1. a brick wall has a total area of 8m^2 of which 2m^2 are windows. The U-values are0.95w/m^2oC for the brickwork and 2.8w/m^2oC for the windows. Calculate the average U-value for the wall.
2. Calaulate the U-value of a cavity wall with a 105mm thick brick leaf, a 50mm unventilated cavity, then a 100mm aerated concrete block inner leaf with a 15mm layer of lightweight plaster. Thermal conductivities in w/m^2oC are brickwork 0.84, aerated concrete blocks 0.19, lightweight plaster 0.16. Standard thermal resistances in m^2oC/w are: intermal surface 0.123, extermal surface 0.055, cavity 0.18
u-value
2014-12-02 5:14 pm
回答 (2)
2014-12-04 2:42 am
✔ 最佳答案
1. Based on the formula : Φ = A × U × (T1 - T2)For the brickwork, Φ = 6m^2 x 0.95w/m^2oC x (T1 - T2)
For windows, Φ = 2m^2 x 2.8w/m^2oC x (T1 - T2)
So total Φ = (6 x 0.95 + 2 x 2.8) x (T1 - T2)
= 11.3 x (T1 - T2)
Average U = Total Φ / Total area x (T1 - T2)
= 11.3 x (T1 - T2)/8 x (T1 - T2) = 11.3/8 = 1.4125w/m^2oC.
2014-12-04 5:12 am
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收錄日期: 2021-04-23 23:44:23
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