Answer:
The effective overall heat transfer coefficient for the combination, [tex]U = 0.19 Btu/hr-ft^2 -F[/tex]
Explanation:
According to the question, the total area includes the areas of the wall, window and door.
Total area, A = 100 * 10 = 1000 ft²
Area of the window, [tex]A_{wind} = 80 ft^2[/tex]
Area of the door, [tex]A_{d} = 8 * 2.5 = 20 ft^2[/tex]
Area of the wall, [tex]A_{wall} = A - (A_{d} + A_{wind} )[/tex]
[tex]A_{wall} = 1000 - ( 80 + 20)\\A_{wall} = 900 ft^2[/tex]
Heat transfer coefficients:
For wall, [tex]h_{wall} = 0.2Btu/hr-ft^2-F[/tex]
For window, [tex]h_{wind} = 0.1Btu/hr-ft^2-F[/tex]
For door, [tex]h_{d} = 0.1Btu/hr-ft^2-F[/tex]
To get the overall heat - transfer coefficient for the combination:
[tex]AU = A_{wall} h_{wall} + A_{wind} h_{wind} + A_{d} h_{d}\\1000U = (900*0.2) + (80*0.1) + (20*0.1)\\1000U = 190\\U = 190/1000\\U = 0.19 Btu/hr-ft^2 -F[/tex]
