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Research Papers

Experimental Investigation of Coil Curvature Effect 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 St.,
Cairo, Egypt
e-mail: me_mohamedreda@yahoo.com

K. M. Elshazly

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

R. Y. Sakr

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

R. K. Ali

Mechanical Engineering Department,
Faculty of Engineering at Shoubra,
Benha University,
108 Shoubra St.,
Cairo, 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 April 5, 2014; final manuscript received September 5, 2014; published online October 28, 2014. Assoc. Editor: Bengt Sunden.

J. Thermal Sci. Eng. Appl 7(1), 011005 (Oct 28, 2014) (9 pages) Paper No: TSEA-14-1067; doi: 10.1115/1.4028612 History: Received April 05, 2014; Revised September 05, 2014

The present work experimentally investigates the characteristics of convective heat transfer in horizontal shell and coil heat exchangers in addition to friction factor for fully developed flow through the helically coiled tube (HCT). 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 counter-flow configuration were constructed with different HCT-curvature ratios (δ) and tested at different mass flow rates and inlet temperatures of the two sides of the heat exchangers. Totally, 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 the two sides of the heat exchangers and the overall heat transfer coefficients increased by increasing coil curvature ratio. The average increase in the average Nusselt number is of 160.3–80.6% for the HCT side and of 224.3–92.6% for the shell side when δ increases from 0.0392 to 0.1194 within the investigated ranges of different parameters. Also, for the same flow rate in both heat exchanger sides, the effect of coil pitch and number of turns with the same coil torsion and tube length is remarkable on shell average Nusselt number while it is insignificant on HCT-average Nusselt number. In addition, a significant increase of 33.2–7.7% is obtained in the HCT-Fanning friction factor (fc) when δ increases from 0.0392 to 0.1194. Correlations for the average Nusselt numbers for both heat exchanger sides and the HCT Fanning friction factor as a function of the investigated parameters are obtained.

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References

Figures

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Fig. 1

Schematic diagram of the experimental apparatus

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Fig. 2

Photo for the experimental apparatus

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Fig. 3

A photo and schematic layout of the test section. (a) Photo of the test section (shell and coil heat exchanger). (b) Schematic layout of the shell and coil heat exchanger.

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Fig. 4

Validation of the experimental data for HCT (δ = 0.0591)

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Fig. 5

HCT average Nusselt number versus HCT Reynolds number at different coil curvature ratios

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Fig. 6

Variation of shell Nusselt number with shell-side Reynolds number at different HCT-curvature ratios

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Fig. 7

Variation of coiled tube Nusselt number with HCT-side Dean number at different HCTs

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Fig. 8

Variation of overall heat transfer coefficient with HCT-side Dean number at different HCTs

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Fig. 9

Average HCT Nusselt number versus Reynolds number at different HCT-inlet temperatures

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Fig. 10

Shell Nusselt number versus shell Reynolds number at different shell inlet temperatures

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Fig. 11

Variation of HCT-Fanning friction factor with HCT-side Reynolds number at different HCT-curvature ratios: (a) Tti = 65 °C, (b) Tti = 55 °C, and (c) Tti = 45 °C

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Fig. 12

Effect of HCT inlet temperature on the HCT Fanning friction factor: (a) δ = 0.1194 and (b) δ = 0.0392

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Fig. 13

Comparison of experimental values for HCT average Nusselt number with that correlated by Eq. (18)

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Fig. 14

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

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Fig. 15

Comparison of experimental values for coiled tube-Fanning friction factor with that correlated by Eq. (20)

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