How can I calculate heat loss from a pipe system in a building with 9 floors?

[bisharat]

halo every one... i have question . if i have pipe inside building with 9 floor's length ,and i have calorie meter between the incoming and outgoing pipe's. how i can calculate the losses of pipe if i now that temperature inside building is 22. i want to be sure that the system working normal. i try to use this formula but not succeed.
Q = (ti - to) / [ln(ro / ri) / 2 π k L] (1)

where

Q = heat transfer from cylinder or pipe (W, Btu/hr)

k = thermal conductivity of piping material (W/mK or W/m oC, Btu/(hr oF ft2/ft))

L = length of cylinder or pipe (m, ft)

π = pi = 3.14...

to = temperature outside pipe or cylinder (K or oC, oF)

ti = temperature inside pipe or cylinder (K or oC, oF)

ln = the natural logarithm

ro = cylinder or pipe outside radius (m, ft)

ri = cylinder or pipe inside radius (m, ft)

pleas help.
thanks

 

[JBA]

Please explain why you feel use of the formula "did not succeed".

 

[bisharat]

i didn't succeed to prove that inside bulding temp' is 22 . maybe i need to use other formula

 

[Nidum]

This may be a problem where most of the heat loss from the pipe occurs by the process of natural convection heat transfer .

The outer wall of the pipe will be at a higher temperature than the room and the air nearest to the pipe will become heated and rise . A flow pattern is established where air at room temperature arrives at the base of the pipe , gets heated progressively , flows up the pipe wall and then recirculates through the room to return at room temperature again to the base of the pipe . This naturally occurring flow continuously carries heat away from the pipe and into the room air .

Solving your problem in practice though will require a lot more work to arrive at a credible model of the complete system before any actual calculations can be attempted .

Tell us more about the installation .

 

[bisharat]

the problem is that i need formula to show that it's ok. about installation it's normal Uninsulated pipe from 1 floor to 9 floor. pleas help

 

[JBA]

Three simple factors you have not stated are: Is the pipe fluid hotter or colder than the target room 22°; is the fluid flowing upward or downward through the pipe; and is the pipe fully exposed to the room air?

Either way, the temperature of the pipe fluid is going to change progressively as it flows from floor to floor and therefore each of the 9 floors will have a different is going to have a separate average fluid temperature, convection air flow and ambient room temperature.

 

[bisharat]

it's that ,the temperature of the pipe fluid is going to change progressively as it flows from floor to floor, but how i can connect the 2 formulas,(1) loss heating from the pipe and (2) the calorie meter between the incoming and outgoing pipe's

 

[JBA]

Ultimately your problem comes down to a heat flow in vs. heat flow out balancing problem.

The heat flow into the floors is the bulk heat heat loss rate in your piping section = (mass flow rate) x (Specific Heat) x (T entering -T leaving) = Q Calories/hr.

The heat flow out is the rate of heat loss from each floor based upon the heat loss thorough the external walls around each floor based upon the wall material heat transfer coefficients and the ambient temperature surrounding the building walls.

But even given this, you will still have to determine how to apportion your total piping heat loss between the 9 successive floor levels since, as I stated above, the heat transfer rate will progressively decline with each succeeding floor along the pipe; and I don't really know what to suggest for dealing with that issue

So, as Nidum stated, you have a number of issues to deal with in trying to determine where you stand relative to your the ultimate temperature goal.

 

[Nidum]

@bisharat : What exactly do you mean by a Calorie meter ?

 

[bisharat]

@Nidum : calorie meter showing different between coming and outgoing pipes.

 

[bisharat]

it's a real problem , i think i can calculate heat lose for ever floor , after that add all of them together, it have the be equal to calorie meter, but again i didn't succeed.

 

[JBA]

Pleased clarify, whether you are trying to match your calculation with an existing condition; or, you are trying to determine if an exposed bare pipe can achieve the 22° ambient floor areas temperature?

 

[Vincenzo]

it's a real problem , i think i can calculate heat lose for ever floor , after that add all of them together, it have the be equal to calorie meter, but again i didn't succeed.

Then you are looking equations for Natural Convection, you must use this eq for heat loss: Q'=h*As*(Tpipe-Tsurround) assuming the pipe is hotter than the room.
To find h refer the natural convection theory.