Heat transfer enhancement by needle-arrayed electrodes ― An EHD integrated cooling system

Abstract Natural convection heat transfer enhanced by electrohydrodynamics (EHD) is experimentally investigated in this work. Four kinds of needle-arrayed electrodes combined with a plate fin heat sink are made and tested under a controlled environment. Previous and present test results show that convection heat transfer is enhanced with the presence of EHD due to corona wind generation by the electron avalanche mechanism. To identify the effect of EHD, the enhancement ratio ( ξ ), defined as the heat transfer coefficient with EHD ( h ec ) relative to that without EHD ( h nc ), is proposed to examine the performance. It is found that the negative corona has a lower threshold voltage and a better performance compared with the positive one. The enhancement ratio increases with electric power input and linearly with the 1/4 power of total corona current. Heat transfer enhancement is evident when a corona discharge above 1 μA is established. For moderate test condition, the enhancement ratio is around 3–5 with a preferable normalized electrode height of around 0.25–0.35 compared to the edge of the heat sink. For a given electrode height, there is an optimal electrode density below which the required area exposed to the corona wind is apparently insufficient, and beyond which the flow interference caused by adjacent electrodes offsets the effective performance. In particular, the enhancement ratio decreases with increasing the heat dissipation as a result of augmented buoyancy convection.

[1]  M. Franke.  Effect of Vortices Induced by Corona Discharge on Free-Convection Heat Transfer From a Vertical Plate , 1969 .

[2]  Jamal Seyed-Yagoobi,et al.  Experimental Investigation of Corona Wind Heat Transfer Enhancement With a Heated Horizontal Flat Plate , 1995 .

[3]  Chi-Chuan Wang,et al.  Orientation effect on natural convective performance of square pin fin heat sinks , 2008 .

[4]  Myron Robinson,et al.  Movement of air in the electric wind of the corona discharge , 1961, Transactions of the American Institute of Electrical Engineers, Part I: Communication and Electronics.

[5]  Avram Bar-Cohen,et al.  Design and analysis of heat sinks , 1995 .

[6]  S. J. Kline,et al.  Describing Uncertainties in Single-Sample Experiments , 1953 .

[7]  H. Bondar,et al.  Effect of neutral fluid velocity on direct conversion from electrical to fluid kinetic energy in an electro-fluid-dynamics (EFD) device , 1986 .

[8]  M. Al-Arabi,et al.  Natural convection heat transfer from isothermal horizontal plates of different shapes , 1976 .

[9]  B. Owsenek,et al.  Theoretical and Experimental Study of Electrohydrodynamic Heat Transfer Enhancement Through Wire-Plate Corona Discharge , 1997 .

[10]  K. G. Kibler,et al.  Electrocooling in gases , 1974 .

[11]  Andrew J. Shine,et al.  Some Effects of an Electric Field on Heat Transfer From a Vertical Plate in Free Convection , 1967 .

[12]  A. S. Mitchell,et al.  Heat transfer by the corona wind impinging on a flat surface , 1978 .

[13]  Myron Robinson,et al.  A History of the Electric Wind , 1962 .

[14]  O. Stuetzer,et al.  Ion Drag Pressure Generation , 1959 .