Two-Phase Refrigerant R-134a Void Fraction and Quality Correlation Study

Abstract

As technology continues evolving and modern aircraft continue incorporating advanced electronics, efficient thermal management systems are becoming crucially important to overcome system instabilities. To create effective thermal control systems, it is imperative to thoroughly examine and account for a variety of potential instabilities, including those likely to occur due to flow boiling. Thermal instabilities can severely damage electronics and harm the overall reliability of the aircraft. These instabilities can be described using both void fraction and quality. Electrical Capacitance Tomography (ECT) allows for the collection of capacitance data from the fluid moving through the tube. The vapor, the liquid, and the transition between the two states will have different permittivity values, depending on the state of the fluid. These permittivity values can be found and recorded by the ECT sensor and easily translated to void fraction measurements. Several existing correlations are present in literature that can be used to convert quality to void fraction, each with varying degrees of accuracy. In most cases, these correlations could not be experimentally validated with the void fractions measured by the ECT instrumentation in the system. In this paper, a review of existing correlations will be conducted, and a new, novel correlation will be developed and validated using data recorded by the ECT sensor. The results of this experiment will significantly enhance the ability of future thermal control systems to swiftly and efficiently adapt to abrupt fluctuations in the thermal loads they are required to manage.