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The total rate of heat transfer between the hot and cold fluids passing through a plate heat exchanger may be expressed as: Q = UA∆Tm where U is the Overall heat transfer coefficient, A is the total plate area, and ∆Tm is the Log mean temperature difference. U is dependent upon the heat transfer coefficients in the hot and cold streams. [2]
Plate heat exchangers also differ in the types of plates that are used, and in the configurations of those plates. Some plates may be stamped with "chevron", dimpled, or other patterns, where others may have machined fins and/or grooves. When compared to shell and tube exchangers, the stacked-plate arrangement typically has lower volume and cost.
Convection, especially Rayleigh–Bénard convection, where the convecting fluid is contained by two rigid horizontal plates, is a convenient example of a pattern-forming system. When heat is fed into the system from one direction (usually below), at small values it merely diffuses ( conducts ) from below upward, without causing fluid flow.
A plate-fin heat exchanger is made of layers of corrugated sheets separated by flat metal plates, typically aluminium, to create a series of finned chambers. Separate hot and cold fluid streams flow through alternating layers of the heat exchanger and are enclosed at the edges by side bars. Principal Components of a Plate Fin Heat Exchanger
The theoretical plate concept was also adapted for chromatographic processes by Martin and Synge. [6] The IUPAC's Gold Book provides a definition of the number of theoretical plates in a chromatography column. [7] The same equation applies in chromatography processes as for the packed bed processes, namely:
[2] Solutions of the heat equation are characterized by a gradual smoothing of the initial temperature distribution by the flow of heat from warmer to colder areas of an object. Generally, many different states and starting conditions will tend toward the same stable equilibrium. As a consequence, to reverse the solution and conclude something ...
When used domestically, such as with fondue, a food warmer may simply be a small vessel containing food upon a trivet which contains a heat source such as a flame or electric element. Some food cookers can then, in essence, become food warmers as they use a reduced heat to maintain a serving temperature. [1] Electric rice cookers do this ...
A hot plate or hotplate is a heated flat surface on a stove or electric cooker on which food may be cooked. [3] It comprises a heated top which is flat and usually circular, and may be made of metal, ceramic, or heat-resistant glass, with resistive wire forming a heating element fitted underneath and a thermostat to control the temperature.