1) A wall is made up of four elements, as follows: ½” wood siding R = 1.0 ½” plywood sheathing R = 0.5 3 ½” fiberglass R = 11 ½” sheetrock R = 0.5 How many Btu per hour would be transferred through a 10 sq. foot section of the wall if the outside is 40ºF colder than the inside. In which direction (in or out) would the heat flow? (Units of R-value are ft2-hr-ºF/Btu) 2) (a) Calculate the hourly heating load of a house in which all exterior surfaces have a thermal resistance of R= 20 ft2hoF/Btu, the inside temperature is 70oF, and the outside temperature is 0oF. The dimensions of the house are 40ft x 40ft x 40ft. (b) calculate the calculation of the infiltration heat loss. Assume K-value of air exchanges per hour is 2. (HINT: Lecture 10, Slide 25 & 32-34) 3) An 80 kg man is standing on ice that can withstand 5000 Pa of pressure. a) If he is standing, having a total contact area from both feet of 0.1 m2. How much pressure is the applying, and will he fall through the ice? b) Suppose the man lies down on the ice, increasing his contact area to 0.8 m2. How much pressure is the applying, and will he fall through the ice?
Energy transfer
The flow of energy from one region to another region is referred to as energy transfer. Since energy is quantitative; it must be transferred to a body or a material to work or to heat the system.
Molar Specific Heat
Heat capacity is the amount of heat energy absorbed or released by a chemical substance per the change in temperature of that substance. The change in heat is also called enthalpy. The SI unit of heat capacity is Joules per Kelvin, which is (J K-1)
Thermal Properties of Matter
Thermal energy is described as one of the form of heat energy which flows from one body of higher temperature to the other with the lower temperature when these two bodies are placed in contact to each other. Heat is described as the form of energy which is transferred between the two systems or in between the systems and their surrounding by the virtue of difference in temperature. Calorimetry is that branch of science which helps in measuring the changes which are taking place in the heat energy of a given body.
1) A wall is made up of four elements, as follows:
| ½” wood siding | R = 1.0 |
| ½” plywood sheathing | R = 0.5 |
| 3 ½” fiberglass | R = 11 |
| ½” sheetrock | R = 0.5 |
How many Btu per hour would be transferred through a 10 sq. foot section of the wall if the outside is 40ºF colder than the inside. In which direction (in or out) would the heat flow? (Units of R-value are ft2-hr-ºF/Btu)
2) (a) Calculate the hourly heating load of a house in which all exterior surfaces have a thermal resistance of R= 20 ft2hoF/Btu, the inside temperature is 70oF, and the outside temperature is 0oF. The dimensions of the house are 40ft x 40ft x 40ft. (b) calculate the calculation of the infiltration heat loss. Assume K-value of air exchanges per hour is 2. (HINT: Lecture 10, Slide 25 & 32-34)
3) An 80 kg man is standing on ice that can withstand 5000 Pa of pressure.
a) If he is standing, having a total contact area from both feet of 0.1 m2. How much pressure is the applying, and will he fall through the ice?
b) Suppose the man lies down on the ice, increasing his contact area to 0.8 m2. How much pressure is the applying, and will he fall through the ice?
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