TAILIEUCHUNG - Heat Transfer Handbook part 88

Heat Transfer Handbook part 88. 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. | LONGITUDINAL FINNED DOUBLE-PIPE EXCHANGERS 865 For the annulus the tube diameter is replaced with the equivalent diameter for pressure loss APf 8Whpf PV2 L 4nhpf pV2L 2 de de The turn loss for both inner pipe and annulus with Nhp hairpins is P 2 2nhp - 1 pV2 Wall Temperature and Further Remarks It may be noted that the wall resistance presents the lowest resistance to the flow of heat between the hot and cold fluids. Hence an excellent approximation to the wall temperature may be obtained via the computation of the product of Ris and the heat flux. Then ifthe hot fluid is carried within the inner tube the wall temperature will be Tw Tb - Risq J where E R- E R-nr Rio rio rdo rmo In the event that the cold fluid is carried in the inner tube the wall temperature will be Tw tb Ri-q J Series-Parallel Arrangements When two streams are arranged for counterflow the LMTD represents the maximum thermal potential for heat transfer that can be obtained. Often on the industrial scale a single process service may entail the use of more han a single long hairpin. It then follows that it is desirable to connect the hairpins in series on both the annulus and inner pipe sides as in Fig. . In this configuration the temperature potential remains the LMTD for counterflow. In some services there may be a large quantity ofone fluid undergoing a small temperature change and a small quantity ofanother fluid undergoing a large temperature change. It may not be possible to circulate the large volume offluid through the required number of haipsins with flee pressure drop i l . IMcr thcee 0 0. -stances the larger volume of fluid may be m an i fol dcd m hhe i I es-praa fl el arragge-ment shown in Fig. . The inner pipe fluid has been split between the exchangers 866 HEAT EXCHANGERS Figure Double-pipe heat exchangers in series. From Kraus et al. 2001 with per- mission. Figure Double-pipe heat exchangers in series-parallel. .

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