Thermal performance improvement of an airline trolley for meal service

This paper deals with the thermal performance improvement of an airplane “trolley” for the meal service. These trolleys are commonly refrigerated by the sublimation of a carbon dioxide mass. The standard trolley performance has been evaluated by an experimental analysis and an overall heat transfer coefficient of 1.75 W/m2 K has been determined in standard operative conditions. The experimental results have been used to design a trolley prototype with ducts for the cold CO2 vapours distribution. The prototype trolley has reduced the food temperature progressive heating and its vertical gradient. A numerical analysis of different trolley configurations has been carried out with an original mathematical model based on a lumped capacitance scheme. An explicit finite difference method has been used to approximate the heat transfer differential equations. A good accordance between numerical simulation results and experimental data has been observed both in standard and in prototype trolley, with errors lower than 0.4%. An accurate CFD analysis of the mass flow rate distribution in the ducts has been carried out in order to evaluate the real distribution and the local velocity of the cold vapours. A feasibility study of the application of thermoelectric cooling system to the trolley has been shown.