摘要:

ABSTRACTNatural convection heat transfer was investigated between aqueous solutions of sodium carboxymethylcellulose (modeled as power law fluids) and a mushroom shaped particle, under transient conditions, with various initial temperature differences. Convective heat transfer coefficients (h) were observed to decrease over time due to thermal equilibration. the average value of h was significantly higher for heating (75 to 310 w/m2‐C) than for cooling (22 to 153 w/m2. C), and decreased with increasing viscosity (CMC concentration). For the lower viscosity ranges, h increased significantly with increasing initial temperature difference. Correlations were developed between Nusselt number and generalized Rayleigh and Fourier number

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1990.tb00062.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTEdible coatings with low potassium sorbate permeability could be used to increase the microbial stability of food surfaces. However, such coatings could induce anaerobic food conditions if their oxygen permeability were low. the oxygen permeability of an edible emulsion film (average thickness, 55 μm), composed of methylcellulose and palmitic acid (weight ratio of 3:1), was evaluated at 24°C, atmospheric pressure, and at different percentages of relative humidity (RH). RH values in the 0–57% range had no significant effect on oxygen transmission rate (OTR); calculated OTR values ranged from 660 to 740 mL O2(STP)/m224h atm. At 79% RH, the OTR doubled to 1,500 mL O2(STP)/m224h atm. This effect correlated well with the moisture isotherm for the film which showed a low moisture content in the 0–57% RH range and a rapid increase at higher RH values. OTR values, particularly at high relative humidity, indicate no risk of developing anaerobic conditions on the food su

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1990.tb00063.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTA sensor has been developed for continuous measurements of the removal of deposit. the sensor, which was based on heat transfer measurements, was also able to measure the wall shear stress.The device was used to study the mechanical effect during cleaning. It was found that the removal rate of deposits, at a surface, could be scaled by the mean wall shear stress. Measurements were performed under both laminar and turbulent flow conditions. the turbulent fluctuations did not influence the removal rate.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1990.tb00064.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTA sensitivity analysis of a one‐dimensional heat transfer model for a heat‐hold‐cool aseptic system of food products containing particulates was completed for eighteen different design, product, and process control parameters. All of the parameters, except the direct effect of the fluid specific heat, were determined to be statistically significant in influencing the accumulated lethality of the processes. the most influential parameters were surface heat transfer coefficient in the hold tube at the fluid‐particle interface, exit temperature of the fluid from the heater, initial temperature, holding tube size, and holding tube‐U value. the process/product‐related parameters that are significant in the establishement of a process are: particle diameter, surface heat transfer coefficient in the hold tube at the fluid‐particle interface, thermal properties of the fluid and particulates, maximum heater velocity ratio, maximum hold tube velocity ratio, surface heat transfer coefficient in the heater at the fluid‐particle interface, product flow rate, and particle

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1990.tb00065.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTUsing homologous series of alcohols and varing temperatures, it has been demonstrated in this study that volatility of alcohols increases upon changes in the system which decrease their solubility in the liquid. Addition of solutes has various effects on volatility, depending upon their ability to interact with water and volatiles. Surface characteristics, including the number of binding sites and surface area, significantly affect interaction. When more than one type of solids is present, alcohols preferentially adsorb to the solid with higher affinity for alcohols, until all binding sites on the solid are occupied. Silica and soy protein increase solubility of alcohols in water by adsorbing them through hydrophobic association and/or hydrogen bonds. Sodium silicoaluminate, xanthan gum and, to some extent, maltodextrin show less interaction with alcohols than with water.

ISSN:0145-8876    

DOI:10.1111/j.1745-4530.1990.tb00066.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY