ClimaCool UCR Remote Air Cooled - Manual (Page 20)

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18
The following information must be known in order to
properly select a ClimaCool remote air-cooled chiller
system:
• System load in Tons
• Chilled water temperature drop (CWTD)
• Leaving chilled water temperature (LCWT)
• Ambient air temperature entering condenser (TA)
• Condenser TD (or CTD)- saturated condensing
temperature minus ambient air temperature
Using Performance Tables
When reading data from the performance tables on
page 10, it is necessary to fi rst calculate the “Saturated
Refrigerant Discharge Temperature” or TSD as follows:
TSD = TA + CTD
TA = Ambient air temperature entering condenser
CTD = Condenser temperature diff erence between
ambient air temperature and saturated
condensing temperature
Given the leaving chilled water temperature (LCWT), and
the calculated TSD, the Capacity in Tons are read from
the appropriate performance table. The performance
tables are based on a 10°F temperature drop in chilled
water. For temperature drops other than 10°F, and/or
for altitudes other than sea level, multiply the Tons by
the factor found in Table 1 on page 21.
Sample Selection
Input Data:
• LOAD = 84 TONS
• CWTD = 8°F
• LCWT = 44°F
• TA = 95°F
• CTD = 30°F
1. Determine saturated discharge temperature (TSD).
TSD = TA + CTD
TSD = 95°F+30°F = 125°F
2. Select the appropriate “Quick Select” table based on
the desired module type (e.g. UCR modules with “H”
style air-cooled condensers). Record the Capacity
and kW of a (1) 70-Ton and (1) 30-Ton module at the
leaving chilled water temperature specifi ed (LCWT)
of 44°F, and at the TSD calculated above at 125°F.
Capacity = 86 Tons, kW = 96
3. To fi nd the equivalent tons capacity at 8°F chiller
drop by a single module tabulated at 10°F drop values,
divide the tons capacity by the factor in Table 1 on
page 21, as:
Capacity Required = 84/0.995= 84.4 Tons
Modules Required = (1) 70-Ton & (1) 30-Ton
Power Input = (96) = 96 kW
At 8°F temperature drop, applying Table 1 on page 21,
performance adjustment factor results in:
Tons = (86) (.995) = 85.6 vs system load of 84
Ton
4. Chilled water fl ow rate is determined as follows:
GPM= (24) (Tons)/ (Chilled Water Temperature
Drop)
or GPM = (24)(Tons)/(CWTD)
GPM = (24) (85.6)/8 = 256.8
To fi nd GPM per module:
GPM/ (# of modules) = 251.1/3 = 83.7
5. Chilled water pressure drops are provided in Figure 1
on page 20. Using the GPM/Module results from step 4
above, refer to Figure 1 on page 20, and read pressure
drop from the middle curve for model UCR070 as:
Pressure Drop = 14 feet of water
Chiller Performance with Glycols
When analyzing performance data of chillers employing
glycol and water solutions, fi rst derive the chiller
performance data (Capacity, kW, GPM and pressure drop)
assuming pure water fl ow through the chiller. Then you
can apply adjustment factors to the performance data
from the pure water case. These factors are found in
Figures AM-1 through Figure AM-4 on pages 20-21, and
depend upon the type and percent of glycol used in
the chiller circuit. Figure AM-1 and Figure AM-2 provide
factors for propylene glycol. Figure AM-3 and Figure AM-4
are for ethylene glycol. The factors in all Figures AM-1
through AM-4 are based on 10°F drop in fl uid temperature
through the chillers, at sea level, and at 95°F entering
condenser air temperature. Figure AM-5 is provided for
solution freeze temperatures of glycol concentrations.
Table 1 on page 21 provides adjustment factors for sea
level changes and chiller temperature drops other than
10°F, all assuming a fouling factor of 0.0001 in the chiller.
Selection Procedure