Numerical Simulation And Optimization Of The Furnace With FLUENT Software

As a main heating equipment in petrochemical industry, furnace consumes a lot of energy. The energy-saving of furnace is the focus of energy conservation links. The study of heat transfer process in the furnace to improve energy efficiency has become the focus of technological innovation. With the basic principles of computational fluid dynamics, the structural parameters and operating conditions of the atmospheric heater, this subject established the mathematical model of tube furnace by the whole-coupling method. According to the established whole-coupling heat transfer model, the steady-state heat transfer process in the furnace was simulated. Compared with the field calibration data, this paper got the optimal simulation model and parameters. At the same time, a plan of enhancing heat transfer was proposed. By analyzing the simulation result before and after optimization, the feasibility of the plan was validated.The processes of fluid flow, combustion and heat transfer between the flue gas and tube without any simplification in the firebox of atmospheric heater were studied with the whole coupling method. The geometrical model and the dividing of grid of the combustor, combustion chamber and furnace tube were generated. The standard k- turbulent model, the non-premixed combustion model and the discrete ordinate transfer radiation model were used to simulate the furnace. The internal emissivity of the furnace tube was defined as 0.8 in the model. Detailed information about the flow field, temperature field, the temperature and heat flux distribution in tube skin was obtained. Results showed that the high velocity of bottom combustors'jet flow resulted in large recirculation zone of flue gas, which played an important role in the uniformity of flue gas temperature in the bottom of the furnace. In addition, non-uniform distribution of temperature and heat flux existed in the furnace tube skin, which affected the service life of furnace tube. Defining the tube skin's heat intensity distribution as the boundary condition, this paper carried out a one-dimensional flow calculation in the pipe using MATLAB programming. The temperature, pressure and gasification rate values in the outlet were calculated by the program, and were consistent with the field calibration result.Based on the results of single tube's simulation, it was concluded that the furnace tube's circumferential and axial distribution of the temperature and heat intensity were not uniformly distributed in the single-sided radiation heating furnace. Front side's heat intensity was significantly higher than the back side's. A certain amount of nail head or fin within an acceptable range of tube's back side can improve the area of access to radiation. After transformation, the finned tube's average radiant intensity increased 7%, and the back side's radiant intensity improved 14%. Meanwhile, the radiant heat intensity of the front side was only 1.18 times of back side's, the distribution of circumferential heat intensity tended to uniform. As a result, the back side's heat intensity, the average heat intensity and the heat intensity distribution in tube circumference were improved by this innovation, also it can improve the thermal efficiency of furnace, extend the safe operation period and achieve energy-saving.