Simulation of Subcooled Flow Boiling on Engine Cooling Jacket with a Bubble Waiting Time Coefficient Model

The objective of this present research is to investigate the influence of bubble waiting time coefficient on subcooled flow boiling heat transfer in internal combustion engines and propose an approach to predict its value. The three-dimension simulated cooling jacket structure of valve bridges for forced water-cooling system was developed respectively. The numerical model for subcooled flow boiling based on two-fluid approach was established and calculated. Numerical results suggest that the bubble departure diameter increases with the increasing wall superheat or decreasing inlet subcooling. And the proportion of the quenching heat flux gradually rises and its peak value is delayed along the direction of the higher wall superheat when the subcooling degree increases. The bubble waiting time coefficient has been found to have a significant impact upon the boiling heat transfer. A prediction model of bubble waiting time coefficient was presented with the verification of Abou-Ziyan’s experimental results. The two-phase subcooled flow boiling model with considering bubble waiting time coefficient may be well applicable to boiling simulation on engine cooling jacket. Finally, the modified boiling model can be used in the calculation of the boiling heat transfer of actual cylinder head. It clearly shows that the calculated temperature is more close to the experimental value with correction in boiling heat transfer area such as bridge zone of exhaust valve and injector nozzle. The maximum deviation of the experimental temperature decreases by 4.61%. While in the areas without boiling, the deviation changes a little with correction.