- #1
ESMAT 1995
- 6
- 0
Homework Statement
so, i had this question where i had a sphere and a cylinder with given dimensions and propreties ( roh, C and k) he also gave me initial temperatures, then both of them dipped in a bath of water of given temperature but unknown h ( convective coefficient) then he gave me the temperature of the sphere after 2 mins and wants the temperature of the cylinder after 5 mins.
The Attempt at a Solution
My first thought was to get h, which is relatively easy but i had a problem choosing between 2 methods, first one was to assume it was a lumped system ( the sphere) and use the exp(Bi*F) rule where the h will be the only unknown, or i can use the Heisler Charts where i have the temperature ratio and the Fourier number and i can use them to get the 1/Bi, in both cases the h will result in a lumped system in the cylinder, but the final temperatures in each case is different ( 5 degrees different) so it's pretty obvious that 1 of them is true, my professor solved using the assumption, but when i asked him he said that would work too but never said which one is more right, so is there any way i can test for the lumped system assumption with an unknown h
a copy of the question is attached ( question number 6)
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