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	\(2500-100,000\)