HEAT TRANSFER DURING MULTI SWIRL JET IMPINGEMENT: EXPERIMENTATION

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 11, November 2018, pp , Article ID: IJMET_09_11_048 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed HEAT TRANSFER DURING MULTI SWIRL JET IMPINGEMENT: EXPERIMENTATION N. V. S. Shankar Research Scholar, Department of Mechanical Engineering, GITAM University, Visakhapatnam, India Dr. H. Ravi Shankar Professor, Department of Mechanical Engineering, GITAM University, Visakhapatnam, India ABSTRACT Of the Active Cooling Techniques, Jet impingement achieves high localized heat transfer rates. Introduction of swirl is one of the methods of augmentation of heat transfer rates. The current work aims at verifying the expression derived in our previous work experimentally. Three cases, for which simulations were performed previously, are executed. The required ducts are manufactured by additive manufacturing. Thermistors are used for measuring temperatures. Anemometer is used to monitor air flow rates. Smoke tests are executed to demonstrate the generation of swirl and then experimentation is executed to study the heat transfer characteristics. The experimental results are in agreement with those of simulation results. Key words: Jet Impingement, Swirl, Heat Transfer, Smoke Test, Thermistors. Cite this Article: N. V. S. Shankar and Dr. H. Ravi Shankar, Heat Transfer During Multi Swirl Jet Impingement: Experimentation, International Journal of Mechanical Engineering and Technology 9(11), 2018, pp INTRODUCTION Increasing processing power of chips is leading to higher heat generation in processors [1]. High temperatures are the primary cause of failure of 67% electronics [2]. Cooling of electronics is thus an important aspect relating to functioning of the equipment. There are two types of cooling: Active cooling and Passive cooling. Passive cooling is the process of cooling without the use of extra energy while active cooling involves use of explicit fluid circulation systems over heat sinks. Jet impingement is an active cooling process in which jet is impinged on the surface to be cooled. Zuckerman and Loir [3], Sagar Chirade [4], Anupam Dewan, et al [5] reviewed the jet impingement process and summarized the correlations of heat transfer during jet impingement. Air jet impingement applications in food processing were presented by A. Sarkar, et al [6]. Simulations and Experimentation were executed by

2 Heat Transfer During Multi Swirl Jet Impingement: Experimentation many researchers to understand the phenomenon of heat transfer. Sajad Alimohammadi, et al [7] used both numerical simulations and experimental procedure to study the heat transfer during unconfined single jet impingement. The Re values simulated are between 6000 and with z/d ranging from 1 to 6. Equation (1) has been proposed Nu Re Pr ( z / D) (1) Benmouhoub and Mataoui [8] used numerical simulations to investigate the heat transfer characteristics when slot jet is impinged on a moving flat plate. Hwang and Cheng [9], [10] used anisotropic t 2 -ε t heat-transfer model together with the anisotropic k-ε turbulence model for simulating heat transfer during swirling couette flow. Rattner [11] performed 1000 cfd simulations to generate the correlations for k factor and Nu during jet impingement in micro fin heat sinks. Equations (2) & (3) were proposed by them. 20 c j dj b Re j p a th j j D j D j j1 k 10 (2) 20 c j dj b Re j p th a j j D j D j 0.29 j1 Pr 10 Nu (3) Nasif, et al [12] used CFD simulations to study the effectiveness of cooling piston with oil jet impingement. SST model was used and RANS equations were solved during this process. Farida Iachachene, et al [13] performed numerical simulations to investigate the heat transfer due to impinging slot jet in a rectangular cavity. Several flow regimes are observed depending on the jet exit in the slot. Numerical correlations are formulated so as to compute the Nusselt number. The Correlation that has been derived is given in equation (4). Nu 10 (66,55 3, 23L L ) Re (4) f f Jia, et al [14] performed numerical simulations to study the effect of upstream and downstream shaped ribs on heat transfer during flow when cooling turbine blades. ν 2 f-kε model is used during simulations. Xu, et al [15], using numerical simulations, investigated the effect of five different types of vortex generator on heat transfer during flow in a rectangular channel. Modak, et al [16] investigated experimentally the use of Cu 2 O-Water nanofluid during single jet impingement form a flat surface. Different values of Re, z/d and concentrations (Φ) are experimented during this process. Ichimiya & Yamada [17] experimentally studied the heat transfer due to circular impinging jet form a confining wall. Shen, et al [18] using CFD techniques, investigated into heat transfer augmentation during jet impingement by the use of dimples and protrusions. Rodriguez, et al [19] compared different methods of modeling helicoloids for generating swirling flow fields. Impact of Re and S on Heat transfer, central recirculating zone are discussed. Numerical simulations carried out for this purpose are presented. Bakirci, et al [20] & Bilen, et al [21] conducted experiments for flow visualization and study heat transfer in both multi-channel impinging jet (MCIJ), Swirling Impinging Jet (SIJ) and conventional impinging jet (CIJ). Experimental results indicated significant improvement in radial uniformity of heat transfer in SIJ compared to the MCIJ and CIJ. Herrada, et al [22] used axisymmetric cfd simulations to study the effect of a swirl number S and a vortex core length d on the mechanical characteristics of the flow at moderate Reynolds numbers. Amini Y, et al [23] practically studied the use of twisted tape inserts in augmenting heat transfer during jet impingement cooling. During this process, the effect of swirl on the surface pressure is studied in detail. Swirling was achieved aerodynamically. Prasad, et al [24] used numerical editor@iaeme.com

