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Unformatted text preview: C/W wall is better insulated and thus it is more energy efficient. 3151 A ceiling consists of a layer of reflective acoustical tiles. The Rvalue of the ceiling is to be determined for winter conditions. Assumptions 1 Heat transfer through the ceiling is onedimensional. 3 Thermal properties of the ceiling and the heat transfer coefficients are constant. Properties The Rvalues of different materials are given in Tables 36 and 37. Analysis Using the available Rvalues, the total Rvalue of the ceiling is determined in the table below. Rvalue, Construction m 2 . C/W 1. Still air, reflective horizontal surface facing up R = 1/h = 1/4.32 = 0.23 2. Acoustic tile, 19 mm 0.32 3. Still air, horizontal surface, facing down R = 1/h = 1/9.26 = 0.11 Total unit thermal resistance (the Rvalue) 0.66 m 2 . C/W Highly Reflective foil 19 mm Acoustical tiles Therefore, the Rvalue of the hanging ceiling is 0.66 m 2 . C/W. 3104...
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 Fall '10
 Dr.DanielArenas
 Thermodynamics, Energy, Mass, Heat

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