Investigation of a Cooling System for A Hybrid Airplane

摘要

Airplane cooling process can be performed with the help of two different techniques. One is global cooling system and the other is local cooling system. The goal of present paper is to investigate both cooling systems which may be good candidates for a future hybrid airplane. In the parametric study of global cooling section, the present research determines the parameters which affect air mass flow rate required to provide the necessary cooling for the electrical components necessary to make a hybrid plane a reality. The analysis is performed for a cooling process based on an open cycle Reverse Brayton cycle or at times called an air refrigeration system. The main components of the cooling system will be a compressor, a heat exchanger and a turbine. Outside air will be drawn and pressurized to a certain pressure using a compressor, and the compressed air will be forced through a heat exchanger to reduce its temperature as low as possible to provide necessary cooling. After that, the air will expand through an expansion device (most cases a turbine) to reduce pressure and temperature to a cycle minimum. Finally, the processed air will now be available to cool the electrical components. We will analyze the above-mentioned options to determine the most economical and or feasible systems by comparing the processed air efficiency with the ram air that may also be used for cooling purposes. The novelty of the present work lies on the concept that, the cooling fluid is air and does not have a weight penalty for the airplane. The later section we discuss an example of a local cooling system. A classic local cooling technique discussed is based on a heat pipe technology. Theoretically, heat pipes can transport heat from a heat source and release it to an ambient heat sink. The paper investigates the thermal performance of thermosiphons of different percentage fills. By detecting various thermal parameters of the manufactured thermosiphons, a general relation between the thermal performance and the percentage fill is drawn. Thermal parameters analyzed include thermal resistance, heat transfer coefficient, and Nusselt number. The present paper shows that as the amount of working fluid increases in a heat pipe, the thermal performance improves till it reaches a limit at 50% fill. As the percentage fill increases beyond 50%, the thermal performance of a thermosiphon remains constant.