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Research Papers

# Effect of Tube Location Change on Heat Transfer Characteristics of Plain Plate Fin-and-Tube Heat Exchangers

[+] Author and Article Information
Jixiang Yin

College of Electrical and Power Engineering,
Taiyuan University of Technology,
Taiyuan 030024, China
e-mail: yjxiangwise@hotmail.com

Zeming He

College of Electrical and Power Engineering,
Taiyuan University of Technology,
Taiyuan 030024, China
e-mail: hzmtyut@163.com

Fuqiang Chen

College of Electrical and Power Engineering,
Taiyuan University of Technology,
Taiyuan 030024, China
e-mail: chenfuqiang10@126.com

Jianzong Ma

College of Electrical and Power Engineering,
Taiyuan University of Technology,
Taiyuan 030024, China
e-mail: majianzong@126.com

Manuscript received January 29, 2013; final manuscript received July 23, 2013; published online November 15, 2013. Assoc. Editor: Zahid Ayub.

J. Thermal Sci. Eng. Appl 6(2), 021005 (Nov 15, 2013) (9 pages) Paper No: TSEA-13-1045; doi: 10.1115/1.4025229 History: Received January 29, 2013; Revised July 23, 2013

## Abstract

Three-dimensional numerical simulations are conducted for the air-side steady laminar flow and heat transfer characteristics of the plate fin-and-tube heat exchanger element. The effects of Reynolds number (Re), tube center location (Lc/D), and fin pitch (H/D) are examined. The Re based on the tube diameter and the air inlet velocity varies from 100 to 5000, the tube center location from 0.75 to 2, and the fin pitch from 0.2 to 0.5. The numerical results show that the increase of Re leads to the increase of heat transfer parameters (such as the span-averaged $Nu¯(x)$, the overall average Nusselt number ($Nu¯f$, $Nu¯f,t$) of the fin as well as fin-and-tube, the fin surface average heat bulk $q¯$) and the averaged pressure drop on cross-sectional $P¯(x)$, and the decrease of the friction factor (f) and the fin efficiency (ηf); moreover, the larger Re is, the smaller the influence on these parameters except the $P¯(x)$. Regarding the effect of tube location (Lc/D), the f is almost insensitive to the Lc/D change, and the overall average Nusselt numbers of the fin as well as fin-and-tube increase with increasing Lc/D, but the $q¯$ and the ηf first gradually increase and then decrease. And so consequently, there exist the optimum Lc/D values corresponding to the largest averaged $q¯$ on the fin surface and the largest ηf, respectively. The investigation ascertains that the region achieving the highest average $Nu¯(x)$ is not always holding the largest $q¯(x)$ and/or the largest ηf for a conjugate heat transfer problem. The H/D has a positive impact on the ηf, namely the larger the H/D, the higher the ηf.

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## Figures

Fig. 1

A representative schematic diagram for finned-tube heat exchanger

Fig. 2

(a) Schematics of one-row tube and plate fin heat exchanger. (b) Finned-tube element as the computational domain.

Fig. 3

Computational domain sketch

Fig. 4

Schematic configuration for the validation of the model and code with a test case. (a) Schematic configuration of a heat exchanger having three tube-rows. (b) Computational domain with a test case.

Fig. 5

Comparison of average Nu¯f,t and friction factor with experimental data [8]

Fig. 6

The effect of Re on the distribution of velocity and temperature (Lc/D = 1.25, H/D = 0.3). (a) Velocity vector for Re = 3750. (b) and (c) Velocity u contour of middle section in z-direction for Re = 500 and 3750. (d) and (e) Isothermal on fin surface for Re = 500 and 3750.

Fig. 7

Variation of cross-sectional P¯(x) and span averaged Nu¯(x) with x and Re. (a) Cross-sectional P¯(x). (b) Span averaged Nu¯(x).

Fig. 8

Span-averaged heat flux q¯(x) as a function of x and Lc/D for Re = 3750

Fig. 9

Variation of the overall average Nu¯f,t with Lc/D and Re

Fig. 10

Variation of the fin surface average heat flux q¯ with Lc/D and Re

Fig. 11

Fin surface average Nu¯f as a function of Lc/D versus Re

Fig. 12

Fin efficiency as a function of Lc/D versus Re

Fig. 13

The effect of Lc/D and Re on friction factor f

Fig. 14

Variation of fin efficiency with Lc/D and fin pitch

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