Nomenclature and Units

Table 1. Notations and units
Notation Quantity Unit

\(A\)

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

Table 2. Typical values of the convection heat transfer coefficient

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

\(2500-100,000\)