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120 KRW
Friction
The load independent friction moment is calculated according to the relation explained in section friction and is
simplified by the operating parameters of bearing 6220 in accordance with the aforementioned operating conditions.
The following applies:
M0 = f0 · 10 -7 · v 2/3 · n 2/3 3
· dm = C1 · v 2/3
Based on arbitrary, but possible operating temperatures, the operating viscosity and the load independent friction
moment as well as the friction energy are calculated in an Excel table.
The load dependent friction moment is likewise calculated according to known relations. In the given example, the
load dependent friction moment is
M 1
= 1148 Nmm
In the following example, the heat is removed only by free thermal convection and the lubrication oilflow.
The following applies for the convection:
t – t u
QL = qLB · –—– · K t · 2 · dm · B · π 10-3
50
For q LB applies 20 · ( 4760/4000 ) -0,34 = 18,85 kW/m² , therefore, if the equation is resolved according to
the operating temperature with the parameters of the example inserted, the linear function in the form of:
is obtained.
Q L = C 2 · t - 11,27
The following applies if the heat has to be removed by the lubricating oil:
We assume an oil flow of VL = 0,5 l/min with a difference of oilinflow and oiloutflow of 6 K
L
Q ÖL = 30 · V VÖL
· (tab – tzu ) = 30 · 0,5 · 6 = 90 W
The temperature dependent results for the friction portions and the estimated heat removal are calculated in an
Excel table:
Operating temperature °C 30 40 50 60 70 80
Operating viscosity mm/s² 183 100 60 39 26 19
Load independent
friction moment
Nmm 2318 2000 1423 1062 824 660
Total friction energy W 954 725 592 509 454 417
Convection W 113 226 338 451 564 677
Total heat removal W 203 316 428 541 654 767
The result of the calculation example is shown in the following diagram.