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  3. 2 doublepaned windows installation of doublepaned windows is an efficient...

Question: 2 doublepaned windows installation of doublepaned windows is an efficient...

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2. Double-Paned Windows. Installation of double-paned windows is an efficient way to reduce heat loss from buildings through the windows. A typical double-paned window consists of two glass panels, separated by a sealed space under vacuum, as shown in Fig. 1. The glass panels have a thickness of 5 mm each, and a thermal conductivity of 1.2 W/mK. The combined convection and radiation heat transfer coefficient h for the inner and the outer the room vacuumoutdoor surfaces (surfaces labeled 1 and 4 in Fig. 1) are 15 W/m2K Surfaces 2 and 3 can be approximated as black surfaces for infrared thermal radiation. The glass panels are opaque to the nfrared radiation, so there is no need to consider thermal radiation through the glass panels. Assume inside the room 「= 20°C, and the outdoor temperature is -2 °C. (a) Draw a thermal resistance network for the double-paned window. (b) What is the rate of heat loss per unit area from the double- paned window? Compare this value to the heat loss rate if only one glass panel is used with the same heat transfer coefficient h. inside Ti-20°C To = 2 °C glass panel glass panel Figure 1 A double-paned window

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