3 replies to this topic

[sandeep chk]

For a gas mixute consisting of different gases flowing through a duct say 100 deg C of known parameters, how to evalute the wall temperature of the duct (assumably the wall is thin enough so that the inside temp and outside temp is same).

[vinay]

For a gas mixute consisting of different gases flowing through a duct say 100 deg C of known parameters, how to evalute the wall temperature of the duct (assumably the wall is thin enough so that the inside temp and outside temp is same).

Dear Sandeep,

For anyone to reply to your query , he must understand the system you are referring to. Please specify what are the conditions outside the duct ? Is it a normal gas duct which in which gases are travelling from one equipment to the other in a plant ? Is it exposed to atmosphere from outside ?

If it is exposed to atmosphere , than you can not simply assume duct outside temperature to be same as duct inside temperature. In any case you need to calculate the duct outside & inside heat transfer coefficients for the fluid flowing there for calculating the wall temperature ( skin temperature) . These kind of calculations you can find in any standard Text book on heat transfer say that by KERN or Mcadams .

Regards,
Vinay

[sandeep chk]

Thanks Vinay,
I will check out and then come back.
Sandeep

[sandeep chk]

With hot air (vel 27 m/s)entering a bare rectangular duct made of MS (hydr radius 0.501 m) of 6.4 m length at 99.4 degC, I calculated the wall temperature to be 88 deg C. Can anybody from experience validate that this 10 degC drop is a reasonable value?