Page 2 - EEC_Fans
P. 2
ir®quipt-A
Blower and Fan
Selection Nomograph
This nomograph will assist you in making a rapid evaluation of Temperature Rise
the airflow required to cool the average electronics enclosure, if
the approximate wattage to be dissipated and the acceptable tem-
perature rise are known.
C F
First, determine the amount of heat to be removed, in watts. Then Airflow Power to be
identify the acceptable rise in temperature. Theoretically , this is (CFM + 25% Dissipated
the maximum allowable component temperature minus the maxi- Safety Factor)
mum anticipated ambient temperature. (Watts)
Lay a straight edge across the nomograph to intersect these two
points. The straight edge will intersect the required volume on the
airflow scale. The nomograph automatically includes a “safety
factor” of 25 percent more air than is dictated by strict adherence
to theoretical considerations. This is expressed by the constant,
1.25, in the first two equations.
Based on standard air density (0.075 lbs. per cubic foot), the
nomograph furnishes quick solutions for the following equations:
CFM = 3.17P (1.25) for temperature rise
TF in degrees Fahrenheit
CFM = 1.76P (1.25) for temperature rise
TC in degrees Celsius
The average temperature rise (TF or TC) in the cabinet equals the
cabinet outlet temperature minus the cabinet inlet temperature.
CFM = Volume flow of cooling air in cubic feet per minute.
P = Power to be dissipated in watts.
The constant, 1.25, represents the “safety factor” discussed above. How to Order
Specific heat of air is considered constant in these formula. If the Add discharge suffix to the basic Model Number from the table
atmosphere density at which the equipment is to operate deviates on the opposite page when ordering. Example: 031-020-701A is a
significantly from standard air density, the following formula will seven-inch high, 360 CFM unit with diagonal rear discharge.
convert the approximation obtained from the nomograph to the
CFM required at the different density:
CFMn = CFM0.075 (0.075)
Pn
Where:
Subscript n = non-standard air density;
Subscript 0.075 = nominal standard air density;
Pn = non-standard air density (lbs. per cubic foot).
E2 Equipto Electronics Corp.4Aurora, IL4800.204.72254630.897.46914Fax 630.897.5314
Blower and Fan
Selection Nomograph
This nomograph will assist you in making a rapid evaluation of Temperature Rise
the airflow required to cool the average electronics enclosure, if
the approximate wattage to be dissipated and the acceptable tem-
perature rise are known.
C F
First, determine the amount of heat to be removed, in watts. Then Airflow Power to be
identify the acceptable rise in temperature. Theoretically , this is (CFM + 25% Dissipated
the maximum allowable component temperature minus the maxi- Safety Factor)
mum anticipated ambient temperature. (Watts)
Lay a straight edge across the nomograph to intersect these two
points. The straight edge will intersect the required volume on the
airflow scale. The nomograph automatically includes a “safety
factor” of 25 percent more air than is dictated by strict adherence
to theoretical considerations. This is expressed by the constant,
1.25, in the first two equations.
Based on standard air density (0.075 lbs. per cubic foot), the
nomograph furnishes quick solutions for the following equations:
CFM = 3.17P (1.25) for temperature rise
TF in degrees Fahrenheit
CFM = 1.76P (1.25) for temperature rise
TC in degrees Celsius
The average temperature rise (TF or TC) in the cabinet equals the
cabinet outlet temperature minus the cabinet inlet temperature.
CFM = Volume flow of cooling air in cubic feet per minute.
P = Power to be dissipated in watts.
The constant, 1.25, represents the “safety factor” discussed above. How to Order
Specific heat of air is considered constant in these formula. If the Add discharge suffix to the basic Model Number from the table
atmosphere density at which the equipment is to operate deviates on the opposite page when ordering. Example: 031-020-701A is a
significantly from standard air density, the following formula will seven-inch high, 360 CFM unit with diagonal rear discharge.
convert the approximation obtained from the nomograph to the
CFM required at the different density:
CFMn = CFM0.075 (0.075)
Pn
Where:
Subscript n = non-standard air density;
Subscript 0.075 = nominal standard air density;
Pn = non-standard air density (lbs. per cubic foot).
E2 Equipto Electronics Corp.4Aurora, IL4800.204.72254630.897.46914Fax 630.897.5314
