Chapter 5 Numerical Methods in Heat Conduction 5-114EThe roof of a house initially at a uniform temperature is subjected to convection and radiation on both sides. The temperatures of the inner and outer surfaces of the roof at 6 am in the morning as well as the average rate of heat transfer through the roof during that night are to be determined. Assumptions 1Heat transfer is one-dimensional since the roof is large relative to its thickness. 2 Thermal properties, heat transfer coefficients, and the indoor temperatures are constant. 3 Radiation heat transfer is significant. 4 The outdoor temperature remains constant in the 4-h blocks. 5 The given time step Δt = 5 min is less than the critical time step so that the stability criteria is satisfied. PropertiesThe conductivity and diffusivity are given to k = 0.81 Btu/h.ft.°F and . The emissivity of both surfaces of the concrete roof is 0.9. α=×−74 106.
This is the end of the preview. Sign up
access the rest of the document.
This note was uploaded on 01/22/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.