Review Problem 3. A glass aquarium is shaped like a cube with sides of length 50
ID: 1456378 • Letter: R
Question
Review Problem 3. A glass aquarium is shaped like a cube with sides of length 50 cm and the glass has a thickness of 8 mm. Suppose you completely fill the aquarium with water and the temperature of the water and glass is 10°C. Without spilling any water, you move the aquarium to a room with constant temperature of 30°C. a) Ignoring evaporation, how much water has spilled out of the aquarium once it equalizes to the new 30°C temperature? b) We now move the aquarium out to the garage where the temperature is 15°C, and the outer surface of the aquarium quickly stabilizes at 20°C. What is the conductive heat current through the walls of the aquarium? c) What is the net heat current from the aquarium due to radiation if the outer surface is 20°C? Assume that the emissivity is 0.8.
Explanation / Answer
initial volume = Vo = l^3 = 0.5^3
coefficient of volume expansion = gamma = 0.000214
change in volume = dV = gamma*Vo*dT
amount of water spilled = dV = 1.5^3*0.000214*(30-10) = 0.000535 m^3
(b)
q = (0.8 W/m oC) (0.5 m) (0.5 m) ((20 oC) - (15 oC)) / (0.008 m)
= 125 (W)
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