Effect of thin porous copper coating on the performance of wickless heat pipe with R134a as working fluid

Abstract

The heat transfer characteristics of a thin porous copper-coated wickless heat pipe using R134a as a working fluid is investigated and is compared for its performance with uncoated wickless heat pipe using the same working fluid. An electroplating process was utilised to form a porous structure of copper over the inner surface of the wickless heat pipe. The experiments were carried out in the heat input range between 50 and 250 W. The thermal resistance of heat pipe at three different inclination angles such as 0°, 45° and 90° with horizontal are investigated. The results showed that 45° inclination has the lowest resistance with significant improvement in heat transfer characteristics. The coated wickless heat pipe exhibited a low thermal resistance when compared to uncoated wickless heat pipe. The condenser and evaporator heat transfer coefficients of a coated wickless heat pipe were found to be higher by about 11% and 25%, respectively, when compared to uncoated heat pipe for a heat flux of 10 kW m−2 and inclination of 45°. The magnitudes of dimensionless numbers (such as, Bo, We, Ku and Co) on coated and uncoated wickless heat pipes are also found.

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Abbreviations

A :

Area (m2)

Bo :

Bond number

Co :

Condensation number

D :

Diameter (m)

g :

Acceleration due to gravity (m s−2)

h :

Heat transfer coefficient (W m−2 K−1)

h fg :

Heat of vaporization (J kg−1 K−1)

k :

Thermal conductivity (W m−1 K−1)

Ku :

Kutateladze number

L :

Length (m)

Q :

Heat input (W)

q :

Heat flux (W m−2)

R t :

Total thermal resistance (°C W−1)

r :

Radius (m)

T :

Temperature (°C)

We :

Webber number

c:

Condenser

e:

Evaporator

v:

Vapour

l:

Liquid

Δx :

Change in any parameter “x

µ :

Viscosity (N s m−2)

ρ :

Density (kg m−3)

σ :

Surface tension (N m−1)

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Acknowledgements

Authors would like to acknowledge the technical support of Mr. Jeyaseelan, Centre for Research in Material Science and Thermal Management, Karunya Institute of Technology and Sciences, Coimbatore, India, during the fabrication of hardwares.

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Correspondence to C. Senthilkumar.

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Senthilkumar, C., Krishnan, A.S. & Solomon, A.B. Effect of thin porous copper coating on the performance of wickless heat pipe with R134a as working fluid. J Therm Anal Calorim 139, 963–973 (2020). https://doi.org/10.1007/s10973-019-08176-x

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Keywords

  • R134a
  • Electroplating
  • Copper coating
  • Heat transfer performance
  • WHP