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Research Papers: Heat Transfer Enhancement

Performance Evaluation of Heat Transfer Enhancement for Offset Strip Fins Used in Plate-Fin Heat Exchangers

[+] Author and Article Information
Yujie Yang

Department of Refrigeration and
Cryogenic Engineering,
School of Energy and Power Engineering,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: yyj_898@stu.xjtu.edu.cn

Yanzhong Li

Department of Refrigeration and
Cryogenic Engineering,
School of Energy and Power Engineering,
Xi'an Jiaotong University,
Xi'an 710049, China
State Key Laboratory of Multiphase Flow in Power Engineering,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: yzli-epe@mail.xjtu.edu.cn

Biao Si

Department of Refrigeration and
Cryogenic Engineering,
School of Energy and Power Engineering,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: si.biao@stu.xjtu.edu.cn

Jieyu Zheng

Department of Refrigeration and
Cryogenic Engineering,
School of Energy and Power Engineering,
Xi'an Jiaotong University,
Xi'an 710049, China
e-mail: zjy.521331@stu.xjtu.edu.cn

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received October 30, 2014; final manuscript received February 27, 2015; published online June 2, 2015. Assoc. Editor: Giulio Lorenzini.

J. Heat Transfer 137(10), 101901 (Oct 01, 2015) (9 pages) Paper No: HT-14-1717; doi: 10.1115/1.4030247 History: Received October 30, 2014; Revised February 27, 2015; Online June 02, 2015

In general, offset strip fin (OSF) used in plate-fin heat exchangers is able to provide a greater heat transfer coefficient than the plain fin with the same cross section, but it will also cause the increase of flow friction and pressure drop owing to the fin offset. A new parameter denoted by Ψ*, called relative entropy generation distribution factor, is proposed in this paper to comprehensively reflect the thermodynamic performance of different passage structures in plate-fin heat exchanger. This parameter physically represents relative changes of entropy generation and irreversibility, which are induced by both heat transfer and friction loss due to the utilization of OSF fins. The high magnitude of Ψ* represents a beneficial contribution of OSF with higher degree of the heat transfer enhancement. The proposed method is more reasonable and comprehensive than either the conventional augmentation entropy generation number, Ns,a, or the entropy generation distribution factor, ψ, to evaluate the heat transfer enhancement for OSF cores subject to various operating conditions. With the proposed method, the relative effects of the geometrical parameters of OSF fins, such as the fin thickness-to-height ratio α, fin density γ, and fin thickness-to-length ratio δ, on the heat transfer enhancement are discussed in detail. The results show that relatively small δ results in a better performance, while the parameter α or γ, which contribute to a higher degree of heat transfer enhancement of OSF fin, should be determined after the selection of the other two geometric parameters.

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References

Figures

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Fig. 1

The geometries and structure parameters of plain plate-fin and OSF fin

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Fig. 2

Schematic diagram of heat transfer process in a plate-fin channel

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Fig. 3

Thermal hydraulic performances of an OSF fin and a plain fin for typical operating conditions

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Fig. 4

Variation of Ns1* with Reo for heat flux

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Fig. 5

Variation of Ns1* with Reo for relative temperature difference

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Fig. 6

Variation of Ns1* with τ0 for irreversibility distribution ratio

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Fig. 7

Variation of Ψ with Reo for heat flux

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Fig. 8

Variation of Ψ with Reo for relative temperature difference

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Fig. 9

Variation of Ψ with τ0 for irreversibility distribution ratio

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Fig. 10

Variation of Ψ* with Reo for different heat fluxes

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Fig. 11

Variation of Ψ* with Reo for relative temperature difference

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Fig. 12

Variation of Ψ* with τ0 for irreversibility distribution ratio

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Fig. 13

Behavior of Ψ* versus α for relative temperature difference

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Fig. 14

Behavior of Ψ* versus δ for mass flow rate

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Fig. 15

Behavior of Ψ* versus γ for relative temperature difference

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Fig. 16

Behavior of Ψ* versus γ for mass flow rate

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Fig. 17

Behavior of Ψ* versus δ for relative temperature difference

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Fig. 18

Behavior of Ψ* versus δ for mass flow rate

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