data obtained from the Rod Bundle Heat Transfer (RBHT) facility was used to determine the heat transfer coefficient in the mixed convection regime, which was found to be significantly larger than those expected assuming purely forced convection based on the inlet flow rate. The inlet Reynolds ( Re ) number for the tests ranged from 500 to 1300, while the Grashof ( Gr ) number varied from 1.5 × 10 5 to 3.8 × 10 6 yielding 0.25 Ri

8 citations


Journal ArticleDOI
Abstract: In this work, a solution technique is proposed by synergistically combining asymptotics and computational fluid dynamics to ascertain a problem of laminar mixed convection heat transfer in a vertical channel. First, numerical simulation is carried out on a vertical channel that consists of an aluminum heater plate assembly at the center of the channel. The numerical model is treated as a conjugate heat transfer problem, and the concept of perturbation and blending is incorporated wherein the limiting solution of natural and forced convection is obtained in terms of average Nusselt number. These correlations are then blended to find a unified composite correlation that work very well for extreme limits of mixed convection. The Richardson number is chosen as an independent variable in the present analysis; as a result, the Nusselt number correlation is cogent for the mixed convection region. Upon performing the numerical simulations, the results of the mixed convection are then compared with experimental results available in the literature for the purpose of validation of the numerical solution. The results of the present work emphasize that, with minimum computational fluid dynamics (CFD) solutions, one can obtain a reasonably good composite correlation for the Nusselt number for mixed convection and also a substantial reduction of computations is possible ensuing an asymptotically flawless solution.

1 citations


Journal ArticleDOI
Abstract: This paper presents the results of numerical analysis of steady laminar natural convection and surface radiation in the two dimensional partially right side open square cavity filled with natural air (Pr = 0.70) as the fluid medium. The cavity has left isothermal hot wall with top, bottom and right adiabatic walls. In the present study, the governing equations i.e. Navier-Stokes Equation in the stream function – vorticity form and Energy Equation are solved for a constant thermophysical property fluid under the Boussinesq approximation. For discretization of these equations, the finite volume technique is used. For the radiation calculations, the radiosity-irradiation formulation is used and the shape factors is calculated by using the Hottel’s crossed-string method. The effects of openings having different dimensions at different positions in the right side wall with the other pertinent parameters like the Rayleigh Number (103 ≤ Ra ≤ 105) and the surface emissivity of walls (0.05 ≤ ε ≤ 0.85) are studied. Correlations are developed for the average convection Nusselt number and the average radiation Nusselt number at left isothermal hot wall for the different geometries of the cavity.

1 citations


Cites background from "A Correlation for Nusselt Number Un..."

  • ...Gnanasekaran and Balaji (2011) developed a correlation for Nusselt number under turbulent mixed convection using transient heat transfer experiments....

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References
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Book
02 Oct 1985-
Abstract: Description of the Inverse Heat Conduction Problem Exact Solutions of the Inverse Heat Conduction Problem Approximate Methods for Direct Heat Conduction Problems Inverse Heat Conduction Estimation Procedures Inverse Convolution Procedures Difference Methods for Solution of the One Dimensional Inverse Heat Conduction Problem Multiple Heat Flux Estimation Heat Transfer Coefficient Estimation Index

1,650 citations



Journal ArticleDOI
Albin A. Szewczyk1Institutions (1)

75 citations


Journal ArticleDOI
Abstract: A numerical investigation of conjugate convection with surface radiation from horizontal channels with protruding heat sources has been carried out. The flow is assumed to be steady, laminar, incompressible, hydrodynamically and thermally developing. Air is considered as the working fluid. The geometric parameters such as spacing between the channel walls, size of the protruding heat sources, thickness of the substrate and the spacing between the heat sources are fixed. Results are presented to show the effect of parameters such as ReS, Gr S ∗ , kp/kf, ks/kf, ep and es on the fluid flow and heat transfer. A correlation for the non-dimensional maximum temperature is also developed using the method of asymptotic expansions.

74 citations


"A Correlation for Nusselt Number Un..." refers background in this paper

  • ...Premachandran and Balaji (2006) carried out numerical studies on conjugate mixed convection with and without surface radiation from channels with volumetric heat generation....

    [...]


Journal ArticleDOI
Abstract: The results of a numerical analysis of the problem of two-dimensional, steady, incompressible, conjugate, laminar, mixed convection with surface radiation in a vertical parallel-plate channel, provided with a flush-mounted, heat generating, discrete heat source in each wall, are presented here. Air, a radiatively non-participating medium, is used as the cooling agent. A computer code based on the finite volume method is written exclusively for solving the above problem. The effect of surface emissivity, aspect ratio, discrete heat source position and modified Richardson number on the fluid flow and heat transfer characteristics is explored. Useful correlations are evolved for the maximum temperature of the left and the right channel walls, the mean friction coefficient and the forced convection component of the mean friction coefficient.

73 citations