Determination of Empirical Heat Transfer Coefficients via CFD to Predict the Interface Temperature of Continuously Slipping Clutches

To optimize the performance of continuously slipping wet friction clutches, it is vital to predict the maximum temperature at the friction surface. Prediction necessitates an accurate mathematical model of the heat transfer coefficient in and around the transmission oil grooves of the wet friction facing. All the relevant dimensionless variables in and around the oil grooves with respect to heat transfer coefficients were identified using Buckingham's ‘Pi’ theorem. Computational fluid dynamics (CFD) was used to create empirical formulas for heat transfer coefficients from relevant dimensionless variables and to study the dynamics of the oil flow through the grooves. Maximum transient temperature at the friction interface was predicted via finite element (FE) code using developed empirical formulas of heat transfer coefficients. Transient temperatures were then measured using thermo-couples for various conditions and groove geometries. An excellent agreement was found between the prediction and the measured data.