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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Measurement and Study on Drying Shrinkage Characteristic of Tobacco Lamina Based on Computer Vision

International audienceAccurate evaluation of shrinkage characteristic for tobacco lamina during drying process is important for optimizing tobacco primary process. The present work developed a detection and characterization method of shrinkage characteristic based on computer vision. Effect of types and dimensions of tobacco lamina on the shrinkage characteristic were investigated and shrinkage rate variation at different drying stages was also analyzed by this method. The results show that percentage reduction of area, which is obtained by detecting tobacco lamina area before and after drying, can be used to reflect the shrinkage characteristic of tobacco lamina. RSD of measurement results by this method is less than 6% under test conditions. Compared with upper tobacco leaf, middle tobacco leaf shows the higher shrinkage rate of 14.3%. Dimensions of tobacco lamina also have significant effect on its shrinkage characteristic. The larger size (up 30mm mesh) tobacco lamina shows a higher shrinkage rate. Shrinkage rate of tobacco lamina is closely related to moisture content variation during drying. The shrinkage of tobacco lamina during drying mainly occurs within the moisture content range of 20% to 14%

Moisture sorption characteristics of freeze-dried human platelets*

Freeze-drying is a promising method for a long-term storage of human platelets. The moisture sorption characteristics of freeze-dried human platelets (FDHPs) were studied in this paper. The moisture sorption isotherms of FDHPs and freeze-dried lyophilization buffer (FDLB) were measured at 4, 25, and 37 °C. The experimental data were fitted to Brunauer-Emmett-Teller (BET) and Guggenheim-Anderson-de Boer (GAB) equations. There were no significant statistical differences (P>0.05) between the sorption characteristics of FDHPs and FDLB at 4 and 25 °C, while FDHPs absorbed more water at 37 °C. The net isosteric heat of sorption was derived. The heat for FDHPs showed an abnormal negative value at low moisture contents when 25 and 37 °C data were used. Dynamic sorption experiments were carried out at 25 °C with environmental water activity controlled at 0.75, 0.85, and 0.90. The moisture diffusion coefficient was fitted to be 8.24×10−12 m2/s when experimental data at initial time were used. These results would be helpful in choosing prehydration and storage condition for FDHPs