How cold can a cooling fan keep things?
Cooling Fan Operation
Electrical components inherently generate heat while in use, and in order for a component to remain in a useful state it must be cooled in some fashion. Components that generate small amounts of heat can be cooled passively or with a simple heat sink. Today's multiple core central processing units, monster graphics processing units, and screaming fast memory modules have increased in clock speed. In the field of electronics, where you add speed, you add additional heat. Where you have excess heat, you need a cooling fan.
Simply put, a fan moves gas from one point to another by creating a pressure differential. The majority of cooling fan applications move air. Fans enhance the convection heat transfer mechanism by increasing the amount of fluid passed over the heat exchanger.
Typical Fan Sizes and Performance
Case fans are normally square in shape and sized in millimeters with 80 mm, 92 mm, and 120 mm being the most common. Case fans are also available in various thicknesses or depths. The depth of the fan housing places a limit on the maximum pitch of the fan blades. Together, the blade pitch and fan speed dictate the fan's air flow rate. Fan air flow is typically measured in cubic feet per minute, and the rotation speed is usually conveyed in revolutions per minute.
Decibel ratings, normally expressed in dBa, should be considered when it is necessary to quietly cool a component or enclosure. Consider this scenario, a hospital patient would not likely appreciate a 120 mm fan, with fuchsia LEDs, running at 3000 RPM near their head while recovering from gall bladder surgery. However, a teenage computer gamer in his parents basement would have little objection to the same fan other than the color of LEDs.
A typical 80 mm case fan running at 2000 RPM will develop a flow rate of 25 CFM and increasing the fan speed to 2700 RPM will bring the flow rate up to approximately 35 CFM. In comparison, some of the more expensive 120 mm fans will move 90 CFM at 2000 RPM.
As with most things, one measure of performance is sacrificed for another. For example, a thin fan will have a low blade pitch. A low blade pitch limits the maximum flow rate of the fan. A thicker fan can utilize blades with a high pitch, in turn increasing the maximum flow rate, but typically with the cost of added noise.
Positive or Negative?
In an application where a fan is installed in or on an enclosure two modes of operation can be employed.
Positive pressure is defined as when the volume of air being introduced into an enclosure is greater than the amount of gas being exhausted. Configuring an enclosure for positive pressure has the advantage of forcing air into all the nooks and crannies of the enclosure.
Negative pressure is exactly the opposite; a greater volume of gas is being expelled from the enclosure than is being supplied. Popular opinion is that an enclosure configured for negative pressure will collect fewer particulates than a positive pressure enclosure, but the jury is still out on that one.
Which Fan is Right For Me?
The number of opinions on fans probably exceeds the amount of fans available on the market. The short answer is that a proper fan specification will consider ambient temperature, cooling demand, size restrictions, and noise level tolerance.
To learn more or to browse a variety of cooling fans, please visit http://www.nmbtc.com/fans/
Electrical components inherently generate heat while in use, and in order for a component to remain in a useful state it must be cooled in some fashion. Components that generate small amounts of heat can be cooled passively or with a simple heat sink. Today's multiple core central processing units, monster graphics processing units, and screaming fast memory modules have increased in clock speed. In the field of electronics, where you add speed, you add additional heat. Where you have excess heat, you need a cooling fan.
Simply put, a fan moves gas from one point to another by creating a pressure differential. The majority of cooling fan applications move air. Fans enhance the convection heat transfer mechanism by increasing the amount of fluid passed over the heat exchanger.
Typical Fan Sizes and Performance
Case fans are normally square in shape and sized in millimeters with 80 mm, 92 mm, and 120 mm being the most common. Case fans are also available in various thicknesses or depths. The depth of the fan housing places a limit on the maximum pitch of the fan blades. Together, the blade pitch and fan speed dictate the fan's air flow rate. Fan air flow is typically measured in cubic feet per minute, and the rotation speed is usually conveyed in revolutions per minute.
Decibel ratings, normally expressed in dBa, should be considered when it is necessary to quietly cool a component or enclosure. Consider this scenario, a hospital patient would not likely appreciate a 120 mm fan, with fuchsia LEDs, running at 3000 RPM near their head while recovering from gall bladder surgery. However, a teenage computer gamer in his parents basement would have little objection to the same fan other than the color of LEDs.
A typical 80 mm case fan running at 2000 RPM will develop a flow rate of 25 CFM and increasing the fan speed to 2700 RPM will bring the flow rate up to approximately 35 CFM. In comparison, some of the more expensive 120 mm fans will move 90 CFM at 2000 RPM.
As with most things, one measure of performance is sacrificed for another. For example, a thin fan will have a low blade pitch. A low blade pitch limits the maximum flow rate of the fan. A thicker fan can utilize blades with a high pitch, in turn increasing the maximum flow rate, but typically with the cost of added noise.
Positive or Negative?
In an application where a fan is installed in or on an enclosure two modes of operation can be employed.
Positive pressure is defined as when the volume of air being introduced into an enclosure is greater than the amount of gas being exhausted. Configuring an enclosure for positive pressure has the advantage of forcing air into all the nooks and crannies of the enclosure.
Negative pressure is exactly the opposite; a greater volume of gas is being expelled from the enclosure than is being supplied. Popular opinion is that an enclosure configured for negative pressure will collect fewer particulates than a positive pressure enclosure, but the jury is still out on that one.
Which Fan is Right For Me?
The number of opinions on fans probably exceeds the amount of fans available on the market. The short answer is that a proper fan specification will consider ambient temperature, cooling demand, size restrictions, and noise level tolerance.
To learn more or to browse a variety of cooling fans, please visit http://www.nmbtc.com/fans/
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