3 N. V. S. Shankar and Dr. H. Ravi Shankar simulations to study the heat transfer from sparse and dense pin fin heat sinks during jet impingement. Zahir U Ahmed, et al [25] used RANS approach with RNG k ε model is used for investigating the effects of inflow conditions on the transition from free-to-impinging and non-swirling-to-swirling (impinging) jets. 2D axi-symmetric analyses are performed during this process. The analyses and swirl numbers tested have targeted flow conditions whereby no vortex breakdown is expected to occur. Kinsella, et al [26] indicated that the main reason for augmentation of heat transfer in swirling jets is due to increase in turbulence. It is also found during their investigations, that at lower H/D ratios, the heat transfer decreases as higher stagnation area is generated because of blockage due to swirl generator. It has also been observed by them that the optimum degree of swirl from a heat transfer perspective is a function of the nozzle to impingement surface spacing. Ortega-Casanova [27], [28] gave expressions relating to heat transfer from a heated plate when subjected to swirl jet impingement. The expressions given are for constant wall boundary conditions. Sergey, et al [29] employed stereo PIV technique using advanced pre- and post-processing algorithms for studying the turbulent swirling jets. During their study, they observed early breakdown of vertex when S=1.0 and 0.71, but a lengthy vertex for S=0.41. The vertex breakdown at higher S values leads to greater turbulent energy and thus significantly large values of the third-order moments determining the turbulent diffusion of the energy. Shuja, et al [30] indicated that swirl increases irreversibility due to heat transfer while reduces fluid friction. Erik [31] gave expressions for mathematically modelling swirling flow and evaluating various parameters in the flow. Koichi Ichimiya and Koji Tsukamoto [32] investigated the heat transfer when swirling laminar jet is being impinged on a flat plate. Ekkad, et al [33] investigated the heat transfer augmentation by inducing swirl in impinging cooling jets by introducing them at an angle during cooling turbine blades. Three different lateral hole configurations with three different Re values are tested. 2. EXPERIMENTAL SETUP Based on the literature reviewed, it can be seen that there are no numerical correlations for Multi-Swirl Jet Impingement. In our past work [34], a set of 42 simulations were executed so as to obtain a relation for predicting heat transfer coefficient during multi-swirl jet impingement with Re ranging from to 33000, swirl generators with angles 0, 90, 180, 360 and z/d ranging from 4.00 to The correlation for calculating Nusselt number is given by equation (5). The heat transfer coefficient is further calculated using equation (6). Nu Re Pr Si I z D ( ) (5) hd Nu (6) K The current work focuses on experimental verification of equation (5). For this purpose, ducts with swirl generators are 3D printed. 3. FABRICATION OF DUCTS Three ducts with swirl angles of 90, 180 and 360, and a duct with no swirl generator are manufactured using additive manufacturing. The ducts are modelled in Creo. Tool paths are generated using Cura. For this PLA material is used. Wanhao Duplicator i3 printer is used to fabricate the ducts. The ducts are printed at a temperature of 205 C at a speed of 20mm/s. Grid infill is used and a wall thickness used is 2mm. Figure 1 shows the fabricated ducts. Each duct contains 9 (3X3) jet exits at pitch of 15mm editor@iaeme.com

Heat Transfer During Multi Swirl Jet Impingement: Experimentation Figure 1 Fabricated ducts 4.

