02 Pure Substances, Ideal Gases
Pure Substances¶
Graph¶
Points¶
| Point | Meaning | \(x\) |
|---|---|---|
| left(f) | compressed/subcooled liquid | N/A |
| f | saturated liquid | 0 |
| f-g | saturated liquid-vapor mixture | \(0<x<1\) |
| g | saturated vapor | 1 |
| right(g) | superheated vapor | N/A |
| c | critical point |
Terms¶
| Term | Meaning | Formula |
|---|---|---|
| \(h_\text{fg}\) | latent heat of vaporisation | \(h_g - h_f\) (or use table) |
| \(\Delta h\) | specific heat extracted | \(m \times h_\text{fg}\) |
| \(x\) | Quality Fraction | \(\frac{m_\text{vap}}{m_\text{tot}}\) |
Compressed liquid¶
Properties are independent of pressure
Therefore, at a given temperature
- \(\nu \approx \nu_f\)
- \(u \approx u_f\)
- \(h \approx h_f\)
Ideal Gases¶
\[ \begin{aligned} PV &= mRT \\ &= n R_u T \\ m &= \frac{PV}{RT} \\ \rho &= \frac{P}{RT} \\ R &= \frac{R_u}{M}, M = \text{Molar Mass (kg/mol)} \\ R_u &= 0.8314 \ \mathrm{kJ/mol \cdot K} \\ &= 8.314 \ \mathrm{J/mol \cdot K} \\ \end{aligned} \]