Heat and Mass Transfer

, Volume 50, Issue 2, pp 275–284 | Cite as

Natural convection heat transfer on surfaces of copper micro-wires

  • Ning Guan
  • Zhigang Liu
  • Chengwu Zhang
  • Guilin Jiang


The natural convection heat transfer characteristics and mechanism for copper micro-wires in water and air were investigated experimentally and numerically. The wires with diameters of 39.9, 65.8 and 119.1 μm were placed horizontally in water inside of a sealed tube and in air of a large room, respectively. Using Joule heating, the heat transfer coefficients and Nusselt numbers of natural convection for micro-wires in ultra pure water and air were obtained. A three dimensional incompressible numerical model was used to investigate the natural convection, and the prediction with this model was in reasonable accordance with the experimental results. With the decrease of micro-wire diameter, the heat transfer coefficient of natural convection on the surface of micro-wire becomes larger, while the Nu number of natural convection decreases in water and air. Besides, the change rate of Nu number in water decreases apparently with the increase of heat flux and the decrease of wire diameter, which is larger than that in air. The thickness of boundary layer on the wall of micro-wire becomes thinner with the decrease of diameter in both water and air, but the ratio of boundary layer thickness in water to the diameter increases. However, there is almost no change of this ratio for natural convection in air. As a result, the proportion of conduction in total heat transfer of natural convection in water increases, while the convective heat transfer decreases. The velocity distribution, temperature field and the boundary layer in the natural convection were compared with those of tube with conventional dimension. It was found that the boundary layer around the micro-wire is an oval-shaped film on the surface, which was different from that around the conventional tube. This apparently reduces the convection strength in the natural convection, thus the heat transfer presents a conduction characteristic.


Heat Transfer Boundary Layer Heat Flux Heat Transfer Coefficient Natural Convection 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols


Outer diameter of micro-wire (m)


Surface area of micro-wire (m2)


Grashof number


Heat transfer coefficient (W/m2 K)


Current (A)


Thermal conductivity (W/m K)


Length of micro-wire (m)


Nusselt number


Quantity of the heat transfer of natural convection, W


Quantity of radiant heat transfer (W)


Rayleigh number


Resistance of micro-wire (Ω)


Temperature difference between micro-wire and room or deionized water (K)


Average temperature of micro-wire (K)


Voltage (V)


Velocity of x-direction (m/s)


Velocity of y-direction (m/s)


Velocity of y-direction (m/s)


x-direction coordinate


y-direction coordinate


z-direction coordinate

Greek symbols


Measuring uncertainty


Density (kg/m3)



Cool side


Effective value





The authors acknowledge the financial support of the National Science Foundation of China (Grant 51176105), Science Foundation of Shandong Province (ZR2011EEQ015).


