Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
heat transfer
Posted 2012年3月7日 GMT-5 09:03 Heat Transfer & Phase Change 2 Replies
Please login with a confirmed email address before reporting spam
hi, I have a question to solve!
A copper tube (with outside diameter 5 cm, inside diameter 2 cm, and length of 1
m) is employed to boil methanol (saturation temperature = 64.5 oC) at its outer
surface. The tube interior is heated by condensing steam under atmospheric
pressure. Estimate the methanol boiled amount in kg/hr if the latent heat of
methanol is 2000 kJ/kg. the thermal conductivity of copper is 250 W/m‧K.
what is latent heat and how to solve this question????
A copper tube (with outside diameter 5 cm, inside diameter 2 cm, and length of 1
m) is employed to boil methanol (saturation temperature = 64.5 oC) at its outer
surface. The tube interior is heated by condensing steam under atmospheric
pressure. Estimate the methanol boiled amount in kg/hr if the latent heat of
methanol is 2000 kJ/kg. the thermal conductivity of copper is 250 W/m‧K.
what is latent heat and how to solve this question????
2 Replies Last Post 2012年3月7日 GMT-5 14:16
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi,
in the best case the condensing steam will keep the inner surface exactly at condensation temperature, 96 - 100 °C, depending on atmospheric pressure and the boiling methanol will keep the outer surface at its boiling temperature. This allows to calculate the best case heat flow and the evaporation rate of the methanol.
The latent heat is the amount of energy required to evaporate on kg of methanol.
This problem in this degree of simplifications can probably be solved using text book formulas. If you want to model it all including the phase change phenomena thing will get tricky.
Cheers
Edgar
in the best case the condensing steam will keep the inner surface exactly at condensation temperature, 96 - 100 °C, depending on atmospheric pressure and the boiling methanol will keep the outer surface at its boiling temperature. This allows to calculate the best case heat flow and the evaporation rate of the methanol.
The latent heat is the amount of energy required to evaporate on kg of methanol.
This problem in this degree of simplifications can probably be solved using text book formulas. If you want to model it all including the phase change phenomena thing will get tricky.
Cheers
Edgar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
As Edgar mentioned, that would provide a best case heat flow estimate. Practically, the outer tube surface will be at a higher temperature that depends on the efficiency of the heat transfer between the tube and the methanol. That will reduce the amount of heat delivered to the methanol.
Note however that the thermal properties you are using are not accurate. The latent heat of methanol is usually around 1200 kJ/kg and the copper thermal conductivity is usually around 400 W/m.K.
Nagi Elabbasi
Veryst Engineering
Note however that the thermal properties you are using are not accurate. The latent heat of methanol is usually around 1200 kJ/kg and the copper thermal conductivity is usually around 400 W/m.K.
Nagi Elabbasi
Veryst Engineering