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

Non-newtonian flow and pressure drop of pineapple juice in a plate heat exchanger

The study of non-Newtonian flow in plate heat exchangers (PHEs) is of great importance for the food industry. The objective of this work was to study the pressure drop of pineapple juice in a PHE with 50º chevron plates. Density and flow properties of pineapple juice were determined and correlated with temperature (17.4 < T < 85.8ºC) and soluble solids content (11.0 < Xs < 52.4 ºBrix). The Ostwald-de Waele (power law) model described well the rheological behavior. The friction factor for non-isothermal flow of pineapple juice in the PHE was obtained for diagonal and parallel/side flow. Experimental results were well correlated with the generalized Reynolds number (20 < Re g < 1230) and were compared with predictions from equations from the literature. The mean absolute error for pressure drop prediction was 4% for the diagonal plate and 10% for the parallel plate.(FAPESP) São Paulo Research Foundatio

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. In addition, the experimental results may support existing theoretical analyses.(CNPq) National Council for Scientific and Technological Development(FAPESP) São Paulo Research Foundatio

Rheology of acid suspensions containing cassava bagasse: Effect of biomass loading, acid content and temperature

[EN] Understanding the characterization and rheological behavior of acid suspensions of cassava bagasse provides essential information for the design of conversion processes. Samples with different cassava bagasse concentrations (0-10% w.w-1), phosphoric acid (0-10% w.w(-1)) at temperatures between 278.13 and 318.13 K were submitted to steady-state flow over a wide range of shear rates (1-265 s(-1)). The biomass particles had considerable residual starch (similar to 50% db), low lignin content and adequate particle size (<200 mu m) for the conversion process. Flow curves were well-fitted to the Herschel-Bulkley model, presenting a Newtonian domain at low solids and acid content and a non-Newtonian behavior with noticeable yield stress and shear-thinning characteristic (n < 1) at above 6% of cassava bagasse. Resistance to flow increased as the solids loading and acid content increased. Temperature dependence could be expressed as a function of an Arrhenius-type equation with good accuracy of fit. (C) 2019 Elsevier B.V. All rights reserved.The authors would like to thank Prof. Rosiane Lopes Cunha and Prof. Ana Carla Kawazoe Sato from University of Campinas (UNICAMP) for their support with particle size analyses. The authors also acknowledge the Sao Paulo Research Foundation - FAPESP (Grant number 2017/06518-2) and the Coordination for the Improvement of Higher Education Personnel -CAPES (Grant number 88881.132626/2016-01) for their financial support.Carregari-Polachini, T.; Mulet Pons, A.; Carcel, JA.; Telis Romero, J. (2019). Rheology of acid suspensions containing cassava bagasse: Effect of biomass loading, acid content and temperature. Powder Technology. 354:271-280. https://doi.org/10.1016/j.powtec.2019.05.086S27128035

Density, refractive index, apparent specific volume, and electrical conductivity of aqueous solutions of poly(ethylene glycol) 1500 at different temperatures

Thermophysical properties of aqueous solutions of poly(ethylene glycol) 1500 g·mol–1 were measured as a function of polymer concentration w=(0.05, 0.10, 0.15, 0.20 and 0.25) and temperature T/K=(288, 293, 298, 303 and 308). Aqueous systems composed of poly(ethylene glycol) are frequently used in processes involving the separation of biological compounds. The density of the solutions varied from (1001.68 to 1042.65) kg·m–3, the refractive index ranged from (1.3377 to 1.3681), the apparent specific volume was between (0.8336 and 0.8528) g·cm–3, and the electrical conductivity varied between (66.22 and 170.29) 10–3 mS·cm–1. Polynomial models for the properties as a function of temperature and poly(ethylene glycol) 1500 g·mol–1 concentration were fitted to the experimental data. Models accounting for combined effects between variables are particularly useful in industrial applications in which physical parameters must be promptly and accurately calculated.We are thankful to the Brazilian agencies CAPES, CNPq, FAPEMIG, and FAPESP for the financial support, fellowships, and grants

Air-drying of fresh and osmotically pre-treated pineapple slices: Fixed air temperature versus fixed slice temperature drying kinetics

In this investigation, the air drying characteristics of fresh and osmotically pre-treated pineapple slices in a tray dryer were studied under different operating conditions. The air velocity varied from 1.5 to 2.5 m/s and the air temperature from 40 to 70 degreesC. The analytical solution of the second Fick's law for an infinite slab was used to calculate effective diffusion coefficients and their temperature dependence could be well represented by an Arrhenius-type equation. Comparison of the results showed that the diffusion coefficients were lower for the pre-treated fruit. By means of automatic control, it was possible to obtain drying curves under conditions of constant product temperature, which showed to be an alternative to reduce the drying time of pineapple slices