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Form QTC4-NM2
Issue date: 05/12/2023
Water treatment
The unit performance provided in the Design Guide
is based on a fouling factor of 0.0001 ft2hr°F/Btu
(0.018 m2/hr°C/kW). Dirt, scale, grease and certain
types of water treatment will adversely affect the heat
exchanger surfaces and as a result the unit performance.
Foreign matter in the water systems can increase the
heat exchanger pressure drop, reducing the flow rate and
causing potential damage to the heat exchanger tubes.
Aerated, brackish or salt water is not recommended
for use in the water systems. Consult a water treatment
specialist to determine whether the proposed water
composition adversely affects the evaporator materials
of carbon steel and copper. The pH value of the water
flowing through the evaporator must be kept in a range
between 7 and 8.5.
Pipework arrangement
The following figure shows a suggested piping ar-
rangement for single unit installations.
Figure 11 - Pipework arrangement
Minimum water volume
It is good practice to include as much water volume
as possible in a chilled water loop. This increases the
thermal mass and flywheel effect within the system
(that is, the more; the better) which in turn promotes
stable water temperature control and increases reliabil-
ity by reducing compressor cycling.
Quantech
For air conditioning applications, a minimum of
3 gal/ton is required, with a preferred gal/ton ratio to
be within the 5 to 8 range. For process applications, a
minimum of 6 gal/ton ratio is required with preference
towards a range of 7 to 11. Install a tank or increase
pipe sizes to provide sufficient water volume.
Leaving water temperature out of
range
The QTC4 chiller line has a maximum leaving water
temperature of 70°F (21.1°C). Where process applica-
tions require a chilled water temperature higher than
what the chiller provides, a simple piping change can
remove the problem. By using a mixture of chiller-
cooled water and returning process water, the chilled
water entering the process can be held at the required
temperature. A tank can also be used to meet high
leaving water temperature requirements.
Each QTC4 evaporator has a minimum and maximum
flow rate. Some process applications require a flow
rate that is out of range for the evaporator. In those ap-
plications, a piping change can remove the problem.
LD15151
Figure 12 - Leaving water temperature out of range
In applications where the required flow rate is less than
the evaporator's minimum allowable, the chilled water
can be recirculated to the chiller.
Section 4 - Installation
suggested layout
4
LD15049
33
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