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.

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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

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