Heat exchangers selection
Heat exchangers selection
(OP)
I need your help.
I am selecting a heat exchanger for my ammonia application.
Here are the known data :
Hot Fluid : water, Tin (inlet temperature) and flow rate.
Cold fluid : ammonia, Tin (inlet temperature) and flow rate.
By selecting a heat exchanger from market, how to calculate the outlet temperature (hot and cold fluid) and drop pressure?
Hopefully these parameters will approach the real condition.
In real, does the flow rate change?
Thank you very much..
I am selecting a heat exchanger for my ammonia application.
Here are the known data :
Hot Fluid : water, Tin (inlet temperature) and flow rate.
Cold fluid : ammonia, Tin (inlet temperature) and flow rate.
By selecting a heat exchanger from market, how to calculate the outlet temperature (hot and cold fluid) and drop pressure?
Hopefully these parameters will approach the real condition.
In real, does the flow rate change?
Thank you very much..





RE: Heat exchangers selection
Q= ṁcp(T1-T2) and Qh=Qc such that ṁhcp(h)(T1(h)-T2(h)) = ṁccp(c)(T1(c)-T2(c)).
Patricia Lougheed
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RE: Heat exchangers selection
Tobalcane
"If you avoid failure, you also avoid success."
RE: Heat exchangers selection
TTFN
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RE: Heat exchangers selection
Q= ṁcp(T1-T2)
By the way, would the manufacturer give the detail performance? In their website, they seldom put it in the spesification sheet. Do you think any other way to predict the outlet temperature? Am i right?
RE: Heat exchangers selection
TTFN
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RE: Heat exchangers selection
Q = UA(LMTD) will tell you what the size of your equipment will be and what the actual outlet temperatures will be. Once you know the actual T1 - T2, you can calculate the first equation and see how much heat transfer you have for the approach temperatures that result from your equipment selection.
Lots of intricate factors go into that simple little "U" value of the equation.
rmw
How did you do that little m(dot) Yoel?
RE: Heat exchangers selection
typically, the responsible process design engineer defines the process conditions (i.e. inlet/outlet P, T, density, viscosity, Cp, flow rates, duty, etc.) for both streams. This information can then be used to properly thermally, hydraulically, and mechanically design a heat exchanger. There are heat transfer specialists that can assist you with the design/rating of the exchanger or you may directly deal with the manufacturer. unless you are skilled with heat transfer methodologies and designs, i highly recommend using the specialists as ammonia is a caustic & a hazardous fluid. the specialists can also specify materials of construction.
good luck!
-pmover
RE: Heat exchangers selection
Dear rmw, in the second equation, how do you calculate the actual temperature if you don't know U?
Thanks.
RE: Heat exchangers selection
RE: Heat exchangers selection
It is interesting.
By the way, how about corected LMTD?
Does it include in the spesification of heat exchangers?
htt
Is it right?
Deltathx said that but i don't know others.
Thanks so much..
RE: Heat exchangers selection
the report you attached suggestes different exchangers that have better U values for each case. that is why you need to try several exchanger types/designs to see what works best for the cost.