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08-01-2019, 03:38 PM #1
Capacity from flow in gallons and given DT
This is a question from an Canadian Exam
A water chiller operates with a 4.4°C (40°F) evaporator temperature, return water temperature of 10°C (50°F) and a 7.2°C (45°F) supply water temperature. The water flow rate is measured at 682.5 L/min (150 imp. gal./min). What is the cooling capacity?
A. 87 000 W / 300 000 Btu/h
B. 109 875 W / 375 000 Btu/h
C. 131 850 W / 450 000 Btu/h
D. 153 825 W / 525 000 Btu/h
I calculated via SI units: Q = (682.5 x 60) x 1 x 2.8 x1.16 (from cal to W) and gave in C which matches the best my answer (133 kW)
All the units in the question in SI are correct converted from the initial IP units. I checked this.
But my answer is apparently incorrect and they say that B is correct, 109 875 W / 375 000 Btu/h.
Their explanation.
Q= m.c.DT in Btu = 500 x 150 x 5 = 375.000 btu/h according to this link
https://greenenergypro.wordpress.com...water-formula/
and other links I found.
If I use on-line conversion tools to convert BTU/h to kW, then I get +/* 454.000 Btu/h
I think i Know where the pitfall is in this one.
Any help is appreciated.
Thanks
PeterIt's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.