Accumulator Sizing and Evaluation Technique Based on Theoretical Optimum System Performance 2005-01-2048
With the introduction of CO2 air conditioning systems for vehicle applications, there was a renewed requirement for improved accumulator design and understanding. A technique was needed to help size accumulators so that they are large enough to function properly but not so large to add unnecessary volume and weight to the A/C system. Also, a better technique was needed to evaluate accumulator designs. Using a clear accumulator and R134a refrigerant, tests were conducted to determine the liquid storage in the accumulator under various operating conditions. The clear accumulator also allowed analysis of several types of accumulator functional failures, such as excess liquid carryover and insufficient liquid/gas separation. An evaluation technique was developed that relied not on comparing one accumulator design to another, as has been done in the past, but rather comparing an accumulator to a system baseline without an accumulator. These no-accumulator tests gave a baseline of optimum system performance, and thus allowed accumulator designs to be compared to the “best case” scenario for a given system. The variations in charge levels between the baseline tests and accumulator tests showed the impact of the accumulator on A/C systems in terms of liquid storage requirements and required system charges. With these techniques, a sizing procedure for accumulators was proposed that can be applied to both R134a and CO2 systems.