4.6. Discussion
The present calculation requires various empirical coefficients and properties. However, it makes the accurate estimation of drying kinetics possible with the application of simple equations, and without requiring any fitting parameters. The coefficients View the MathML source, and hsh relate to heat transfer from the dryer to products. Their values are largely dependent on the design of the dryer and the layout of the products. The values for View the MathML source and View the MathML source relate to the efficiency of the heating devices with which the freeze-dryer is equipped. Heating efficiency depends on the design of equipment. Thus, the position, material, color, etc. could all affect the values of these coefficients. If the drying chamber is large enough, the mean effect of radiative heat from the chamber wall becomes negligible, so that View the MathML source and View the MathML source have much smaller values than those used in this study. The heat transfer from the shelf to the products is reflected in the value of hsh. The arrangement of product placements (e.g. product layout on a shelf, use of plastic tray, etc.) in a dryer could be optimized by tuning these values. Higher View the MathML source, and hsh values indicate improved heat transfer, but are not always effective for reducing drying time. The calculation of the present model could assist in the estimation of the resultant efficacies against the tuning of heat transfer efficiencies.