Fan Sizing
Fan Sizing
(OP)
I have a room I need to cool 5-10°F, using outside air only. The volume of the room is 20,000 cuft. The heat load is 200KW. What is the CFM of my fan?
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RE: Fan Sizing
Is your outdoor temp 10-15 degF cooler than what you want your indoor conditions to be? Plug in to the formula and what do you get?
knowledge is power
RE: Fan Sizing
RE: Fan Sizing
Thank you Sir, sorry for the brain fart....
knowledge is power
RE: Fan Sizing
RE: Fan Sizing
RE: Fan Sizing
RE: Fan Sizing
knowledge is power
RE: Fan Sizing
RE: Fan Sizing
RE: Fan Sizing
RE: Fan Sizing
It is an electrical room with 3 1900kw VFDs and several MCCs. I have not done this type of calculations in 25 years rusty and not trusty.
the VFDs are ~96.5 eff.=66.5kw x 3 = 199500w + other equipment; roughly total 250kw.
250,000 watts is my heat loss from the equipment = 853,035 btu/hr
I want the temperature in the room no greater than 85°F therefore max delta T=19
Q = 1.08 CFM delta T
do the math and ........41571 cfm
my room is 20,000cuft about 2 min to exchange the air.
Does the room melt?
Thanks for all of your inputs even the ones that provided no help
and your right I need help but that is what this site is all about, have a great day!
RE: Fan Sizing
RE: Fan Sizing
RE: Fan Sizing
RE: Fan Sizing
RE: Fan Sizing
but in winter where you have to provide heat to a space, you can keep 85F in a space by using supply air of 100F or more depend on the situation.
RE: Fan Sizing
RE: Fan Sizing
RE: Fan Sizing
I may have stated the problem incorrectly lead you down the wrong path, I apologize. I want to limit the rise to 15 degrees. So, for a typical summer looking at 95F, you need about 210 CFM for every KW, therefore, revised heat loss of 220KW gives me about 46,200 CFM.
working out q=1.08cfm delta you get approx. the same thing. using 220kw~751,000btu/hr
thanks
RE: Fan Sizing
Best to you,
Goober Dave
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RE: Fan Sizing
RE: Fan Sizing
in practice, it is impossible to get any meaningful heat rejection with delta t bellow 10-15, so at best you can reach 110-115 degrees with heat rejection.
RE: Fan Sizing
Looking at a average summer day 95f so a rise if ten degrees in the room is acceptable
RE: Fan Sizing