tailieunhanh - Heat Transfer Handbook part 51

Heat Transfer Handbook part 51. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | 492 FORCED CONVECTION EXTERNAL FLOWS where Nu is as defined for the two-dimensional strip Pec Uo 2xs ts 2a and A P is the source surface area perimeter ratio. The correlations of eqs. and are valid for 103 Pec 105 5 2xs ts 2ts 150 and ws ts 5 where ws is the heat source width. Additional detailed treatments of the subject have been compiled by Ortega 1996 . Two-Dimensional Block Array Figure shows the pertinent dimensions all nondimensionalized by the plate spacing for the two-dimensional block array. Arvizu and Moffat 1982 performed experiments for heat transfer from aluminum blocks in forced airflow in such channels. The parameter ranges covered are Ph 1 2 1 and 1 7 s 1 2 3 6 and 8 and 2200 RePh UPh v 12 000 Ph dimensional block height. For s 2 the heat transfer coefficients for a fixed Ph almost collapse into a single curve. The effect of Ph on heat transfer is laigf for tightly pladed MocIcs for s when Ph is increased from 1 7 to 1 2 the Nusselt number almost doubles. However Lehman and Wirtz 1985 found a near collapse of heat transfer data of various Ph ranging from 1 2 to 1 6 with s Ph and Pt Ph 4. The data of Lehman and Wirtz 1985 were obtained for 1000 ReP 12 000 and Pt 2. A visualization study was also conducted by Lehman and Wirtz and it revealed modes of convection that depend on the block spacing. Forclose block spacing s Pt cavity-type flow is formed in the interblock space indicating that the forward and back surfaces of the block do not contribute much to the heat transfer. When the spacing is widened to s Pt 1 signiecant cavity-channel flow interactions were observed. Davalath and Bayazitoglu 1987 performed numerical analysis on a three-row block array placed in a parallel-plate channel. Heat transfer correlations were derived for the cases where the following dimensions are ixed at Pt s Ph 1 f2 and t . The Reynolds number is defined as Re U0H v where U0 is the average velocity in the .