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Refrigerant and Lubricant Distribution in MAC System
Abstract:
This paper presents experimental results for refrigerant and
lubricant mass distribution in a typical automotive A/C (MAC)
system.
Experiments were conducted by closing valves located at the
inlet and outlet of each component after reaching steady state,
isolating the refrigerant and lubricant in each component.
Refrigerant mass is recovered in a separate vessel using liquid
nitrogen to reduce refrigerant vapor pressure to near vacuum. The
overall weight is determined within ±1% after the separation of
refrigerant and lubricant. The mass of lubricant is determined by
using three different techniques: Remove and Weigh, Mix and Sample,
and Flushing. The total mass of lubricant in the system is
determined with ±2.5% uncertainty on average. R134a and R1234yf are
used with PAG 46 oil as working fluid at different Oil Circulation
Ratio (OCR), ranging from 2% to 4%. Experiments are conducted in
two standard testing conditions: I35 and L35 (SAE Standard
J2765).
R134a and R1234yf exhibit similar results in terms of
refrigerant and lubricant retention. Higher mass flow rate does not
significantly change the refrigerant distribution, but a lower
lubricant retention in the evaporator is observed. It is found that
only about a quarter of the total mass of lubricant resides in the
compressor.