Study of Convective Heat Transfer through Micro Channels with Different Configurations

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1 International Journal of Current Engineering and Tecnology E-ISSN , P-ISSN INPRESSCO, All Rigts Reserved Available at ttp://inpressco.com/category/ijcet Researc Article Study of Convective Heat Transfer troug Micro Cannels wit Different Configurations D. S. Godake * and Rakes Siddeswar Mecanical Engineering Department, JSPM s JSCOE, Hadapsar, Savitribai Pule Pune University, Pune, Maarastra, India Accepted 02 Marc 2016, Available online 15 Marc 2016, Special Issue-4 (Marc 2016) Abstract Te micro cannel eat sinks play a very important role in te functioning of te micro-electronic components. In tis paper te focus is on te convective eat transfer performance of te micro cannels wit different geometric configurations. Te eat transfer performance is a function of surface area available for te eat transfer and te eat transfer coefficient of te eat carrying medium. An experimental eat transfer analysis is carried out wit different configurations of micro cannels. Micro cannels wit four different configurations are fabricated using Poto Cemical Macining Process. Te performance analysis is done in te range of 15 to 50, wit different inlet flow velocities and te experimental analysis empasis te fact tat te geometrical configuration of te cannel as a considerable effect on te micro cannel eat transfer performance and in turn on te performance of te micro-electronic components. Keywords: Convective Heat transfer, Convective Heat Transfer Coefficient, Micro- cannel, Nusselts Number,. 1. Introduction 1 Size reduction is te buzzword in te modern electronic industry. But wit te reduction in component size, different new problems like eat dissipation becomes critical and sometimes tese devices fails due to overeating. Terefore it is very muc important to dissipate te eat developed by suc small equipments wit faster rate or witin very sort span of time. Te most promising solution for tis problem is te introduction of micro or mini cannels into te eat sinks. Te main purpose of introducing micro- cannel or mini cannel is to increase te surface area wic is exposed for eat transfer. Numerous works ave been reported relating to eat transfer as well as pressure drop wit different geometrical configurations. However tere still a lot of scope remaining for researc on eat transfer & pressure drop in te micro- cannel. Te main objective of tis paper is to study te convective eat transfer in micro- cannel and also te effects of various parameters suc as Reynolds number, inlet velocity of cooling fluid and rise in temperature of cold fluid. Tis paper mainly focuses on eat transfer troug different configurations of micro- cannels suc as straigt, square, triangular, circular and te comparison between tem. Napon et al. (2009) studied te convective eat transfer & pressure drop in te micro- cannel eat *Corresponding autor: D. S. Godake sink. Kayepour et al. (1997) studied te effects of compressibility and rarefaction on te gas flows in micro-cannels. Cen (1998) numerically analyzed te flow caracteristics in micro-cannels. Ambatirudi et al. (2000) analyzed te eat transfer in micro-cannel eat sinks. Ng and Po (2001) applied te CFD for analysis of liquid flow in te double layer microcannel. Zao and Lu (2002) presented te analytical and numerical study effect of porosity on te termal performance a micro-cannel eat sink. Xuan (2003) investigated te effect of te termal and contact resistances of ceramic plate in termoelectric microcoolers. Hao and Tao (2004) applied a numerical model to analyze te pase-cange flow in micro-cannels. Bowmil (2005) studied on te steady-state convective eat transfer of water from an in-line four electronic cips in a vertical rectangular cannel. Zang et al. (2005) reported te study of a single-pase eat transfer of micro-cannel eat sink for electronic packages. Didarul (2007) investigated te eat transfer and fluid flow caracteristics of finned surfaces. Zen et al. (2007) compared te 3-D and 2-D DSMC eat transfer of flow-speed sort micro-cannel flows. Wang et al. (2008) numerically studied te gas flow and eat transfer in a micro-cannel using DSMC wit uniform eat flux boundary condition. 2. Experimental Apparatus Te experimental setup consists of mainly tree parts wic are eater assembly, temperature measuring unit, and different geometries of micro- cannels. 1 MIT College of Engineering, Pune, India, AMET 2016, INPRESSCO IJCET Special Issue-4 (Marc 2016)

