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【正文】 B ReB 23,000 can be expressed as the correlation coefficient is r = .The flow resistance correlation in the ranger of 7,000 B ReB 23,000 can be expressed as – 14and the correlation coefficient for above equation is r = .It can be seen from Figs. 5 and 6 , that the Nusselt number Nu and pressure drop will increase with the increase of Renumber, and under the same shell side velocity and with different tube velocities for FBSTHX the heat transfer and flow resistance characteristic in shell side are almost the same, which prove the good repetition of the 7 and 8 show the heat transfer and flow resistance characteristics for SBSTHX. The lines shown in these figures were fitted by the method of least squares,and the heat transfer correlation in the range of 4,000 B ReB 15,000 can be expressed as the correlation coefficient for above equation is r = .The flow resistance correlation in the ranger of 4,000 B ReB 15,000 can be expressed as Eqs. 16– 17 and the correlation coefficients are r = ,r = respectively.As shown in Figs. 7 and 8 , the Nusselt number Nuand pressure drop will increase with the increase of Renumber.Under the same shell side velocity and with different tube velocity for SBSTHX the heat transfer and flow resistance characteristic are almost same, which prove the goodrepetition of the experiments. The parison of Nunumber and pressure drop D p inshell side between FBSTHX and SBSTHX can be seen in Figs. 9 and 10. Nusselt number Nu increases with the increase of Reynolds number Re for the two heat exchangers, and the pressure drop increases with the increase of the Reynolds number Re for both heat exchangers. From the figures it can be observed that, with same Renumber, the Nunumber of FBSTHX is about 50% of that of SBSTHX, but the pressure drop D p of the former is only 30% of that of the latter. This is because the fluid flow in shell side of flower baffle heat exchanger is longitudinal, but the fluid flow in shell side of segmental baffle heat exchanger is transverse. As a result, the heat transfer of the flower baffle heat exchanger is less than that of the segmental baffle heat exchanger. Because of this, the pressure drop in shell side of flower baffle is also less than that of the segmental baffle heat exchanger.Figure 11shows the prehensive parison of performance Nu/ Dp between FBSTHX and SBSTHX. With sameRenumber, the prehensive performance Nu/ Dp of FBSTHX is about 60% higher than that of SBSTHX.To sum up, in the same shell side Re, the shell side Nuof FBSTHX is less than that of the SBSTHX, and the pressure drop of the former is also less than that of the latter, but the decreasing amplitude of the flow resistance is larger than that of the heat transfer. As a result, the prehensive performance Nu/D p of FBSTHX is higher than that of the SBSTHX. Therefore, it could be concluded that with same pressure drop, the Nunumber of the FBSTHX is higher than that of the SBSTHX.6 Experimental uncertainty analysisThe experimental uncertainty of the present work is determined by using the method presented by Ref. [14].The uncertainty calculation method involves calculating derivatives of the desired variable with respect to individual experimental quantities and applying known uncertainties. According to Ref. [ 14], the experimental uncertainty is defined as follow:Where R=f(X1,X2,...,Xn),X1,X2,...,Xn are the variables that absolute uncertainties of X1,X2,...,Xn.The uncertainties involved in the friction factors for FBSTHX and SBSTHX are 177。 and177。%, respectively,and the uncertainties involved in the Nunumber for FBSTHX and SBSTHX are within 177。 and 177。%,respectively.7 ConclusionThe characteristics of heat transfer and flow resistance forthe FBSTHX and the SBSTHX have been experimentally investigated. And performance parisons between the FBSTHX and the SBSTHX are conducted. The heat transfer and flow resistance correlation for SBSTHX and FBSTHX were developed based on the experiment results. The experimental results showed that under circumstanceof the sameRenumber both in shell and tube side, the Nusselt number Nufor FBSTHX is about 50% of that of SBSTHX while the pressure drop of the former is about 30% of the latter. But the prehensive performanceNu/Dp of the former is 60% higher than that of the latter. For the sake of energy saving in designing heat exchangers, both heat transfer enhancement and flow resistance increase should be taken into consideration. By properly designing FBSTHX the heat transfer and pressure drop performance can be improved relative to the traditional SGSTHX.References1. Qian SW (2002) Handbook for heat exchanger design. ChemicalIndustry Press, Beijing (in Chinese)2. Mukherjee R (1992) Use doublesegmental baffles in the shellandtube heat exchangers. Chem Eng Prog 88:47–523. Li H, Kottke V (1999) Analysis of local shell side heat and masstransfer in the shellandtube heat exchanger with discanddoughnut. Int J Heat Mass Transf 42:3509–35214. Li H, Kottke V (1998) Effect of baffle spacing on pressure dropand local heat transfer in shellandtube heat exchangersfor staggered tube arrangement. Int J Heat Mass Transf41(10):1303–13115. Lei YG, He YL, Rui L et al (2008) Effects of baffle inclinationangle on flow and heat transfer of a heat exchanger with helicalbaffles. Chem Eng Process 47(12):2336–23456. Lei YG, He YL, Pan C et al (2008) Design and optimization of heatexchangers with helical baffles. Chem Eng Sci 63(17):4386–43957. Dong QW, Wang YQ, Liu MS (2008) Numerical and experimental investigation of shell side characteristics for rod baffleheat exchanger. Appl Therm Eng 28:651–6608. Peng B, Wang QW, Zhang C et al (2007) An experimental studyof shellandtube heat exchangers with continuous helical baffles.J Heat Transf 129:1425–14319. Kara YA, Guraras OA (2004) Computer program for designing ofshellandt
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