Conversion problem
Conversion problem
(OP)
Hi all,
I have been trying to use a heat exchanger formula and have been unable to get it to work out in both imperial and metric numbers. This leads me to believe I have something wrong. I am trying to solve for flow, using Load, density, Specific Heat,Delta T. When I convert each units and run the equation again in english units I don't get the same answer for flow. I get 1.5 lpm in metric, in english it should come out to 4 gpm,instead I get 2.6 gpm. The coolant is water @20C. Appreciate any help.
I have been trying to use a heat exchanger formula and have been unable to get it to work out in both imperial and metric numbers. This leads me to believe I have something wrong. I am trying to solve for flow, using Load, density, Specific Heat,Delta T. When I convert each units and run the equation again in english units I don't get the same answer for flow. I get 1.5 lpm in metric, in english it should come out to 4 gpm,instead I get 2.6 gpm. The coolant is water @20C. Appreciate any help.
Thanks
Bill





RE: Conversion problem
Thanks
Bill
RE: Conversion problem
TTFN
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[IMG ]
RE: Conversion problem
C*9/5 +32
Thanks
Bill
RE: Conversion problem
Good luck,
Latexman
RE: Conversion problem
Good luck,
Latexman
RE: Conversion problem
You yourself stated that the temperature of the coolant is 20°C, which means that the 4°C is the temperature DIFFERENCE. Temperature difference in Farenheit:
T1*9/5+32 - T2*9/5+32 = (T1-T2)*9/5, where T1-T2=4°C
TTFN
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[IMG ]
RE: Conversion problem
I am using Q*7.481/(T*60*Cp*p)
T=Delta T
Cp=Specific Heat
p=Density
Q=Load
cu ft of water = 7.481 lbs
Thanks
Bill
RE: Conversion problem
TTFN
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[IMG ]
RE: Conversion problem
Thanks
Bill
RE: Conversion problem
FWIW, 1ft^3 of water is 7.48 GALLONS. Not Lb(m?).
And 1ft^3 is 62.4 lbm
RE: Conversion problem
Thanks
Bill
RE: Conversion problem
I can scan my sheet if needed.
RE: Conversion problem
Q=1500w
Delta T=4 C
Cp=4.182 J/gC
p=998.29 kg/m3
When I use the above in the formula I get 1.5 l/m
The problem occurs when I convert.
If I take the equivalent english units for the above
Q=5118 btu/hr
Delta T=7.2 F
Cp=0.99885 btu/lb F
p=62.321 lb/ft3
insert the new values into the formula, I should come out with 0.396. The problem is I get 1.42 gpm which of course is not equivalent to 1.5 l/m?
I was asking for help, because its not obvious to me where the error is? Using the same formula with either units should give equivalent answers? Correct?
The only thing that I didn't look at was Specific gravity. I believe its not involved becasue waters Sg =1.
Thanks
Bill
RE: Conversion problem
Q=1500W
Delta T=4C (or 4K)
Cp=4.182J/gK
P=998.3kg/m^3
Nets you 5.39 L/min.
RE: Conversion problem
I am using 1500*1000/4*4.182*998.3*60
What am I missing?
Thanks
Bill
RE: Conversion problem
TTFN
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[IMG ]
RE: Conversion problem
Oh, see, I got the units wrong, W = J/s, because I did it by hand.
TTFN
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[IMG ]
RE: Conversion problem
I recommend you do unit conversions such that you can visually cancel units, or use a program similar to IRstuff's suggestion.
RE: Conversion problem
Thanks
Bill