Compact cooling systems are a refrigerating devices that generate low temperatures by transferring heat. For example, mini liquid chillers, portable or mobile refrigerators, and industrial dehumidifiers. Generally, a micro cooling unit consists of a miniature compressor, a condenser, an expansion valve( capillary), an evaporator, a driver board, filter dryer, and other electric refrigerated parts. The refrigerant flows and circulates through the systems, achieving phase change by absorbing heat and releasing heat repeatedly, to efficiently cool heat sources to temperatures below the surroundings or cool the hot precise equipment. This is called the cooling cycle.
Refrigeration oil is also called lubricating oil. It’s used to lubricate the sliding components in the refrigeration compressor. In the mini refrigeration compressor, the refrigeration oil is mainly used for lubrication, sealing, cooling, energy regulation, and noise reduction.
If say the role of the refrigeration compressor is similar to the human heart in compact cooling systems, then the refrigeration oil can be considered as human blood in the systems. The oil fulfills vital tasks in the air-conditioning system and other refrigeration systems. It is discharged from the mini-size compressor, traveling with the refrigerant in the micro refrigeration system.
Thus, it is imperative that the oil is miscible and fully soluble in one another at working temperatures. This provides good oil return and lubricity for the mini inverter compressor while avoiding heat transfer losses in the evaporator. The refrigeration oil needs to circulate through the cooling cycle and return to the dc compressor without building up and blocking the lines so that adequate oil is maintained inside the compressor.
Refrigeration Oil’s Benefits
In the mini refrigeration compressor, refrigerant oil mainly plays the role of lubrication, sealing, cooling, noise reduction and energy regulation.
1) Lubrication: it can lubricate the surface of moving components in the compressor, reduce resistance and friction, reduce power consumption, and extend the service life of the mini rotary compressor.
2) Cooling: it can take away the heat generated by friction on the moving surface in time to prevent the temperature rise of the compressor or the compressor from being burned out.
3) Sealing: Lubricating oil penetrates into the sealing surface of each friction part to form an oil seal, which prevents the leakage of refrigerant.
4) Reduce compressor noise: Lubricating oil constantly washes the friction surface, takes away the debris, and can reduce the wear of friction parts.
5) Energy regulation: For refrigeration compressors with an energy regulation mechanism, the pressure of refrigeration oil can be used as the power of energy regulation machinery
The refrigeration oil is completely dissolved in the refrigerant in the compact refrigeration systems and air conditioning refrigeration systems and circulates with the refrigerant in the refrigeration system.
Refrigeration Oils Requirements
Due to the different use occasions and refrigerants, the choice of refrigeration oil for refrigeration equipment is not the same. The requirements for refrigeration oil are as follows:
(1) Freezing Point. Under experimental conditions, the temperature at which the lubricating oil cools to stop flowing is called the freezing point. The freezing point of the lubricating oil used in microclimate cooling units should be as low as possible. For example, for the compressor with R134a, the point of refrigeration oil should be below -55°C. Otherwise, the circulation of the refrigerant would be affected and the flow resistance will be increased, resulting in poor heat transfer.
(2) Viscosity. The viscosity is an important parameter in the characteristics of refrigeration oil. Different types of refrigerant must be matched to different refrigeration oil. If the viscosity of the refrigeration oil is too large, the mechanical friction power, friction heat, and starting torque will increase. On the contrary, if the viscosity is too small, the required oil film can not be formed between the sliding parts, which leads to the lubrication and cooling effect cannot be achieved.
(3) Turbidity Point. The turbidity point of refrigeration oil refers to the temperature at which paraffin begins to precipitate in the frozen oil when the temperature decreases to a certain value, making the lubricating oil turbid. The turbidity point of the refrigerant oil used in micro refrigeration units should be lower than the evaporating temperature of the refrigerant, otherwise, it will cause throttle blockage or affect the heat transfer performance.
(4) Flash Point. The flash point of refrigeration oil refers to the lowest temperature at which the lubricating oil is heated until its steam comes into contact with the flame. The flash point of refrigerated oil used in micro cooling modules must be more than 15 ~ 30℃ higher than the discharge temperature, so as to avoid the combustion and coking of lubricating oil.
(5) Others such as chemical stability and oxygen resistance, moisture and mechanical impurities, and insulation properties, should be considered to ensure the system performs with reliability, safety, and efficiency.
Steps for Refilling the Refrigeration Oil?
(1) Check the brand and quality of the oil. The lubricating oil added should be of the same brand as the oil in the system, and the quality should meet the requirements of the compressor.
(2) Pour the new refrigeration oil into a clean, dry measuring cup
(3) Use a syringe to extract the oil from the cup
(4) Use the syringe to drive the oil into the compressor(As shown below)
(5) Pull out the syringe and completed the operation.
Make sure the syringe is inserted just far enough to reach the inner chamber to allow air to purge but not to contact internal electrics, which might cause damage.
Oil Type for MOIR’s miniature refrigeration compressor
MOIR engineered and manufactured a lineup of the miniature compressor to meet the growing segment market in micro cooling. The mini compressor is a new hermetic motor type micro dc compressor. It is a variable-speed dc rotary compressor driven by a controller. Designed to optimize space and weight, the miniature compressor is widely used in many small water chillers and compact and mobile air conditioning refrigeration.
MOIR compressors are designed and tested for the operation R134a refrigerants. R134a refrigerant is associated with strict requirements for the internal cleanliness of the compact cooling system. It requires the exclusive use of polyolester oil(POE) as a lubricant. The lubricating oil type recommended is POE RL-68H. This special lubricant RL-68H is compatible with the R134a refrigerant and is used for high reliability. The oil has excellent thermal stability and wears resistance properties. Other types of oil are not allowed to be added to the system.
MOIR’s Compact Cooling System
MOIR is a compact cooling systems manufacturer with decade’s experience of small-scale vapor compression refrigeration technology. Our standard cooling systems include mini water chiller modules, dc condensing units.
MOIR compressor cooling unit is a circulatory cooling subsystem. It is made up of a miniature compressor with R134a/R290 refrigerant, the smallest condenser and radiator, an evaporator (heat exchanger), a thermal expansion valve, a driver board, and other electric parts. Micro cooling systems are widely used in many active thermal management applications in compact spaces like chips and semiconductors, laser and life science, racing and motorsports, EV battery pack, personal cooling, medical and aesthetic, beverage dispenser, and other small cooling needs.
Powered by our top-efficiency compressors, our small cooling modules feature compact, lightweight, and smallest footprint advantages and perform with outstanding efficiency and reliability. This ensures an excellent combination of micro-environmental impact and maximum performance.
- Precise temperature control within ±0.1°C
- Cooling capacity varies from 100 to 1000W
- 4x to 6x more efficient than thermoelectrics
- >90,000 hours MTBF
- Customized solutions are available
- Outstanding cooling performance
- DC power produced by batteries, fuel cells, vehicle alternators, and solar panels.
Aside from the standard liquid chiller systems, we also can support and work closely with you for custom-made refrigeration solutions accordingly to your specific demand. Free free to contact us for an evaluation of your requirements and solutions.
