Parameter Generation and Control 9354-4250, Инструкция по установке и эксплуатации

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PGC, Inc 500-1000 CFM Air Handler May 2006
Appendix A A-4
D
ESCRIPTION OF
O
PERATION
The 500-1000 CFM Conditioner is a self-contained conditioner designed to control dry-bulb
temperatures over a range of 7°C – 60°C (44.6ºF - 140ºF), dependent upon the size and
construction of the test chamber. The dry-bulb temperature is held to ± 0.2°C and relative
humidity constancy to ± 0.5% with dew points above 5°C (41°F).
The temperature of the water spray saturator controls the dew point of the discharge air. When in
Rh Cascade or Slow Damper mode, the water temperature in the saturator is varied slowly in
response to a humidity control system. This allows the system to respond to wide load variations
while retaining the basic stability of a spray system. When in Two-Temperature mode, the user
establishes the air and water temperatures.
M
EASUREMENT OF
T
EST
C
HAMBER
C
ONDITIONS
Precise control of temperature and humidity within the test chamber is obtained by accurately
measuring the dry-bulb temperature and the dew point temperature of the air in the test chamber
or the duct. The temperature of the water in the spray chamber controls the dew point
temperature, and is measured prior to the spray nozzles.
When operating in one of the spray modes, the dew point of the air exceeds the water temperature
by approximately 1°C for each 10°C difference between the air and water temperatures. During
the ramp portion of program cycling, the dynamic heat exchange process that takes place makes it
difficult to establish any exact relationship. When operating in the Two-Temperature mode, refer
to the air/Rh/water spray graph provided with the unit for air and water temperatures necessary
for the desired relative humidity.
A
IR
F
LOW
As the air enters the conditioner through the round, flexible duct connection in the removable top
cover. The process blower, located beneath this cover, will force the air into the conditioning
section. Entering the conditioning section, the air first encounters the by-pass damper; the
damper determines the volume of air that enters the saturator, and the volume that is bypassed
around the saturator. When the damper is fully closed, all of the air is forced through the water
spray. As the air passes through the water spray, it is saturated and cooled, nearly to the water
temperature. This method provides a stable dew point for the air as it leaves the saturator section.
The chilled and saturated air then passes through the water droplet eliminator to remove any free
moisture that may be present. The air then continues over the dry-bulb heaters, where it is heated
to the desired chamber air temperature (without affecting the dew point) and is returned to the
chamber through the round, flexible duct connection on the left end of the conditioner.
When the damper is fully open, most of the air bypasses the water spray and travels directly to the
air heaters. The bypassed air is then mixed with any air that traveled through the saturator section
and then returns to the test chamber. The spray bypass damper will be automatically positioned
by the actuator operating on a control signal derived from the duty cycle of the air heater. The
position of the damper can range from 0% to 100% open.
The dew point of the air stream is controlled even when most of the air is bypassed around the
water spray saturator. The air bypass damper is not 100% efficient, allowing some air to enter the
water spray saturator even when closed.