1. On Correlating Experimental Pressure Flow And Heat Transfer Measurements From Silicon Microchannels With Theoretical Calculations Cormac EasonNiall O’KeeffeRyan EnrightTara Dalton Stokes Research Institute, University of Limerick, Co. Limerick, Ireland cormac.eason@ul.ie

2. Causes Of Inconsistencies Electric double layer Loss of the continuum assumption validity due to small length scales Fluid property changes along the channel Inherent difficulties in taking measurements from flows at microscale High uncertainties in results derived from experimental measurements

3. Micro Scale Friction Factors Steinke and Kandlikar (2006) compiled 220 sets of data for single phase flow in microchannels between 1 and 1200 µm in diameter and reported experimental data varying over approximately an order of magnitude around theoretical laminar flow values Garimella (2006) also plotted pressure flow data from microchannels from several researchers, showing the same trend of inconsistency in friction factors from paper to paper

4. Micro Scale Nusselt Numbers Garimella (2006) plots a drastic variation in Reynolds number Nusselt number correlations measured from microchannels over the past 15 years Bavière et al (2006) measured heat transfer from a parallel plate channel, accounting for variation in the channel surface temperature along the channel allowed the measured data to correlate with conventional heat transfer laws in laminar and turbulent regimes Numerical simulation of heat transfer has produced good correlation with experimental data in work by Lee and Garimella (2006), and Tiselj et al (2004), indicating that while standard correlations may not work, numerical simulation can correlate well with experimental data for specific test systems

5. Flow Loop Layout

6. Detail of Manifold Arrangement Thermocouple Locations in Each Manifold 

7. Experimental Ranges and Uncertainties Percent Uncertainty DRIEKOH 233.7 0.430.15 6.33.3 10.75 0.980.9 0.160.15 3.82.9 0.610.35

8. Channel Area Measurement

9. Channel Dimensions D h (µm) A (µm) DRIE305.28 KOH317.35360.66

10. Theoretical Pressure Drop Area Compensation Eason (2005) (Darcy’s Equation)

11. Friction Factors for Rectangular Channels Rohsenhow (1985)

12. Trapezoidal Channel Correlation Rohsenhow (1985)

13. Rectangular Channel Nu Correlations These correlations are also used to predict the heat transfer from the inlet and exit manifolds allowing this effect to be subtracted from the experimental data Schmidt (1985)

14. Muzychka and Yovanovich Correlation (2004)

15. Muzychka and Yovanovich Correlation

16. Manifold Entrance and Exit Losses Manifold friction losses are calculated using Darcy’s Equation as described earlier A M is the manifold flow area divided by the number of channels (22 for this work) Rohsenhow (1985)

17. Results

21. Correlations?

22. Results

24. Conclusions The fRe values from the system are less than predicted by both developing and fully developed theory. Though the DRIE channel data does not show an experimentally significant deviation from theory, this deviation is still unexpected as previous pressure flow work on similar channels correlated extremely well with theory The limited depth of field of the optical microscope used in measuring the channels may have caused unforseen errors in measuring the channels compared to previous SEM measurements Accounting for the effect of manifold heating on the heat transfer from the channel is essential to the correct interpretation of the data from the system The Nusselt number measured for this work shows a strong linear dependence on the Reynolds number Numerical simulation of the test system will be performed in order to conclude as to the validity of the Nusselt number data

25. Questions?

26. References Bavière, Roland, Michel Favre-Marinet, Stéphane Le Person, 2006, “Bias effects on heat transfer measurements in microchannel flows”, International Journal of Heat and Mass Transfer, 2006, Article in Press. Bejan, A., 2000, Shape and Structure, From Engineering to Nature, Cambridge University Press, Cambridge, UK. Çengel, Yunus A., 1998, Heat Transfer A Practical Approach, International Edition, WCB McGraw-Hill. Choi, S.B.; R.F. Barron, R.O. Warrington, 1991, “Fluid flow and heat transfer in microtubes”, Micromech. Sensors Actuat. Syst. ASME DSC 32 (1991) 123–134. Eason, C., T. Dalton, C. O'Mathúna, O. Slattery, M. Davies, 2005. “Direct Comparison Between Five Different Microchannels, Part 1: Channel Manufacture and Measurement”, Heat Transfer Engineering, 26(3):79-88, Taylor and Francis Inc. Eason, C., T. Dalton, C. O'Mathúna, O. Slattery, M. Davies, 2005. “Direct Comparison Between Five Different Microchannels, Part 2: Experimental Description and Flow Friction Measurement”, Heat Transfer Engineering, 26(3):89-98, Taylor and Francis Inc. Eason, Cormac, 2005, “Measurement of Pressure Drop and Heat Transfer Analysis of Microchannels”, PhD Thesis, University of Limerick, Ireland. Garimella, Suresh V., 2006, “Advances in mesoscale thermal management technologies for microelectronics”, Microelectronics Journal 37 (2006) 1165-1185 Judy, J.; D. Maynes, B. W. Webb, 2002. “Characterization of frictional pressure drop for liquid flows through microchannels”, International Journal of heat and mass transfer 45 (2002) 3477-3489. Lee, P.S., S.V. Garimella, 2006, Thermally developing flow and heat transfer in rectangular microchannels of different aspect ratios”, International Journal of Heat Transfer, article in press. Li, Zhou; Ya-Ling He, Gui-Hua Tang, Wen-Quan Tao, 2007, “Experimental and numerical studies of liquid flow and heat transfer in microtubes”, International Journal of Heat and Mass Transfer (2007), Article in Press. Muwanga R., I. Hassan, 2006, “Local Heat Transfer Measurements in Microchannels Using Liquid Crystal Thermography: Methodology Development and Validation”, Journal of Heat Transfer, July 2006, Vol. 128, pp. 617-626. Muzychka, Y. S. and M. M. Yovanovich, 2004. “Laminar Forced Convection Heat Transfer in the Combined Entry Region of Non- Circular Ducts”, Journal of Heat Transfer, Transactions of the ASME, February 2004, Vol. 126, pp. 54-61. Rohsenow, W.M., J.P. Hartnett, E.N. Ganić, (ed.), 1985, Handbook of Heat Transfer Fundamentals, 2nd Edition, McGraw-Hill Book Company. Schmidt, F. W., presented in Shah, R. K. and A. L. London, 1978, “Laminar Flow Forced Convection in Ducts”, Academic, New York, 1978. Shen, S., J.L. Xu, J.J. Zhou, Y. Chen, 2005, “Flow and heat transfer in microchannels with rough wall surface”, Energy Conversion and Management 47 (2006) 1311-1325. Steinke, Mark E., Satish G. Kandlikar, 2006, “Single-phase liquid friction factors in microchannels”, International Journal of Thermal Sciences, article in press. Tiselj, I; G. Hetsroni, B. Mavko, A. Mosyak, E. Pogrebnyak, Z. Segal, 2004, “Effect of axial conduction on the heat transfer in micro-channels”, International Journal of Heat and Mass Transfer 47 (2004) 2551-2565.