Originally Posted by Shannow
Mola, the heat in a journal bearing is generated within hte bearing, rather than conducted through it the oil film
I am not sure what you are referring to since you didn't quote a specific sentence, but the temperature rise in a journal bearing is due to a number of factors including 1) the shearing of and pressure peaks in the wedge's oil film and 2) friction due to the time the journal and bearing are in mixed or boundary regime conditions.
Quote
Effect on power loss
Commonly the phenomenon of friction is perceived as an action of rubbing of two solid objects over each other. However in the hydrodynamic bearings there is no direct contact between the bearing and journal surfaces. They are separated with a film of fluid lubricant which is adhered to the both surfaces.
As the journal surface moves it produces movement of the lubricant. Velocity of the lubricant is varying in the direction across the film thickness. It has the maximum value at the journal surface and gradually decreases to zero at the bearing surface. The oil film may be presented as having many layers moving relatively to each other. Such motion produces a shear force between the adjacent layers. The force contradicts to the rotation of the journal. This force is called hydrodynamic friction. Hydrodynamic friction causes a loss of power which is converted into heat and dissipated in the lubricant, the engine parts and the ambient atmosphere.
https://www.substech.com/dokuwiki/d...hydrodynamic_friction_of_engine_bearings
Heat from the block is also conducted down to the journal bearing area in terms of thermal energy movement from the combustion chamber down to the lower end.
The movement of lubricating oil in and out of the eccentric wedge is essentially a movement of oil via
convection, so it is the convection (fluid movement} of the oil that transfers thermal energy out of the bearing. Temperature rise in the bearing is due to both mixed or boundary regime conditions AND the
Conduction of thermal energy from the oil to the journal and bearing surfaces and is dependent upon the oil's dwell time in the wedge. However, the
bulk of thermal energy
transfer is due to convection (flow) of the oil.
see page 162 of the this reference:
Fundamentals of Fluid Film Journal Bearings and Modeling