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Article
Publication date: 1 September 1995

Koki Kishinami, Hakaru Saito and Jun Suzuki

Combined free and forced laminar air convective heat transfer from avertical composite plate with isolated discontinuous surface heating elementshas been studied numerically and…

71

Abstract

Combined free and forced laminar air convective heat transfer from a vertical composite plate with isolated discontinuous surface heating elements has been studied numerically and experimentally. The problem has been simplified by neglecting heat conduction in unheated elements of the plate to accomplish a better understanding of the complicated combined/complicated convection problem. In this study, it is most important in explaining the heat transfer behaviour to clarify the interactions between buoyancy and inertia forces in the convective field and also the coupling effects of unheated elements upon the combined flow fields. Therefore, the temperature distributions of the wall surface and local Nusselt number, obtained by numerical calculations and experiments, have been discussed based on the various parameters associated with the present convection problem, i.e., Grashof number GrL, Reynolds number ReL, geometry factor D/L and stage number N. Heat transfer characteristics Nut/Re1/2L of this combined and coupled convection of air are presented as a function of a generalized coupling dimensionless number GrL/Re2L, and stage number N for certain values of the geometry factor of D/L.

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International Journal of Numerical Methods for Heat & Fluid Flow, vol. 5 no. 9
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 September 1998

Koki Kishinami, Hakaru Saito, Jun Suzuki, Ahmed Hamza H. Ali, Hisashi Umeki and Noriyuki Kitano

Combined forced and free laminar convective heat transfer on a vertical plate with a backward‐facing step has been studied numerically and experimentally, considering the effects…

375

Abstract

Combined forced and free laminar convective heat transfer on a vertical plate with a backward‐facing step has been studied numerically and experimentally, considering the effects of the interaction between the buoyancy and inertia forces which play a significant role in this phenomenon with the step‐geometry factor of d/L. The convective heat transfer behavior in connection with the reattachment and recirculation flows appearing in the step region has been investigated based on the numerical calculations and Mach‐Zehnder interferometer measurement under the wide range of the thermal condition. The behaviors of local Nusselt number NuL, velocity and temperature boundary layers and streamline fields in the recirculating region have been discussed for the various parameters of Grashof number GrL, Reynolds number ReL and the geometry factor d/L. The characteristic behavior of this convection heat transfer, including the vortex flow mode in the recirculating region and the unstable fluctuating mode near the reattaching point appearing at the specific condition, has been clarified numerically and experimentally by introducing the generalized coupling parameter GrL/ReL2 and geometry factor d/L.

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International Journal of Numerical Methods for Heat & Fluid Flow, vol. 8 no. 6
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 August 1998

Ahmed Hamza H. Ali, Koki Kishinami, Yutaka Hanaoka and Jun Suzuki

A two‐dimensional numerical study was carried out to investigate laminar forced‐convection heat transfer characteristics of air flow in a two parallel plate channel with offset…

610

Abstract

A two‐dimensional numerical study was carried out to investigate laminar forced‐convection heat transfer characteristics of air flow in a two parallel plate channel with offset plates and heated by a radiation heat flux. The SIMPLE method was used for the numerical prediction of the flow and thermal fields. The flow field temperature boundary conditions were obtained by applying the energy balance equation to boundary elements. The ray tracing technique was used to obtain the net absorbed radiation fractions in the boundary elements. The numerical results were validated with measured temperature values and experimentally calculated values of local Nusselt number (Nux), and a reasonable agreement was shown. Then the numerical simulation was used to study effects of design parameters on the convective heat transfer coefficient. It was found that in Re numbers from 650 to 2,550, the optimum spacing of offset plates relative to the nearest channel wall was around one third of the channel height. Also, the optimum offset plates’ numbers can be calculated based on one offset plate length being equal to one and a half times the channel hydraulic diameter. A correlation of average Nusselt number between the flowing air and the offset plates was obtained as follows; —Nu = 1.81 Re 0.352Pr1/3(Dh/l)1/2.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 8 no. 5
Type: Research Article
ISSN: 0961-5539

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