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Research Papers: Evaporation, Boiling, and Condensation

Enhanced Heat Transfer and Fouling Propensity of Diamond-Like Carbon Coated Smooth and Finned Tubes During External Nucleate Boiling

[+] Author and Article Information
M. Reza Malayeri

School of Chemical and Petroleum Engineering,
Shiraz University,
Shiraz, Iran;
Institute of Process and
Environment Engineering,
Technische Universität Dresden,
Dresden 01069, Germany
e-mails: malayeri@shirazu.ac.ir; reza.malayeri@tu-dresden.de

M. Evangelidou

Institute of Thermodynamics and
Thermal Engineering (ITW),
University of Stuttgart,
Pfaffenwaldring 6,
Stuttgart D-70550, Germany

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received October 21, 2015; final manuscript received March 23, 2016; published online April 26, 2016. Assoc. Editor: Amitabh Narain.

J. Heat Transfer 138(8), 081502 (Apr 26, 2016) (7 pages) Paper No: HT-15-1663; doi: 10.1115/1.4033210 History: Received October 21, 2015; Revised March 23, 2016

Smooth DLC (diamond-like carbon) coated surfaces can profoundly mitigate scaling during pool boiling of calcium sulphate solutions. Previous investigations though carried out mostly for the smooth surfaces rather than structured, i.e., finned tubes. This study compares experimental results of DLC coated smooth and finned tubes at clean and fouling conditions. Fouling runs were conducted during pool boiling of saturated CaSO4 solution of 1.6 g/L at 300 kW/m2. The substrate of the attempted tubes was stainless steel and finned tubes of 19 and 40 fins per inch were used. The DLC coated smooth tube showed an enhanced clean heat transfer up to 50% and reduced fouling resistance compared to the uncoated smooth tube. After a short operating time, though, the coated smooth tube reached an asymptotic fouling resistance of 0.00005 m2 K/W whereas for the uncoated smooth tube, it was 4.8 times higher. DLC coating of the finned tubes with the physical vapor deposition (PVD) technique implicated difficulties. The base surface of the finned tubes was defectively coated. The defectiveness of the coating was attributed to the limitation of the PVD for coating of structured surfaces.

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References

Figures

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Fig. 1

Sketch of the boiling rig

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Fig. 2

Construction of investigated tubes

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Fig. 6

Bubble behavior on smooth tube during boiling of (a) distilled water and (b) 1.0 g/L CaSO4 solution at 100 kW/m2 at clean condition

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Fig. 7

A DLC 19 fpi coated tube before and after cleaning with water and a soft brush

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Fig. 10

Fouling behavior of uncoated and coated smooth tubes with time during boiling of 1.6 g/L CaSO4 at 300 kW/m2

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Fig. 11

Fouling layer on DLC coated smooth tube after 3928 min boiling of 1.6 g/L CaSO4 solution at 300 kW/m2

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Fig. 8

Heat transfer coefficient of uncoated and DLC coated 19 fpi tube during boiling of 1.6 g/L CaSO4 under clean conditions

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Fig. 9

Heat transfer coefficient of uncoated and DLC coated 40 fpi tube during boiling of 1.6 g/L CaSO4 under clean conditions

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Fig. 12

Fouling behavior of uncoated and DLC coated 19 fpi tube with time during boiling of 1.6 g/L CaSO4 at 300 kW/m2

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Fig. 3

Heat transfer coefficient of uncoated and DLC coated smooth tube during boiling of distilled water at different heat fluxes

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Fig. 4

Heat transfer coefficient of uncoated and DLC coated smooth tube during boiling of 1.6 g/L CaSO4 at different heat fluxes

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Fig. 5

Comparison of bubble behavior on DLC coated and uncoated stainless steel tubes during boiling of distilled water at different heat fluxes

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