Normally, At, is selected between 20 and 40°F. Since qT will exceed qt, not all the flow will enter the film. Some will surround the bearing or flow through the feed groove and act as a cooling medium for heat transfer through the bearing walls or for cooling the fluid that does enter the bearing surface q;.

example This example demonstrates the use of the design curves and how to perform a simplified heat balance in a bearing analysis. In this example, we know these values:

Bearing type: two-groove cylindrical Bearing length L = 3 in (76 mm) Bearing diameter D = 6 in (152 mm) LID = 0.5

N = 1800 rpm; v = 1800 X p/30 = 188.5 rad/s Bearing load v = 6000 lb (2721 kg) Inlet temperature , = 120°F (49°C) Lubricant = SAE 20

Bearing radial clearance c = 0.003 in (0.076 mm)

NOTE: A general rule of thumb is that cIR = 0.001.

Assume an average lubricant temperature of 130°F - m (SAE 20 at 130°F) = 4.5 X 10-6 reyn (lb • s/in2) (31 X 10-3 Pa • s)

- = 0.0307 lb/in3(849.7 kg/m3) (average value for most oils)

Cp = 0.5Btu/lb • F° (2093 J/kg • C°) (average value for most oils)

Compute the following:

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