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RESEARCH PAPERS

# Convective Cooling of a PCB Like Surface With Mixed Heating Conditions in a Vertical Channel

[+] Author and Article Information

Department of Mechanical Engineering, The University of Auckland, Auckland, New Zealand 1142v.yadav@auckland.ac.nzDepartment of Mechanical Engineering, Indian Institute of Technology, Kanpur, India 208 016v.yadav@auckland.ac.nz

Keshav Kant1

Department of Mechanical Engineering, The University of Auckland, Auckland, New Zealand 1142keshav@iitk.ac.inDepartment of Mechanical Engineering, Indian Institute of Technology, Kanpur, India 208 016keshav@iitk.ac.in

1

Corresponding author.

J. Electron. Packag 129(2), 129-143 (Jul 23, 2006) (15 pages) doi:10.1115/1.2721084 History: Received July 13, 2005; Revised July 23, 2006

## Abstract

Printed circuit boards (PCBs) with uniform surface temperature and uniform wall heat flux are ideal to study. However, in reality, the heating conditions existing on the PCB surfaces are much different from the ideal ones. Present attempts have been made to study different combinations of uniform heat flux (UHF) and uniform wall temperature (UWT) heating conditions on a single surface and to develop more realistic relationships between various flow and thermal parameters for evaluating the local and averaged Nusselt number. Both the numerical and experimental investigations were undertaken to study partial and mixed UHF and UWT heating conditions on a buoyancy assisted convection cooling of simulated PCB forming one wall of the vertical channel while, the other wall was kept insulated. The current work considers moderate to high flow Reynolds number $(14.1×103≤Re≤2.35×105)$ in the channel and range of heat fluxes near that occurring in electronic cooling applications using air as a coolant $(0.0. Data for heat flux and Nusselt number occurring at various locations of the plate surface under different heating conditions are presented to analyze variation patterns; and an empirical relation is put forward which is capable of predicting Nu under the heating conditions mentioned. The empirical expression obtained can be used for getting an optimized layout of the PCBs inside the equipment cabinet, thus resulting in better design for more reliable and safe operation under potentially harsh environment and/or maximum load condition.

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## Figures

Figure 1

Computational domain

Figure 2

Effect of grid spacing in x direction up on the number of iterations for: (a) UHF; and (b) UWT conditions

Figure 3

Schematic of the experimental setup

Figure 4

Schematic for heated zones

Figure 5

Sketch showing the: (a) positions of thermocouples at a zone on channel wall; and (b) locations for velocity measurement (all dimensions are in mm)

Figure 6

Comparison of present work with previously available results

Figure 7

Comparison of calculated Nu trends with the available data

Figure 8

Variation in Gr∕Re2 with change in flow and thermal conditions

Figure 9

Effect of rise in heat flux at UHF portion (f) of simulated PCB upon the heat flux dissipation from (UWT) region (a)rL=0.2; (b)rL=0.4; (c)rL=0.6; and (d)rL=0.8

Figure 10

Comparison of calculated Nu trends with the experimental data at low flow velocity (rL=0.2; rq=0.05, 0.2, 0.4, and 1.0)

Figure 11

Comparison of calculated Nu trends with the experimental data at low flow velocity (rL=0.6; rq=0.05, 0.2, 0.4, and 1.0)

Figure 12

Comparison of calculated Nu trends with the experimental data at medium flow velocity (rL=0.2; rq=0.05, 0.2, 0.4, and 1.0)

Figure 13

Comparison of calculated Nu trends with the experimental data at medium flow velocity (rL=0.6; rq=0.05, 0.2, 0.4, and 1.0)

Figure 14

Comparison calculated Nu trends with the experimental data at moderately high flow velocity (rL=0.2; rq=0.05, 0.2, 0.4, and 1.0)

Figure 15

Comparison of calculated Nu trends with the experimental data at moderately high flow velocity (rL=0.6; rq=0.05, 0.2, 0.4, and 1.0)

Figure 16

Comparison of results based on empirical relation (Eq. 22) with similar data in the literature

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