BTU requirements for a Jacketed Pipe
BTU requirements for a Jacketed Pipe
(OP)
So there is an exhaust pipe that releases steam at 326C. This pipe needs to have a jacket placed on it to keep the steam at an elevated temp. so that particles to do not clog the pipe as they cool. This is an 8" pipe that is 10' long. I am trying to figure out how to set up an equation to determine how many BTU's are required to keep this pipe 326-331C. I will also need to set this up to determines the BTU/hr requirements for flow of ambient air flowing through the pipe. I am not sure of the flow rate of the steam at this point. Any tips of how to set this up? Obviously this not pure stiseam but that is not of importance at this time.





RE: BTU requirements for a Jacketed Pipe
Sounds like the pipe is short enough that you could just insulate to keep it and the steam hot.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: BTU requirements for a Jacketed Pipe
RE: BTU requirements for a Jacketed Pipe
What's the exit temp now.
Calculate the BTU transferred to the pipe from the internal flow of steam/air across the boundary film, through the pipe and insulation and the outer boundary layer with the ambient air by finding the overall heat transfer coefficient for the first foot of the 10 foot pipe. That will be the largest BTU loss per foot length of pipe. Just use that for the remaining 9 feet to get a conservative end temp.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: BTU requirements for a Jacketed Pipe
i don't know the exit temp now. the pipe is only used a few times a year.
RE: BTU requirements for a Jacketed Pipe
As long as you have some temperature differential to work with, insulation will be far and away the most efficient solution. Then if you still need temperature to be increased, however you wind up doing it, it will probably be a much smaller capacity system. Maybe just simple electric tracing would work.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: BTU requirements for a Jacketed Pipe
need to keep the pipe as hot as possible to keep it from becoming fouled
think i am making progress though
basicly breaking it into two parts. heat lost thru insulation + {q=UA(dtm)}
still working on it but seem to be moving forward
hell, even learing something while doing it
RE: BTU requirements for a Jacketed Pipe
Once you have the radial heat loss, you can apply the log temperature drop rule to get a more accurate loss in temperature along the length of pipe, or you can leave it quick and dirty like I suggested before.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: BTU requirements for a Jacketed Pipe
Good luck,
Latexman
RE: BTU requirements for a Jacketed Pipe
question on the film coefficients. not sure which one to use for the steam. still looking into that one
RE: BTU requirements for a Jacketed Pipe
> identify allowable external surface temp; 60°C would minimize burn hazard
> identify ambient temp; say 25°C
> guess at an insulation thickness; say 1-in Styrofoam equiv. material.
Simultaneous solve for thickness
sigma*area.cond*(T.gas-T.surf)/thk = htc.conv*area.conv*(T.surf-T.amb)
where:
sigma --> thermal conductivity of insulator
area.cond --> effective area of insulator
T.gas --> gas temp
T.surf --> exterior surface temp of insulation, assume that the pipe has negligible resistance
thk --> thickness of insulator
htc.conv --> convection coefficient
area.conv --> convection area
T.amb --> ambient temp
I get something like 1.6-in of Styrofoam for htc = 7.5W/m^2*K, which results in heat flow of 981W
TTFN
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RE: BTU requirements for a Jacketed Pipe
RE: BTU requirements for a Jacketed Pipe
TTFN
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RE: BTU requirements for a Jacketed Pipe
rho*A*c*dT/dt=U*p*(T0-T)
solution:
Tf-T0=(Ti-T0)e^-zt
since t=L/v, this becomes
Tf=T0-(Ti-T0)*e^(-zL/v)
z=Up/(rho*A*c)
L= length of pipe
rho=density
A= cross sectional area pipe
p= perimeter of pipe
c= specific heat
t=transit time (time it takes fluid to reach end of pipe
Ti= entering temperature
Tf temperature at end of pipe
T0= ambient temperature
RE: BTU requirements for a Jacketed Pipe
I have a hard time seeing there's much of a temperature drop over 10' of 8" pipe with 4" of insulation.
RE: BTU requirements for a Jacketed Pipe
RE: BTU requirements for a Jacketed Pipe
the overall conductance from the gas to ambient.
I think you had better review the subject of heat transfer to get a better understanding of your problem.
I don't have a reference but others on this forum could point you to online sources if you don't have one.
RE: BTU requirements for a Jacketed Pipe
Me too. I almost thought it was a homework problem because of that.
If it ain't broke, don't fix it. If it's not safe ... make it that way.