Smartcool, Precision air conditioning, Design data – water cooled & free cooling – Airedale SmartCool 11-233kW User Manual
Page 22
SmartCool
TM
- D
Precision Air Conditioning
22
Precision Air Conditioning
Installation, Maintenance and Commissioning Manual :6877419 02/2013
Design Data – Water Cooled & Free Cooling
Dry Cooler (kW)
The dry cooler design duty is equivalent to the Total Heat of Rejection (THR) from the indoor unit.
This value can be taken from the performance data in the technical manual using the following.
Parameters required are:
·
Ambient conditions (°C dB) Airedale recommend a 10°C lower than the EWT.
·
Glycol content (%)
·
Entering & leaving water/glycol temperatures (°C) (EWT and LWT)
·
Mean condensing temperature (°C) Based on 5°C above leaving water/glycol temperature
Calculation of Design
Volumetric Flow Rate (l/s)
The maximum design volumetric flow rate can be calculated using the following equation:
V&
=
Q
r x Cp x ΔT
Where:
Q
=
Total Heat Rejection (kW).
DT
=
Temperature Difference between Water/Glycol Entering/ Leaving (°C).
r
=
Density. Refer to table below.
Cp
=
Specific heat capacity. Refer to table below.
Calculation of Indoor Unit
Pressure Drop (
DPs)
The maximum indoor unit pressure drop can be calculated using the following equation:
DPs= DPw x Pc
Using the volumetric flow rate calculated above, the pressure drop (
DPw) can be taken from the
relevant pressure drop graph..
Where:
DPs
=
Maximum Water/Glycol Pressure Drop for the indoor unit (kPa).
DPw
=
Equivalent Water Pressure Drop for indoor unit (kPa).
P
c
=
% Glycol Pressure Drop Correction Factor @ 20°C Water Temperature.
Refer to table below.
The resultant pressure drop (
DPs) is the maximum pressure drop based on the indoor unit
running at the prescribed conditions.
This will typically occur when the water/glycol temperature is approximately 20°C and the
water/glycol is being circulated through the free cooling coil and through the water cooled
condenser.
The indoor unit pressure drop will reduce at other operating conditions.
Specific Heat Capacity (Cp)
Water/Glycol Temperature °C
Ethylene Glycol (Volume) / Freezing Point °C
0% / 0°C
10% / -4°C
20% / -9°C
30% / -15°C
40% / -23°C
F
c
F
c
F
c
F
c
F
c
20
4.183
3.972
3.815
3.645
3.468
25
4.181
3.981
3.826
3.660
3.485
30
4.179
3.989
3.838
3.674
3.502
35
4.178
3.998
3.849
3.688
3.518
40
4.179
4.007
3.861
3.702
3.535
45
4.181
4.015
3.872
3.716
3.552
Density (
r)
Water/Glycol Temperature °C
Ethylene Glycol (Volume) / Freezing Point °C
0% / 0°C
10% / -4°C
20% / -9°C
30% / -15°C
40% / -23°C
F
c
F
c
F
c
F
c
F
c
20
998
1013
1030
1045
1060
25
997
1012
1028
1043
1058
30
996
1010
1026
1041
1055
35
994
1008
1024
1039
1053
40
992
1006
1022
1036
1050
45
990
1003
1020
1035
1048
Pressure Drop Correction
Factor (P
c)
Water/Glycol Temperature °C
Ethylene Glycol (Volume)
0%
10%
20%
30%
40%
P
c
P
c
P
c
P
c
P
c
20
0.983
1.0125
1.054
1.0958
1.15
In
s
ta
ll
a
tion