The overall heat transfer coefficient (the U-value) of a wall under winter design conditions is U = 2.25 W/m² · K. Now a layer of 100-mm face brick is added to the outside, leaving a 20-mm air space between the wall and the bricks. Determine the new U-value of the wall. Also, determine the rate of heat transfer through a 3-m-high, 7-m-long section of the wall after modification when the indoor and outdoor temperatures are 22°C and 225°C, respectively.

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Face brick Existing wall