ESDU 97019:2010

INTRODUCTION

This Data Item describes the use of ESDUpac A9719 which provides
a computer program for determining the equilibrium temperatures and
heat flow rates in a network of heat conducting and dissipating
components. The thermal network analysis implemented by the program
is quite general but is most immediately applicable to
self-contained bearing assemblies such as dry rubbing bearings,
rolling element bearings, fluid film bearings lubricated by oil or
grease, and oil-impregnated porous bearings. The program
incorporates representations of a number of standard parts, such as
shaft and bush parts, that can be combined to model the heat
generation, conduction and dissipation (by convection and
radiation) in the complete assembly.

The temperatures in a bearing assembly might need to be
estimated so that wear rates and load limits can be determined or
operating film thickness and power loss be estimated. Also, an
estimate of reservoir or sump temperature might allow thermal
degradation of lubricants and lubricant life to be assessed. The
temperatures at other points in the assembly might also need to be
determined. For example, bearing temperatures are usually measured
at the bearing back rather than at the friction surface and it may
be required to predict this temperature for comparison with test
results. Temperatures at external surfaces may also be required for
assessment of any safety hazard.

Another important reason for pursuing such an analysis is to
identify thermal conditions that could lead to problems or failure
in operation. For example, if the predicted temperature for the
inner race of a rolling bearing were considerably higher than that
of the outer race a loss of diametral clearance, and consequential
risk of thermal runaway, would be indicated.

The program implements much of the heat transfer and heat
dissipation analysis methods described in a previously issued set
of Data Items numbered 78026, 78027, 78028, 78029 and 79002 (see
Derivations 6 to 10) and provides a replacement for the manual
method of determining the equilibrium conditions in a bearing
assembly described in those Data Items. The Items can be referred
to for the theoretical basis of some of the analysis and for
discussion of practical considerations.

This document does not provide a preview.