Moisture distribution

Initial moisture distribution refers to the moisture distribution throughout a sohd at the start of diying. 

The diffusion equation for the falling-rate drying period for a slab can be derived from the diffusion equation if one assumes that the surface is diy or at an equilibrium moisture content and that the initial moisture distribution is uniform. For these conditions, the following equation is obtained ... 

Estimating Minimum Sample Quantity for Moisture Measurement Estimates of material quantity for testing moisture content depend on mechanisms of moisture distribution in the material. Moisture is physically retained on particle surfaces, chemically adsorbed on surfaces and within pores of particulate solids, and contained as an internal constituent of solids. Significant internal moisture is most often encountered in organic and agricultural source materials. 

Sample quantity to estimate moisture for specific material is influenced to various levels of significance by properties such as particle-size range as well as relative amounts or moisture distributed among denoted forms of retention. Practical sample size estimates require background knowledge of parameters derived from experience for specific materials. More detailed examination of moisture-sampling aspects is provided in reference texts (Pitard). 

Age appears to improve the flowability of certain materials. This is probably the result of particle-surface oxidation, more even moisture distribution, and the rounding of particle corners caused by handhng. 

A diagnosis of possible damage should be made before beginning repairs with other construction measures [48,49]. There should be a checklist [48] of the important corrosion parameters and the types of corrosion effects to be expected. Of special importance are investigations of the quality of the concrete (strength, type of cement, water/cement ratio, cement content), the depth of carbonization, concentration profile of chloride ions, moisture distribution, and the situation regarding cracks and displacements. The extent of corrosion attack is determined visually. Later the likelihood of corrosion can be assessed using the above data. 

Fig. 4.7.8 Moisture distribution in lasagna three sheets. The image data at one time point pasta as a function of distance from the surface is shown by the insert. The lighter gray is to the center (0.1 cm). The moisture profiles directly proportional to moisture content and are extracted from the central sheet of a set of occurs at the edge of the pasta sheet.

McCarthy, K.L., Gonzalez, J.J., and McCarthy, M.J. 2002. Changes in moisture distribution in lasagna pasta post cooking. J. Food Sci. 67, 1785-1789. 

Effect of particle size. Reducing the particle size in the bed will reduce the size of the pores and the waists, and will increase the entry suction potential of the waists. This increase means that the percentage variation in suction potentials with depth is reduced, and the moisture distribution is more uniform with small particles. 

Oliver, T. R. and Newitt, D. M. Trans. Inst. Chem. Eng. 27 (1949) 9. The mechanism of drying of solids. Part II. The measurement of suction potentials and moisture distribution in drying granular solids. 

In addition to substantial differences in the sorption behavior of products, the moisture distribution in each vial of one charge must be considered when the SD process is developed. Pikal and Shaw [1.59] studied this distribution in dextran 40, human serum albumin (HSA), bovin somatotropin (BST) and glycine. Thirty vials where filled with 10 or 20 mm cake thickness, loaded on shelves at 5 °C, cooled to -40 °C and frozen in 30-45 min. Tc was determined for all products as >-12 °C. In Table 1.10.6 the water content of four products is shown in four different positions... 

Fig. 101.2. Moisture distribution inside the described rubber stoppers that were autoclaved at 121 °C for 30 min and then dried at 100 °C for different times (Figure 7 from [1.180])...

We have performed experiments on fired-clay bricks, because they show almost no adsorption of ions at the pore wall. As an example of a typical experiment, we first discuss the results for a 3 M NaCl solution. A few representative moisture profiles are shown in figure 3. This figure shows that the moisture profiles are nearly flat, which indicates that the moisture distribution within the sample remains homogeneous during this evaporation experiment, i.e., up... 

Assuming a uniform distribution of moisture content in the initial state, i.e. 0(r. t) t=o 6o, we find the following solution for moisture distribution in the cylinder... 

The basic statement of this paper is that the magnitude of the drying induced stresses depends on the moisture distribution. The greater the non-uniformity in the distribution, the greater stresses arise in the dried body. 

This chapter is a continuation of the preceding one. Herein we shall consider the moisture-distribution in packings under various natural conditions. The laws discussed have an important bearing on soil-moisture studies, particularly capillarity. 

Buckingham showed that the relation between p and the moisture-content Mc could be ascertained from measurement of the equilibrium moisture distribution (which is very slowly attained and never certain) in a vertical column of soil, whose lower end was in water and upper end protected from evaporation. Consider the work required to move a small mass of water from x to x + dx, the capillary potentials being and ( p + (b p/bx)dx), respectively. The total work done against capillary potential is therefore... 

Studies in the physical properties of soil. V. The hysteresis effect in capillary properties, and the modes of moisture distribution associated therewith. Ibid., 20 97-116. 

Dolby, R.M. 1965. Changes in moisture distribution caused by partial reworking of butter shortly after churning. J. Dairy Res. 32, 263-267. 

Muller, L.L. 1952. A method for determining the moisture distribution in butter and a review of its applications. Aust. J. Dairy Technol. 7, 44-51. 

Because there is such a wide selection available, rational choice of the necessary excipients and their concentration is required. Consideration must also be given to cost, reliability, availability, and international acceptability. Although generally considered inert, formulation incompatibility of excipients is also necessary. Lactose, for example, can react with primary and secondary amines via its aldehyde group by Maillaird condensation reaction [6], and calcium carbonate is incompatible with acids due to acid-base chemical reaction and with tetracyclines due to complexation. Additionally, excipients can contribute to the instability of the active substance through moisture distribution. 

Barrett, A., Cardelo, A., Maguire, P., and Peleg, M. (2005). Moisture distribution and textural changes in stored model sandwiches. J. Texture Stud., 36, 569-589. 

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