Kan-Ichi Hayakawa

Three-dimensional heat and moisture transfer with viscoelastic strain-stress formation in composite food during drying

Abstract A simulation model was developed for three-dimensional heat and moisture transfer and viscoelastic hygrostress formation in a composite body undergoing drying. In the model the chemical potential of moisture in the body was used as a mass transfer potential since different materials had different affinities to moisture. The governing equations were solved numerically by a finite element method. The model was validated experimentally through drying experiments using triply layered brick shaped samples made of the hydrates of starch granules and of 3: 1 mixture of starch granules and sucrose.

Recommended design parameters for thermal conductivity probes for nonfrozen food materials

Abstract This paper analyzes the various design parameters of the thermal conductivity (k) probe and makes design recommendations for applications for nonfrozen food materials. The k probe is a simplified application of the line-heat source theory, but this simplification contributes to the instrument error which can be minimized by paying particular attention to the size of the k probes and materials of construction. As the diameter of the k probe decreases, its accuracy increases; however, small k probes are difficult to make. Therefore, it is recommended that users design their k probes using the highest acceptable error for their intended applications.

- VISCOELASTIC STRAIN-STRESS AND HEAT/MOISTURE TRANSFER -

ABSTRACT The theoretical analysis was developed to predict the deformation characteristic of formed clay during a drying process in a ceramic production. The three dimensional strain-stress distribution as well as heat and moisture transfer in a slab shape of clay were simultaneously analyzed by a finite element method. Linear viscoelasticity was assumed for the strain-stress analysis to account the effect of creep. The calculated result agreed well with an experimental result performed for a slab clay heated by hot air flow during the preheating and constant drying rate periods. A large tensional stress, which may generate a crack, was observed initially around the surface area. It was also found that the time behavior of the volume change of the formed clay is significantly influenced on the drying conditions and/or the drying rate.

Mathematical methods for estimating proper thermal processes and their computer implementation.

Publisher Summary This chapter discusses on the mathematical methods for estimating proper thermal processes and their computer implementation. The basic principles for determining proper heat processes are described in the first section. It explains the published procedures for determining proper heat processes. The computerized estimation of heat processes is discussed at length. The chapter looks into the programs for estimating parametric values and programs for estimating heat processes without manual calculations. Mathematical procedures for heat process evaluation have been modified and improved by many research workers. Although most of the major problems were solved by these workers, further research which needs to be done in the future is discussed in this chapter.

Hygrostress-multicrack formation and propagation in cylindrical viscoelastic food undergoing heat and moisture transfer processes

Several foods stress-crack during heat and moisture transfer processes without careful process control. Since published simulation studies on stress-cracking were scarce, the present study aimed to develop and validate a model for simulating heat and moisture transfer, hygrostress crack formation and propagation in cylindrical, viscoelastic food. For this, an improved Luikovs model for heat and moisture transfer was used together with the virtual work principle of a viscoelastically deforming body, a critical tensile stress criterion for stress crack formation and a crack-tip-opening-angle criterion for stress crack propagation.

Heat Transfer During Freezing and Thawing of Foods

Publisher Summary Food engineers dealing with the freezing or defrosting of foods are often faced with the need to predict temperature history curves, and freezing or thawing times. Such knowledge may help them in the design and optimization of equipment, the evaluation of storage and handling practices, and the prediction of quality losses during storage. Common practice, however, is to rely mainly on empirical experiences for these predictions. This is due to the limited availability of theoretical formulas that can be applied properly for such complicated systems as foodstuffs; the fact that all available formulas are, at best, taken as approximations and correction factors must be employed. The marked variability in the thermal properties of individual foodstuffs resulting from varietal differences, agricultural practices, seasonal variations, growth locations, and the likes. As these parameters appear in the theoretical formulas, their availability becomes of major importance. This chapter summarizes the available procedures for predicting temperature distribution and temperature history curves, and for predicting the freezing or thawing times of frozen foods.

Thermodynamically Interactive Heat and Mass Transfer Coupled With Shrinkage and Chemical Reactions

A new mathematical model was developed for simulating simultaneous heat and moisture transfer in an anisotropic body with chemical reactions and volumetric changes. This was accomplished by modifying Luikov’s model by expressing a local pressure change in terms of changes in local temperature, vaporization ratio and shrinkage. A generally applicable computer program was developed by using the developed mathematical model and by applying an alternate direction general implicit finite defference method. An overall body shape was assumed to be a body of rotation or an infinite column, both having arbitrary cross-sectional shapes. A limited parametric analysis was performed to examine the influence of selected, key physical properties on heat and moisture transfer in an oblate body.

Charts for Calculating Average Temperature of Thermally Conductive Food in a Cylindrical Can during Heat Processing

Summary A procedure was developed for calculating the average temperature of conductive food in a cylindrical can during the cooling phase of heat processing. To assist this calculation, charts were prepared by using a formula for temperature distribution in a finite cylinder. A sample calculation is given for a can of 9.09% bentonite suspension.

Heat and Moisture with Thermodynamically Interactive Fluxes and Volumetric Changes. III. Computer Simulation

A generally applicable computer program was developed for estimating transient state moisture concentration and temperature distributions and volumetric shrinkage of food undergoing drying. The program used a modified Luikov’s model and numerical solution algorithms previously developed. An overall shape of food was assumed to be a body of rotation or infinite column, both with any arbitrary cross-sectional contour. Heat and moisture transfer in a spherical sample was simulated using the developed computer program. The simulation results agreed well with published experimental data. According to additional sample simulations, convective surface mass transfer coefficient and moisture diffusivity influenced heat and moisture transfer in an oblate sample while convective surface heat transfer coefficient and Soret diffusivity did not.

A method for calculating the ratio of each possible type of triglyceride in natural fat

A generalized method for calculating the weight ratios or mole fractions of triglycerides in natural fat is developed by applying Vander Wal’s method for calculating the mole fractions. In the proposed method a generating function is introduced to calculate the mole fractions of triglycerides.