2 D. S. Godake et al Study of Convective Heat Transfer troug Micro Cannels wit Different Configurations A. Heater assembly Te eater assembly is as sown in fig.1. For te preparation of eater assembly, initially a wooden block is taken of dimension 130*70 mm as a base. On tis wooden base asbestos seet of 130*70 is placed as insulating material. Now on tis asbestos seet eating coil wit Mica seet is placed and finally over tis surface Aluminum seet of tickness 0.5mm is placed for uniform eating. seet & wooden plate. Te LM35 termocouples are used to measure te temperate of inlet & outlet water to and from te micro- cannel. 3. Design of Micro Cannels Design Process A. Selection of Geometries Te following geometries are selected, Rectangular Square Triangular Circular B. Designing of geometries All geometries are designed by keeping surface area and dept of micro cannel as constant. Fig.2.1 Heater Assembly B. Temperature Measuring Unit Tis unit is used for measuring inlet & outlet temperature of water to and from te micro cannel eat sink. It consists of electronic components like LM35 (Integrated Circuit Temperature Sensor), Microcontroller Board, Potentiometer. Fig.3.1 Design of Micro Cannel C. Preparation of AutoCAD Drawing In order to design te different geometrical configurations micro cannel eat sink very careful approac as to be adopted. By using AutoCAD 2015 CAD drawings are prepared for different configurations of micro cannels. Fig.2.2 Temperature Measuring Unit Different Geometries of Micro- Cannels are used in tis study. For te preparation of tese different configurations of micro- cannel, Copper is selected as raw material due to its iger eat transfer capability. To study te eat transfer troug micro- cannels. Following types of micro cannel Configurations are selected rectangular, Square, Triangular and Circular. For manufacturing of tese configurations a nonconventional macining process suc as Poto Cemical Macining is used. After preparation of different configurations of micro- cannels tey are placed on te eater element and to avoid leakage between te test plate & eater element Teflon coating is provided on te cannel. An AC supply is power source for eaters. Te rear side of eater is insulated wit a tick Mica resistant seet followed by acrylic Fig.3.2 Rectangular Micro Cannel Fig.3.3 Triangular Pattern Micro Cannel 2 MIT College of Engineering, Pune, India, AMET 2016, INPRESSCO IJCET Special Issue-4 (Marc 2016)

3 D. S. Godake et al Study of Convective Heat Transfer troug Micro Cannels wit Different Configurations Q eater = V* I (2) Te average eat transfer rate, Q avg, used in te calculation is determined from te eat transferred to te cooling water and te eat supplied to te eat source as follows: Q avg = [(Q w + Q eater) / 2] (3) Fig.3.4 Square Pattern Micro Cannel Te average eat transfer coefficient can be calculated from Q avg = m. A m ( T LMTD) (4) T LMTD= [ ( ) ] [ ( ) ] [ ( ) ] [ ( ) ] (5) T s,avg = average surface temperature ( 0 C) A m = surface area of te micro-cannel (mm 2 ) Fig.3.5 Circular Pattern Micro Cannel D. Selection of cold fluid To find te eat transfer rate troug different geometrical configurations of micro cannels water is considered as cooling fluid. E. Selection of Raw Material Te Copper is selected as a raw material by considering following properties, Melting temperature: C Termal conductivity: 401 W/m.K Electric resistivity: nω.m(20 0 C) Size: 50mm*70mm Cannel widt: 2 mm Cannel eigt: 500 µm 4. Calculations Te Heat transferred to te cooling water in te test section, Q w, is given by, Q w = m wcp w [(T w,ave) out (T w,ave) in] (1) Te average eat transfer coefficient is presented in terms of average Nusselts Number as given bellow, Nu = (6) K = Termal Conductivity of water (W/mK) D = Hydraulic diameter of cannel (mm) Te Reynolds number based on D of micro- cannel is, Re = u D / ν (7) D = u = Water velocity (m/s) ν = Kinematic viscosity (m 2 /s) A cs = Cross sectional area of micro- cannel (mm 2 ) P = Wetted perimeter (mm) 5. Results and Discussions 5.1 Analysis of Square Micro Cannel Table 5.1 Results of Square Micro Cannel m w = Mass flow rate of water (Kg/Sec.) Cp w = Specific eat capacity of water(kj/kgk) (T w,ave) out & (T w,ave) in are te average outlet and inlet water temperatures respectively. Heat added to te micro-cannel is given by, Sr. No (Experimental) (Teoretical) % Deviation From Fig. 5.1 it is clear tat te value of eat transfer coefficient goes on increasing wit increase in te 3 MIT College of Engineering, Pune, India, AMET 2016, INPRESSCO IJCET Special Issue-4 (Marc 2016)

