IT Cooling
LogiCool
OnRak
IT Cooling
17
Technical, Installation and Maintenance Manual :6912497 V1.8.0 _08_2014
Ethylene Glycol Correction Factors
Calculation of Design
Volumetric Flow Rate (l/s)
The maximum design volumetric flow rate can be calculated using the following equation:
V
=
Q
U
x Cp x
ǻ
T
Where:
Q
=
Cooling Capacity (kW).
'
T
=
Temperature Difference between Water/Glycol Entering/ Leaving (°C).
U
=
Density of Glycol/Water mixture at design condition. Refer to table below.
Cp
=
Specific heat capacity at design condition. Refer to table below.
Calculation of Indoor Unit
Pressure Drop (
'
P
s
)
The maximum indoor unit pressure drop can be calculated using the following equation:
'
Ps=
'
Pw x P
F
Using the volumetric flow rate calculated above, the pressure drop (
'
P
w
) can be taken from the relevant
pressure drop graph..
Where:
'
P
s
=
Maximum Water/Glycol Pressure Drop for the indoor unit (kPa).
'
P
w
=
Equivalent Water Pressure Drop for indoor unit (kPa).
P
F
=
% Glycol Pressure Drop Correction Factor @ 10°C Water Temperature.
Refer to table below.
The resultant pressure drop (
'
P
s
) 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 10°C.
The indoor unit pressure drop will change 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
Cp
Cp
Cp
Cp
Cp
10
4.193
4.064
3.918
3.773
3.606
Density (
U
)
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
U
U
U
U
U
10
998
1008
1018
1027
1037
Pressure Drop Correction
Factor (P
F
)
Water/Glycol Temperature °C
Ethylene Glycol (Volume)
0%
10%
20%
30%
40%
P
F
P
F
P
F
P
F
P
F
10
0.983
1.0125
1.027
1.045
1.067
(1) All data based upon ASHRAE fundamentals 2001.
