Q12. The data below is for the wall in a building: Item external surface Brick insulation Heavy concrete block plaster The heat transfer coefficients for the surfaces are: convective radiant convective radiant internal surface thickness (mm) conductivity (W/mK) 105 25 200 13 i. ii. The wall has a surface area of 10 m². (a) Determine: 0.84 0.035 0.25 0.16 18 W/m²K 4.5 W/m²K 3.0 W/m²K 5.0 W/m²K the total resistance of the wall (R₁) [0.189 K/W] [0.53 W/m²K] the U value of the wall (b) when the temperature indoors is 20°C and the temperature outdoors is 1°C, determine: (c) the rate of heat loss through the wall (d) the temperature of the inside surface of the wall [100 W] [18.7 °C] Q13. What should the thickness of insulation in the above wall be increased to so as to give a 50% reduction in U value and what would be the new inside surface temperature? [91 mm, 19.4°C]

Elements Of Electromagnetics
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Q12. The data below is for the wall in a building:
Item
Brick
insulation
Heavy concrete block
plaster
external surface
thickness (mm) conductivity
(W/mK)
internal surface
105
25
The heat transfer coefficients for the surfaces are:
convective
radiant
convective
radiant
200
13
The wall has a surface area of 10 m².
(a) Determine:
0.84
0.035
0.25
0.16
18 W/m²K
4.5 W/m²K
3.0 W/m²K
5.0 W/m²K
i. the total resistance of the wall (R₁)
[0.189 K/W]
ii.
the U value of the wall
[0.53 W/m²K]
(b) when the temperature indoors is 20°C and the temperature outdoors is
1°C, determine:
(c) the rate of heat loss through the wall
(d) the temperature of the inside surface of the wall
[100 W]
[18.7 °C]
Q13. What should the thickness of insulation in the above wall be increased to
so as to give a 50% reduction in U value and what would be the new
inside surface temperature?
[91 mm, 19.4°C]
Transcribed Image Text:Q12. The data below is for the wall in a building: Item Brick insulation Heavy concrete block plaster external surface thickness (mm) conductivity (W/mK) internal surface 105 25 The heat transfer coefficients for the surfaces are: convective radiant convective radiant 200 13 The wall has a surface area of 10 m². (a) Determine: 0.84 0.035 0.25 0.16 18 W/m²K 4.5 W/m²K 3.0 W/m²K 5.0 W/m²K i. the total resistance of the wall (R₁) [0.189 K/W] ii. the U value of the wall [0.53 W/m²K] (b) when the temperature indoors is 20°C and the temperature outdoors is 1°C, determine: (c) the rate of heat loss through the wall (d) the temperature of the inside surface of the wall [100 W] [18.7 °C] Q13. What should the thickness of insulation in the above wall be increased to so as to give a 50% reduction in U value and what would be the new inside surface temperature? [91 mm, 19.4°C]
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