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Reducing Pressure Drop in Microscale Channel Using Constructal Theory

Authors: K. X. Cheng, A. L. Goh, K. T. Ooi


The effectiveness of microchannels in enhancing heat transfer has been demonstrated in the semiconductor industry. In order to tap the microscale heat transfer effects into macro geometries, overcoming the cost and technological constraints, microscale passages were created in macro geometries machined using conventional fabrication methods. A cylindrical insert was placed within a pipe, and geometrical profiles were created on the outer surface of the insert to enhance heat transfer under steady-state single-phase liquid flow conditions. However, while heat transfer coefficient values of above 10 kW/m2·K were achieved, the heat transfer enhancement was accompanied by undesirable pressure drop increment. Therefore, this study aims to address the high pressure drop issue using Constructal theory, a universal design law for both animate and inanimate systems. Two designs based on Constructal theory were developed to study the effectiveness of Constructal features in reducing the pressure drop increment as compared to parallel channels, which are commonly found in microchannel fabrication. The hydrodynamic and heat transfer performance for the Tree insert and Constructal fin (Cfin) insert were studied using experimental methods, and the underlying mechanisms were substantiated by numerical results. In technical terms, the objective is to achieve at least comparable increment in both heat transfer coefficient and pressure drop, if not higher increment in the former parameter. Results show that the Tree insert improved the heat transfer performance by more than 16 percent at low flow rates, as compared to the Tree-parallel insert. However, the heat transfer enhancement reduced to less than 5 percent at high Reynolds numbers. On the other hand, the pressure drop increment stayed almost constant at 20 percent. This suggests that the Tree insert has better heat transfer performance in the low Reynolds number region. More importantly, the Cfin insert displayed improved heat transfer performance along with favourable hydrodynamic performance, as compared to Cfinparallel insert, at all flow rates in this study. At 2 L/min, the enhancement of heat transfer was more than 30 percent, with 20 percent pressure drop increment, as compared to Cfin-parallel insert. Furthermore, comparable increment in both heat transfer coefficient and pressure drop was observed at 8 L/min. In other words, the Cfin insert successfully achieved the objective of this study. Analysis of the results suggests that bifurcation of flows is effective in reducing the increment in pressure drop relative to heat transfer enhancement. Optimising the geometries of the Constructal fins is therefore the potential future study in achieving a bigger stride in energy efficiency at much lower costs.

Keywords: Constructal theory, enhanced heat transfer, microchannel, pressure drop.

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Tuckerman, D.B. and R. Pease, High-performance heat sinking for VLSI. Electron Device Letters, IEEE, 1981. 2(5): p. 126-129.
[2] Garimella, S.V. and C. Sobhan, Transport in microchannels-a critical review. Annual review of heat transfer, 2003. 13(13).
[3] Phillips, R.J., Forced-convection, liquid-cooled, microchannel heat sinks. 1988, DTIC Document.
[4] Kong, K.S. and K.T. Ooi, A numerical and experimental investigation on microscale heat transfer effect in the combined entry region in macro geometries. International Journal of Thermal Sciences, 2013. 68: p. 8-19.
[5] Mohammed, H., P. Gunnasegaran, and N. Shuaib, Numerical simulation of heat transfer enhancement in wavy microchannel heat sink. International Communications in Heat and Mass Transfer, 2011. 38(1): p. 63-68.
[6] Sui, Y., et al., Fluid flow and heat transfer in wavy microchannels. International Journal of Heat and Mass Transfer, 2010. 53(13): p. 2760-2772.
[7] Steinke, M.E. and S.G. Kandlikar. Single-phase liquid heat transfer in plain and enhanced microchannels. in ASME 4th International Conference on Nanochannels, Microchannels, and Minichannels. 2006. American Society of Mechanical Engineers.
[8] Goh, A.L., K.T. Ooi, and S. Ulrich, Nature-inspired enhanced microscale heat transfer in macro geometry in 2014 IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems 2014, IEEE: Orlando, FL p. 397-403.
[9] Bejan, A., Constructal-theory network of conducting paths for cooling a heat generating volume. International Journal of Heat and Mass Transfer, 1997. 40(4): p. 799-816.
[10] Wechsatol, W., S. Lorente, and A. Bejan, Tree-shaped insulated designs for the uniform distribution of hot water over an area. International Journal of Heat and Mass Transfer, 2001. 44(16): p. 3111-3123.
[11] Bejan, A. and S. Lorente, Design with constructal theory. 2008.
[12] Zhang, H., S. Lorente, and A. Bejan, Vascularization with trees that alternate with upside-down trees. Journal of Applied Physics, 2007. 101(9): p. 094904.
[13] Gosselin, L. and A. Bejan, Tree networks for minimal pumping power. International Journal of Thermal Sciences, 2005. 44(1): p. 53-63.
[14] Chen, Y., et al., Thermal and hydrodynamic characteristics of constructal tree-shaped minichannel heat sink. AIChE Journal, 2009: p. NA-NA.
[15] ANSYS, ANSYS CFX-Solver Theory Guide 2010, ANSYS Inc.
[16] Lee, Y.J., P.S. Lee, and S.K. Chou, Numerical Study of Fluid Flow and Heat Transfer in the Enhanced Microchannel With Oblique Fins. Journal of Heat Transfer, 2013. 135(4): p. 041901.
[17] Alharbi, A.Y., D.V. Pence, and R.N. Cullion, Fluid Flow Through Microscale Fractal-Like Branching Channel Networks. Journal of Fluids Engineering, 2003. 125(6): p. 1051