1 Aircraft Cooling 陈江平 上海交通大学制冷研究所 Simple Gas Refrigeration Cycle Compressor 1st step : The hot air coming from the engine bleed air system first goes through a flow control valve whose main function is to adjust the airflow to the required level necessary to cool the cabin. 2nd step : This air then flows into the primary heat exchanger cooled down during flight by ram air. Air temperature and pressure are consequently decreased. This ram air is generated by the aircraft flight speed and is driven into the primary heat exchanger by a special scoop. This scoop has often a variable geometry electrically driven depending on of the flight phase (take off, cruise, etc.). 5 th step : The " dried air" can now enter the turbine stage, the final step of the travel! In a turbine the air expands and its temperature and pressure are decreased. The temperature is very close to zero degrees celsius or even negative. 3 rd step : The air now enters the air cycle machine compressor stage where the pressure is raised, As well as the temperature. The air enters into the main heat exchanger cooled by ram air.The air temperature is decreased. 4 th step : All the next operations will be dedicated to water extraction to avoid icing before the air enters the turbine stage where the temperature is going well below zero degrees celsius at the outlet. Now the air goes across a reheater, then in a condenser where water is converted from vapor to thin water drops. These drops are finally removed from the airflow in the water extractor. Cycle Calculation