International Engineering Research Journal NUMERICAL INVESTIGATION OF HEAT TRANSFER ENHANCEMENT OF FLOW OVER THE BUMPS IN CIRCULAR PIPE

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1 Special Edition PGCON-MECH-7 International Engineering search Journal NUMERICAL INVESTIGATION OF HEAT TRANSFER ENHANCEMENT OF FLOW OVER THE BUMPS IN CIRCULAR PIPE Puja Waghmare, Prof. Ravi H.C. PG student, Mechanical Engineering Department, Savitribai Phule Pune University, DYPSOEA, Ambi, Pune, Maharashtra, India. Assistant Professor, Mechanical Engineering Department, Savitribai Phule Pune University, DYPSOEA, Ambi, Pune, Maharashtra, India. Abstract The heat exchanger applications in refrigeration, automobile, process industries used heat transfer enhancement technology. The present work on heat transfer with bump in circular pipe. The effect of bumps in a circular pipe is a good way to promote the flow mixing in a pipe. By using bump in a circular pipe it can help us to increase the heat transfer enhancement. The aspect ratio of bump was.. The laminar flow model is used for analysis. The bump surface act as extended surface (fin surface) and the main purpose of extended surface to increase the heat transfer rate. The effect of pressure variation and heat transfer enhancement was studied. Keywords: Heat transfer enhancement, circular pipe, Extended Surface (Bumps), Heat transfer rate, Heat transfer coefficient, CFD Analysis. Introduction There are two types of enhancement method used in heat transfer. One is active and another is passive. The fins, surface roughness, twisted tape inserts and coiled tube, which are generally referred to as passive technique. While fluid vibration, electrostatic fields or mechanical stirrers, where there is need of external source is call as active method. In present paper bumps are used to passive method. The Velocity of fluid is flow parameter used to vary ynolds number. Computational Fluid Dynamic a Numerical method tool is used to see the effect of bumps on heat transfer.. Data duction The data reduction of the measured results is summarized in the following procedures: The local heat transfer coefficient was calculated from the total net heat transfer rate and the difference of the local wall temperature and the local bulk mean air temperature. Qa h = AsTs Ta Qa = a p T T = (T in T out) Ta = Tin Tout a = Q a Nu =. x.8 x Pr. As for most cases of the internal convection heat transfer, the fluid properties are evaluated at the mean temperature of the fluid in the duct. The ynolds number was defined by = ρv μ V = Q Ac. Experimental Set up and procedure The apparatus consists of a centrifugal blower unit fitted with a circular tube, which is connected to the test tube located in horizontal orientation.. HP blower is used to blow air through test section. Length of a test tube is mm. K type thermocouple is used to measure temperature of air and heated test section.five thermo couples are embedded on the walls of the tube and one thermocouple is placed in the air stream at the exit of the test section to measure the temperature of flowing air. The digital device temprature indicator is used to display the temperature measured by thermocouple at various position. The test tube of 9mm inside diameter and mm outer diameter is used for experimentation. A U tube manometer measures the pressure drop across the test section filled with water. The diameter of the orifice is mm and coefficient of discharge is.6. The circuit is designed for a load voltage of - V; with a maximum current of A. Difference in the levels of manometer fluid represents the variations in the flow rate of air. The velocity is measured by turbine type animometer. Ts = T + + T u = h k

2 Special Edition PGCON-MECH-7 diameter is mm and height of mm.as shown in fig.. Wire cutting was used to cut bump from base surface Fig.: Schematic of Experimental Set up. Fig.: manufactured bumps photo. CFD Simulation CFD Simulation was carried on ansys software. Geometry was created in ICEM software. In same software tetra-meshing which is unstructured mesh is used for meshing of geometry. Fig.: Experimental set up. Manufacturing of the Test Tubes with Bumps:. Manufacturing of the Test Tubes: Plain tube Aluminium of diameter mm (OD) with 9mm (ID) and mm length was used prepare test tube. Pipe is cut along the axis to form two halves. Tube is cut by gas wire cutting method. Thermal paste was used to paste bumps in circular pipe. Fig.: Geometry of smooth pipe Fig. 6: Geometry of bump pipe Fig.: Photograph of Test tube without bumps and test tube with bumps. Manufacturing of Bumps: Vertical milling operation was use to create bumps from aluminum plate of thickness mm. The bump 6. Modelling and Meshing in ICEM CFD This involves conversion from three dimensional CREO model into CFD element to create the meshing element. Then, the succeeded meshing models were exported to FLUENT for the analysis.

