1. Window Comparison Kasey Pearce ME 340 W10

2. Is Double or Triple Pane Better? Are double pane windows just as effective as triple pane? My father who owns a window business seems to think so, and I researched what he has told thousands of customers to keep him honest.

3. Experiment Used a single pane, double pane, triple pane setup. Hot (325 K (ie Arizona)), Cold (250K), and Windy (vel=13.4m/s) days. Double pane and triple pane windows had Argon as the insulating gas, double strength low e glass, with a single strength pane in the middle for the triple pane. Assumed no radiation (transparent – though triple pane does have much less transparency than the single pane). Assumed 1-D, steady flow. Free convection negligible on inside because the Ra < 1708 which means air cannot circulate.

4. Calculations To hot325 Ti300 To cold250 vel wind13.4 vel no wind2 kglass1 k glass single1.4 k argon1.77E-02 k air out cold2.23E-02 k air out hot2.82E-02 L pane single1.59E-03 L pane3.18E-03 L gap double1.27E-02 L gap triple7.14E-03 visc cold1.14E-05 visc hot1.84E-05 Pr cold7.20E-01 Pr hot7.04E-01 Hot ReNuhRglass innerR gap innerR glass midR gap outerRglass outerRconv outRtotR windowQ 1.09E+051.95E+025.48E+003.18E-034.03E-011.13E-034.03E-013.18E-031.82E-019.96E-018.14E-01-2.51E+01 Cold ReNuhRglass innerR gap innerR glass midR gap outerRglass outerRconv outRtotR windowQ 1.75E+052.49E+025.55E+003.18E-034.03E-011.13E-034.03E-013.18E-031.80E-019.94E-018.14E-015.03E+01 Windy ReNuhRglass innerR gap innerR glass midR gap outerRglass outerRconv outRtotR windowQ 1.17E+061.90E+034.24E+013.18E-034.03E-011.13E-034.03E-013.18E-032.36E-028.37E-018.14E-015.97E+01

5. Results

7. The three windows by the numbers Results Res of window (m^2*K/W) SingleDoubleTriple 0.00130.7230.814 Results Q (W/m^2) SingleDoubleTriple Hot-135-27.6-25 Cold27655.450.3 Windy20206759.7

8. Conclusion The double pane window lets 5 times less heat transfer on a cold day than the single pane whereas the triple pane is 5.5 times less. The windy day comparison was a surprising. The windy day shows the difference in resistance of the window with hardly any resistance due to convection outside, and thus is shown how drastic the thermal resistance is between a single and double pane. The double versus triple is still improved, but not a change that would be noticed by homeowners. In the end it looks like my father has kept his integrity!

9. Error Possible sources of error could arise in the radiation heat transfer. I did not take into account the radiation for example in the Hot days on the triple pane, where it would make a difference. Also forced convection was used as the outside condition on all three days, where free convection might have given a closer approximation on a stagnant day.