Question

Problem 5: Suppose a house's walls are 14 cm thick and and have an average thermal conductivity twice that of glass wool. Substance Glass wool Wool Glass Human body Ceramic Wood Air Fatty tissue Styrofoam Thermal conductivity (J/s.m.) 0.042 0.04 0.84 0.2 0.84 0.08-0.16 0.023 0.2 0.010 Otheexperta.com Part (a) Calculate the rate of heat conduction, in watts, through the house's walls. Assume there are no windows or doors. The surface area of the walls is 105 m and their inside surface is at 18°C, while their outside surface is at 4.95°C Numeric : A numeric value is expected and not an expression. Q/A - Part (b) How many 1.00-kw room heaters would be needed to balance the heat transfer due to conduction? Round your answer to the nearest integer value. Numeric : A numeric value is expected and not an expression. N- Problem 6: The rate of heat conduction out of a window on a winter day is rapid enough to chill the air next to it. Substance Glass wool Wool Glass Human body Ceramic Wood Air Fatty tissue Styrofoam Thermal conductivity (J/s.m.) 0.042 0.04 0.84 0.2 0.84 0.08-0.16 0.023 0.2 0.010 Ctheexperta.com To see just how rapidly the windows transfer heat by conduction, calculate the rate of conduction, in watts, through a 3.05- m2 window that is 0.605 cm thick if the temperatures of the inner and outer surfaces are 5.1°C and -7.5°C, respectively. This rapid rate will be maintained by the interior heating of the house. Numeric : A numeric value is expected and not an expression Qar-

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Answer 1

The house walls thickness = d=14 cm Themal Conducti retively 2x .042 Ils mee Now heat conduction rate & -K (02-01) (02-01A 24.042 X 618-4,95). d X 105 = 822015 watt. = .822 Kwatt. Only one 1 kW room heater is regured to balance the heat transfar. For window t KA (02-06) d 27.042 x 3.058 12.6 2 533.57 watt