• Marco Bonifaccino

How car Air Conditioning works and removes the heat

Updated: May 10

Your car Air Conditioning (A/C) system works just like a refrigerator or home air conditioning units. The purpose of the system is to remove hot air and moisture from the passenger compartment to make you more comfortable while you drive. The basic concept is that a chemical called refrigerant loops from the evaporator (5) to the condenser (2) where it releases the heat into the atmosphere outside.

What causes heat to move?

Heat always moves from the hotter objects to the colder one. Whenever there is a transfer difference between two objects, the heat energy will be transferred from the warmer object to the cooler one until both objects stabilize at the same temperature.

This is known as the Fourier's law (or law of heat transfer), and is the basis of air conditioning operation.

When a hot cup of coffee is set aside for some time, it becomes cold. Heat moves out of the hot 194°F (90°C) coffee into the cooler 77°F (25°C) surrounding air. In time the coffee will reach the temperature of the surrounding air.

How the air conditioner works to remove the heat.

Air conditioners do not cool hot air. Rather, they remove heat to create cooler air temperatures. Although it may feel as though the air blowing out your vents has been through a freezer, in fact, the heat has simply been removed.

Here’s how an air conditioner works to remove heat (Air recirculation on).

  1. Air conditioning removes heat from the vehicle by drawing air with excess heat in through a vent. Here, an evaporator (5) coil absorbs heat from the air. When it meets the air, the liquid refrigerant inside the heat-absorbing evaporator coil changes into a gas and continues to the compressor (1).

  2. The compressor then tightly squeezes this gas form between two solid objects, which raises the pressure of the refrigerant, and so temperature according to the Ideal gas law, and readies it for the condenser (2).

  3. The refrigerant next travels to the condenser, where it meets the outside air. The outside air absorbs the heat, lowering the temperature and causing the refrigerant to shift from a vapor state to a liquid.

  4. Cooled, liquid refrigerant then cycles back through the expansion valve (4) which regulates its flow back into the evaporator to repeat the cooling process.

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