The experimental setup uses six 100K NTC thermistors which used for measuring temperature.

This fabricated circuitry is shown in figure 3.

One is placed at the duct exit to measure T as shown in figure 5.

Another thermistor is placed at the exit of complete setup so as to read exit air temperature T e.

The mass flow rate is measured using vane anemometer. This shown in figure 6.

4 Heat Transfer During Multi Swirl Jet Impingement: Experimentation Figure 1 Fabricated ducts 4. EXPERIMENTAL SETUP The schematic of the experimental setup at given in [35] is shown in figure 2. The experimental setup uses six 100K NTC thermistors which used for measuring temperature. These thermistors are interfaced to computer using Intel Edison using resistance break circuit shown in figure 8. This fabricated circuitry is shown in figure 3. Of the six thermistors, four are placed on 60mm X 60mm X 15mm Aluminium plate as in figure 4. One is placed at the duct exit to measure T as shown in figure 5. Average of the temperature measured by the thermistors on the Al block gives T. Another thermistor is placed at the exit of complete setup so as to read exit air temperature T e. The heat transfer coefficient is computed using equation (7). The mass flow rate is measured using vane anemometer. This shown in figure 6. Complete experimental setup is shown in figure 7. It may be noted that the heat input is given using Thermoelectric Chip. mc ( T T ) ha( T T ) (7) p e av Figure 2: Schematic of Experimental Setup used Figure 3: Thermistor setup used for measuring temperatures Figure 4: Thermistors placed on Aluminum block Figure 5: Thermistor placed at duct exit Figure 6: Flow exit from blower editor@iaeme.com

The increasing cone angle indicates the increase in swirl. This is shown in figure 9. It may be noted that the smoke tests are captured using high speed camera at 960fps.

5 N. V. S. Shankar and Dr. H. Ravi Shankar Figure 7: Complete Experimental Setup Figure 8: Resistance break circuit used for interfacing thermistors 5. RESULTS AND DISCUSSION Smoke tests are initially performed using the ducts. With the increase in swirl angle, an increase in cone angle of the jet exiting the nozzles in the duct are observed. The increasing cone angle indicates the increase in swirl. This is shown in figure 9. It may be noted that the smoke tests are captured using high speed camera at 960fps. The cone for 360 swirl generator could not be captured as the spreading of smoke is very high due to large cone angle. The blower generates an air flow with a velocity of 16m/s. This is directed via duct on to aluminium plate via nine nozzles with diameter of 10mm each. As indicated heat input is given using a TEC. Temperatures are noted when steady state is reached. Table 1 summarizes the experimental data. T av denotes the average surface temperature. T indicates the air exit temperature from the nozzle. T e indicates the air exit temperature from the experimental setup. Heat Transfer Coefficient is computed using expression (7). In all the cases, H/D is maintained at 4. The error that was obtained during experimentation is around 13% indicating the validity of the expression derived. Figure 9: Smoke Test Result. Starting from left (a) No Swirl generator used, (b) with 90 helix swirl generator, (c) with 180 Helix swirl generator, (d) with360 Helix swirl generator Table 1: Experimental Data Name Tav T Te Exit Velocity (m/s) Exit mass Heat flow Rate Removed (Kg/S) (W) Surface Area Heat Transfer Coefficient Experimental Heat Transfer Coefficient Simulated Error No Swril % Swirl % Swirl % editor@iaeme.com

