As an acoountant in charge of reducing expenditures for a local company, you thi

Question

As an acoountant in charge of reducing expenditures for a local company, you think you can save considerable money on fuel costs by lowering the room temperature of the building for daily use. In the morning, the interior temperature is typically 34.6 F degree and the thermostat is typically set for 70.7 F degree. Instead, you propose to lower the thermostat to 60.1 F degree. Currently the building measures 23.5 x 54.9 x 14.5 feet.

1- How much heat will be saved each morning by bringing the building up to the new operating temperature of 60.1 F degree instead of 70.7 F degree? Ignore heat and air losses to the outside and consider air an ideal diatomic gas. Assume that in the morning the pressure in the room is atmospheric.

2- The electricity rate in your area is $ 5.56 per kilowatt- hour. How much money (in dollars ) is saved each morning by only heating the room to the new operating temperature?

Explanation / Answer

for 1st case heat needed = Q=Cp* v*density*dT = 5/2+8.31*(7.1628*16.734*4.4196)*15*1.225 J=(104833.1549286 )J

for 2nd case the heat needed= 10.8*(7.1628*16.734*4.4196)*21*1.225=146766.41J;

heat saved = (34231.23* 1.225)J;=41933.28J= 41.933kJ

money saved 41.993/5.56 $= 7.54$

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