cooling systems

the refrigerant

The key to how a refrigerator or other cooling system works is the refrigerant. A refrigerant is a substance such as FreonTM that has a low boiling point and changes between liquid and gaseous states as it passes through the refrigerator. As a liquid, the refrigerant absorbs thermal energy from the cool air inside the refrigerator and changes to a gas. As a gas, it transfers thermal energy to the warm air outside the refrigerator and changes back to a liquid. Work is done by a refrigerator to move the refrigerant through the different components of the refrigerator.

how a refrigerator works

A refrigerator must do work to reverse the normal direction of thermal energy flow. Work involves the use of force to move something, and doing work takes energy. In a refrigerator, the energy is usually provided by electricity. You can read in detail in the Figure 1.1 how a refrigerator does its work.

purpose of a cooling system

A refrigerator is an example of a cooling system. Another example is an air conditioner. The purpose of any cooling system is to transfer thermal energy in order to keep things cool. A refrigerator, for example, transfers thermal energy from the cool air inside the refrigerator to the warm air in the kitchen. If youve ever noticed how warm the back of a running refrigerator gets, then you know that it releases a lot of thermal energy into the room. Q: Thermal energy always moves from a warmer area to a cooler area. How can thermal energy move from the cooler air inside a refrigerator to the warmer air in a room? A: The answer is work.

instructional diagrams

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questions

work as defined in physics always involves

``````a) force.

b) motion.

c) energy.

-->  d) all of the above
``````

most cooling systems get energy from electricity.

``````-->  a. true

b. false
``````

in a cooling system, the refrigerant

``````a) has a high boiling point.

-->  b) absorbs thermal energy from air inside the refrigerator.

c) pumps cool air into the refrigerator.

d) two of the above
``````

the refrigerant changes between solid and liquid states as it passes through the refrigerator.

``````a. true

-->  b. false
``````

as a liquid the refrigerant transfers thermal energy to the outside air.

``````a. true

-->  b. false
``````

diagram questions

No diagram questions associated with this lesson