Abstract： The most popularly used fin types in compact heat exchangers are the serrated fins, wavy fins, louvered fins and plain fins. Amongst these fin types the serrated fins assume lot of importance due to its enh...Abstract： The most popularly used fin types in compact heat exchangers are the serrated fins, wavy fins, louvered fins and plain fins. Amongst these fin types the serrated fins assume lot of importance due to its enhanced thermo-hydraulic performance. Thermo-hydraulic design of CHEs （Compact heat exchangers） is strongly dependent upon the predicted/measured dimensionless performance （Colburnj factor and Fanning friction vs. Reynolds number） of heat transfer surfaces. This paper describes the numerical analysis to study the heat transfer coefficient and friction factor of Serrated fins in water medium. CFD （Computational fluid dynamics） methodology has been used to develop the single phase water heat transfer coefficient and friction factor correlations for serrated fins using ANSYS Fluent 14.5. The results are compared with previous air-cooled models and experimental results of water. The water cooled CFD analysis results shows that the Prandtl number has a large effect on the Nusselt number of the serrated fin geometry. Finally, the generalized correlations are developed for serrated fins taking all geometrical parameters into account. This numerical estimation can reduce the number of tests/experiments to a minimum for similar applications.展开更多
Single phase heat transfer analysis of water and R134a refrigerant （liquid phase） has been carried out using CFD （Computational fluid dynamics） approach for rectangular channel with smooth wavy fin. Colburnj facto...Single phase heat transfer analysis of water and R134a refrigerant （liquid phase） has been carried out using CFD （Computational fluid dynamics） approach for rectangular channel with smooth wavy fin. Colburnj factor and Fanning friction factorf are predicted for wavy fin. The correlations are developed at Reynolds number range of 100-15,000. The effect of fin geometry （fin spacing, fin height, wave height and wave length） on the enhanced heat transfer and pressure drops are investigated. Results show that there is no significant variation off factor for water and liquid R134a at constant Reynolds number. However variations inj factor were observed at constant Reynolds number. Colburnj factor and Fanning friction factorfcorrelations are proposed in terms of Re and geometry parameters （h/s, a/s, L/a） for water and liquid refrigerant R134a in the present study. Two separate equations are proposed for the low and high Re regions i.e. between Re of 100-1,000 and Re of 1,000-15,000.展开更多
Friction stir welding(FSW)has been extensively adopted to fabricate aluminium alloy joints by incorporating various welding parameters that include welding speed,rotational speed,diameters of shoulder and pin and tool...Friction stir welding(FSW)has been extensively adopted to fabricate aluminium alloy joints by incorporating various welding parameters that include welding speed,rotational speed,diameters of shoulder and pin and tool tilt angle.FSW parameters significantly affect the weld strength.Tool tilt angle is one of the significant process parameters among the weld parameters.The present study focused on the effect of tool tilt angle on strength of friction stir lap welding of AA2014-T6 aluminium alloy.The tool tilt angle was varied between 0°and 4°with an equal increment of 1°.Other process parameters were kept constant.Macrostructure and microstructure analysis,microhardness measurement,scanning electron micrograph,transmission electron micrograph and energy dispersive spectroscopy analysis were performed to evaluate the lap shear strength of friction stir lap welded joint.Results proved that,defect-free weld joint was obtained while using a tool tilt angle of 1°to 3°.However,sound joints were welded using a tool tilt angle of 2°,which had the maximum lap shear strength of 14.42 kN and microhardness of HV 132.The joints welded using tool tilt angles of 1°and 3°yielded inferior lap shear strength due to unbalanced material flow in the weld region during FSW.展开更多
文摘Abstract： The most popularly used fin types in compact heat exchangers are the serrated fins, wavy fins, louvered fins and plain fins. Amongst these fin types the serrated fins assume lot of importance due to its enhanced thermo-hydraulic performance. Thermo-hydraulic design of CHEs （Compact heat exchangers） is strongly dependent upon the predicted/measured dimensionless performance （Colburnj factor and Fanning friction vs. Reynolds number） of heat transfer surfaces. This paper describes the numerical analysis to study the heat transfer coefficient and friction factor of Serrated fins in water medium. CFD （Computational fluid dynamics） methodology has been used to develop the single phase water heat transfer coefficient and friction factor correlations for serrated fins using ANSYS Fluent 14.5. The results are compared with previous air-cooled models and experimental results of water. The water cooled CFD analysis results shows that the Prandtl number has a large effect on the Nusselt number of the serrated fin geometry. Finally, the generalized correlations are developed for serrated fins taking all geometrical parameters into account. This numerical estimation can reduce the number of tests/experiments to a minimum for similar applications.
文摘Single phase heat transfer analysis of water and R134a refrigerant （liquid phase） has been carried out using CFD （Computational fluid dynamics） approach for rectangular channel with smooth wavy fin. Colburnj factor and Fanning friction factorf are predicted for wavy fin. The correlations are developed at Reynolds number range of 100-15,000. The effect of fin geometry （fin spacing, fin height, wave height and wave length） on the enhanced heat transfer and pressure drops are investigated. Results show that there is no significant variation off factor for water and liquid R134a at constant Reynolds number. However variations inj factor were observed at constant Reynolds number. Colburnj factor and Fanning friction factorfcorrelations are proposed in terms of Re and geometry parameters （h/s, a/s, L/a） for water and liquid refrigerant R134a in the present study. Two separate equations are proposed for the low and high Re regions i.e. between Re of 100-1,000 and Re of 1,000-15,000.
基金Aeronautical Development Agency (ADA), Bangalore, India, for the financial support to carry out this investigation through an R&D project No: FSED 83.07.03
文摘Friction stir welding(FSW)has been extensively adopted to fabricate aluminium alloy joints by incorporating various welding parameters that include welding speed,rotational speed,diameters of shoulder and pin and tool tilt angle.FSW parameters significantly affect the weld strength.Tool tilt angle is one of the significant process parameters among the weld parameters.The present study focused on the effect of tool tilt angle on strength of friction stir lap welding of AA2014-T6 aluminium alloy.The tool tilt angle was varied between 0°and 4°with an equal increment of 1°.Other process parameters were kept constant.Macrostructure and microstructure analysis,microhardness measurement,scanning electron micrograph,transmission electron micrograph and energy dispersive spectroscopy analysis were performed to evaluate the lap shear strength of friction stir lap welded joint.Results proved that,defect-free weld joint was obtained while using a tool tilt angle of 1°to 3°.However,sound joints were welded using a tool tilt angle of 2°,which had the maximum lap shear strength of 14.42 kN and microhardness of HV 132.The joints welded using tool tilt angles of 1°and 3°yielded inferior lap shear strength due to unbalanced material flow in the weld region during FSW.
