Chapter 3 Steady Heat Conduction3-33ETwo of the walls of a house have no windows while the other two walls have 4 windows each. The ratio of heat transfer through the walls with and without windows is to be determined. Assumptions1Heat transfer through the walls and the windows is steady and one-dimensional. 2 Thermal conductivities are constant. 3 Any direct radiation gain or loss through the windows is negligible. 4 Heat transfer coefficients are constant and uniform over the entire surface. PropertiesThe thermal conductivity of the glass is given to be kglass= 0.45 Btu/h.ft⋅°F. The R-value of the wall is given to be 19 h.ft2⋅°F/Btu. Analysis The thermal resistances through the wall without windows are 2m480ft)ft)(4012(==AF/Btuh0411417.000052.003958.00010417.0F/Btuh00052.0)ft480(F).Btu/h.ft4(11F/Btuh03958.0)m480(F/Btuhft19F/Btuh0010417.0)ft480(F).Btu/h.ft2(111,2222wall22°⋅=++=++=°⋅=°==°⋅=°==°⋅=°==owallitotalooiiRRRRAhRkALR
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