Selection Procedures
The chiller capacity tables on the following pages cover the most frequently encountered leaving water temperatures. For temperature drops other than 10°F [5.6°C], refer to Table
Additional chiller selections and performance information can be obtained through your local Trane sales office.
To select a Trane
1.Design load in tons of refrigeration
2.Design chilled water temperature drop
3.Design leaving chilled water temperature
4.Entering condenser water temperature
Evaporator flow rate (gpm) can be determined by using the following formula:
gpm = | Tons x 24 |
| Chilled Water T (F) |
Condenser flow rate (gpm) can be determined by using the following formula:
gpm =
24 x (tons + (0.285 x compressor kW) Condenser Water T (F)
Table
Fouling | Water |
| Evap. |
| Cond. |
Factor | Delta T | Capacity | GPM | kW | GPM |
| 8 | 0.997 | 1.231 | 1.000 | 0.997 |
0.00010 | 10 | 1.000 | 1.000 | 1.000 | 1.000 |
| 12 | 1.007 | 0.829 | 1.001 | 1.006 |
| 14 | 1.012 | 0.714 | 1.001 | 1.010 |
| 16 | 1.017 | 0.628 | 1.002 | 1.014 |
Note:
This selection procedure is for water only as the solution.
Scroll Liquid Chiller — (CGWF) — Selection Example:
Given:
System Load = 40 tons
Leaving Chilled Water Temperature (LCWT) = 44°F [6.7°C]
Entering Condenser Water Temperature (EWT) = 85°F [29.4°C]
Leaving Condenser Water Temperature (LWT) = 95°F [35°C]
Chilled Water Temperature Drop
=10°F [5.6°C]
1.From Table
2.To determine the evaporator and condenser water pressure drops, the flow rates (gpm) must be determined. Using the formula above, this unit would require an evaporator flow rate of 95 gpm and a condenser flow rate of 115 gpm. (Compressor kW is found in the same table as the capacity.) The Evaporator Pressure Drop Curve, Chart
3.The final unit selection is:
—Quantity (1) CGWF 40
—Cooling Capacity = 39.4 tons
—Entering/Leaving Chilled Water Temperatures = 54/44°F [12.2/6.7°C]
—Chilled water flow rate = 95 gpm
—Evaporator water pressure drop = 13.8 feet
—Cooling water flow = 115 gpm
—Condenser water pressure drop = 14 feet
—Compressor power input = 30.3 kW
—Unit EER = 15.6
Compressor Chiller – (CCAF) – Selection Example:
Select the unit for the following conditions:
A compressor chiller is required to produce 45 tons when matched with an
1.Select the nominal unit size. The performance data is tabulated by leaving chilled water temperature. For example, the standard unit capacities at 44°F [6.7°C] leaving chilled water temperature are found on page 21. The system that best meets the tonnage requirement is a CCAF 50 matched with a CAUC C50. The unit capacity is 47.1 tons with a kW input of
56.3.The compressor chiller EER is
2.Calculate the required chilled water flow rate.
3. gpm = | Tons x 24 |
| Chilled Water T (F) |
From this example, | |
gpm = | 47.1 x 24 = 113 |
| 10 |
4.Determine the evaporator water pressure drop. The evaporator water pressure drop is located on page 22. Entering the evaporator chart at 113 gpm, the pressure drop for a CCAF 50 evaporator is 7.9 feet.
5.Unit Selection
The above procedure shows the proper selection for this example is a CCAF 50 with a CAUB C50 condenser operating as follows:
—Capacity = 47.1
—Entering/leaving chilled water temperature = 54/44°F [12.2/6.7°C]
—Chilled water flow rate = 113 gpm
—Evaporator water pressure drop = 7.9 feet
—Compressor power input = 56.3
—Unit EER = 10.0
15 |
