What does hpr mean in oil?

They must also be miscible with the refrigerant and not produce any chemical reaction that modifies the lubricating oil. Since the mixture will pass through it, it's necessary to have a freezing temperature that's much lower than the one of the evaporator.

In summary, a lubricating oil must comply with the thermal, rheological and chemical properties that not any substance can offer, in fact we must bear in mind that there is no lubricating oil that is ideal and 100% compliant with all the requirements, so When talking about a special oil due to its thermal resistance, it means that it especially meets that characteristic.

There are oils. The lubricating oils used in the fridge are made from synthetic and mineral sources.

Mineral lubricating oils can be classified by their main family of chemical compounds.

Paraffin. Naphthenic. There are aromatics

The naphthenic family have excellent dielectric behavior and are the most used in the refrigeration industry.

PONA is an analysis that can be used to find out if an oil is in this family.

The manufacturing process of a lubricating oil of mineral origin begins with the primary distillation of crude oil and goes through multiple purification processes where many unwanted chemical compounds are eliminated

If the waxes are present in the system, they will form plugs and prevent the proper operation of the system.

The aromatic family is rarely used because they are less stable and more reactive than the paraffinic family, which makes them unsuitable for use in a refrigeration system. The lubricating oils of these families are used in other industries.

Synthetic lubricating oils have some advantages over mineral oils, one of which is that they are made up of a single chemical compound with defined properties, while mineral lubricating oils are made up of a mixture of chemical compounds, where each one has different properties.

Other advantages of synthetic lubricating oils are.

Absolutely free of waxes. Lower freezing temperatures. The chemical and thermal stability is greater.

There is susceptibility with new generation refrigerants.

Synthetic lubricating oils can be used in the fridge, but not all of them can be used because they produce chemical reactions with the refrigerants that have harmful effects on the system.

The polyoilester family of synthetic lubricating oils are recommended for use in refrigerated systems.

They are good lubricating oils, but precautions must be taken because they react with water.

Mineral and synthetic lubricating oils are made by chemical reactions.

The tests are basic Some of the laboratory tests for lubricating oils are mentioned.

The freezing temperature of a lubricating oil is determined by placing a sample in a glass cylinder, surrounded by a solution of CO2 and alcohol in a thermos, and then placing it in a copper container.

As the lubricating oil mixes with the refrigerant, it will circulate throughout the system in a way that will allow it to flow at a low temperature in the compressor and a high temperature in the evaporator.

The lubricating oil should be lubricating even after mixing with a refrigerant. The capillary tube viscometer is recommended to determine the kinematic viscosity.