4 D. S. Godake et al Study of Convective Heat Transfer troug Micro Cannels wit Different Configurations value of. Tere is around 30 % deviation of experimental value of eat transfer coefficient from teoretical value. From Fig.5.3 it is clear tat te value of eat transfer coefficient goes on increasing wit increase in te value of. Tere is around 28 % deviation of experimental value of eat transfer coefficient from teoretical value. Fig.5.1 Variation of Heat Transfer Coefficient w. r. t. 5.2 Analysis of Rectangular Micro Cannel Table 5.2 Results of Rectangular Micro Cannel Sr. No. % (Teoretical) (Experimental) Deviation From Fig.5.2 it is clear tat te value of eat transfer coefficient goes on increasing wit increase in te value of. Tere is around 12 % deviation of experimental value of eat transfer coefficient from teoretical value. Fig.5.3 Variation of Heat Transfer Coefficient w. r. t. 5.4 Analysis of Circular Micro Cannel Table 4.4 Results of Circular Micro Cannel Sr. No. (Experimental) (Teoretical) From Fig.5.4 it is clear tat te value of eat transfer coefficient goes on increasing wit increase in te value of. Tere is around 14 % deviation of experimental value of eat transfer coefficient from teoretical value. Fig. 5.2 Variation of Heat Transfer Coefficient w. r. t. Fig.5.4 Variation of Heat Transfer Coefficient w. r. t. 5.3 Analysis of Triangular Micro Cannel Table 5.3 Results of Triangular Micro Cannel Sr. No. (Experimental) (Teoretical) Fig.5.5 Outlet Temperature of Cooling Fluid Vs 4 MIT College of Engineering, Pune, India, AMET 2016, INPRESSCO IJCET Special Issue-4 (Marc 2016)

5 D. S. Godake et al Study of Convective Heat Transfer troug Micro Cannels wit Different Configurations Fig.5.6 sows variation of experimental value of eat transfer coefficient wit respect to. Here also for triangular geometry te experimental value of eat transfer coefficient is iger as compared wit remaining tree geometries. For triangular geometry te value of eat transfer coefficient is % more tan square geometry, % more tan rectangular and % more tan circular geometry. Fig. 4.8 sows te variation of teoretical value of eat transfer coefficient wit respect to. For triangular geometry te teoretical value of eat transfer coefficient is iger as compared wit rest tree geometries. For triangular geometry te value of eat transfer coefficient is % more tan square geometry, % more tan rectangular and % more tan circular geometry. Fig.5.9 Teoretical Nusselts Number Vs Reynolds Number Fig.5.6 Experimental Heat Transfer Coefficient Vs Fig.5.7 sows variation of experimental value of eat transfer coefficient wit respect to. For triangular geometry te experimental value of Nusselts Number is iger as compared wit rest tree geometries. For triangular geometry te value of Nusselts Number is % more tan square geometry, % more tan rectangular and % more tan circular geometry. Fig.5.9 sows te variation of teoretical value of Nusselts Number wit respect to. For triangular geometry te teoretical value of Nusselts Number is iger as compared wit rest tree geometries. For triangular geometry te value of Nusselts Number is % more tan square geometry, % more tan rectangular and % more tan circular geometry. 5.5 Deviation of Experimental Heat Transfer Coefficient from Teoretical Value Table 5.5 Deviation of Experimental Heat Transfer Coefficient from Teoretical Value Fig.5.7 Experimental Nusselts Number Vs Reynolds Number Fig.5.8 Teoretical Heat Transfer Coefficient Vs Square Micro Cannel (Experimental) (Teoretical) Rectangular Micro Cannel (Experimental) (Teoretical) Circular Micro Cannel (Experimental) (Teoretical) Triangular Micro Cannel (Experimental) (Teoretical) MIT College of Engineering, Pune, India, AMET 2016, INPRESSCO IJCET Special Issue-4 (Marc 2016)

