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Natural convection in a parallel-plate vertical channel with discrete heating by two flush-mounted heaters: effect of the clearance between the heaters

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Abstract

In this study, natural convection in a vertical channel is studied experimentally and numerically. One of the channel walls is heated discretely by two flush-mounted heaters while the other is insulated. The effects of the clearance between the heaters on heat transfer and hot spot temperature while total length of the heaters keeps constant are investigated. Four different settlements of two discrete heaters are comparatively examined. Air is used as the working fluid. The range of the modified Grashof number covers the values between 9.6 × 105 and 1.53 × 10.7 Surface to surface radiation is taken into account. Flow visualizations and temperature measurements are performed in the experimental study. Numerical computations are performed using the commercial CFD code ANSYS FLUENT. The results are represented as the variations of surface temperature, hot spot temperature and Nusselt number with the modified Grashof number and the clearance between the heaters as well as velocity and temperature variations of the fluid.

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Abbreviations

D:

Channel depth [m]

D h :

Hydraulic diameter [m]

g :

Gravitational acceleration [m/s2]

\( {Gr}_{Dh}^{\ast } \) :

Modified Grashof number

h :

Convective heat transfer coefficient [W/m2K]

k :

Thermal conductivity [W/mK]

L:

Channel length [m]

Nu :

Nusselt number

q :

Heat flux [W/m2]

s :

Clearance between the heaters [m]

t :

Thickness [m]

T :

Temperature [°C]

α :

Thermal diffusivity [m2/s]

β :

Thermal expansion coefficient of the fluid [1/K]

ε :

Surface emissivity

υ :

Kinematic viscosity of the fluid [m2/s]

ρ :

Density [kg/m3]

cond :

Conductive

conv :

Convective

cu:

Copper

f :

Fluid

in:

Inlet

ins:

Insulator

out:

outlet

tot:

Total

0:

Reference

p:

Polycarbonate

rad :

Radiative

s:

Solid

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Acknowledgements

This study is supported by The Scientific and Technological Research Council of Turkey (TUBITAK) with project number of 114 M589.

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Authors and Affiliations

  1. Department of Mechanical Engineering, Gumushane University, 29100, Gumushane, Turkey

    Bugra Sarper

  2. Department of Mechanical Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey

    Mehmet Saglam, Orhan Aydin & Mete Avci

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  1. Bugra Sarper
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Correspondence to Orhan Aydin.

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On behalf of all authors, Prof. Orhan Aydin, the corresponding author of this article states that there is no conflict of interest.

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Sarper, B., Saglam, M., Aydin, O. et al. Natural convection in a parallel-plate vertical channel with discrete heating by two flush-mounted heaters: effect of the clearance between the heaters. Heat Mass Transfer 54, 1069–1083 (2018). https://doi.org/10.1007/s00231-017-2203-4

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