Numerical and experimental investigation of flow boiling heat transfer coefficient according to engine operating condition

Approximately one third of fuel heat release of an IC engine is delivered to environment by cooling system. Cooling more than a limit, decreases efficiency of engine and lower than a limit, causes vapor layer formation on the surface of water jacket and reduction of heat transfer and failure components. Behavior of heat transfer coefficient in boiling depends on heat flux. This coefficient increases during nucleate boiling and decreases during film boiling. In this research, an experimental setup was designed to investigate the effect of heat flux on heat transfer from coolant. This study carried out with two base fluid, distilled water and mixture of distilled water and ethylene-glycol (50-50) and measurement of surface temperature. With consider that boiling flow takes place on hot spot of water jacket with low speed of coolant, therefore, velocity range in exhaust valve bridge has considered. Effect of inlet velocity and coolant temperature in constant heat flux on surface temperature and heat transfer coefficient, has been investigated. Up to experimental results, numerical simulation carried out with CFD software. The numerical results have good agreement with experimental data.