Water Flow vs Temp Difference........
Water Flow vs Temp Difference........
(OP)
We have a water/glycol brazed plate heat exchanger. In general terms, should we expect the delta T to increase with increased flow or decrease?
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Water Flow vs Temp Difference........
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Water Flow vs Temp Difference........Water Flow vs Temp Difference........(OP)
We have a water/glycol brazed plate heat exchanger. In general terms, should we expect the delta T to increase with increased flow or decrease?
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RE: Water Flow vs Temp Difference........
Tata
RE: Water Flow vs Temp Difference........
Q = htc*area*deltaT. If Q is constant and htc increases, then deltaT decreases, doesn't it?
TTFN
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RE: Water Flow vs Temp Difference........
If you increase the flow on the water side, the heat transfer cofficient on that side will increase, of course, increasing the overall heat transfer coefficient. This will increase the delta T on the other side. However, I don't think it will increase the overall heat transfer coefficient enough to result in a higher delta T on the water side.
As IRStuff pointed out, the water side delta T is inversely proportional to the flow rate if the Q is constant. It's a pretty good bet that the effect of the water flow is greater than the effect of the increased heat load.
Speco
RE: Water Flow vs Temp Difference........
Thank you all very much for your input!!
RE: Water Flow vs Temp Difference........
Q = M*cp*ΔT
with cp = water specific heat capacity
RE: Water Flow vs Temp Difference........
Tata
RE: Water Flow vs Temp Difference........
The fact is, we sometime get a little sloppy in our terminology. Delta T can mean three different things in a heat exchanger.
1. The hot fluit change in temperature. Usually T1-T2
2. The cold fluid change in temperature. Usually t2-t1
3. The effective temperature temperature difference between the fluids, or Log Mean Temperature Differenct (LMTD)
In IRStuff's posting, he meant LMTD
In Ione's posting, he meant the temperature change in either fluid.
I believe the original poster was referring to one of the fluid temperature changes.
Speco
RE: Water Flow vs Temp Difference........
I will endeavour to be more precise with my future postings as it is quite clear that a thread can come unravelled if not properly mended. One could say "a stitch in time saves 9". No more punny references, I promise!!
thank you all again!!
CamLoch
RE: Water Flow vs Temp Difference........
In the limiting (absurd) case, an infinite coolant flow would result in a zero deltaT across the inlet and outlet, since you would now have an infinite heat sink.
TTFN
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RE: Water Flow vs Temp Difference........
RE: Water Flow vs Temp Difference........
Let's not forget that no matter how much we improve one individual heat transfer coefficient, the overalll heat transfer coefficient would stay at a value smaller than the lowest of both individual values.