Question

Consider a 1.2-m-high and 2-m-wide double-pane window consisting of two 3-mm-thick layers of glass (k = 0.78 W/m K) separated by a 12-mm-wide stagnant air space (k = 0.026 W/m K). Determine the steady rate of heat transfer through this double-pane window. R . and all the surface temperatures (inner and outer of each pane) within the circuit (which you will draw and correctly label) for a day during which the room is maintained at 24°C while the temperature of the outdoors is -5°C. Take the convection heat transfer coefficients on the inner and outer surfaces of the window to be: hinde = 10 W/m2K and houtside = 25 W/m2.K, and disregard any heat transfer by radiation. DRAW CIRCUIT IN THIS SPACE: Assumptions Heat transfer through the window is steady since the indoor and outdoor temperatures remain constant at the specified values. Heat transfer is one-dimensional since any significant temperature gradients will exist in the direction from the indoors to the outdoors. Thermal conductivities of the glass and air are constant. Heat transfer by radiation is negligible.

Answer 1

ty=3mm (thickness of glass) ta 12 mm (thickness of Air) Room outside of -5°C Toi 24°C h; = 10 W kg = 0.78 W/mk ka a 0.026 W/mk A = 1.242 = 2.4 m² h = 25 W/m²K WA Resistance network RS RO na au nori i m Road to try to w 3x3 . . . * ), . . 0.78X 2.4 2-HAHAHAHAHAHAHA Ra - . 0.026 X 2.4 1 - - 1 Ri= I = - h A 2 K/W. 10 X2 4 10 Rtotal - Rot 2 Rg + Rat Ri - 1/60 + 12 + 15 16 + 2 y = 0.2538 o Q = Too, j - To,o – 24-(-5) = 114.242 W Rtotal 8.2538