3 Special Edition PGCON-MECH Table no. Grid independent study 7.. Pressure Variation of smooth and bump pipe: Fig.7: Tetra meshing of smooth pipe The pressure variation of smooth pipe is as shown in fig.9 there is a pressure drop of. Pa. Fig.8: Tetra Meshing of bump pipe 6. Boundary Conditions Fig.9: Pressure variation of smooth pipe V m/s The pressure variation of bump pipe is as shown in fig. there is a pressure drop of. Pa. Following are the boundary conditions used for CFD simulation: Inlet : Velocity inlet Outlet: zero gauge pressure Heat source : Constant Temperature 7. sult and Discussion 7. CFD sults: 7.. Grid Independent study: For accuracy checking grid independent study is required for any CFD analysis. So global scale factor varies from to and observed the pressure drop across the test section. It was observed that gsf at gives optimum mesh count and further increasing mesh count will not affect the result accuracy. Global Scale factor of Elements of Nodes Pressure drop Pa Accuracy 6 8 Fig.: Pressure variation of bump pipe V m/s 7.. Temperature Variation of smooth and bump pipe: The temperature variation of smooth pipe is as shown in fig. there is a temperature of smooth pipe is K. 67.7

4 Special Edition PGCON-MECH-7 Fig.: Temperature variation of smooth pipe V m/s The temperature variation of bump pipe is as shown in fig. there is a temperature of bump pipe is K. Fig. Velocity variation of bump pipe V m/s From the Fig., it is observed that the heat transfer coefficient increases with increase in ynolds no. As ynolds no. increases, the air flow will cause more turbulence so due to which the heat transfer rate will increase. it is observed that the Circular pipe without using bumps gives the less heat transfer coefficient with the use of bumps in the Circular pipe create more turbulence which increases the heat transfer coefficient. Fig.: Temperature variation of bump pipe V m/s 7.. Velocity Variation of smooth and bump pipe: The velocity variation of smooth pipe is as shown in fig.. Heat transfer Co-efficent h_plain Pipe h_bump Pipe Fig.: Variation of Heat Transfer coefficient Vs ynolds From the Fig.6, it is observed that the nusslet number increases with increase in ynolds no.in Circular pipe with using bumps As compared to the Circular pipe without using bumps. Fig.: Velocity variation of smooth pipe V m/s The velocity variation of bump pipe is as shown in fig.. Nu 8 6 Nu_p Nu_b

5 Special Edition PGCON-MECH-7 Fig.6: Variation of Nusselt Vs ynolds From the Fig.7, it is observed that the Variation of heat transfer enhancement ratio Vs ynolds is high in Circular pipe with using bumps As compared to the Circular pipe without using bumps Prerssure drop Ratio ΔP_b/ΔP_ p Nu_b/Nu_p... Nu_b/Nu_ p Fig.9: Variation of Pressure drop ratio Vs ynolds 7. Experimrntal sults: In this fig., it is observed that the value of heat transfer coefficeint of smooth pipe is experimentaly lower as compared with the CFD analysis results. It showes that there is a deviation of -9%. Fig.7: Variation of heat transfer enhancement ratio Vs ynolds From the Fig.8, it is observed that the Variation of pressure drop Vs ynolds is high in Circular pipe with using bumps. Pressure drop Pa ΔP_p ΔP_b Heat Transfer Co efficent 8 6 h_cfd h_exp Fig.: Variation of Heat Transfer Coefficient Vs ynolds In this fig. it is observed that the value of Nusselt of smooth pipe is experimentaly lower as compared with the CFD analysis results. It showes that there is a deviation of -9% of Nussult. Fig.8: Variation of Pressure drop Vs ynolds From the Fig.9, it is observed that the Variation of pressure drop ratio Vs ynolds is high in Circular pipe with using bumps. Nu Nu_CFD Nu_EXP

