Core process

Heat Transfer

5 self-contained study topics — notes, diagrams, formulas, and worked examples for exams and GATE.

Topics

Conduction Through Walls
Steady conduction is solved with Fourier’s law recast as a thermal-resistance network: the heat rate equals the overall temperature difference divided by the sum of series resistances L/(kA) for walls or ln(r₂/r₁)/(2πkL) for pipes.
$Thermal resistance R_{th} = \frac{L}{(kA)} for plane wall$
Convective Heat Transfer Coefficients
Convective heat transfer is characterised by the coefficient h in Newton’s law of cooling; h is found from dimensionless correlations of the form Nu = C·Re^m·Pr^n after checking whether the flow is laminar or turbulent.
$Pr = \mu \frac{Cp}{k}; Re = \rho V \frac{D}{\mu}$
Boiling and Condensation
Boiling and condensation involve phase change at a surface, giving very high coefficients; the boiling curve maps heat flux against wall superheat through nucleate, transition and film regimes, with the critical heat flux marking the dangerous peak.
Radiation Exchange
Radiative exchange scales with the fourth power of absolute temperature and with emissivity; net transfer between grey surfaces combines their emissivities and the geometric view factor that fixes what fraction of one surface’s radiation reaches the other.
$\sigma = 5.67 \times 10^{-8} \frac{W}{m^{2}}K^{4}$
Heat Exchanger Design
Exchanger duty is q = UA·ΔT_lm, where the log-mean temperature difference accounts for the varying gap along the length and U bundles all film, wall and fouling resistances in series; when outlet temperatures are unknown you switch to the effectiveness-NTU method.
$F correction factor for multi-pass shell-and-tube: q = U A F \Delta T_{lm}$