exhaust Calculation

[edenriquez0601]

is this the correct computation for exhaust

example:

floor area A
bldg height B
product vol C

Ventilation
Air Change D

Exhaust fan A x B x C x D / 60

= CFM Exhaust fan

 

[MintJulep]

Yes, provided that A B C and D use a set of units consistent with the use of CFM as the desired result.

 

[317069]

what did you mean by product vol

 

[edenriquez0601]

production volume of the warehouse!
to mintjulep how about the air change is there any standard for all location?
if no how to compute the air change of the area?

 

[MintJulep]

Can I change my answer?

C doesn't belong in the formula.

 

[edenriquez0601]

what do you mean it doesnt belong on the formula?
you mean the product volume?

 

[EnergyProfessional]

I think a legitimate question is wha tyou actually want to do? Are you designign ventilation for a warehouse? It looks like you got some sort of reference that takes into account what product is stored, like chemicals or other off-gasing products woudl impact ventilation.

whatever reference or code you have will tell you how to apply the values.

Most normal warehouses regualted by code just use area. Soemtimes volume etc. If you have specific components, you need to reference those guides. The code often doesn't address such specific cases. Also refer to OSHA or guidelines of that specific industry. If you store flux-capacitors, the National Flux Capacitor Association (google for NFCA) may have guidelines that you may apply while meeting or exceeding code.

 

[edenriquez0601]

its only a loading area of a dhl but there is no ventillation in st so very hot inside
my clients want a 2 exhaust fan and 1 fresh air the area is 104.96ft width 167.28ft length and 29.52ft heigth.
that is the formula that im using.and the air change is 3min per hour. the output is 5370 cfm and the supply air is 9586.is this is correct?can you help please.thanks is advance

 

[317069]

- client want two exhaust fans and one for supply, are selling tomato, you have to say how many fan do you want not him?????????????????
- where is [C] in your calculation
- How did you calculate supply rate, 9586cfm

 

[edenriquez0601]

the client want only two exhaust.
the calculation of the supply is CFM multiply by 105% it is possible that for that area is only two exhaust?

 

[chicopee]

It all depends on what you are trying to ventilate as your statement product volume indicate some type of chemicals being stored, dispensed or used. If it is a chemical with permissible exposure limit(PEL)normally identified in the chemical MSDS, then, your ventilation flow rate must be based on keeping the room environment to the PEL or less. If it is to keep the room environment below the lowest flammable limit then your flow rate must maintain a level, I believe at 20% of that lower explosive limit which would still be excessive for humans to enter. Obviously OSHA has ventilation rates based on floor areas which obviates the need to know the generation rate of the chemical vapors, however, calculations based on floor areas may be insufficient therefore generation rates of vapor must be determined. You'll have to give the readers a little more information as to your desired knowledge.

 

[chicopee]

It all depends on what you are trying to ventilate as your statement product volume suggest some type of chemicals being stored, dispensed or used. If it is a chemical with permissible exposure limit(PEL)normally identified in the chemical MSDS, then, your ventilation flow rate must be based on keeping the room environment to the PEL or less. If it is to keep the room environment below the lowest flammable limit then your flow rate must maintain a level, I believe at 20% of that lower explosive limit which would still be excessive for humans to enter. Obviously OSHA has ventilation rates based on floor areas which obviates the need to know the generation rate of the chemical vapors, however, calculations based on floor areas may be insufficient therefore generation rates of vapor must be determined. You'll have to give the readers a little more information as to your desired knowledge.

 

[edenriquez0601]

is this the correct computation for exhaust

example:

floor area A
bldg height B
product vol C

Ventilation
Air Change D

Exhaust fan A x B x C x D / 60

= CFM Exhaust fan

=supply CFM * 105%

 

[MintJulep]

No.

 

[edenriquez0601]

anyone can give me some formula for this.
im still learning for calculating the exhaust.please

 

[317069]

- still where is [C] in you exhaust calculation.
- supply calculation is cfmx105%, cfm of what, do you mean exhaust cfm, if this is the case then how come 5370x105/100 = 9586 ??????????

 

[edenriquez0601]

this is how

floor areas is 7,276 sqf (A)
bldg ht is 29.52 f (B)
= 214,787.52
Production vol * 50% (C)
= 107,393.76
Air Change * 3% (D)
= 322,181.28
/ 60
= 5,369.70 CFM

is this is correct?
Im Still learning how to compute!

 

[317069]

- how did you calculate the area A.
- why did you choose C as 50%.
- how did you calculate supply cfm

 

[dynamo78]

@Ed,lets simplify it for you. the volume we are talking about here is the volume of the building to be ventilated. so in your case, Area x Height: 7276 sqft x 29.92 ft= 217,698 cuft
Since you are not clear in your design intent, For a simple ware house, a.06 cuft/min per sqft(ASHRAE std) of the ware house is use here so you needed a fan or fans with a 436.56 CFM approx; 450 CFM,you may needed two @ 250 CFM each. but this is not enough to conclude that it meets your requirements. if you consider occupancy, then 5 person per 1000 sqft,means you have to to consider 15 people, are they smoker? like other friends here, if you consider the PEL, you may use the air change method too.
Next, How do you convey the air to the fan,with duct or without,if ducted,calculate the static pressure necessary to overcome the air resistance in the ductworks.

Hope that helps

 

[edenriquez0601]

L x W x H
its only a loading bay of DHL