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Research Papers

# Effect of Coil Torsion on Heat Transfer and Pressure Drop Characteristics of Shell and Coil Heat Exchanger

[+] Author and Article Information
M. R. Salem

Mechanical Engineering Department,
Faculty of Engineering at Shoubra,
Benha University,
108 Shoubra Street,
Cairo 11629, Egypt
e-mail: me_mohamedreda@yahoo.com

K. M. Elshazly

Mechanical Engineering Department,
Faculty of Engineering at Shoubra,
Benha University,
108 Shoubra Street,
Cairo 11629, Egypt
e-mail: drkaramelshazly@yahoo.com

R. Y. Sakr

Mechanical Engineering Department,
Faculty of Engineering at Shoubra,
Benha University,
108 Shoubra Street,
Cairo 11629, Egypt
e-mail: rsakr85@yahoo.com

R. K. Ali

Mechanical Engineering Department,
Faculty of Engineering at Shoubra,
Benha University,
108 Shoubra Street,
Cairo 11629, Egypt
e-mail: ragabkhalil1971@gmail.com

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received May 4, 2014; final manuscript received February 11, 2015; published online November 11, 2015. Assoc. Editor: P. K. Das.

J. Thermal Sci. Eng. Appl 8(1), 011015 (Nov 11, 2015) (7 pages) Paper No: TSEA-14-1115; doi: 10.1115/1.4030732 History: Received May 04, 2014

## Abstract

The present work introduces an experimental study of horizontal shell and coil heat exchangers. Characteristics of the convective heat transfer in this type of heat exchangers and the friction factor for fully developed flow through their helically coiled tube (HCT) were investigated. The majority of previous studies were performed on HCTs with isothermal and isoflux boundary conditions or shell and coil heat exchangers with small ranges of HCT configurations and fluid-operating conditions. Here, five heat exchangers of counterflow configuration were constructed with different HCT torsions ($λ$) and tested at different mass flow rates and inlet temperatures of both sides of the heat exchangers. In total, 295 test runs were performed from which the HCT-side and shell-side heat transfer coefficients were calculated. Results showed that the average Nusselt numbers of both sides of the heat exchangers and the overall heat transfer coefficient increase by decreasing coil torsion. At lower and higher HCT-side Reynolds number ($Ret$), the average increase in the HCT-side average Nusselt number ($Nu¯t$) is of 108.7% and 58.6%, respectively, when $λ$ decreases from 0.1348 to 0.0442. While, at lower and higher shell-side Reynolds number ($Resh$), the average increase in the shell-side average Nusselt number ($Nu¯sh$) is of 173.9% and 69.5%, respectively, when $λ$ decreases from 0.1348 to 0.0442. In addition, a slight increase of 6.4% is obtained in the HCT Fanning friction factor ($fc$) at lower $Ret$ when $λ$ decreases from 0.1348 to 0.0442, and this effect vanishes with increasing $Ret$. Furthermore, correlations for $Nu¯t$, $Nu¯sh$, and $fc$ are obtained.

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## Figures

Fig. 1

Schematic diagram of the experimental apparatus

Fig. 2

Photograph for the experimental apparatus

Fig. 3

A photograph and schematic layout of the test section (a) photograph of the test section (shell and coil heat exchanger and (b) schematic diagram of the shell and coil heat exchanger

Fig. 4

Validation of the experimental data for HCT (λ=0.0895)

Fig. 5

Variation of HCT average Nusselt number with HCT-side Reynolds number at different coil torsions (Tt,i=55 °C)

Fig. 6

Variation of HCT average Nusselt number with HCT-side Reynolds number at different HCT inlet temperatures (λ = 0.0895)

Fig. 7

Variation of shell-average Nusselt number with shell-side Reynolds number at different HCT torsions (Tsh,i=20 °C)

Fig. 8

Variation of HCT Fanning friction factor with HCT-side Reynolds number at different HCT torsions (Tt,i=55 °C)

Fig. 9

Shell Nusselt number versus shell Reynolds number at different shell inlet temperatures (λ = 0.0895)

Fig. 12

Comparison of experimental values for shell average Nusselt number with that correlated by Eq. (20)

Fig. 13

Comparison of experimental values for coiled tube-Fanning friction factor with that correlated by Eq. (21)

Fig. 11

Comparison of experimental values for HCT average Nusselt number with that correlated by Eq. (19)

Fig. 10

Effect of HCT-side inlet temperature on the HCT Fanning friction factor; (a) λ = 0.0442 and (b) λ = 0.1348

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