{"title":"Visual Study on Flow Patterns and Heat Transfer during Convective Boiling Inside Horizontal Smooth and Microfin Tubes","authors":"V.D. Hatamipour, M.A. Akhavan-Behabadi","volume":45,"journal":"International Journal of Mechanical and Mechatronics Engineering","pagesStart":898,"pagesEnd":905,"ISSN":"1307-6892","URL":"https:\/\/publications.waset.org\/pdf\/9289","abstract":"Evaporator is an important and widely used heat\r\nexchanger in air conditioning and refrigeration industries. Different\r\nmethods have been used by investigators to increase the heat transfer\r\nrates in evaporators. One of the passive techniques to enhance heat\r\ntransfer coefficient is the application of microfin tubes. The\r\nmechanism of heat transfer augmentation in microfin tubes is\r\ndependent on the flow regime of two-phase flow. Therefore many\r\ninvestigations of the flow patterns for in-tube evaporation have been\r\nreported in literatures. The gravitational force, surface tension and\r\nthe vapor-liquid interfacial shear stress are known as three dominant\r\nfactors controlling the vapor and liquid distribution inside the tube. A\r\nreview of the existing literature reveals that the previous\r\ninvestigations were concerned with the two-phase flow pattern for\r\nflow boiling in horizontal tubes [12], [9]. Therefore, the objective of\r\nthe present investigation is to obtain information about the two-phase\r\nflow patterns for evaporation of R-134a inside horizontal smooth and\r\nmicrofin tubes. Also Investigation of heat transfer during flow\r\nboiling of R-134a inside horizontal microfin and smooth tube have\r\nbeen carried out experimentally The heat transfer coefficients for\r\nannular flow in the smooth tube is shown to agree well with Gungor\r\nand Winterton-s correlation [4]. All the flow patterns occurred in the\r\ntest can be divided into three dominant regimes, i.e., stratified-wavy\r\nflow, wavy-annular flow and annular flow. Experimental data are\r\nplotted in two kinds of flow maps, i.e., Weber number for the vapor\r\nversus weber number for the liquid flow map and mass flux versus\r\nvapor quality flow map. The transition from wavy-annular flow to\r\nannular or stratified-wavy flow is identified in the flow maps.","references":"[1] Bergles, AE & Suo, M. Investigation of boiling water flow\r\nregimes at high pressure. In: Proc. Heat Trans. Fluid Mech.\r\nInstitute. Stanford Press, p. 77-79 (1966)\r\n[2] Schultz, R.R. & Cole, R. Uncertainty Analysis in Boiling\r\nNucleation, AIChE Symp. Series, Vol.75, No.189, pp. 32-38,\r\n(1979)\r\n[3] Agrawal, K.N. & Varma, H.K. & Lal, S.N. Heat Transfer\r\nDuring Forced Convection Boiling of R12 Under Swirl Flow,\r\nASME J. Heat Transfer, Vol. 108, pp. 567-573, (1986)\r\n[4] Gungor, K.E. & Winterton, R.H. Simplified General Correlation\r\nfor Saturated Flow Boiling and Comparison of Correlations to\r\nData\", Industrial & Engineering Chemistry Process Design and\r\nDevelopment, Vol. 65, pp.148-156, (1987)\r\n[5] Carey VP. Liquid-vapor phase-change phenomena. Washington\r\n(DC): Hemisphere Pub. Co, (1992)\r\n[6] Thors, P. & Bogart, J.E. In-Tube Evaporation of HCFC-22 with\r\nEnhanced Tubes, J. Enhanced Heat Transfer, Vol. 1, pp. 365-\r\n377, (1994)\r\n[7] Webb, R.L. Principles of Enhanced Heat Transfer, John Wiley\r\nand Sons, New York (1994)\r\n[8] Chamra, L. & Webb, R. & Randlett, M. Advanced Microfin\r\nTubes for Evaporation, International Journal of Heat and Mass\r\nTransfer, Vol. 39 (9), pp.1827-1838, (1996)\r\n[9] Kattan, N. & Thome, J.R. & Favrat, D. Flow boiling in\r\nhorizontal tubes: Part 1: development of a diabatic two-phase\r\nflow pattern map. Journal of Heat Transfer ;120:140-7.( 1998)\r\n[10] Muzzio, A. & Niro, A. & Garavaglia, M. Flow patterns and heat\r\ntransfer coefficients in flow-boiling and convective\r\ncondensation of R22 inside a microfin tube of new design, in:\r\nHeat Transfer 1998, Proceedings of 11th IHTC, Kyongju,\r\nKorea, vol. 2, , pp. 291-296 ( 1998)\r\n[11] Stoecker, W.F. Industrial refrigeration handbook, Mc Graw\r\nHill Companies, Inc. (1998)\r\n[12] Ming-huei, Yu. & Tsun-kuo, Lin & Chyuan-chyi, Tseng Heat\r\ntransfer and flow pattern during two-phase flow boiling of R-\r\n134a in horizontal smooth and microfin tubes. International\r\njornal of refrigeration (2001)\r\n[13] Sonntag, R.E. & Borgnakke, C. & Van Wylen, G.J.\r\nFundamentals of Thermodynamics, John wiley and sons, New\r\nYork, (2003)\r\n[14] Thome, J.R. Engineering Data BookIII, by Wolverin tube, Inc.\r\n(2004-2006)","publisher":"World Academy of Science, Engineering and Technology","index":"Open Science Index 45, 2010"}