Radiation, heat transfer

In conduction, heat is conducted by the transfer of energy of motion between adjacent molecules in a liquid, gas, or solid. In a gas, atoms transfer energy to one another through molecular collisions. In metallic solids, the process of energy transfer via free electrons is also important. In convection, heat is transferred by bulk transport and mixing of macroscopic fluid elements. Recall that there can be forced convection, where the fluid is forced to flow via mechanical means, or natural (free) convection, where density differences cause fluid elements to flow. Since convection is found only in fluids, we will deal with it on only a limited basis. Radiation differs from conduction and convection in that no medium is needed for its propagation. As a result, the form of Eq. (4.1) is inappropriate for describing radiative heat transfer. Radiation is... 

Variables that regulate gaseous heat transfer radiation are (1) blanket thickness, (2) average temperature of the complete blanket including flame, if any, and (3) concentration of triatomic molecules (principally H2O and CO2). 

Na temperature (K) Convection heat transfer Radiation heat trasfer Total heat transfer... 

Heat conduction, convection, boiling heat transfer, radiation, transient heat transfer, forced flow in pipes and packed beds, mass transfer by diffusion, and diffusion in porous solids. 

There is, of course, still another heat transfer situation, namely, radiative heat transfer. Radiation has no parallel process in terms of mass transfer. 

The third mode of heat transfer, radiation, does not depend on any medium for its transmission. In fact, it takes place most freely when there is a perfect vacuum between the emitter and the receiver of sueh energy. This is proved daily by the transfer of energy from the sun to the earth across the intervening spaee. 

Many investigators have attempted to explain the effects of humidity on drying rates and the existence of inversion temperatures. The explanations are usually based on changes that occur in convective heat transfer, radiation heat transfer, and mass transfer as the humidity and temperature of the gas stream change. 

Convection heat transfer Radiation heat transfer... 

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