Consider a room with a 1.8-m-high and 2.0-m-wide double-pane window consisting of two 4-mm-thick layers of glass separated by a 10-mm-wide stagnant air space. The convection heat transfer coefficients on the inner and outer surfaces of the window are 12 W/m2 K and 25 W/m2 K, respectively, while the average thermal conductivity of glass is 0.78 W/m K; and the air, 0.026 W/m K. If the room is maintained at 22 oC, the outside temperature is -4 oC and heat transfer due to radiation can be neglected, determine: (i) Draw the sketch and thermal resistance network; (ii) the total thermal resistance; (iii) the steady rate of heat transfer through this double-pane window; (iv) the temperature of the inner surface of the window.
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(a) |
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Consider a room with a 1.8-m-high and 2.0-m-wide double-pane window consisting of two 4-mm-thick layers of glass separated by a 10-mm-wide stagnant air space. The convection heat transfer coefficients on the inner and outer surfaces of the window are 12 W/m2 K and 25 W/m2 K, respectively, while the average thermal conductivity of glass is 0.78 W/m K; and the air, 0.026 W/m K.
If the room is maintained at 22 oC, the outside temperature is -4 oC and heat transfer due to radiation can be neglected, determine: |
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(i) |
Draw the sketch and thermal resistance network; |
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(ii) |
the total thermal resistance; |
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(iii) |
the steady rate of heat transfer through this double-pane window; |
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(iv) |
the temperature of the inner surface of the window. |
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(b) |
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If a fuel contains 86% C, 9% H2, 1% S and 4% ash (silica) by mass, determine: |
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(i) |
the total oxygen needed; |
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(ii) |
the total air needed; |
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(iii) |
the stoichiometric air/fuel ratio. |
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