Numerical Simulation of Impinging Jet with Mist Injection

Abstract

Two-phase CFD calculations using commercial code Fluent were employed to calculate the air and droplet flows with and without mist in an impinging jet. The effects of phase changing of the water droplets, the mist injection rate, the heat flux of target and the geometrical parameters of the slot were studied to reveal the cooling effectiveness. The results show that the key enhancement mechanism of mist/air impinging jet is the effect of evaporation of the droplets. The wall temperature significantly decreased because of mist injection and the injection of 5% mist has a strengthen of cooling effectiveness with 89% enhancement. This enhancement would be reduced by higher heat flux of target wall. Concentration plays a major role in the cooling performance. Increasing the mist ratio makes the cooling strengthen significantly. A mist of 5% can provide a cooling enhancement of 32% at stagnation than the mist of 1%. The effect of the mist ratio on cooling declines gradually from the impingement area to the downstream area. A fit width and height ratio had a major impact on the cooling performance of mist/air impinging jet. For constant mist/air mass flow and inlet width b, when H/b increases, the heat transfer coefficient increases first and then decreases; for constant mist/air mass flow and impinging distance H, the heat transfer coefficient increases as H/b increases.