Rise in Temperature due to Heat Losses
Rise in Temperature due to Heat Losses
(OP)
I have a very unusual problem. I was asked to compute the temperature rise in an enclosed cylinder that has a motor running inside. And the cylinder is underwater (seawater) with no ventilation.
I am a CE and have no experience in this area. I know that the heat losses due to the motor inefficiency is 1HP and have the cylinder dimensions and material props.
I need to figure out when the system reaches steady-state and what the temperature inside will be at that time.
I am a CE and have no experience in this area. I know that the heat losses due to the motor inefficiency is 1HP and have the cylinder dimensions and material props.
I need to figure out when the system reaches steady-state and what the temperature inside will be at that time.





RE: Rise in Temperature due to Heat Losses
You have, more or less, a liquid cooling problem, which does require knowing the temperature of the water, and the flow thereof, around the cylinder.
TTFN
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RE: Rise in Temperature due to Heat Losses
RE: Rise in Temperature due to Heat Losses
I was thinking that if I could relate the power losses to the change in temperature over time, and compute the heat transfer rate between the cylinder (we are trying both aluminum and stainless steel) and the water I could figure out when the system would reach steady state. Am I totally off base in this thinking?
RE: Rise in Temperature due to Heat Losses
You should be able to find the equations needed in the above mentioned book.
Then all you have to do is calculate at which temperature difference 1 HP is transfered.
I am sure this will be close enough for your purposes.
RE: Rise in Temperature due to Heat Losses
Depending on what the motor is driving, some of the motor's 1 HP output may be deposited inside the enclosure cylinder. For example, if the motor is driving a ventilation fan within the enclosure, then all of the fan's energy will be converted to heat, and the enclosure must reject 932 Watts. If the motor is driving a sea water circulating pump, then virtually all of the 1 HP energy will leave the enclosure with the water, and only 186 Watts must be removed from the enclosure via heat transfer.
RE: Rise in Temperature due to Heat Losses
For calm air you can take a heat exchange coefficient of 10 W/m2°C. For water I guess that the coefficient is beyond 100 W/m2°C (can be determined by using a textbook, possibly the one referenced is also OK).
So the air side exchange dominates, and you can conservatively use an overall coefficient of H=10 W/m2°C.
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RE: Rise in Temperature due to Heat Losses
TTFN
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