6 D. S. Godake et al Study of Convective Heat Transfer troug Micro Cannels wit Different Configurations From above graps it is clear tat for every geometrical configuration 1. Wit increase in outlet temperature of water tere is increase in Nusselts number in turn increase in eat transfer. 2. Wit decrease in surface temperature of eat sink tere is increase in Nusselts number in turn increase in eat transfer. 3. Wit increase in eat transfer coefficient of water tere is increase in Nusselts number in turn increase in eat transfer. 4. As temperature rise of cooling water in case of triangular micro cannel is muc iger as compared wit rest tree configurations. 5. Te increase in eat transfer coefficient of cooling water in triangular micro cannel is around 15 20% more tan rectangular micro cannel, 25 30% more tan circular micro cannel and 50 55% more tan square micro cannel. As te value of eat transfer coefficient is more in triangular micro cannel terefore, it is concluded tat te triangular geometrical configuration is best suited to ave iger eat transfer troug te micro cannel. Conclusions Different geometrical configuration of copper micro cannels is analyzed for teir eat transfer performance in tis work. Te results sow tat te geometrical configuration of te micro cannel affects te eat transfer performance of te micro cannel eat sink to a considerable extent. Comparatively te triangular configuration resulted in giving better performance wen compared to oter types used in tis experimentation. Acknowledgements I am tankful to my guide Prof. Rakes Sideswar for is guidance and being source of motivation to complete te work. I am also tankful to Prof. B. P. Ronge, Principal, SVERI s COE, Pandarpur, Prof. P. M. Pawar, Dean (R & D), SVERI s COE, Pandarpur, Prof. N. D. Misal, Principal, SVERI s COE (POLY), Pandarpur for providing all facilities witout wic tis work would not ave been possible. I am tankful to my Micro- fluidics LAB Team for teir tecnical elp and suggestions. References P. Napon et al. (2009), Study on te convective eat transfer and pressure drop in te micro-cannel eat sink, International Communications in Heat and Mass Transfer, 36, H. P. Kayepour et al, Effects of compressibility and rarefaction on gaseous flows in micro-cannel, Numerical Heat Transfer, 32 (1997) C. S. Cen (1998), Numerical analysis of gas flow in Micro cannels, Numerical Heat Transfer, 33, K. H. Ambatirudi et al. (2000), Analysis of conjugate eat transfer in micro cannel eat sinks, Numerical Heat Transfer, 37, E. Y. K. Ng et al. (2001), CFD analysis of double- layer micro cannel conjugate parallel liquid flows wit electric double-layer effects, Numerical Heat Transfer, 40, C. Y. Zao et al. (2002), Analysis of micro cannel eat sink for electronics cooling, International Journal of Heat and Mass Transfer, 45, X. C. Xuan (2003), Investigation of termal contact effect on termoelectric coolers, Energy Conservation and Management, 44, Y. L. Hao et al. (2004), A numerical model for pase-cange suspension flow in micro-cannels, Numerical Heat Transfer, 46, H. Bowmil (2005), Convection eat transfer from discrete eat sourced in a liquid cooled rectangular cannel, Applied Termal Engineering, 25, H. Y. Zang (2005), Single-pase liquid cooled micro cannel eat sink for electronic packages, Applied Termal Engineering, 25, I. M. Didarul (2007), Study on eat transfer and fluid flow caracteristics wit sort rectangular plate fin of different pattern, Experimental Termal and Fluid Science, 31, C. E. Zen et al. (2007), Comparison of 3-D and 2-D DSMC eat transfer calculations of flow-speed sort micro cannel flows, Numerical Heat Transfer, 52, Q. W. Wang et al. (2008), Numerical investigation of rarefied diatomic gas flow and eat transfer in a micro cannel using DSMC wit uniform eat flux boundary condition Part I: numerical metod and Validation, Numerical Heat Transfer, 53, Q. W. Wang et al. (2008), Numerical investigation of rarefied diatomic gas flow and eat transfer in a micro cannel using DSMC wit uniform eat flux boundary condition Part II: applications, Numerical Heat Transfer, 53, Nomenclature A Area (m2) Cp Specific Heat, (kj/kgk) D Hydraulic Diameter, (m) Heat Transfer Coefficient, (kw/m 2 K) k Termal Conductivity, (W/mK) m Mass Flow Rate, (kg/s) Nu Nusselts Number ΔP Pressure Drop, (kpa) Pr Prandtl Number P Wet Perimeter, (m) Q Heat Transfer Rate, (W) Re T Temperature, ( C) u Velocity, (m/s) ρ Density, (kg/m 3 ) w Water Subscripts avg in out Average Inlet Outlet 6 MIT College of Engineering, Pune, India, AMET 2016, INPRESSCO IJCET Special Issue-4 (Marc 2016)