PREDICTION OF CONVECTIVE HEAT TRANSFER COEFFICIENTS AND EXAMINATION OF THEIR EFFECTS ON DISTORTION OF CYLINDRICAL TUBES QUENCHED BY GAS COOLING

摘要

The primary objectives of this study are to model the nature ofthe high-turbulence complex quenching cooling-gas flow, with flowseparations, and to examine its effects on the resulting distortions,here of bearing steel tubes. A k-∈ turbulent flow and heat tran-sfer model we have adopted was found to predict the convective heattransfer coefficient distribution reasonably well for Reynolds numberup to about (0.3) 10~6. At higher Reynolds number (here examined upto 10~6) it predicts them reasonably well in most of the cylinderwindward and leeward zones, and predicts well the angles at whichtransition to turbulent starts and at which the flow separates, aswell as the existence of two maxima and two mininia in the heattransfer coefficient. It, however predicts values about 100 higherthan those available from the available experimental data in thelaminar-to-turbulent boundary layer transition zone. This model, aswell as available experimental and representative data, were used todefine the distributions of the convective heat transfer coefficientaround the body surface as the boundary condition of a finite-elementprogram developed at the Swedish institute for Metals Research forPredicting the temperature distribution history, phasetransformations, distortions and mechanical properties of quenchedsteel bodies. The dependence of the distortions on the extent ofconvective heat transfer coefficient nonunifornity was analyzed.