TED-AJ03-211 FLOW AND HEAT TRANSFER AROUND A SQUARE BLOCK SIMULATING A PACKAGE OF ELECTRONIC EQUIPMENT

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概要

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• Many researches have been carried out to investigate the forced convection heat transfer from rectangular blocks, simulating packages of electronic equipment. However, it is difficult to obtain a general correlation concerning the heat transfer, because it depends on many factors. In the present study, distributions of local heat transfer from a low-height square block were measured. Experiments were carried out under the condition of a laminar duct flow, in which most packages of compact electronic equipment are situated. The height and the side lengths of the square block were 2 mm and 45 mm, respectively. The mean air velocity in the rectangular duct ranged from 0.24 to 4 m/s, and the duct height ranged from 3.8 to 10 mm. The surface of the block was heated under the condition of constant heat flux. Temperature distribution on the block was measured by an infrared camera from upside of the duct through a sapphire window. Figure A-1 shows the streamwise distribution of Nusselt number on the top face of the block at the center cross section. Based on the theory of laminar flat boundary layer, the Nusselt number distribution can be approximated as [numerical formula], (A-1) where Re^* is modified Reynolds number including the effect of duct opening ratio β, and C is a constant depending on a thermal boundary condition. The above equation agrees well with the present experiment, regardless of the mean velocity U_m and the duct height H_D. Figure A-2 shows a correlation between average Nusselt number on the top face of the block, Nu_m, and modified Reynolds number based on the block length L. The Nusselt number is expressed within ±5% as Nu_m=0.54(Re_L^*)^<0.5> (Re_L^*=1000-50000). (A-2) The above correlation can be rewritten as Nu_m=0.61 Pr^<1/3>(Re_L^*)^<0.5> (Re_L^*=1000-50000).(A-3) It was confirmed from the comparison with many previous researches that Eq. (A-3) approximates the average Nusselt number on the top face of a low-height block in a laminar flow, regardless of configurations of a block and a duct.[figure]

• 一般社団法人日本機械学会の論文

著者

• Nakamura Hajime

  Dept. Of Mech. Engng. National Defense Academy

• Igarashi Tamotsu

  Dept. Of Mech. Engng. National Defense Academy

関連論文

• TED-AJ03-211 FLOW AND HEAT TRANSFER AROUND A SQUARE BLOCK SIMULATING A PACKAGE OF ELECTRONIC EQUIPMENT

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