What is an oil separator?
The function of the oil separator is to separate the lubricating oil in the high-pressure steam discharged from the refrigeration compressor to ensure the safe and efficient operation of the device. According to the oil separation principle of reducing the airflow speed and changing the airflow direction, the oil particles in the high-pressure steam are separated under the action of gravity. Generally, when the air velocity is below 1 m/s, the oil particles with a diameter of more than 0.2mm in the steam can be separated. The commonly used oil separator has four kinds of washing type, centrifugal type, packing type and filtration type.
An oil separator is installed between the compressor outlet and the condenser inlet.
Through the separation, the heat transfer effect in the condenser and the evaporator is improved.
The oil separator is more important for systems with poor miscibility between lubricant and working medium.
2. Working principle
The simple working principle of the oil separator: the high-pressure gas (gaseous working medium and lubricating oil) from the compressor enters the oil separator, enters the guide vanes of the oil separator, and flows spirally along the guide vanes, relying on centrifugal force and gravity, Separate the lubricating oil from the working medium gas and flow down along the inner wall of the cylinder. The working medium gas is led out of the oil separator from the central pipe through the multi-empty baffle. The separated lubricating oil is concentrated in the lower part of the oil separator and can be discharged regularly, or the floating ball valve can be used to automatically return the lubricating oil to the crankcase of the compressor. The flow velocity in the centrifugal swirl channel is recommended to be: ammonia 10-25 m/s, freon 20-20 m/s.
In the vapor compression refrigeration system, the compressed ammonia vapor (or Freon vapor) is in a superheated state of high pressure and high temperature. Because it is discharged when the flow rate is fast and the temperature is high. Part of the lubricating oil on the cylinder wall is inevitably discharged into oil vapor and oil droplet particles together with refrigerant vapor due to high temperature. And the higher the exhaust temperature and the faster the flow rate, the more lubricating oil is discharged. Filter oil separator Filter oil separator is used in Freon refrigeration system, often called Freon oil separator.
Filter-type oil separator: When the high-pressure refrigerant gas discharged from the compressor enters the separator, due to the large flow cross section, the gas flow rate suddenly decreases and changes direction, plus the filtering effect of several layers of metal wire mesh during the intake, that is, the mixing The lubricating oil in the gas refrigerant is separated and dripped to gather at the bottom of the container. When the amount of accumulated lubricating oil reaches a certain height, it returns to the compressor crankcase through the automatic oil return valve. In normal operation, due to the intermittent work of the float valve, the return pipe is hot and cold, the pipe is hot when the oil is returned, and the pipe is cold when the oil is not returned. If the oil return pipe has been cold or hot, this indicates that the float valve has failed and must be overhauled. Manual oil return valve can be used for oil return during overhaul. This kind of oil separator is simple in structure, easy to manufacture, and widely used, but the oil separation effect is not as good as the filler type.
Centrifugal oil separator: The centrifugal oil separator has a good oil separation effect and is suitable for large refrigeration systems. The exhaust gas of the compressor enters the cylinder along the tangential direction through the inlet pipe of the oil separator, and then rotates at a high speed along the spiral guide vane. Flow from top to bottom. By centrifugal force, the oil droplets with high density in the exhaust gas are separated on the cylinder wall, flow down along the wall and deposit at the bottom of the cylinder. The steam is led out through the perforated plate in the outlet pipe in the center of the cylinder. A floating ball valve is installed on the side of the cylinder. When the oil level rises to the upper limit, the lubricating oil opens the valve core through the floating ball valve and automatically discharges oil to the compressor crankcase or oil collector. Some are also provided with a cooling water jacket outside the oil separator, so that the mixed vapor is cooled by the cooling water in it and further separated by reducing the flow rate and changing the flow direction.