Friction losses in valves and fittings for power-law fluids

Data on pressure drop were obtained in stainless steel, sanitary fittings and valves during laminar and turbulent flow of aqueous solutions of sucrose and xanthan gum, which were selected as model fluids. The rheological properties of these solutions were determined and the power-law model provided the best fit for experimental data. Friction losses were measured in fully and partially open butterfly and plug valves, bends and unions. Values of loss coefficients (k f) were calculated and correlated as a function of the generalized Reynolds number by the two-k method. The model adjustment was satisfactory and was better in the laminar flow range (0.976 < r² < 0.999) than in the turbulent flow range (0.774 < r² < 0.989). In order to test the adequacy of the results for predicting loss coefficients during flow of real fluids, experiments were conducted with coffee extract. Comparison between experimental and predicted loss coefficients showed very good agreement.455463Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Application of compression test in analysis of mechanical and color changes in grapefruit juice powder as related to glass transition and water activity

Physicochemical and structural properties of grapefruit juice powder were studied as affected by water activity. Powdered juice was obtained by freeze-drying and equilibrated at different water vapor pressure atmospheres in order to give samples with water activity in the range of 0-084 The mechanical properties of the powder were measured by confined compression tests and the compressed samples, which presented uniform surface and thickness, were subjected to color analysis The maximum force attained during the compression tests and the color coordinates could be quantified with good reproducibility. The results were related to water activity and to glass transition temperature The occurrence of mechanical changes in the powder was shown to precede significant color changes with increasing water activity. Considering the susceptibility to stickiness, the stability limit was observed at T-T(g) approximate to 2 degrees C, with a high degree of mechanical changes being detected at T-Tg 16 degrees C, whereas for significant color changes this critical temperature difference was around 32 degrees CAuthors thank the Ministerio de Educacion y Ciencia and the Fondo Europeo de Desarrollo Regional (FEDER) for the financial support throughout the projects AGL2002-01793 and AGL 200505994. Vania R. N. Tells acknowledges the support of the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) as an external grant (Proc. BEX 4452/06-2).Telis, VRN.; Martínez Navarrete, N. (2010). Application of compression test in analysis of mechanical and color changes in grapefruit juice powder as related to glass transition and water activity. Food Science and Technology. 43(5):744-751. https://doi.org/10.1016/j.lwt.2009.12.007S74475143

Friction losses in valves and fittings for power-law fluids

Data on pressure drop were obtained in stainless steel, sanitary fittings and valves during laminar and turbulent flow of aqueous solutions of sucrose and xanthan gum, which were selected as model fluids. The rheological properties of these solutions were determined and the power-law model provided the best fit for experimental data. Friction losses were measured in fully and partially open butterfly and plug valves, bends and unions. Values of loss coefficients (k f) were calculated and correlated as a function of the generalized Reynolds number by the two-k method. The model adjustment was satisfactory and was better in the laminar flow range (0.976 < r² < 0.999) than in the turbulent flow range (0.774 < r² < 0.989). In order to test the adequacy of the results for predicting loss coefficients during flow of real fluids, experiments were conducted with coffee extract. Comparison between experimental and predicted loss coefficients showed very good agreement.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Forced Convection To Laminar Flow Of Liquid Egg Yolk In Circular And Annular Ducts

The steady-state heat transfer in laminar flow of liquid egg yolk-an important pseudoplastic fluid food-in circular and concentric annular ducts was experimentally investigated. The average convection heat transfer coefficients, determined by measuring temperatures before and after heating sections with constant temperatures at the tube wall, were used to obtain simple new empirical expressions to estimate the Nusselt numbers for fully established flows at the thermal entrance of the considered geometries. The comparisons with existing correlations for Newtonian and non-Newtonian fluids resulted in excellent agreement. The main contribution of this work is to supply practical and easily applicable correlations, which are, especially for the case of annulus, rather scarce and extensively required in the design of heat transfer operations dealing with similar shear-thinning products. 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K., Bhatti, M. S. Laminar convective heat transfer in ducts, in: S. akaç, R. K. Shah, W. Aung (Eds.), Handbook of single-phase convective heat transfer, John Wiley & Sons, New York, p. 3.1-3.137 (1987)Shah, R.K., London, A.L., (1978) Laminar flow forced convection in ducts, , Academic Press, New YorkShih, Y.P., Tsou, J.D., Extended leveque solutions for heat-transfer to power law fluids in laminar-flow in a pipe (1978) Chemical Engineering Journal and the Biochemical Engineering Journal, 15 (1), p. 55Sieder, E.N., Tate, G.E., Heat transfer and pressure drop of liquids in tubes (1936) Industrial and Engineering Chemistry, 28, p. 1429Skelland, A.H., Asymptotic rates of heat or mass transfer in non-Newtonian laminar flow (1967) Industrial & Engineering Chemistry Fundamentals, 6 (1), p. 148Tanaka, M., Mitsuishi, N., Non-Newtonian laminar heat transfer in concentric annuli (1975) Heat Transfer Japanese Research, 4, p. 26Telis-Romero, J., Cabral, R.A.F., Gabas, A.L., Telis, V.R.N., Rheological properties and fluid dynamics of coffee extract (2001) Journal of Food Process Engineering, 24 (4), p. 217Telis-Romero, J.T., Polizelli, M.A., Gabas, A.L., Telis, V.R.N., Friction Losses in Valves and Fittings for Viscoplastics Fluids (2005) Canadian Journal of Chemical Engineering, 83, p. 181Telis-Romero, J., Thomaz, C.E.P., Bernardi, M., Telis, V.R.N., Gabas, A.L., Rheological properties and fluid dynamics of egg yolk (2006) Journal of Food Engineering, 74, p. 191Trombetta, M.L., Laminar forced convection in eccentric annuli (1971) International Journal of Heat and Mass Transfer, 14 (8), p. 1161Vick, B., Ozisik, M.N., Effects of axial conduction and convective boundary-conditions in slug flow inside a circular tube (1981) Journal of Heat Transfer-Transactions of the Asme, 103 (3), p. 43