Drying physical principles

For the following discussion, we will chose the method of freeze-concentration, as it combines well with the ensuing freeze drying process. A solution of fmctose in water will be selected as a practical example for illuminating the physical principles. 

Wetting is an important aspect of the SDR. If the disk is not wetted then dry spots are created and rivulets are formed, which significantly reduce the transport rates achieved on the disk. Hartley and Murgatroyd provided a list of theoretical models for calculating the wetting film for liquid flows under gravity. The equations derived for these models were based on physical principles rather than empirical data but have compared favorably with experimental results. Because... 

The industrial separators may be divided, according to physical principles, into three main groups as follows mechanical separators (dry or wet), electrostatic precipitators, and industrial filters. 

Third, several important chemical and physical principles are involved in the various modules that constitute lithography, covering preparation of the lithographic substrates (be they lithographic plates or silicon wafers), coating and deposition of resist solutions on appropriate substrates affording thin dry films, exposure of the dry films to actinic radiation, thermal processing of the exposed films, development of the exposed and baked films to afford the... 

Azeotropes. One solvent may form azeotropes with another solvent due to molecular association. This physical principle can be exploited in several ways. The most important in solvent applications is the possibility of reducing the boiling temperature (some azeotropes have lower boiling point) therefore an applied product such as a coating may lose its solvents and dry faster. The formation of such azeotrope also lowers flash point by which it increases hazards in product use. The formation of an azeotrope is frequently used to remove water from a material or a solvent. It affects the results of a distillation since azeotrope formation makes it difficult to obtain pme components from a mixture by distillation. Azeotrope formation can be suppressed by lowering the boiling point (distillation under vacuum). One benefit of azeotropic distillation is the reduction in the heat required to evaporate solvents. 

Borisov Yu Ya, Gynkina NM. Acoustic drying. In Rosenberg LD, ed. Physical Principles of Ultrasonic Technology. Vol. 2. New York Plenum Press, 1973, pp 381-473. 

In industrial and also in culinary practice, methods based on physical principles are widely used in addition to these chemical methods of food preservation. Of these, it is primarily food preservation by heat treatment (pasteurisation and sterilisation), cold (chilling and freezing), drying (dehydration), irradiation, and more recently by high pressure, which attract the most attention. 

Sections should be cut dry, and then picked up with a sable brush and put down carefully so that the broadest part of the roll just touches the surface of a small pool of glycerol on a microscope slide. If, now, the microscope slide be warmed, either on a hot plate set at a low temperature (say 150 °C) or above a low Bunsen flame, then as the thermoplastic softens the surface tension forces will pull the section down into the surface and render it completely flat. Rarely can a problem have been so efficiently solved by the simple application of physical principles. 

Principles of the methods employed to sterilize pharmaceutical products are described in Chapter 20. The British Pharmacopoeia (1993) recommends autoclaving and filtration as suitable methods applicable to aqueous liquids, and dry heat for non-aqueous and dry sohd preparatiorrs. The choice is determined largely by the ability of the formulation and container to withstand the physical stresses apphed by moist heat... 

The adventitious discovery, in prehistory, of the analgesic soporific and the euphoriant properties of the dried sap from the flower bulb of the poppy, papaver somnifemm, has been treated too often elsewhere to warrant repetition. By the nineteenth century organic chemistry had advanced far enough so that the active principle from opium had been isolated, purified, and crystallized. Increasing clinical use of this compound, morphine (1-1), and its naturally occurring methyl ether codeine (1-2) disclosed a host of side effects, the most daunting of which was, and stUl is, these compounds propensity for inducing physical dependence. 

For the structural analysis of cyclic fatty acid derivatives (polymerized drying oils, copolymerization products of fatty oils with various hydrocarbons), in principle the same graphical methods can be developed as have been described for the investigation of hydrocarbon mixtures. However, the construction of useful graphical representations is hampered by the fact that reliable data on physical constants are restricted to the normal saturated fatty acids and their methyl and ethyl esters the synthesis of pure unsaturated fatty acids is already extremely difficult, to say nothing of more complicated cyclic or branched compounds. 

Liquid infiltration into dry porous materials occurs due to capillary action. The mechanism of infiltrating liquids into porous bodies has been studied by many researches in the fields of soil physics, chemistry, powder technology and powder metallurgy [Carman, 1956 Semlak Rhines, 1958]. However, the processes and kinetics of liquid infiltration into a powdered preform are rather complex and have not been completely understood. Based on Darcy s fundamental principle and the Kozeny-Carman equation, Semlak Rhines (1958) and Yokota et al. (1980) have developed infiltration rate equations for porous glass and metal bodies. These rate equations can be used to describe the kinetics of liquid infiltration in porous ceramics preforms, but... 

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