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04.10.16

With LiquiSonic® to the optimum oil circulation ratio

For the lubrication of compressors in air-conditioning systems, refrigerant oils circulate in the refrigeration cycle, however, they reduce the cooling effectiveness. Therefore, continuous monitoring of the oil content is especially important in the development of air-conditioning systems in order to determine the optimum oil circulation ratio (OCR) that depends on the used refrigerant, compressor and process conditions. The concentration measurement of oil in the refrigerant places high demands on the analysis. On the one hand, there are high pressures, which may be up to 150 bar in case of CO2. On the other hand, the refrigerant is a gas at ambient pressure, which makes manual sampling and offline analysis almost impossible.

With the LiquiSonic® OCR analyzer by SensoTech, specifically designed for refrigerant applications, the oil circulation ratio in the refrigerant can be monitored online and directly in the process using sonic velocity measurement. Due to the chemical and physical properties of refrigerants, sonic velocity measurement is ideal for determining the concentration. The LiquiSonic® sensor is installed in the pipeline and combined with a pressure transducer. Additionally, two Pt1000 temperature probes are integrated in the sensor, so that from the values sonic velocity, temperature and pressure the temperature- and pressure-compensated oil concentration can be calculated in real time. The measurement accuracy is ± 0.1% m and the sensors are completely maintenance-free due to the robust design.

At temperatures between -30 °C (-20 °F) and 120 °C (250 °F), the sensors can be used in oil/refrigerant mixtures such as polyester oils (POE), polyalkylene (PAG), polyalphaolefins (PAO), hydrofluorocarbons (HFCs) R134a, 1234yf, carbon dioxide R744 or ammonia R717 in various industries like automotive or building air-conditioning. The LiquiSonic® controller displays and stores the real-time information. Via 4-20 mA signal, digital outputs, serial interfaces, fieldbus or Ethernet, the controller can be integrated into the network and control system.

Download PDF: Application report "Oil in refrigerant"