Equivalent water temperature in a parallel and series piping systems

[Diabolico]

My question is: How do you find the equivalent water temperature in a series or parallel system? Ex: you have 4 gpm of water @ 45 C splitting into two legs of which one 1gpm leg absorbs 2 kW of heat and the other 3 gpm leg absorb 1 kW. Whatis the equivalent temperature coming out of these two leags in parallel?? I am almost sure I know how to do this but I need to confirm and make sure I am not missing something.

Thanks in advance

 

[insult2injury]

If you are sure about the volumetric flow rates then...

Q = m_dotC_p[Δ]T

I2I

 

[vpl]

Diabolico

Couple questions

1) Why are your temperature and heat flux in SI units and your flow rate in American standard?

2) Do the fluids ever join back together?

3) What do you mean by "equivalent temperature"?

Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[BigInch]

Good question! Maybe he's like me, American, but in a very strange place where the speedometer is in MPH and the speed limits and distances on the road signs are in KM!

I, as Patricia also does, ask the same question about what you consider is equivalent temperature. There's a temperature of one gallon in one pipe and there's a temperature for a different gallon in another pipe. They only equalize if you mix them again, otherwise they're independent of one another.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[zdas04]

Doesn't the title of the thread answer that question? He has a temperature of the combined stream from the m_dotC_p?T equation by avergaging the volume-weighted outlet temperatures, now if he runs just one loop what would the outlet temperature be. It is one of the few problems I actually remember from Nuclear Power School in 1972.

David

 

[BigInch]

Could be. "How do you find the equivalent water temperature, "in a series or parallel system"

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[Diabolico]

The 1gpm stream would heat up to 52.6 C, while the 3gpm stream will heat up to 46.3 C. What is the resulting temeperature when these two streams converge again to 4gpm??

 

[IRstuff]

It's the weighted average, as stated above.

TTFN

 

[vpl]

zdas

It is one of the few problems I actually remember from Nuclear Power School in 1972.

Your statement is one of the reasons I asked about the mismatch in units. This sounds an awful lot like a homework problem.

Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[zdas04]

vpl,
Doesn't it though. That equation has stuck with me longer than anything else and the numbers are too clean to be anything but a homework problem, hope he gets what he needs before this thread gets zapped.

David

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[25362]

Diabolico, to estimate the final combined stream temperature you don't even need to calculate the increase in temperature of each stream as long as they mix again and you know the total heat transferred to both streams.

4 gpm = 899.4 kg/h @ 45^oC
Cp = 0.997 kcal/(kg.^oC)
3 kW = 2579.5 kcal/h
[Δ]t = 2579.5[÷](899.4[×]0.997) = 2.88^oC