6 Special Edition PGCON-MECH-7 Fig.: Variation of Nusselt ratio Vs ynolds 9. Conclusion This paper work show that the Circular Pipe with using bumps is leads to greater heat transfer enhancement. The Bumps surface it can also called as artificial surface act as extended surface (fin surface) and the main purpose of extended surface to increase the heat transfer rate. The advantages of the internal bumps are fluid mixing is more and boundary layer separation occurs in Circular Pipe which will help in heat transfer.. maining Work The experimental validation of the aluminium pipe with bumps is remaining. ferences ) Johann Turnow,Nikolai Kornev,Valery Zhdanov, Egon Hassel, Flow structures and heat transfer on dimples in a staggered arrangement, International Journal of Heat and Fluid Flow,,, pp ) Yu Rao, Chaoyi Wana, Yamin Xu, An experimental study of pressure loss and heat transfer in the pinfin-dimple channels with various dimple depths, International Journal of Heat and Mass Transfer,,, pp ) C. Bi, G.H. Tang, W.Q. Tao, Heat transfer enhancement in mini-channel heat sinks with dimples and cylindrical grooves, Applied Thermal Engineering,,, pp. - ) S.A. Isaev, N.V. Kornev, A.I. Leontiev, E. Hassel, Influence of the ynolds number and the spherical dimple depth on turbulent heat transfer and hydraulic loss in a narrow channel, International Journal of Heat and Mass Transfer,,, pp ) Jonghyeok Lee, Kwan-Soo Lee, Correlations and shape optimization in a channel with aligned dimples and protrusions, International Journal of Heat and Mass Transfer,, 6, pp.-. 6) Somin Shin, Ki Seon Lee, Seoung Duck Park, Jae Su Kwak, Measurement of the heat transfer coefficient in the dimpled channel:effects of dimple arrangement and channel height, Journal of Mechanical Science and Technology, 9,, pp ) YuChen, Yong Tian Chew, Boo Cheong Khoo, Enhancement of heat transfer in turbulent channel flow over dimpled surface, International Journal of Heat and Mass Transfer,,, pp ) Yu Rao a,yamin Xu, Chaoyi Wana, An experimental and numerical study of flow and heat transfer in channels with pin fin-dimple and pin fin arrays, Experimental Thermal and Fluid Science,, 8, pp ) Nopparat Katkhaw, NatVorayos, Tanongkiat Kiatsiriroat, Yottana Khunatorn, Damorn Bunturat, AtipoangNuntaphan, Heat transfer behavior of flat plate having ellipsoidal dimpled surfaces, Thermal engineering,. ) M. Siddique, A. A. Khaled, N. I. Abdulhafiz, and A. Y. Boukhary, cent Advances in Heat Transfer Enhancements : A view port, International Journal of Chemical Engineering,, id.66 ) Raju R.Yenare, Prof Kundlik V.Mali., Experimental Study for Heat Transfer Enhancement Due To Surface Roughness at Laminar Flow, Int. Journal of Engineering search and Applications,, pp.9- ) J.E. Kim, J.H. Doo, M.Y. Ha, H.S. Yoon, C. Son, Numerical study on characteristics of flow and heat transfer in a cooling passage with protrusion-in-dimple surface, International Journal of Heat and Mass Transfer,,, pp ) Hemant C. Pisal, Avinash A. Ranaware, Heat Transfer Enhancement by Using Dimpled 6

7 Special Edition PGCON-MECH-7 Surface, IOSR Journal of Mechanical and Civil Engineering, pp.7-. ) Sumantha Acharya.,Experimental and comoutational study of heat/ma transfer and flow steucture of four dimple array in square channel,journal Turbomachinery, ) Cengel, Y. A., Heat and Mass Transfer: A Practical Approch, rd ed., Tata McGraw Hill, New York,, pp