I understand how we heat them, by putting energy into the system. but how do we use the energy to cool them down?
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Heat always transfers and disperses through many different processes in an attempt to reach equilibrium, that is everything and everywhere being the same temperature. This is of course not possible, at least not in a time frame smaller than billions and billions of years and does not concern us.
The point is that heat transfers, and while the thermal conductivity of different materials may be different and some may be very good insulators, ultimately it’s not possible to entirely trap and maintain heat so it will eventually cool down. This is a process that we can accelerate and take advantage of to cool down objects or spaces for various reasons.
In the case of refrigerators or air conditioners the main way this is achieved is through essentially displacing the heat elsewhere, and if you do this fast enough you can lower the temperature faster than it can heat up from ambient temperature. Of course all that means that the heat has to go somewhere which is why the back of refridgerators or the external A/C units blow out fairly hot air when in operation, much warmer than the ambient air.
“Heat” is the **quantity** of thermal energy in a substance. “Temperature” is the **concentration** of thermal energy in that same substance.
Heat moves from regions of high concentration to regions of lower concentration. From high temperature to lower temperature.
If you keep the same amount of energy in a substance, but reduce the volume that substance occupies, the concentration of thermal energy increases. The temperature rises, even though no thermal energy was added or removed.
If you keep the same amount of thermal energy in the substance, but increase the volume the substance occupies, you decrease the temperature.
To cool something, you first increase the pressure of a gas. Temperature rises. Heat flows from high temperature gas to ambient temperature environment, until the compressed gas temperature equalizes with ambient. Now you put the compressed gas next to the object you want to cool, and you expand it. Temperature falls. The heat from the object flows into the gas, lowering the temperature of the object, and raising the temperature of the gas.
Now take the gas away from the object, and compress the gas again, repeating the cycle.
“Heat” is the **quantity** of thermal energy in a substance. “Temperature” is the **concentration** of thermal energy in that same substance.
Heat moves from regions of high concentration to regions of lower concentration. From high temperature to lower temperature.
If you keep the same amount of energy in a substance, but reduce the volume that substance occupies, the concentration of thermal energy increases. The temperature rises, even though no thermal energy was added or removed.
If you keep the same amount of thermal energy in the substance, but increase the volume the substance occupies, you decrease the temperature.
To cool something, you first increase the pressure of a gas. Temperature rises. Heat flows from high temperature gas to ambient temperature environment, until the compressed gas temperature equalizes with ambient. Now you put the compressed gas next to the object you want to cool, and you expand it. Temperature falls. The heat from the object flows into the gas, lowering the temperature of the object, and raising the temperature of the gas.
Now take the gas away from the object, and compress the gas again, repeating the cycle.
“Heat” is the **quantity** of thermal energy in a substance. “Temperature” is the **concentration** of thermal energy in that same substance.
Heat moves from regions of high concentration to regions of lower concentration. From high temperature to lower temperature.
If you keep the same amount of energy in a substance, but reduce the volume that substance occupies, the concentration of thermal energy increases. The temperature rises, even though no thermal energy was added or removed.
If you keep the same amount of thermal energy in the substance, but increase the volume the substance occupies, you decrease the temperature.
To cool something, you first increase the pressure of a gas. Temperature rises. Heat flows from high temperature gas to ambient temperature environment, until the compressed gas temperature equalizes with ambient. Now you put the compressed gas next to the object you want to cool, and you expand it. Temperature falls. The heat from the object flows into the gas, lowering the temperature of the object, and raising the temperature of the gas.
Now take the gas away from the object, and compress the gas again, repeating the cycle.
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