2.7.17 Cooling Tower Fan
Cooling Tower Fans are used to cool condenser water in water cooled chiller systems. Water cooled chillers provide the most efficient means of creating
chilled water. They are as much as 20% more efficient than air cooled chillers. Depending on climate, cooling towers are often the most energy efficient
method of cooling the condenser water from chillers.
They cool the condenser water by evaporation.
The condenser water is sprayed into the cooling tower onto the cooling towers “fill” to increase its surface area. The tower fan blows air through the fill
and sprayed water to aid in the evaporation. Evaporation removes energy from the water dropping its temperature. The cooled water collects in the
cooling towers basin where it is pumped back into the chillers condenser and the cycle is repeated.
2.7.18 The VLT Solution
With a frequency converter, the cooling towers fans can be controlled to the required speed to maintain the condenser water temperature. The frequency
converters can also be used to turn the fan on and off as needed.
Several features of the Danfoss HVAC dedicated frequency converter, the HVAC frequency converter can be utilized to improve the performance of your
cooling tower fans application. As the cooling tower fans drop below a certain speed, the effect the fan has on cooling the water becomes small. Also,
when utilizing a gear-box to frequency control the tower fan, a minimum speed of 40-50% may be required.
The customer programmable minimum frequency setting is available to maintain this minimum frequency even as the feedback or speed reference calls
for lower speeds.
Also as a standard feature, you can program the frequency converter to enter a “sleep” mode and stop the fan until a higher speed is required. Additionally,
some cooling tower fans have undesireable frequencies that may cause vibrations. These frequencies can easily be avoided by programming the bypass
frequency ranges in the frequency converter.
Water Inlet
Water Outlet
CHILLER
Temperature
Sensor
BASIN
Conderser
Water pump
Supply
2 Introduction to VLT HVAC Drive
VLT
®
HVAC Drive Design Guide
28
MG.11.B9.02 - VLT
®
is a registered Danfoss trademark
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