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CHPA S
ERIES
2.5.8
Cooling Considerations
The CHPA is forced-air cooled. The exhaust air from the CHPA may be at a relatively high
temperature (approximately 35°C above ambient temperature), and heat dissipation may be as
high as 2000 watts. To prevent excessive heat buildup in the rack cabinet, it is recommended
that the exhaust air be ducted away from the CHPA; an air duct is provided for this purpose.
The external ducting must have a cross-sectional area at least equal to that of the exhaust
opening. Minimum airflow required for proper cooling of the CHPA is 120 CFM at sea level
(540 LB/HR). To meet this airflow requirement, external back pressure or intake drag must be
limited to 0.10 inch of water column (0.25 cm). Exhaust duct bends and transitions must be
smooth and bend radii should be as large as possible to promote proper cooling.
Generally speaking, a 0.10 inch H
corresponds to approximately 10 ft in length. It is therefore recommended that for longer duct
runs, a transition be made to perhaps 8-inch duct as near the CHPA exhaust as possible; 8-inch
plumbing will significantly reduce pressure drop and permit much longer duct runs. Use of 4-
inch-diameter ducting should be strictly avoided.
It is highly recommended that a heating, ventilation, and air-conditioning (HVAC) engineer be
consulted before ducting is installed as insufficient cooling will significantly impact TWT
(traveling wave tube) longevity.
2-6
0 pressure drop in a 5-inch-diameter flex-type hose
2
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REPRODUCTION OR RELEASE WITHOUT EXPRESS PERMISSION IS STRICTLY PROHIBITED
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.R
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