## 5 Conclusions
### Nomenclature  
\begin{tabular}{l l} \(k\) & Discrete-time instants. \\ \(f_{\rm s}\) & Sampling frequency. \\ \(R\) & Universal gas constant, in \({\rm J/(mol\cdot K)}\). \\ \(a\) & Duct valve opening. \\ \(k_{c}\) & Pressure loss coefficient. \\ \(T_{i}\) & Inside carriage temperature, in K. \\ \(T_{e}\) & Outside carriage temperature, in K. \\ \(T_{0}\) & Atmospheric temperature at sea level, in K. \\ \(T_{H}\) & Atmospheric temperature at altitude \(H\), in K. \\ \(P_{i}\) & Internal pressure, in Pa. \\ \(P_{e}\) & External pressure, in Pa. \\ \(P_{O}\) & Internal partial oxygen pressure, in Pa. \\ \(P_{H}\) & Atmospheric pressure at altitude \(H\), in Pa. \\ \(P_{0}\) & Atmospheric pressure at sea level, in Pa. \\ \(P_{if}\) & Internal pressure under the impact of air ducts, in Pa. \\ \(P_{ig}\) & Internal pressure under the impact of airtight gaps, in Pa. \\ \(P_{id}\) & Internal pressure under the impact of carbody deformation, in Pa. \\ \(P_{iO_{2}}\) & Internal pressure under the impact of the oxygen supply, in Pa. \\ \(P_{iT}\) & Internal pressure under the impact of temperature, in Pa. \\ \(P_{sop}\) & Internal partial oxygen pressure standard, in Pa. \\ \(n_{i}\) & Internal air polytropic index. \\ \(n_{g}\) & Leaked gas polytropic index. \\ \(n_{O}\) & Internal oxygen polytropic index. \\ \(q_{n}\) & Mass flow rate of the fresh air fan, in kg/s. \\ \(q_{f}\) & Volumetric flow rate through the fan, in m\({}^{3}\)/h. \\ \(q_{O}\) & Mass flow rate of oxygen-enriched air, in kg/s. \\ \(q_{w}\) & Mass flow rate of the exhaust fan, in kg/s. \\ \(q_{g}\) & Mass flow rate through carriage leakage gaps, in kg/s. \\ \(\rho_{i}\) & Internal air density, in kg/m\({}^{3}\). \\ \(\rho_{e}\) & External air density, in kg/m\({}^{3}\). \\ \(\rho_{O}\) & Internal oxygen concentration, in kg/m\({}^{3}\). \\ \(S\) & Equivalent leakage area of the carbody, in m\({}^{2}\). \\ \(v_{e}\) & Airflow velocity on the external side of the equivalent leakage hole, in m/s. \\ \(M_{i}\) & Average molar mass of internal air, in kg/mol. \\ \(M_{e}\) & Average molar mass of external air, in kg/mol. \\ \(M_{O}\) & Molar mass of oxygen, in kg/mol. \\ \(\theta\) & Carbody deformation coefficient. \\ \(V\) & Carriage volume, in m\({}^{3}\). \\ \(V_{0}\) & Initial carriage volume, in m\({}^{3}\). \\ \(m_{i}\) & Internal air mass, in kg. \\ \(m_{O}\) & Internal oxygen mass, in kg. \\ \(x_{g}\) & Oxygen mass fraction in infiltrated air. \\ \(x_{e}\) & Oxygen mass fraction in fresh air. \\ \(x_{i}\) & Oxygen mass fraction in exhaust air. \\ \(x_{O}\) & Oxygen mass fraction in oxygen-enriched air. \\ \(N\) & Number of passengers and crew in the carriage. \\ \(m_{r}\) & Oxygen consumption by the human body, in kg/s. \\ \(Q\) & Heat exchange in the carriage, in W. \\ \(Q_{1}\) & Heat transfer through the carbody enclosure, in W. \\ \(Q_{2}\) & Heat dissipation by occupants, in W. \\ \(Q_{3}\) & Heat dissipation from lighting and other equipment, in W. \\ \(Q_{4}\) & Heat transfer from fresh air in the air conditioning system, in W. \\ \(Q_{5}\) & Heat transfer from infiltrated air, in W. \\ \(Q_{6}\) & Heating output of the air conditioning system, in W. \\ \(\kappa\) & Heat transfer coefficient, in W/m\({}^{2}\cdot\) K. \\ \end{tabular}