Conduction problem


by shaka23h
Tags: conduction
shaka23h
shaka23h is offline
#1
Nov25-06, 06:47 PM
P: 40
The temperature in an electric oven is 160 C. The temperature at the outer surface in the kitchen is 38.6 C. The oven (surface area = 1.44 m2) is insulated with material that has a thickness of 0.0249 m and a thermal conductivity of 0.0405 J/(s m C). (a) How much energy is used to operate the oven for 3.88 hours? (b) At a price of $0.10 per kilowatt-hour for electrical energy, what is the cost (in dollars) of operating the oven?


OK I know to use the Conduction of Heat Through A material on this problem

Q = (k A Delta T) t/ L

After plugging in my values Q = [.045 J/ (s.m.C (degrees)] (1.44m ^2) (160 degrees - 38.6 degrees)(13968 sec) (hours converted to seconds) / 0.0249 m


I get my answer to be 4412945.581 J? This should be my energy value right? The Q in this case is my energy expenditure?


I plugged this answer in for the webbased solution but it was incorrect.

Thanks for ur help

Jason
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OlderDan
OlderDan is offline
#2
Nov26-06, 01:43 PM
Sci Advisor
HW Helper
P: 3,033
Quote Quote by shaka23h View Post
The temperature in an electric oven is 160 °C. The temperature at the outer surface in the kitchen is 38.6 °C. The oven (surface area = 1.44 m2) is insulated with material that has a thickness of 0.0249 m and a thermal conductivity of 0.0405 J/(s m C°). (a) How much energy is used to operate the oven for 3.88 hours? (b) At a price of $0.10 per kilowatt-hour for electrical energy, what is the cost (in dollars) of operating the oven?


OK I know to use the Conduction of Heat Through A material on this problem

Q = (k A Delta T) t/ L

After plugging in my values Q = [.045 J/ (s.m.C (degrees)] (1.44m ^2) (160 degrees - 38.6 degrees)(13968 sec) (hours converted to seconds) / 0.0249 m


I get my answer to be 4412945.581 J? This should be my energy value right? The Q in this case is my energy expenditure?


I plugged this answer in for the webbased solution but it was incorrect.

Thanks for ur help

Jason
Ya gotta use da right numbas


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