How Does The Refrigerant Move And Achieve Cooling/Heating Inside of The Copper Pipes?

Many people may ask a question that seems simple: Why can the air conditioner cool once it connects to the power supply? And what happened inside of the copper pipe?

The answer is the refrigerant circulation. The key point of cooling is not the cold air itself, but the continuous flow, phase transition, and energy transportation process of the refrigerant inside the copper pipes.

I. An air conditioner is not to "create cold" but to "transfer heat."

Here is a common misconception to clarify: the basis of the air conditioner is not to produce cooling but to remove heat from interior to exterior. While the "deliveryman" is the refrigerant that flows inside the copper pipe. The tube is just the vessel; what actually contributes to the cooling process is the absorption and releasing of the energy at the different states of the refrigerant.

II. Why is "copper" pipe necessarily needed?

Being selected as the piping material of the cooling system benefits from its three advantages:

Good thermal conductivity: it conduces to the heat exchange of refrigerant and air.

High-temperature and corrosion resistance: it adapts to the frequent exchange of the refrigerant in high- and low-pressure conditions.

High reprocessability with reliable hermeticity: it is easy to weld and bend, reducing the risk of leakage.

III. 4-steps circulation of the refrigerant in copper pipe

1. Compressing: convert low-pressure gas into high-pressure, high-temperature gas

At a state of low pressure and low temperature, the refrigerant is sucked in by the compressor; after being compressed, it becomes high pressure and high temperature. At this time, the temperature of the refrigerant is much hotter than outside of the room.

2. Condensing: release heat outside, convert refrigerant from gas to liquid

The high-pressure, high-temperature refrigerant (gas state) goes into the condenser (copper pipe + fins), changing from a gas state into a liquid state and releasing heat to the air outside through copper pipes.

The key point here is the process from gas to liquid will release much heat.

3. Throttling: sudden decrease of pressure, preparing for the heat absorption

Being condensed, the refrigerant becomes high pressure with a medium temperature but in a liquid state.

After passing through a small part (capillary or electronic expansion valve), the refrigerant pressure decreases suddenly, and together with the temperature, it becomes a low-temperature, low-pressure state mixed with gas and liquid.

4. Evaporating: absorb heat inside, create "cooling"

The low-pressure, low-temperature refrigerant (gas state) goes into the evaporator (copper pipe + fins). At this time the indoor temperature is higher than the refrigerant, which absorbs heat from the refrigerant through copper pipes and changes from a liquid state into a gaseous state.

Evaporating is the process of absorbing heat, so that's why the indoor air has been cooled.

IV. Why is the phase transition so important to the refrigerant?

If the refrigerant uses normal liquid or gas, then the cooling efficiency will be very low.

Absorbing or releasing a large amount of potential heat during the phase transition is the biggest value for the refrigerant. With the same temperature difference, it will transfer more heat than normal substances.

That's why, by flowing backwards and forwards in the copper pipe, a little refrigerant could cool and heat the whole room.

V. Heat exchange efficiency depends on the design of copper deeply

Whether the refrigerant could work efficiently, it not only depends on itself but also on if:

The copper pipe size is reasonable;

The piping length is suitable;

The fins structure and the distance between pipes;

The inside surface of the copper pipe is clean and oil-free;

Those details will directly affect the cooling speed, COP/EER, systematic stability, and lifespan.