Development of lumped-parameters models for the thermal evaluation and air quality in aircrafts

Abstract

Aircraft cabins are a challenging category when dealing with thermal comfort and air quality inside means of transport. Two simplified dynamic models are developed. The first one is a lumped resistance-capacitance model for assessing the cabin thermal behaviour during the cruise phase. The fuselage is discretised into several slices and each one is represented through an RC network consisting of eleven nodes, thirteen resistances and three capacities. A thermal balance equation is set for each node and the linear system is solved to calculate the air and surfaces’ temperatures. The model is validated by comparison with literature experimental data from ten flights, showing that the predicted temperatures agree well with the measured ones, presenting an RMSE of 1.5, 1.9 and 1.3 °C for cabin air, floor and cabin internal surface temperatures, respectively. A sensitivity analysis is conducted, for which the internal air temperature increases linearly with occupancy rate and decreases with cruising altitude. Secondly, an air quality model is proposed to evaluate the presence of pollutants inside the cabin, based on a simple concentration balance equation. Ventilation flow rates recommended from standards and a recirculation rate below 50-60% should be set to maintain acceptable CO2 levels.