Convective heat transfer modelling in dry-running polymer spur gears

Abstract

Heat convection is an important phenomenon in the process of cooling polymer spur gears running in dry conditions, which ultimately affects the strength of the gears. In order to gain some insight into this phenomenon, a numerical heat convection model for polymer spur gears is proposed in this work, which is based on a detailed CFD simulation of the gears in operating conditions and it allows us to investigate the heat convection through their external surfaces.The performance of this numerical model is illustrated with several examples, in which a parametric study has been conducted to observe the variation of the heat transfer coefficients with the face width and the angular speed of the gears. The results obtained from this parametric study are compared to those obtained from a representative classical heat convection model, observing that the relative differences between them in terms of heat transfer coefficients can be as high as 125%.Finally, a new optimized heat convection model for polymer spur gears running in dry conditions is proposed, in which the convective heat transfer coefficients for the external surfaces of the gears are calculated from empirical equations based on the Newton’s law of cooling. This optimized model has lower computational cost than the numerical one, while it provides an important increase of the accuracy of the classical heat convection models, reducing the maximum relative differences to 10%.