In-situ Charge Determination for Vapor Cycle Systems in Aircraft (Postprint)

The Air Force Research Laboratory AFRL, in cooperation with the University of Dayton Research Institute UDRI and Fairchild Controls Corporation, is operating an in-house advanced vapor compression refrigeration cycle system VCS test rig known as ToTEMS Two-Phase Thermal Energy Management System. This test rig is dedicated to the study and development of VCS control and operation in support of the Energy Optimized Aircraft EOA initiative and the Integrated Vehicle ENergy Technology INVENT program. Previous papers on ToTEMS have discussed the hardware setup and some of the preliminary data collected from the system, as well as the first steps towards developing an optimum-seeking control scheme. A key goal of the ToTEMS program is to reduce the risk associated with operating VCS in the dynamic aircraft environment. One of the key questions regarding the operability of VCS in aircraft which will be addressed is the in-situ measurement of refrigerant charge within the VCS system. Several potential methods of determining whether an appropriate charge of refrigerant exists will be discussed. An appropriate charge level is one which enables safe and efficient operation of the VCS over its designed operating envelop.