ENHANCEMENT OF CONVECTIVE HEAT TRANSFER IN INTERNAL FLOWS USING AN ELECTRICALLY-INDUCED CORONA JET

ENHANCEMENT OF CONVECTIVE HEAT TRANSFER IN INTERNAL FLOWS USING AN ELECTRICALLY-INDUCED CORONA JET Reza Baghaei Lakeh Ph.D. Candidate

PRESENTATION OUTLINE Corona Discharge Corona Wind and Ion-Drag Flows Applications Bif Brief Literature t Review Ion-Drag flow in Circular Tubes Formulation of the Problem Preliminary Results Proposed Research Conclusion

CORONA DISCHARGE Ionization of a neutral gas surrounding a conductor Strong electric field near a sharp electrode Ionization of neutral molecules

CORONA DISCHARGE Ion generation mechanisms: α process (electron impact ionization) γ process (electron emission from cathode) Field Emission (Electron Quantum Tunneling ) Electrons in a metal see a surface potential barrier due to the material s work function. Gomer, Field Emission and Field Ionization, 1961 For strong enough electric fields, the electrons can tunnel through the barrier and materialize in the gap space.

CORONA WIND AND ION-DRAG FLOWS Engineering point of view neglect Sheath Layer! Injection of the ions (O + 2+ and N + 2 ) Dragging the neutral molecules and imposing a bulk flow referred as Corona Wind or Ion-Drag flow

CORONA WIND AND ION-DRAG FLOWS Castellanos, Electrohydrodynamics, 1998

APPLICATIONS Ion-Drag pumps Garimella, 2009 Adamiak, 2004 Electrostatic Precipitators Heat Transfer Enhancement EHD Thrusters Drag Reduction Cooling Lerner, 2000 Go, 2010

BRIEF LITERATURE REVIEW Experimental Circular Tube Pioneers: Velkoff (1963) and Moss (1966) Influence of Electric Field on the flow field and heat transfer Suggested Flow Field based on Heat Transfer Augmentation: S.M. Macro, H.R. Velkoff, Effect of Electrostatic, ASME Paper No. 63-HT-9, 1963 R.A. Moss, J. Grey, Proceeding of Heat Transfer and Fluid Mechanics Institute, Santa Clara, CA, 1966

BRIEF LITERATURE REVIEW Ohadi and Nelson (1987) Experimental Circular tube Noticeable heat transfer enhancement Noticeable pressure drop M.M. Ohadi, D.A. Nelson, S. Zia, International Journal of Heat and Mass Transfer, 1987

BRIEF LITERATURE REVIEW Experimental, Numerical Seyed-Yagoobi and Owsenek EHD flow by electric conduction Dielectric liquid refrigerants (Dissociation & Recombination) Heat Transfer enhancement in channels and ducts B.L. Owsenek, J. Seyed-Yagoobi,, Journal of Heat Transfer, 1997

BRIEF LITERATURE REVIEW Garimella (Cooling Technology Research Center) Experimental, Numerical Ion- Drag flows in micro-scale Low voltage ionization (Quantum Tunneling) Enhancement of heat transfer in internal and external flows D.B. Go, S.V. Garimella, T.S. Fisher, IEEE 10th Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronics Systems, 2005

BRIEF LITERATURE REVIEW Experimental, Numerical Lai et al EHD gas pumps using needle-to-ring electrodes Noticeable delivery of airflow Developed the EHD Drying mechanisms Oscillatory flows F.C. Lai, J. Mathew, Journal of Heat Transfer, 2007

BRIEF LITERATURE REVIEW Experimental, Numerical Molki et al. Electrically-induced Secondary flow fields Effect of corona discharge on natural convection Heat Transfer enhancement in channels with rectangular, triangular and circular cross sections M. Molki, K.L. Bhamidipati, International Journal of Heat and Mass Transfer, 2004

BRIEF LITERATURE REVIEW Experimental Localized Hot Spot Cooling Wire-to-Rod Go and Balagopal (2011) Counter-flow ionic wind and impingement-like effect Cooling as much as 5K Go and Balagopal, ESA Annual Meeting on Electrostatics, 2011

