Lesson 5.3 - More Cooling Technologies

Did you ever think about how a refrigerator or air conditioner works?  It is an interesting technology that is similar to how your body keeps cool on a hot day. 

Read Keeping it Cool on page 101 in your textbook to learn more about refrigeration technologies and how they work. Then, answer the following.

Question 1. What is "cooling by evaporation"?

Question 2. How does the perspiration on your body keep you cool?

The next six questions are about refrigerators.

Question 3. What is the name of the fluid used?         

Question 4. What is the state of the coolant that is pumped into the inside of the refrigerator?  

Question 5. What is the state of the coolant that leaves the inside of the refrigerator and travels to the compressor? 

Question 6. What is the purpose of the compressor?

Question 7. Why are the cooling coils hot when the refrigerator is working?

Question 8. The coolant evaporates when it is inside the refrigerator.  How is this possible if the inside of the refrigerator is cold?  

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. What is "cooling by evaporation"?

Cooling by evaporation describes cooling systems such as your body, refrigerators, and air conditioners, which use the evaporation of a liquid to remove heat.  
In the case of refrigerators, a coolant is used to accomplish the removal of heat from the inside of the refrigerator and transfer it to the air in the room.  In the case of air conditioners, the coolant is used to accomplish the removal of heat from the room (or house or car) to the air outside the house or car.  In both cases, the coolant evaporates to transfer the heat. 

Question 2. How does the perspiration on your body keep you cool?

In the case of your body, perspiration (water) produced by your body evaporates from your skin and uses body heat to evaporate.  This results in heat being transferred from your body to the surroundings.

Question 3. What is the name of the fluid used?  

The name of the fluid used in a refrigerator is "coolant".  

Question 4. What is the state of the coolant that is pumped into the inside of the refrigerator?

The coolant that is pumped into the inside of the refrigerator is a liquid.

Question 5. What is the state of the coolant that leaves the inside of the refrigerator and travels to the compressor? 

The coolant that leaves the inside of the refrigerator and travels to the compressor is a gas.

Question 6. What is the purpose of the compressor? 

The purpose of the compressor is to force the gaseous coolant to be converted to a liquid.

Question 7. Why are the cooling coils hot when the refrigerator is working?

The cooling coils are hot when the refrigerator is working because the hot liquid coolant is transferring heat to the coils.

Question 8. The coolant evaporates when it is inside the refrigerator.  How is this possible if the inside of the refrigerator is cold?

The coolant has a very low boiling point (the temperature at which a liquid becomes a gas).  The boiling point of some coolants can be as low as -30°C or more.  Therefore, the liquid coolant evaporates easily even in very cold freezers.    


Go to the next page to check your understanding of this lesson.