Airedale OnRak 3kW 35kW - Manual (Page 17)

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Technical, Installation and Maintenance Manual :6912497 V1.5.0 02_2013
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

x Cp x ΔT
Where:
Q
= Cooling Capacity (kW).

T = Temperature Difference between Water/Glycol Entering/ Leaving (°C).

= 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 (

Ps)
The maximum indoor unit pressure drop can be calculated using the following equation:

Ps=

Pw x P

Using the volumetric flow rate calculated above, the pressure drop (

Pw) can be taken from the relevant
pressure drop graph..
Where:
 Ps = Maximum Water/Glycol Pressure Drop for the indoor unit (kPa).
 Pw = Equivalent Water Pressure Drop for indoor unit (kPa).
P  = % Glycol Pressure Drop Correction Factor @ 10°C Water Temperature.
Refer to table below.
The resultant pressure drop (  Ps) 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 (

)
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
    
10 998 1008 1018 1027 1037
Pressure Drop Correction
Factor (P

)
Water/Glycol Temperature °C
Ethylene Glycol (Volume)
0% 10% 20% 30% 40%
P  P  P  P  P 
10 0.983 1.0125 1.027 1.045 1.067
(1) All data based upon ASHRAE fundamentals 2001.