Nomenclature and Units

$A$

Area

$m^{2}=10^{6} \mathrm{mm}^{2}=10^{4} \mathrm{cm}^{2}$

$\rho$

Density

$k g / m^{3}=10^{3} g / c m^{3}$

$t$

Time

$S$ (second)

$T$

Temperature

$C$ (degree Celsius), $K$ (degree Kelvin)

$C_p$

Specific heat

$J / k g C=J / k g K$

$k$

Conductivity

$W / m C=W / m K$

$h$

Convection heat transfer coefficient

$W / m^{2} C=W / m^{2} K$

$q$

Rate of heat transfer

$W$

$\sigma$

Stefan Boltzmann constant

$W / m^{2} K^{4}$

$\mathcal{E}$

Emmissivity

Process

$h$ $\left(\mathrm{W} / \mathrm{m}^{2} \cdot \mathrm{K}\right)$

Free convection

Gases

$2-25$

Liquids

$50-1000$

Forced convection

Gases

$25-250$

Liquids

$100-20,000$

Convection with phase change

Boiling or condensation

$2500-100,000$