Reliable and Durable Performance - · PDF file How to calculate the performance of a STD...
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Transcript of Reliable and Durable Performance - · PDF file How to calculate the performance of a STD...
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Cooling Effect per Tube at Air Velocity 3 m/sAir Pressure Drop
Oil Pressure Drop in the Connections with Different Bore Diameters
Oil Pressure Drop in Tubes of Different Lengths
Correction Factor for Cooling Effect at Different Air Flows
Vers
ion
1, 2
013.
11 S
etra
b
1 2 3 4 5 6 7 8 9 10 m/s
1600
1400
1200
1000
800
600
400
200
0
Pa
0.5 1 1.5 2 2.5 3 3.5 4 lit/min/tube
7
6
5
4
3
2
1
0
W/C/tube
6
1
9Series
1 2 3 4 5 6 7 8 9 10 m/s
2.5
2.0
1.5
1.0
0.5
0
Factor
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 lit/min
160
140
120
100
80
60
40
20
0
kPa
10 mm13 mm
16 mm
Oil viscosity cSt 20
0.5 1 1.5 2 2.5 3 3.5 4 lit/min/tube
100
90
80
70
60
50
40
30
20
10
0
kPa
9
6
1
Series
Oil viscosity cSt 20
Reliable and Durable PerformanceSetrab STD Oil Coolers are used in low to medium-
pressure systems or in circulation systems where the oil
cooler is vital to achieve reliable and durable performance.
For example, in hydraulic systems, engines, transmissions,
transformers, and fuel coolers.
Calculation service
Contact your nearest dealer or distributor if you need
help to dimension a cooler for your needs.
www.setrab.comwww.facebook.com/setrabcooling
How to calculate the performance of a STD ProLine oil cooler The graphs are simplified representations of computer software calculations. The resolution of the graphs may result in bias either up or down depending on cooler and parameter. The graphs should however give a good indication of what to expect from the cooler.
Case
I want to calculate the performance of a STD613 with an AN10 connection.
The input data is
Oil inlet temperature: 110 °C
Oil flow: 32 lit/min
Ambient air temperature: 25 °C
Air flow: 8 m/s
1. Determine the number of oil tubes on your
selected oil cooler:
F. ex. STD113, STD613 and STD913 have 13 oil tubes, STD119, STD619 and STD919 have 19 oil tubes, and so on.
2. Calculate the oil flow per tube and minute, (32 lit/min) / (13 oil tubes) = 2.46 lit/min/tube.
3. From the graph “Cooling effect per tube at air velocity 3 m/s” find the value for W/°C/tube for a series 6 oil cooler at 2.46 lit/min/tube. The value is roughly 5 W/ °C/tube. This means the heat rejection is 5 W for every °C of temperature difference between oil inlet and ambient tem-perature and tube. In this case the temperature difference is 85 °C, since inlet oil temperature is 110 °C and ambient is 25 °C (110 °C - 25 °C = 85 °C). We have 13 tubes so the heat rejection is 13 tubes x 85 °C x 5W = 5 525 W (5.5 kW) at 3 m/s.
4. The air velocity is 8 m/s so we need to adjust the calculation slightly. From the graph “Correc-tion factor for cooling at different air flows” find the factor for 8 m/s. In this case roughly 1.7. The heat rejection at 8 m/s is 1.7 times higher than for 3m/s. Multiply 5 525 W with 1.7 = 9 392 W (9.4 kW). In other words, the heat rejection for this cooler is 9.4 kW at the conditions in the above case.
Air side pressure drop
1. Air side pressure drop
In the graph for “Air side pressure drop” find the value for 8 m/s, roughly 950 Pa. Please note that most installations cannot translate more than 15-20 % of vehicle speed into air velocity through the matrix of the oil cooler if mounted in the ram air.
If a fan is used the pressure curve of the fan determines the amount of air passing through the matrix of the oil cooler. Please refer to the fan data sheet for more information.
2. Oil side pressure drop
Oil side pressure drop is a combination of pres-sure drop created when the oil passes through the connection, and the pressure drop created when the oil passes through each oil tube.
Add the values from graphs “oil pressure drop in the connections with different bore diameters” and “oil pressure drop in tubes with different lengths”.
Oil pressure drop connections, roughly 10 kPa.
Oil pressure drop tubes, roughly 30 kPa.
The oil side pressure drop is roughly 10 kPa + 30 kPa = 40 kPa (0.4 bar).
Please note that too high an oil pressure drop can
create pressure spikes and activation of pressure
relief valves. For reliable and durable operation keep
oil side pressure drop low when dimensioning the
cooler and connecting hoses.