6 Heat Transfer During Multi Swirl Jet Impingement: Experimentation 6. CONCLUSIONS This work is continuation of our previous work published in [34]. The work aims at verifying the expression that is derived for computing Nusselt number and thus heat transfer coefficient, in our past work, for Multi-Swirl Jet impingement cooling. When experimenting 9 (3X3) jets are used. The ducts are fabricated using additive manufacturing techniques using PLA material. Thermistors are used for measuring temperature. Anemometer is used for measuring air velocity. Initially smoke tests are performed to demonstrate the swirl generated. Experimentation is then performed to compute the heat transfer rates. The heat transfer rates computed from experimental data are in agreement with that of numerically simulated values. REFERENCES [1] Wikipedia, List of CPU power dissipation figures, [2] VORTEC: Innovative Compressed Air Technologies, Electronic Equipment Failures: Cause, Effect and Resolution. p , [3] N. Zuckerman and N. Lior, Jet impingement heat transfer: Physics, correlations, and numerical modeling, Adv. Heat Transf., vol. 39, no. C, pp , [4] S. Chirade, S. Ingole, and K. K. Sundaram, Review of Correlations on Jet Impingement Cooling, Int. J. Sci. Res. ISSN (Online Index Copernicus Value Impact Factor, vol. 14, no. 4, pp , [5] A. Dewan, R. Dutta, and B. Srinivasan, Recent Trends in Computation of Turbulent Jet Impingement Heat Transfer, Heat Transf. Eng., vol. 33, no. 4 5, pp , [6] A. Sarkar, N. Nitin, M. V. Karwe, and R. P. Singh, Fluid Flow and Heat Transfer in Air Jet Impingement in Food Processing, J. Food Sci., vol. 69, no. 4, pp. CRH113-CRH122, [7] S. Alimohammadi, D. B. Murray, and T. Persoons, Experimental Validation of a Computational Fluid Dynamics Methodology for Transitional Flow Heat Transfer Characteristics of a Steady Impinging Jet, J. Heat Transfer, vol. 136, no. 9, p , [8] D. Benmouhoub and A. Mataoui, Turbulent Heat Transfer from a Slot Jet Impinging on a Flat Plate, J. Heat Transfer, vol. 135, no. 10, p , [9] J.-J. Hwang and C.-S. Cheng, Augmented Heat Transfer in a Triangular Duct by Using Multiple Swirling Jets, J. Heat Transfer, vol. 121, no. 3, pp , [10] J.-J. Hwang and B.-Y. Chang, Effect of Outflow Orientation on Heat Transfer and Pressure Drop in a Triangular Duct with an Array of Tangential Jets, J. Heat Transfer, vol. 122, no. 4, pp , [11] A. S. Rattner, General Characterization of Jet Impingement Array Heat Sinks With Interspersed Fluid Extraction Ports for Uniform High-Flux Cooling, J. Heat Transfer, vol. 139, no. 8, p , [12] G. Nasif, R. M. Barron, and R. Balachandar, Numerical Simulation of Piston Cooling With Oil Jet Impingement, J. Heat Transfer, vol. 138, no. 12, p , [13] F. Iachachene, A. Mataoui, and Y. Halouane, Numerical Investigations on Heat Transfer of Self-Sustained Oscillation of a Turbulent Jet Flow Inside a Cavity, J. Heat Transfer, vol. 137, no. 10, p , [14] R. Jia, B. Sund n, and M. Faghri, Computational Analysis of Heat Transfer Enhancement in Square Ducts With V-Shaped Ribs: Turbine Blade Cooling, J. Heat Transfer, vol. 127, no. 4, p. 425, [15] Z. Xu, Z. Han, J. Wang, and Z. Liu, The characteristics of heat transfer and flow resistance in a rectangular channel with vortex generators, Int. J. Heat Mass Transf., vol. 116, pp , [16] M. Modak, S. S. Chougule, and S. K. Sahu, An Experimental Investigation on Heat Transfer Characteristics of Hot Surface by Using CuO Water Nanofluids in Circular Jet Impingement Cooling, J. Heat Transfer, vol. 140, no. 1, p , editor@iaeme.com

