Numerical Simulation And Study Of Noise Reduction On An Air Duct Of Indirect Cooling Refrigerator

With the improvement of people's living standard and comfort of home environment,more attention is being paid to the performance of the domestic refrigerator,Optimization of refrigerator air duct and noise has an important practical role for energy conservation and improve the quality of life.Based on computational fluid dynamics(CFD)and computational aerodynamic noise,the flow characteristic and the aerodynamic noise of the air duct of indirect refrigerator are studied with the commercial CFD software FLUENT in this dissertation,in order to offer a guideline for the optimization design of the air duct of indirect refrigerator enterprise and to reduce the test time aiming for air duct optimization.The main research contents include:1)The flow field and sound field of the flow of air duct of indirect refrigerator is simulated by commercial CFD software FLUENT,based on a numerical model of the discharge air flow and the aerodynamic noise of air duct.The methods for coupling the moving zone and the immobile zone,and setting other numerical parameters are analyzed and discussed.2)Based on the numerical model of aerodynamic noise,the noise source and the aerodynamic noise category are analyzed and summarized,together with the noise frequency characteristics.The results of numerical simulation show that the dipole acoustic sources locating at the wall of air outlet,the guide plate and the impeller are the main sources,and that the total noise in air duct is a combination of discrete and indiscrete noises.The results can be helpful for reducing the design noise in the air duct of indirect refrigerator.3)Based on the numerical model of the discharge air flow of refrigerator's air duct under working conditions that centrifugal fan is at three difference rotational speeds,the aerodynamic noise corresponding characteristics are studed;Also,the causes of tail edge vortex shedding in guide plate and the impeller blade is analyzed and summarized and the relationship between the vorticity and aerodynamic noise is summarized;the influences of the guide plate,the impeller and the angle of outlet wall on the flow and noise of air duct are analyzed in details.4)The accuracy of numerical model is validated by the comparison between experimental and numerical results,which supports the universal application feasibility of our model.For the numerical aspect,the independence of the simulation result on the computational zone and the mesh number is analyzed.By comparing the experimental and numerical results,we find that the errors between the simulated and measured results for noise distribution and its spectrum characteristics field of the air duct of indirect refrigerator are acceptable.5)Two noise-reducing methods,the frequency migration based method and the runner improving method,are analyzed and suggested to reduce the total noise,which can provide some suggestions for reducing the noise emission from the air duct of indirect refrigerator.