Automotive Air Conditioning heat get inside a vehicle

Air Conditioning
heat get inside a vehicle

Air Conditioning car

What is heat?

To understand just how an air conditioning system works, we must first understand the
nature of heat.

For a simple definition we may say that heat is energy. The meshing of gears, the turning of
wheels cause friction which results in heat. Combustion (fire) gives off heat. The burning of
sun radiates heat to the earth's surface.
Heat in the correct amount will provide life and comfort. Heat in either extreme - extreme to
much or to little - will be uncomfortable.
The control of temperature means the control of comfort.
Air conditioning is a method of controlling heat.
When is heat hot?
When is heat cold?
All substances contain heat. Something "feels" hot when it is warmer than our body
temperature. When something contains less heat than our bodies, we say it feels cold!
Cold is merely the removal of some heat.
Science tells us that a measurement called "Absolute Zero" is the point at which all heat is
removed from an object (approximately -273 C). Any substance above this absolute zero
temperature retains some heat.
All substances contain heat:
The average person requires a comfort zone of approximately 21 C to 26 C, with a relative humidity of 45 to 50%. In this temperature and humidity range, we feel most comfortable. All objects within this  same range are comfortable to touch. As the temperature of anything goes
above or below this range, we think of it as HOT or COLD.
feel most comfortable

Heat measurement:

A temperature reading gives us the heat intensity of a substance and not the actual quantity of heat. Heat quantity is measured in "KILOCLORIES" (KCAL's). One KCAL is the amount of heat required to raise the temperature of one kilogram of water one degree Celsius (at sea level). This quantity measurement is used in air conditioning to describe heat transferduring changes of state.

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 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 (90 C) coffee into the cooler (25 C) surrounding air. In time the coffee will reach the temperature of the surrounding air.

heat transfer

How does heat get inside a vehicle?
When a car is driven or parked in the sun, heat enters the vehicle from many sources.
These sources include:
- Ambient air
- Sunlight
- Engine heat
- Road heat
- Transmission
- Exhaust heat
All of these and other miscellaneous heat sources, increase the air temperature within the
vehicle. In a high ambient temperature situation, (e.g. on a 37 C day), the interior of a
vehicle left standing in the sun with windows closed could reach 65 - 70 C!

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