7 N. V. S. Shankar and Dr. H. Ravi Shankar [17] K. Ichimiya and Y. Yamada, Three-Dimensional Heat Transfer of a Confined Circular Impinging Jet with Buoyancy Effects, J. Heat Transfer, vol. 125, no. 2, p. 250, [18] Z. Y. Shen, Q. Jing, Y. H. Xie, and D. Zhang, Thermal Performance of Miniscale Heat Sink with Jet Impingement and Dimple/ Protrusion Structure, J. Heat Transf. Asme, vol. 139, no. 5, pp. 1 8, [19] S. B. Rodriguez and M. S. El-genk, Recent Advances in Modeling Axisymmetric Swirl and Applications for Enhanced Heat Transfer and Flow Mixing, Two Phase Flow, Phase Change and Numerical Modeling, in Two Phase Flow, Phase Change and Numerical Modeling, vol. ISBN: 978, Intech Open Publications, 2011, pp [20] K. Bakirci and K. Bilen, Visualization of heat transfer for impinging swirl flow, Exp. Therm. Fluid Sci., vol. 32, no. 1, pp , [21] K. Bilen, K. Bakirci, S. Yapici, and T. Yavuz, Heat transfer from a plate impinging swirl jet, Int. J. Energy Res., vol. 26, no. 4, pp , [22] M. A. Herrada, C. Del Pino, and J. Ortega-Casanova, Confined swirling jet impingement on a flat plate at moderate Reynolds numbers, Phys. Fluids, vol. 21, no. 1, [23] Y. Amini, M. Mokhtari, M. Haghshenasfard, and M. Barzegar Gerdroodbary, Heat transfer of swirling impinging jets ejected from Nozzles with twisted tapes utilizing CFD technique, Case Stud. Therm. Eng., vol. 6, pp , [24] K. L. Prasad, A. Ramakrishna, and N. V. S. Shankar, Numerical Simulation for Studying Heat Transfer in Multi Jet Impingement on Sparse and Dense Pin Fin Heat Sinks, vol. 2, no. 9, pp , [25] Z. U. Ahmed, Y. M. Al-Abdeli, and M. T. Matthews, The effect of inflow conditions on the development of non-swirling versus swirling impinging turbulent jets, Comput. Fluids, vol. 118, no. SEPTEMBER 2015, pp , [26] C. Kinsella, B. Donnelly, and D. B. Murray, Heat Transfer Enhancement From a Horizontal Surface impinged with swirl jets, in 5th European thermal-sciences conference, 2008, p. 8. [27] J. Ortega-Casanova, CFD and correlations of the heat transfer from a wall at constant temperature to an impinging swirling jet, Int. J. Heat Mass Transf., vol. 55, no , pp , [28] J. Ortega-casanova, Numerical Simulation of the Heat Transfer from a Heated Solid Wall to an Impinging Swirling Jet, in Two Phase Flow, Phase Change and Numerical Modeling, Intech Open Publications, 2011, pp [29] S. V. Alekseenko, A. V. Bilsky, V. M. Dulin, and D. M. Markovich, Experimental study of an impinging jet with different swirl rates, Int. J. Heat Fluid Flow, vol. 28, no. 6, pp , [30] S. Z. Shuja, B. S. Yilbas, and M. Rashid, Confined swirling jet impingement onto an adiabatic wall, Int. J. Heat Mass Transf., vol. 46, no. 16, pp , [31] E. R. Fledderus, Mathematical Modelling in Swirling Flows: a Hamiltonian perspective, University of Twente, [32] K. Ichimiya and K. Tsukamoto, Heat Transfer Characteristics of a Swirling Laminar Impinging Jet, J. Heat Transfer, vol. 132, no. September, p , [33] S. V. Ekkad, G. Pamula, and S. Acharya, Influence of Crossflow-Induced Swirl and Impingement on Heat Transfer in a Two-Pass Channel Connected by Two Rows of Holes, J. Turbomach., vol. 123, no. 2, p. 281, [34] N. V. S. Shankar and H. R. Shankar, Heat Transfer During Multi Swirl Jet Impingement, Int. J. Mech. Eng. Technol., vol. 8, no. 9, pp , [35] N. V. S. Shankar and H. R. Shankar, Experimental Investigation into Heat Transfer during Swirl Jet Impingement, Int. J. Appl. Eng. Res., vol. 13, no. 7, pp , editor@iaeme.com

HEAT TRANSFER DURING MULTI SWIRL JET IMPINGEMENT

HEAT TRANSFER DURING MULTI SWIRL JET IMPINGEMENT International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 9, September 2017, pp. 349 356, Article ID: IJMET_08_09_037 Available online at http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=8&itype=9