HEAT TRANSFER
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Elaboration of Syllabus – HEAT TRANSFER
Steady state and temperature gradient. Thermal conductivity; co-efficient of thermal conductivity, Use of good and poor conductors, Searle’s experiment, (Lee’s Disc method is not required). Convection with examples.
Black body is now called ideal or cavity radiator and black body radiation is
cavity radiation; Stefan’s law is now known as Stefan Boltzmann law as Boltzmann derived it theoretically. There is multiplicity of technical terms related to thermal radiation – radiant intensity I(T) for total radiant power (energy radiated/second) per unit area of the surface, in W/m2 , I (T) =σ T4
; dimension and SI unit of σ. For practical radiators I =∈. σ T4 where ∈ (dimension less) is called emissivity of the surface material; ∈=1 for ideal radiators. The Spectral radiancy R(λ). I (T)= ∫ R(λ)dλ.
Graph of R(λ) vs λ for different temperatures. Area under the graph is I(T). The λ corresponding to maximum value of R is called λmax; decreases with increase in temperature.
Wien’s displacement law; Stefan’s law and Newton’s law of cooling. [Deductions from Stefan’s law not necessary]. Greenhouse effect – self explanatory