  1. 1.
    Guo ZY (2000) Frontier of heat transfer-microscale heat transfer. Adv Mech 30(1):1–6Google Scholar
  2. 2.
    Siddique M, Alhazmy M (2008) Experimental study of turbulent single-phase flow and heat transfer inside a micro-finned tube. Int J Refrig 31:234–241CrossRefGoogle Scholar
  3. 3.
    El-Genk MS, Yang IH (2009) Numerical analysis of laminar flow in micro-tubes with a slip boundary. Energy Convers Manage 50:1481–1490CrossRefGoogle Scholar
  4. 4.
    Malsch D, Kielpinski M, Merthan R, Albert J, Mayer G, Köhler JM, Süße H, Stahl M, Henkel T (2008) μPIV-analysis of Taylor flow in micro channels. Chem Eng J 135:S166–S172CrossRefGoogle Scholar
  5. 5.
    Lee J, Mudawar I (2009) Critical heat flux for subcooled flow boiling in micro-channel heat sinks. Int J Heat Mass Transf 52:3341–3352CrossRefGoogle Scholar
  6. 6.
    Pascual CC, Stromberger JH, Jeter SM, Abdel-Khalik SI (2000) An expirical correlation for electrohydropdynamic enhancement of natural convection. Int J Heat Mass Transf 43(11):1965–1974CrossRefGoogle Scholar
  7. 7.
    Hata K, Takeuchi Y, Shiotsu M, Sakurai A (1999) Natural convection heat transfer from a horizontal cylinder in liquid sodium. Nuclear Eng Design 194:185–196CrossRefGoogle Scholar
  8. 8.
    Olivier R, Darina BM, Tadhg SO’D (2008) Natural convection heat transfer from two horizontal cylinders. Exp Therm Fluid Sci 32(8):1702–1709CrossRefGoogle Scholar
  9. 9.
    Cheng CY (2009) Natural convection boundary layer on a horizontal elliptical cylinder with constant heat flux and internal heat generation. Int Commun Heat Mass Transf 36(10):1025–1029CrossRefGoogle Scholar
  10. 10.
    Harsini I, Ashjaee M (2010) Effect of adiabatic wall on the natural convection heat transfer from a wavy surface created by attached horizontal cylinders. Exp Therm Fluid Sci 33(7):666–676CrossRefGoogle Scholar
  11. 11.
    Ali RT, Mahmood Y (2010) Experimental and numerical study of frost formation by natural convection over a cold circular cylinder. Int J Refrig 33(7):1444–1458CrossRefGoogle Scholar
  12. 12.
    Mamun MM, Anwar HM, Manosh CP (2006) Natural convection flow from an isothermal horizontal circular cylinder in presence of heat generation. Int J Eng Sic 44(13–14):949–958MATHGoogle Scholar
  13. 13.
    Tzeng PY, Soong CY, Liu MH, Yen TH (2008) Atomistic simulation of rarefield gas natural convection in a finite enclosure using a novel wall-fluid molecular collision rule for adiabatic solid walls. Int J Heat Mass Transf 51(3–4):445–456CrossRefMATHGoogle Scholar
  14. 14.
    Hu XJ, Jain A, Goodson KE (2008) Investigation of the natural convection boundary condition in microfabricated structures. Int J Therm Sci 47(7):820–824CrossRefGoogle Scholar
  15. 15.
    Mahmoud S, Al-Dadah R, Aspinwall DK, Soo SL, Hemida H (2011) Effect of micro fin geometry on natural convection heat transfer of horizontal microstructures. Appl Therm Eng 31(5):627–633CrossRefGoogle Scholar
  16. 16.
    Buonomo Bernardo, Manca Oronzio (2012) Transient natural convection in a vertical microchannel heated at uniform heat flux. Int J Heat Mass Transf 56(1):35–47Google Scholar
  17. 17.
    Yang DW, Huang SB, Lin RY (2006) An experimental on micro natural convection heat transfer characters. J Eng Thermophys 27(2):301–303Google Scholar
  18. 18.
    Hou YL, Wang XC, zhang CW, Liu ZG (2007) Experimental study on heat transfer of natural convective flow between micro-wire and air. J Eng Thermophys 28(3):460–462Google Scholar
  19. 19.
    Guan N, Liu ZG, Liang SQ, Zhang CW (2009) Investigation on heat transfer of natural convective flow between micro-wire and air. J Beijing Univ Technol 35(7):977–981Google Scholar
  20. 20.
    Tao WQ (2001) Numerical heat transfer [M]. Xian Jiaotong University Press, Xian, p 242Google Scholar
  21. 21.
    Yang SM (1997) Heat transfer [M]. High Education Press, Beijing, p 217Google Scholar
  22. 22.
    Wu JM, Tao WQ (2004) Numerical computation of laminar natural convection heat transfer around a horizontal compound tube with external longitudinal fins. J Eng Thermophysics 25:92–94Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Ning Guan
    • 1
  • Zhigang Liu
    • 1
  • Chengwu Zhang
    • 1
  • Guilin Jiang
    • 1
  1. 1.Energy Research Institute of Shandong Academy of SciencesJinanChina

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