Why are the thin tubes of air conditioners called liquid tubes

What is an air conditioner liquid pipe?
The inner and outer units of the air conditioner are connected by two copper pipes, the thick one is the air pipe and the thin one is the liquid pipe.

Why is the air-conditioning liquid pipe thin and the air pipe thick?
The thickness of the liquid pipe and the thin air pipe is determined by the working principle of the air-conditioning refrigerant.
Air conditioning refrigeration principle:
Similar to the refrigerator, the gaseous working medium (Freon or substitute) is pressurized by the compressor to become liquid, and the heat is released through the radiator (when the compressor is working, the outside of the refrigerator is heated, and the outdoor unit of the air conditioner blows hot air). ). The liquid working medium flows into the condenser, the pressure is reduced and evaporates into a gaseous state, and at the same time absorbs a large amount of heat to make the refrigerator and air conditioner refrigerate.
The compressor is not compressed air, but a compressed refrigerant - Freon (R18 or R22, generally R22).
Freon is gaseous at normal temperature and pressure. When compressed by an external force (compressor), it becomes a high-pressure liquid state. When liquid Freon is re-gasified into a gaseous state, it will absorb a lot of heat, thereby reducing the outside temperature. This is the air conditioner. Refrigeration principle.
Why are the thin tubes of air conditioners called liquid tubes?
Because when the refrigerant is compressed by the compressor, the high-temperature and high-pressure gas comes out, and then passes through the condenser of the outer unit to dissipate heat, and then turns into a low-pressure and low-temperature liquid from the thin tube into the inner unit to blow out cold air; when heating, the refrigerant is compressed. After the compressor is compressed, the high-temperature and high-pressure gas comes out, and then enters the internal machine from the thick pipe, and the hot air is blown out by the internal machine fan to cool down, and then becomes liquid and then returns to the compressor from the thin pipe, so the thin pipe is also called the liquid pipe.

Air conditioners add fluid is to increase the tube or small tube
Fill the large pipe with refrigerant. For the air conditioning unit, the specification of the low-pressure system pipeline is larger than that of the high-pressure system pipeline, that is to say, the thick pipe is the low-pressure pipe. The filling of refrigerant is achieved by the pressure difference between the refrigerant tank and the refrigerant in the system pipeline. Therefore, it is necessary to add refrigerant from the needle valve on the low-pressure pipeline shut-off valve.