Chapter 5: Thermodynamics - Homework
 
1. Explain the Celsius and Fahrenheit temperature scales. The Celsius scale is based on water. The Fahrenheit scale is considered to be more human related, i.e. body temperature and the temperate sea water freezes.
 
2. Explain the difference between heat and temperature. Heat is the amount of energy a substance has. Temperature is how hot or cold something is.
 
3. What is R-Value used for? R-value is the measure of the thermal resistivity of the material.
 
4. Can you have ice and water at the same temperature? Explain. Yes, they are just in different phases and the water has more heat then the ice.
 
5. Explain how a heat pump functions. A liquid is evaporated forming a cold gas. The gas absorbs heat from the outside environment. The warmer gas is compressed thus raising the temperature of the gas. The gas loses heat to the interior of the home and becomes a liquid and the cycle repeats.
 
6. If you have 100 grams of water and the temperature is raised from 15oC to 85oC. How much heat was gained by the water?

 
7. Convert 30oF to Celsius
 
8. Convert 30oC to Fahrenheit.
 
9. What is a phase change? Phase change is changing from one state of matter to another, which requires either releasing energy or absorbing.
 
10. What is Conduction? Heat transfer in a solid.
 
11. What is Convection? Heat transfer in a liquid or gas.
 
12. What is Radiation (as it refers to heat)? Heat transfer via electromagnetic energy.
 
13. What is a heating degree day? The difference between the average daily temperature and 65oF, when the average temperature is less than 65oF.
 
14. What is a cooling degree day? The difference between the average daily temperature and 65oF, when the average temperature is greater than 65oF.
 
15. How many heating degree days do we have in Kentucky? About 5000.
 

16. If a wall is composed of Insulated Aluminum siding, plywood (.75"), fiberglass insulation (3") and wallboard (.5"). Assume the wind on the outside is 5 mph and 0 on the inside. The wall is 22 ft long and 8 ft high. Determine the R-value of the wall. From your value for question 15 determine the heat lost by the wall in one heating season.

A=176ft2
Rvalue = 16.16