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P110_2008_Week_6

# P110_2008_Week_6 - P120 Exam I 2008 Avg 86.2 110 = 78 14 12...

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P120 Exam I 2008 Avg: 86.2/110 = 78% 0 2 4 6 8 10 12 14 55 60 65 70 75 80 85 90 95 100 105 110 More Bin Frequency Series1

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Infiltration Q = 0.018 Btu/ft 3 .hr.F o V K T Here K is the number of “Air exchanges per hour” and V is the interior volume of the house/building. Note: some exchange of air is necessary (you need to breath!), and this is not readily apparent in this figure.
Some typical R values Material Thickness R (ft 2 .h. o F/Btu) Hardwood 1” 0.81 Concrete block 8” 1.25 1-pane window 0.125” 0.88 2-pane window 0.5” air 1.72 Fiberglass 7” 21.8 Polyurethane 1” 6.3 Nylon carpet 1” 2.0 Wood siding 0.5” 0.81 Plywood 0.5” 0.627 Plasterboard 0.5” 0.45 Steel 1” 0.0032

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Degree-Days Heating/Cooling http://www.ersys.com/usa/18/1836003/wtr_norm.htm Indianapolis
Price of Natural Gas (dollars/MBtu wholesale I believe) http://futures.tradingcharts.com/chart/NG/W

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“Low-e” (emissivity) coatings on windows Conducting oxide Double metal layer Single metal layer Phys. Today Nov. 2000
Basic Heat Engine Efficiency = η = W/Q H = (Q H -Q C )/Q H Recall that this works because the entropy increase at T c is greater than the entropy decrease at T H .

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Heat Pumps (one system: heating and cooling) As we saw with heat engines, the second law of thermodynamics puts limits on how much cooling you can get for a given amount of work (entropy of the Universe must not decrease!! => Heat out to warm reservoir must exceed heat in from cold res.) Heat output is greater than work in!
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