Origin of Heat Transfer. Particular Laws

In Section 1.1 we classified the problems of mechanics, extended this classification to thermal problems, and distinguished between thermodynamically determined and undetermined problems. Then we stated the need for particular laws of heat transfer for 

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That is, the heat flux is constant at any cross section of the plate. However, for the size of a heat transfer device, say for a heater providing this flux through the walls of a room to be heated, we need the specific value of this constant. Thermodynamics is silent to this need, The attempt to find an answer for this need is the origin of (conduction) heat transfer. Since the statement of our example specifies the temperatures of two surfaces, we need a relation between heat flow and temperature, Q = f(T), which is phenomenologically provided by heat transfer. Observations show that any relation of this nature is dependent on the medium it applies to and, consequently, is a particular law. The remainder of this section is devoted to particular laws of heat transfer. We begin with the particular law associated with our illustrative example. 

Structural features of disperse systems, in particular the existence of the electrical double layer (EDL), are responsible for a number of peculiar phenomena related to heat and mass transfer and electric current propagation in such systems. The description of electromagnetic radiation propagation is also included in this chapter. These features are utilized in numerous practical applications and underlie methods used to study disperse systems. These methods include particle size distribution analysis, studies of the surface structure and of near-surface layers, the structure of the EDL, etc. In the most general way the most transfer phenomena can be described by the laws of irreversible thermodynamics, which allow one to carry out a systematic investigation of different fluxes that originate as a result of the action of various generalized forces. 

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