Lesson 2.5 - Controlling Heat Transfer

The average home has numerous devices made to keep things hot or cold.  The refrigerator, freezer, vacuum bottles, coolers, insulated lunch bags, and coffee mugs are a few of these devices.  Do you think a vacuum bottle is a simple technology? 

Read page 117 to find out. Then, answer these questions.

Question 1. Why is a vacuum bottle given that name? 

Question 2. How is heat transfer by conduction reduced in a vacuum bottle? 

Question 3. How is heat transfer by convection reduced in a vacuum bottle? 

Question 4. What is the purpose of the outer plastic case in a vacuum bottle? 

Question 5. Have ever seen a cooler that has a silver lining?  What type of heat transfer does the silver lining reduce?

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. Why is a vacuum bottle given that name? 

A vacuum bottle is given that name because of the partial vacuum between the two layers of glass.  You may be more familiar with the name Thermos bottle, which is a brand name.  Thermos was one of the first manufacturers of the vacuum bottle, and the brand name became synonymous with the type of insulated bottle.

Question 2. How is heat transfer by conduction reduced in a vacuum bottle? 

Heat transfer by conduction is reduced by the double glass walls of the bottle.  Because the glass walls do not touch each other, conduction is not possible.

Question 3. How is heat transfer by convection reduced in a vacuum bottle? 

Heat transfer by convection is reduced by the partial vacuum between the double glass walls of the bottle.

Question 4. What is the purpose of the outer plastic case in a vacuum bottle?

The outer plastic case protects the glass bottle from breaking easily.  The vacuum bottle can withstand minor bumps and falls because of the outer plastic cover.  Without the plastic cover, the glass bottle would break easily.

Question 5. Have ever seen a cooler that has a silver lining?  What type of heat transfer does the silver lining reduce? 

You may have seen a cooler like the one in the photograph.  The silver lining prevents heat transfer by radiation.

 


Go to the next page to continue Lesson .