where N = rotating speed, rpm


A = surface area of bearing = pDL, in2 (m2) u = surface speed = p^Q^ in/s (m/s)

Substituting, we obtain m L DN

In obtaining approximate losses for estimation purposes, the concentric clearance c is substituted for the local film thickness h.

If we consider the previous example where D = 5 in (127 mm), L = 5 in (127 mm), c = 0.0025 in (0.064 mm), N = 5000 rpm, and m = 2 X 10-6 lb • s/in2 (14 X 10-3 Pa • s), the horsepower loss is

FHP = (766,000)(0.0025) = 16.32 hp Note that for thrust bearings, the frictional horsepower loss is mN2 OD4 - ID4

where OD = outside diameter ID = inside diameter

A general rule of thumb is that the frictional horsepower in a thrust bearing is approximately twice that in a journal bearing.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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