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Research Papers: Heat Exchangers

Second-Law Thermodynamic Comparison and Maximal Velocity Ratio Design of Shell-and-Tube Heat Exchangers With Continuous Helical Baffles

[+] Author and Article Information
Qiu-Wang Wang1

State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, Chinawangqw@mail.xjtu.edu.cn

Gui-Dong Chen

State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, Chinachengd514@163.com

Jing Xu

State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, Chinaxujing_nanjing@163.com

Yan-Peng Ji

State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, Chinajyp.2008@stu.xjtu.edu.cn

1

Corresponding author.

J. Heat Transfer 132(10), 101801 (Jul 27, 2010) (9 pages) doi:10.1115/1.4001755 History: Received December 10, 2009; Revised March 24, 2010; Published July 27, 2010; Online July 27, 2010

Shell-and-tube heat exchangers (STHXs) have been widely used in many industrial processes. In the present paper, flow and heat transfer characteristics of the shell-and-tube heat exchanger with continuous helical baffles (CH-STHX) and segmental baffles (SG-STHX) were experimentally studied. In the experiments, these STHXs shared the same tube bundle, shell geometrical structures, different baffle arrangement, and number of heat exchange tubes. Experimental results suggested that the CH-STHX can increase the heat transfer rate by 7–12% than the SG-STHX for the same mass flow rate although its effective heat transfer area had 4% decrease. The heat transfer coefficient and pressure drop of the CH-STHX also had 43–53% and 64–72% increase than those of the SG-STHX, respectively. Based on second-law thermodynamic comparisons in which the quality of energy are evaluated by the entropy generation number and exergy losses, the CH-STHX decreased the entropy generation number and exergy losses by 30% and 68% on average than the SG-STHX for the same Reynolds number. The analysis from nondimensional correlations for Nusselt number and friction factor also revealed that if the maximal velocity ratio R>2.4, the heat transfer coefficient of CH-STHX was higher than that of SG-STHX, and the corresponding friction factor ratio kept at constant fo,CH/fo,SG=0.28.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of continuous helical baffled STHX (CH-STHX)

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Figure 2

Baffle layout of heat exchangers

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Figure 3

Heat exchanger tube arrangement

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Figure 4

Experimental loops

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Figure 5

Comparison of experimental data with results from Bell–Delaware design method

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Figure 6

Heat transfer rate and heat transfer coefficient versus mass flow rate

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Figure 7

Pressure drop versus mass flow rate

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Figure 8

Entropy generation number and exergy loss versus Reynolds number

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Figure 9

Nusselt number versus Reynolds number

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Figure 10

Friction factor versus Reynolds number

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Figure 11

Maximal velocity ratio versus heat transfer coefficient

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Figure 12

Reynolds number versus maximal velocity ratio

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