NVH Optimization of Refrigerator Tubings for Structure Borne Noise Reduction Through Numerical Simulations

Abstract

The recent stipulated guidelines on the noise levels in few regions of the world has fostered competition for quieter products, across various sectors from automobile to home appliances. Also, the customer expectations and preferences have encouraged the demand for quieter products. Domestic refrigerators are no exceptions to these advancements. The refrigerators have different components like compressor and fans which are responsible for noise generations. The compressor is one of the important and primary sources for vibration and noise generation, because of its intense inherent excitations. Many factors are influencing the compressor excitations such as type of the refrigerant, amount of the charge, compressor construction, operating speed etc. The suction and discharge tube (condenser tube) are very vulnerable to these compressor excitations as they are brazed directly to the compressor, unlike the baseplate which is generally equipped with isolation. Noise radiation from the condenser tube can add to the overall noise level of the refrigerator. Hence condenser tubes need to be routed with specific shapes for the noise reduction without altering core performance of the refrigerator. The study entails assessment of the condenser tube through series of testing or Computer Aided Engineering (CAE) simulations. In current work, Experimental Modal Testing (EMT) was performed and Frequency Response Function (FRF) were measured on the condenser tube at component and system level. A Finite Element Model (FEM) was developed using commercial software code and the FRF simulation results were validated with the test results to a high degree of accuracy, through appropriate representation of mass, local and global stiffness of the system. It was seen that variations in the interfacing conditions such as tube-plate connectivity, tube-plate thickness and compressor shell thickness were having significant impact on dynamic behavior of the condenser tube. The validated FE modelling strategy was further leveraged for the optimization of the tube shapes to improve the Noise Transfer Function (NTF) and has been demonstrated as a case study.