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28-01-2014, 04:04 PM #1
How to estimate the capacity of a chilled water AHU designed for office comfort
I have a very old model AHU manufactured by YORK Borg Warner. The name plate of the AHU is missing too.
Is there a general rule of thumb to estimate the cooling capacity by the surface area of the chilled water coil?
Or by blower motor horsepower etc?
Thank you for any input.
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28-01-2014, 06:02 PM #2
Re: How to estimate the capacity of a chilled water AHU designed for office comfort
If it is working you can find the duty from the flow rate and the delta t
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28-01-2014, 09:04 PM #3
Re: How to estimate the capacity of a chilled water AHU designed for office comfort
Q = m x Cp x p x DT
The difference between genius and stupidity is that genius has its limits.
Marc
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28-01-2014, 09:16 PM #4
Re: How to estimate the capacity of a chilled water AHU designed for office comfort
Can't give you Rep Marc...must spread it around etc lol..
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28-01-2014, 09:46 PM #5
Re: How to estimate the capacity of a chilled water AHU designed for office comfort
Thanks anyway Frank
The difference between genius and stupidity is that genius has its limits.
Marc
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29-01-2014, 02:58 PM #6
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29-01-2014, 07:18 PM #7
Re: How to estimate the capacity of a chilled water AHU designed for office comfort
Airflow (volume) over the coil, air on temps, air off temps.
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30-01-2014, 02:41 AM #8
Re: How to estimate the capacity of a chilled water AHU designed for office comfort
Delta T DB will give sensible heat capacity, Delta h will give total heat, probably the water test would be easier
Q= water flow rate x DT x 4.2kj/Kg ' C
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30-01-2014, 06:48 AM #9
Re: How to estimate the capacity of a chilled water AHU designed for office comfort
for example:
Air quantity =370CFM
Temperature of air entering the coil DB = 78F
" WB = 67F
Temperature of air leaving the coil DB = 59F
" WB = 57F
Enthalpy of air at 67F WB = 31.62 BTU/lb
Enthalpy of air at 57F WB = 24.48 BTU/lb
enthalpy deference = 7.14BTU/lb
capacity = 4.5*370*7.14= 11888 BTU/lb