Thermal testing has proven that natural convection cooling is not adequate for today's smaller, high power density enclosures. Heat dissipation by forced convection (fan cooling) is the most frequently used method of cooling. Forced-air cooling systems can provide heat transfer rates that are 10 times greater than those achievable with natural convection and radiation, but even this is not adequate to cool faster electronic components when they are located in hostile plant environments.
Consider Vortex CoolingA vortex cooler enclosure cooler uses a vortex tube to convert a filtered compressed air supply into cooled air without the use of electricity, ammonia or other refrigerants. A vortex tube produces cooled air by forcing filtered, compressed air through an internal generation chamber and then in a centrifugal path along its inner walls at a high rate of speed (1,000 rpm) toward the control valve (hot exhaust). The remainder of the high-speed air is forced to counterflow up through the center of the high-speed airstream. As it passes through the center of the generation chamber, it slows down and gives up heat before finally exiting through the opposite end as cooled air.
Both the high-speed air and the slower moving airstream rotate at the same angular velocity. This is because intense turbulence at the boundary between the two streams and throughout both streams locks them into a single mass (as rotational movement is regarded). The slower speed inner stream is a forced vortex because its rotational movement is controlled by an outside influence other than the conservation of angular momentum.
The cooled air produced by the tube inside the enclosure cooler is discharged into the enclosure while hot air in the enclosure is vented outside the box into the surrounding area through a built-in relief valve. The built-in relief valve and the cooler-to-enclosure seal maintain the integrity of NEMA or JIC boxes. Air introduced into the enclosure is filtered before it enters the vortex cooler, creating a clean, cool and controlled environment inside the enclosure and helping to keep controlled processes up and running. An added benefit is that the enclosure cooler produces a slight positive pressure inside the cabinet to keep out dust and dirt.
Sidebar: Vortex Cooler Q & AHow Much Inline Pressure Does a Vortex Cooler Enclosure Cooler Need?
These coolers are designed to use a filtered factory compressed air supply of 80 to 100 psig. Unless compressed air pressures fluctuate widely or run considerably higher than 110 psig, do not use a pressure regulator to reduce the inlet pressure. Pressures lower than 80 psig limit inline airflow and produce a slightly warmer airflow into the enclosure, reducing the BTU/hr cooling capacities of the coolers.
What Inlet Line Size Do I Install?
A vortex cooler enclosure cooler with up to a 5,000 BTU/hr capacity can be supplied using 3/8" schedule 40 pipe that has a drop (distance from the main supply) of less than 10'. A 3/4" schedule 40 pipe would be used for a distance up to 50'.
Rubber hose with a suitable pressure rating can be used to supply the coolers. A 1/2" hose is used in place of a 3/8" pipe; 3/4" hose is used in place of a 1/2" pipe; and 1" hose is used in place of a 3/4" pipe. Only new rubber hose should be used to supply vortex coolers. A used rubber hose normally will have cuts on the inside wall (inside diameter) and be contaminated from inadequate filtration of particulate and oils. Select the compressed air line size appropriately and remember that lower inline pressures will produce a greater inline pressure drop and subsequent lower airflow and BTU/hr cooling capacity.
How Do I Remove Moisture, Dirt And Oil from Compressed Air?
All compressed air systems will have condensed water, rust (scale) and dirt in the lines. To remove this contamination from the compressed air, a 5 micron filter-separator (preferably with an automatic drain) is recommended for use with vortex coolers.
A dryer usually is not required for proper operation except when the normal relative humidity level is high (as you would find near any large body of water such as the Great Lakes). A desiccant dryer can be used in the inlet line to eliminate condensed water vapor in the supply. The dryer should be rated to produce an atmospheric dew point lower than the output temperature of enclosure cooler.
It is not necessary to supply lubricated air to a vortex cooler; in fact, oil and oil aerosols must be removed from the compressed air supply.
Is Maintenance Required?
Because these enclosure coolers have no moving parts, they are reliable and require little maintenance. It is only necessary to change the elements in the filters at regularly scheduled intervals. A minimum interval of six months is recommended; however, the cleanliness of the compressed air supply will determine the change frequency of the filter element.