1. Heat loss through a double pane window Modern double pane windows have good heat insulation because they consist of two layers of glass with a space between. The space between can be filled with an inert gas (to prevent any water condensation between the panes) or with vacuum. =30C;T4=0C First, determine how well Argon gas does as an insulator. That is, determine the heat flux lost per meter squared through the window (perhaps with the circuit analogy) using the following information: Each glass pane is 4mm thick The gap is 3mm The inside wall temperature is 30C and the outside wall temperature is 0C (assume constant surface temperature not a convective boundary) Glass thermal conductivity kglass=0.8W/mK Argon thermal conductivity kargon=0.016W/mK (assume only conduction, no convection) Glass is a gray body with emissivity =0.9 Stefan-Boltzmann constant =5.67108W/m2K4 (a) Find the thermal resistor value for the glass panes in K/W (b) Find the thermal resistor value for the Argon gas layer in K/W (c) Neglecting radiation, find the heat flux through the three-layer system (glass, Argon, glass) in W/m (d) Neglecting radiation, find the inner temperatures of the glass ( T2 and T3 ) in K (e) Assume that the gap is evacuated and that heat transfers across it by radiation only. What is the heat loss in this case (please feel free to assume that glass conductivity is high enough to assume that the glass panes are uniform temperature for this radiation calculation). (in W/m2 ) (f) Suppose instead of the double pane you used a single pane of glass at 8mm thickness. What is the heat loss in this case? 1. Heat loss through a double pane window Modern double pane windows have good heat insulation because they consist of two layers of glass with a space between. The space between can be filled with an inert gas (to prevent any water condensation between the panes) or with vacuum. =30C;T4=0C First, determine how well Argon gas does as an insulator. That is, determine the heat flux lost per meter squared through the window (perhaps with the circuit analogy) using the following information: Each glass pane is 4mm thick The gap is 3mm The inside wall temperature is 30C and the outside wall temperature is 0C (assume constant surface temperature not a convective boundary) Glass thermal conductivity kglass=0.8W/mK Argon thermal conductivity kargon=0.016W/mK (assume only conduction, no convection) Glass is a gray body with emissivity =0.9 Stefan-Boltzmann constant =5.67108W/m2K4 (a) Find the thermal resistor value for the glass panes in K/W (b) Find the thermal resistor value for the Argon gas layer in K/W (c) Neglecting radiation, find the heat flux through the three-layer system (glass, Argon, glass) in W/m (d) Neglecting radiation, find the inner temperatures of the glass ( T2 and T3 ) in K (e) Assume that the gap is evacuated and that heat transfers across it by radiation only. What is the heat loss in this case (please feel free to assume that glass conductivity is high enough to assume that the glass panes are uniform temperature for this radiation calculation). (in W/m2 ) (f) Suppose instead of the double pane you used a single pane of glass at 8mm thickness. What is the heat loss in this case
