Determination of Oil Circulation Ratio in Cooling Systems

Relevant for air-conditioning manufacturer, compressor manufacturer, research institutes, test bench engineering

OCR Measurement in Cooling Processes

The focus of OCR measurements is the optimization of cooling systems to increase the efficiency of the cooling process and to decrease operating costs. A main factor in terms of efficiency is the Oil Circulation Ratio (OCR). The oil in the refrigerant is essential for the lubrication of the compressor but negatively affects the thermodynamic properties of the refrigerant. Therefore the determination of the ideal mixing ratio is extremely important for maximum effectiveness with minimum wear rates of the compressor.

Anton Paar offers a wide range of customer specific solutions to develop, control and ensure the correct OCR in real time. Solutions for all established and new refrigerants are provided.

Process Sound Velocity Sensor L-Sonic 6100

For common refrigerants (chlorofluorocarbons = e.g. R134a, R1234yf, R410a, R32) a sound velocity measurement is used to determine the OCR. The sound velocity is specific to every medium and concentration.

Process Density Sensor L-Dens 7400 

Experience has shown that sound velocity does not provide reliable results for OCR measurement with CO2

For successful OCR measurements with CO2, Anton Paar develops applications with a high-pressure density sensor that can withstand up to 180 bar.


  • Real time information on oil concentration
  • Optimized measurement principles for increased test efficiency
  • Avoids human and sampling errors
  • Customer specific solutions
  • Application development for CO2 measurements

Learn more about the L-Sonic 6100

Learn more about the L-Dens 7400




Configuration for CFCs

L-Sonic 6100 version LS
Pressure sensor
Pico 3000 version AO or mPDS 5

Configuration for R744

L-Dens 7400 version HAS HP
Pressure sensor
Pico 3000 or mPDS 5

Typical working conditions CFCs

Temp. range: 20 to 65 °C
Pressure range: 0 to 30 bar
Oil concentration range: 0 to 7 %

Typical working conditions R744

Temp. range: 0 to 44 °C
Pressure range: 60 to 130 bar
Oil concentration range: 0 to 10 %

Other relevant instruments


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