This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Study of Flashing Flows Entering Evacuated Sampling Cylinders for Oil Circulation Rate Measurement in an Automotive Air Conditioning System
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 11, 2023 by SAE International in United States
Annotation ability available
The oil circulation rate (OCR) is a deciding factor for the performance of automotive air conditioning systems at both the system and component levels. OCR is defined as the percentage by mass of oil present in a representative sample of oil-refrigerant mixture drawn from the system at steady state. In recent years, many industries are opting for low-OCR compressors, and so the OCR values are getting smaller, making it even more important to be able to accurately measure the OCR in the system. All the different OCR measurement techniques rely on the ASHRAE Standard 41.4 for proper calibration. This standard describes OCR measurement using a sampling technique which involves connecting an evacuated sampling cylinder at the liquid line of the system at steady state to draw a sample containing the liquid mixture of refrigerant and oil. However, several factors such as orientation of sampling cylinder and valve opening speed can affect the OCR results. The flow entering the sampling cylinder initially consists of both liquid refrigerant and liquid oil. As the valve on the sampling cylinder is opened, the refrigerant undergoes flashing followed by recompression and re-condensation of vapor refrigerant, and simultaneous filling up with liquid mixture until pressure equalization between the system supply line and evacuated sampling cylinder is achieved. This two-phase, two-component, phase changing flow is complex, and for the present study, flow visualization using a high-speed camera and analytical tools are used to study the flashing flow of pure refrigerant entering an evacuated sampling cylinder. The obtained results are used to compare with those obtained with oil-refrigerant mixture to shed light on how parameters such as sampling cylinder orientation and valve opening speed can affect the measured OCR values.
CitationHaider, S., Wang, X., and Elbel, S., "Study of Flashing Flows Entering Evacuated Sampling Cylinders for Oil Circulation Rate Measurement in an Automotive Air Conditioning System," SAE Technical Paper 2023-01-0140, 2023, https://doi.org/10.4271/2023-01-0140.
- Radermacher , R. , Cremaschi , L. , and Schwentker , R.A. Modeling of Oil Retention in the Suction Line and Evaporator of Air-Conditioning Systems HVAC&R Research 12 1 2006 35 56 10.1080/10789669.2006.10391166
- Youbi-Idrissi , M. and Bonjour , J. The Effect of Oil in Refrigeration: Current Research Issues and Critical Review of Thermodynamic Aspects International Journal of Refrigeration 31 2 2008 165 179 10.1016/j.ijrefrig.2007.09.006
- Shen , B. and Groll , E.A. A Critical Review of the Influence of Lubricants on the Heat Transfer and Pressure Drop of Refrigerants, Part 1: Lubricant Influence on Pool and Flow Boiling HVAC&R Research 11 3 2005 341 359 10.1080/10789669.2005.10391142
- Liu , X. and Hrnjak , P. Oil Effects on Performance of Automobile A/C System Proceedings of the International Refrigeration and Air Conditioning Conference West Lafayette, IN, USA 2016
- Wang , X. , Haider , S.A. , Hrnjak , P. , and Elbel , S. Transient Migration of Oil at Compressor Discharge and Suction during Startup Proceedings of the International Refrigeration and Air Conditioning Conference West Lafayette, IN, USA 2022
- Wang , X. , Haider , S.A. , Hrnjak , P. , and Elbel , S. Transient Oil-Refrigerant Mixture Migration and Change of Properties at Compressor Shutdown Proceedings of the International Refrigeration and Air Conditioning Conference 2022 West Lafayette, IN, USA
- Xu , J. and Hrnjak , P. Quantification of Flow and Retention of Oil in Compressor Discharge Pipe International Journal of Refrigeration 80 2017 252 263 10.1016/j.ijrefrig.2017.05.004
- ASHRAE Standard Committee 2015
- Wujek , S.S. and Hrnjak , P. Effects of Oil on a Transcritical Carbon Dioxide Air Conditioning Systems–Some Experiences Proceedings of the International Refrigeration and Air Conditioning Conference West Lafayette, IN, USA 2006
- Haider , S.A. , Wang , X. , and Elbel , S. Oil Circulation Rate Measurements with Flow-through and Evacuated Type Sampling Cylinders Proceedings of the International Refrigeration and Air Conditioning Conference West Lafayette, IN, USA 2022
- Haider , S.A. , Wang , X. , and Elbel , S. Effects of Orientation and Valve Opening Speed on Oil Circulation Rate Measurements Using an Evacuated Type Sampling Cylinder Proceedings of the International Refrigeration and Air Conditioning Conference West Lafayette, IN, USA 2022
- Liao , Y. and Lucas , D. Computational modelling of flash boiling flows: A literature survey International Journal of Heat and Mass Transfer 111 2017 246 265 10.1016/j.ijheatmasstransfer.2017.03.121
- Pinhasi , G.A. , Ullmann , A. , and Dayan , A. Modeling of Flashing Two-Phase Flow Reviews in Chemical Engineering 21 3-4 2005 133 264 10.1515/REVCE.2005.21.3-4.133
- Inampudi , S.T. , Botticella , F. , and Elbel , S. Comparative Experimental Analysis of Different Compressor Capacity Modulation Strategies in R410A Chiller with Focus on Seasonal Performance Proceedings of the International Refrigeration and Air Conditioning Conference West Lafayette, IN, USA 2022
- AHRI Standard 2017 240
- REFPROP, NIST 2018
- Brandt , M.J. , Johnson , K.M. , Elphinston , A.J. , and Ratnayaka , D.D. Twort’s Water Supply Butterworth-Heinemann 2016 10.1016/B978-0-08-100025-0.00018-1