ION-DRAG FLOW IN CIRCULAR TUBES Wire tube Radial body force Navier Stokes u t u. u P ρ ν 2 u ρ c E ρ General view: Wangnipparnto et al., Journal of Energy Conversion and Management, 2003

FORMULATION OF THE PROBLEM Maxwell Equations in Electrohydrodynamics reduce to Gauss s Law Maxwell Faraday equation Continuity Magnetic field equations (rarely needed in Electrohydrodynamics)

FORMULATION OF THE PROBLEM Electric Potential Gauss s Law Conservation of electric charge Electric current density Ion mobility is the dominant term of current density Charge Convection Electric Conduction Charge Diffusion

FORMULATION OF THE PROBLEM Boundary Conditions i Electric Potential (Elliptic PDE) V = Vo @ emitting electrode (Wire) V = 0 @ collecting electrode (Tube) Charge Density (Hyperbolic PDE) ρ = ρc,o @ emitting electrode ρc,o is found by measuring the time-average corona current experimentally. M. Molki, K.L. Bhamidipati, International Journal of Heat and Mass Transfer, 2004

ELECTRIC FIELD RESULTS Method of characteristics + + + Fluctuations in FVM Solution Method of Characteristic Finite Volume Method Baghaei Lakeh, R., Molki, M., ASME International Mechanical Engineering Congress & Exposition, 2009

FLOW FIELD RESULTS Concentric configuration Hydrostatic condition Eccentric configuration Secondary Flow Field Recirculation Zones Corona Jet Baghaei Lakeh, R., Molki, M., Journal of Fluids Engineering, 2010

HEAT TRANSFER ENHANCEMENT The corona-induced jet flow can significantly enhance the local heat transfer. Hot Components Molki, M., Baghaei Lakeh, R., 63rd Annual Meeting of the American Physical Society, Division of Fluid Dynamics, 2010 Temperature distribution

PROPOSED RESEARCH Ion-Drag flows in channels Heat Transfer Enhancement Generating pumping effect Disturbing the Boundary Layer Parallel Electric Force Secondary Flows Fields Direction of electric body-force in parallel configuration Corona Jet

PROPOSED RESEARCH Corona Jet Circular Tube (eccentric wire electrode) Rectangular Channel with Rectangular Channel with longitudinal flat electrodes

PROPOSED RESEARCH Methodology Electric Field Analytical (Method of Characteristics) Computational (Finite Volume Method) Programming the code in C++ Experimental (Measurement of time-averaged corona current) Interpolating electric body-force between Electric Field and Flow Field grid points Flow User-Defined-Function (UDF) Field Commercial CFD Software, ANSYS FLUENT 13 Heat Transfer Temperature field Heat Transfer Enhancement

PROPOSED RESEARCH Extensive Grid Refinement Study according to Fluids Engineering g Division of ASME. * Verification And Validation Comparison with Comparison with available Experimental simplified Analytical l literature. solutions * Celik, I.B., Journal of Fluids Engineering, 2010 * Roache, P.J., Proceedings of Quantification of Uncertainty in Computational Fluid Dynamics, 1997

PROPOSED RESEARCH Expected Results Distributions of Electric field and Charge density : Circular channels with centered wire electrode Rectangular channels with parallel longitudinal electrode arrays. Secondary flow field on the cross section of the channels or along the channel axis The effect of electric body-force on the buoyancy y y y driven flows

PROPOSED RESEARCH Expected Results Distribution of temperature fields in various configurations in rectangular and circular channels. The enhancement level of convective heat transfer using electrically-driven secondary flow fields in fully developed and developing regions of channels. Developing the targeted-cooling method by corona jets in circular and rectangular geometries.

CONCLUSION Corona Discharge may lead to formation of Ion-Drag flows or corona wind. The electrically-induced secondary flow fields can be used for many applications including Heat Transfer Enhancement. The ion-drag flows in some configurations lead to formation of a corona jet which may be used in different applications. The proposed research studies the enhancement of heat transfer in internal flows and develops the idea of targeted spot cooling using a corona jet.

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