Numerical Simulationsof Heat Transfer Properties Of Furance Of Supercharged Boiler

Supercharged boiler supplies air by turbo unit,fuel combusts in the furnace under the condition of pressure boost,supercharged boiler has high heat load in the furnace,small volume and many other advantages.For other boilers,the heat transfer in the furnace is mainly based on the radiation heat transfer,and the convective heat transfer quantity is small,and it can be neglected in the thermodynamic calculation,so there is a certain deviation in the study of the thermodynamic characteristics.The numerical simulations were used to study the heat transfer characteristics of the supercharged boiler furnace.According to the actual size of 103 t/h supercharged boiler furnace,the flow behavior was predicted based on the FLUENT software platform using the RNG k-?turbulence mode,the convective heat transfer between the gas and the heating surface of the furnace was simulated.Simulations showed that when three burners were put at each side,gas between burners exists interference which increases non uniform distributions of the radial and axial velocity field and temperature field.The backflow of gas in the exit region helps to bring the high temperature gas back to the inlet of the burner.This improves ignition and combustion.Three different pressures(0.1,0.19 and 0.25MPa)and loads(50%,80% and 100%)are analyzed.The convection heat transfer coefficient between the gas and the heating surface of the furnace is Nu=0.06Pr0.333Re0.8.The flow behavior of gas was simulated at the low loads in the range of 20-30%.When each side owns a burner(total two burners),simulation of flow process of the furnace gas and prediction of convective heat transfer between the heating surfaces were performed,and the distributions of gas velocity and temperature are obtained.The convection heat transfer coefficient between the gas and the heating surface of the furnace is Nu=0.3Pr0.333Re0.835 based on simulated temperatures of gas.