1. The performance requirements of refrigeration oil display cabinet
Frozen oil and refrigerant strong solubility, and with the refrigerant into the refrigerated display cabinet condenser and evaporator, therefore, frozen oil not only plays a role of lubrication and cooling to the moving parts, and not to the refrigeration system. Therefore, the physical, chemical and thermal properties of frozen oil shall meet the following requirements:
1. The viscosity is appropriate. Viscosity is the quantity of fluid viscosity. Viscosity is divided into two kinds: dynamic viscosity and motion viscosity. The viscosity decreases with the increase of temperature, and increases with the increase of pressure. Viscosity is a major performance indicator of frozen oil, so it is usually used to divide the brand by the value of kinematic viscosity. Different refrigerants are used to use different viscosity (label). If R12 is mutually soluble with frozen oil, the frozen oil should be diluted and the frozen oil with high viscosity should be used. The refrigeration system has low working temperature and should be used for freezing oil with low viscosity. The refrigeration system is high in temperature and should be used with high viscosity oil. The high-speed reciprocating compressor and rotary compression machine should use high - viscosity oil.
2. The turbidity point is below the evaporation temperature. There is a trace of paraffin wax in the frozen oil. When the temperature drops to a certain value, the wax begins to precipitate out, and the temperature is called a turbid point. Frozen oil cloud point must be below the evaporating temperature of refrigeration system, because of the frozen oil and refrigerant dissolve each other, and as the refrigerant cycle through the relevant part of the refrigeration system, frozen after the precipitation of paraffin oil, will be blocked parts throttle hole and narrow, or deposited on the inner surface of the evaporator coil, the heat transfer effect is poor.
3. The freezing point is low enough. When the freezing oil loses its fluidity, the temperature is called freezing point, and the freezing point is always lower than the turbidity point. Frozen oil freezing point must be low enough to R12, R22 as refrigerant compressor, its freezing oil freezing point should be less than one 30 ~ 40 ℃ respectively, a 55 c. When the refrigerant is dissolved in freezing oil, its freezing point will be reduced. Such as frozen oil into R22, its freezing point than the pure oil reduce 15 ~ 30 ℃.
4. The flash point is high enough. The lowest temperature that occurs when the freezing oil is in contact with the flame is called the flash point of the frozen oil. Frozen oil flash point should be higher than the compressor exhaust temperature of 20 ~ 30 ℃, in order to avoid freezing oil decomposition, carbon, worsen lubrication and sealing performance. Using R12 or R22 for refrigerant compressor, its freezing oil flash point should be above 160C; In the high temperature environment, such as tropical (about 50 ℃) under the use of air conditioner, the frozen oil flash point should be above 190 ℃.
5. Chemical stability is good. And frozen oil in refrigerant, metal system, if the temperature is higher, is under the catalysis of metal, will break down, polymerization, chemical reactions such as oxidation, the acid corrosion has generated. Therefore, the frozen oil with good chemical stability has low acid value. The allowable acid value of all kinds of refrigerated oil.
6. Low impurity content. Refrigerant, refrigeration oil if mixed with trace water in the solution, will accelerate the acidification of the solution, make the refrigeration system appear harmful phenomena of copper plating, and reduce the compressor motor insulation. Therefore, the water content of 1kg of frozen oil should be less than 40mg. Frozen oil in the process of production while through strict dehydration processing, but it has a strong water imbibition, therefore, to do well in the refrigeration oil storage container seal work, don't let it contact with the natural air for a long period of time. If the freezing oil contains mechanical impurities, it will accelerate the wear of the motor parts and cause the oil road to be blocked, so the frozen oil should not contain the mechanical impurities.
7. Good insulation. The motor winding of the enclosed compressor and its terminal are in direct contact with the freezing oil. Therefore, it is required to have good insulation performance. Pure frozen oil is generally good in insulating properties, but if oil contains water, dust and other impurities, its insulation performance will be reduced. The insulation of frozen oil can be represented by breakdown voltage. The breakdown voltage method is: pour the oil into a pair of 2. 5 mm clearance of glass container of electrode, the electrode increased after the power supply voltage, until the insulation of the frozen oil are destroyed and the thrum of intense, the voltage value is the breakdown voltage of oil. The breakdown voltage of the frozen oil requires above 25kV.