The use of damping material in industrial machines

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Rigid-Frame Porous Material Acoustic Attenuation on Compressor Discharge

Standards have limited the allowable noise levels in different situations, requiring the study of solutions at the source, in the path or the receiver. Muffler is the major factor influencing the noise of rotary compressor. Control and analyze the acoustic characteristics of muffler is essential. Porous materials have been studied and widely applied to reduce aircraft and vehicular noise or industrial problems in general. Generally, designers use absorbing materials available on the market, however they are not always adequate to the problem when there is the presence of another gas, for example in hermetic compressors. Thus it is proposed to model the propagation in rigid porous material, characterize and develop the porous metal optimizing your acoustical absorption performance, when applied in a cavity. Direct techniques for measuring the material properties such as resistivity, porosity, tortuosity and characteristic thermal and viscous length will be studied

Noise Generation in Household Refrigerators: An Experimental Study on fluid Borne Noise

The oscillatory pressure disturbance created by the refrigerant flow through pipes and components is one of the main sources of noise in household refrigerators. This type of excitation is transmitted to the pipes and travels through the structure reaching the cabinet and other parts exposed to the air, where audible airborne sound waves are created. In order to get a better understanding of this type of noise a household refrigerator was especially instrumented with thermocouples, absolute and dynamic pressure transducers and accelerometers. Tests were carried out at different operating conditions, when it was found that the compressor was the main source of excitation, practically affecting the entire refrigeration loop. It was also found that the flow velocity at the outlet of the capillary tube was high enough to induce significant vibrations in the evaporator. Finally, it was found that the entrance of vapor bubbles in the capillary tube produces sporadic and strong excitations. However those excitations do not travel very far along the flow, being attenuated by the condenser and the evaporator, but can nevertheless be transmitted to the pipes. In view of the collected database, comments and suggestions concerning the design of household refrigerators are presented and discussed

Noise Characteristics Improvements for a New Generation of Variable Capacity Compressor using Linear Motor Technology

The household appliances market noise levels requirements have rapidly increased in the last years. Despite the traditional approach for defining noise requirements focused on steady-state sound power levels, the transient noise is becoming a key factor in defining sound quality specification. Variable speed compressor technologies lead to a significant advantage on this aspect since in standard operation conditions the compressor runs at relatively low speeds for most of the time. Linear motor driven reciprocating compressors present great advantages since this technology allows dealing with cooling capacity variation without changing the motor speed. This allows also easier and more effective design of lower noise generation. This paper presents the benefits of the variable capacity, linear motor driven reciprocating compressors over rotary motor driven reciprocating compressors, either at variable capacity and fixed speeds. Emphasis is given to the physical phenomena and engineering advantages of the linear motor concept

Shape Optimization of a Compressor Supporting Plate Based on Vibration Modes

In typical household refrigeration systems, the compressor is structurally connected to the cabinet through an assembly composed of rubber mounts and a steel support plate, usually called base-plate. This plate works as a vibration energy path from the compressor to other refrigerator components, and its dynamic behavior must be known in order to avoid the coincidence of resonances and operational frequencies , a situation in which the energy flow is maximized. One way to design a support that satisfies this requirement is to optimize the shape of the plate, locating its structural modes as far as possible from the operational frequency and first harmonics. In this work, the Finite Element Method (FEM) is used to solve the eigenvalue problem and to parameterize the optimization procedure, which is based on positioning of the nodes of a design region (the plate) in a FEM simplified model. Due to the large number of variables, a gradient-based method is adopted. The objective of the methodology is to maximize the difference between two adjacent eigenvalues near the fundamental operation frequency of the compressor, in order to obtain a large and effective bandgap. A geometrical constraint is imposed to the problem and it is represented by a maximum allowed deformation of the plate. The gradients needed are obtained using elementary stiffness and mass matrices information. The obtained results show that the procedure leads to a new shape which ensures the desired dynamic characteristics for the support plate

Verificação de encaminhamento de pacientes ao serviço de fisioterapia após cirurgia para tratamento de câncer de mama

O câncer de mama é o que mais acomete mulheres. O tratamento pode incluir procedimentos radicais e/ou conservadores, que causam impacto direto sobre a vida das pacientes. A fisioterapia tem papel importante, prevenindo sequelas e melhorando a qualidade de vida. O objetivo foi verificar o encaminhamento de pacientes ao serviço de fisioterapia após cirurgia para tratamento de câncer de mama em hospital do sistema único de saúde em Cacoal-RO. Trata-se de um estudo retrospectivo analítico, de pacientes submetidas a procedimentos cirúrgicos para tratamento de câncer de mama, através de consulta de 53 prontuários no Hospital Regional de Cacoal, no período de novembro de 2015 á outubro de 2016, que apresentaram idade média de 54,62 ± 11,41 anos, faixa etária de 33 a 84 anos, onde 33,96% com idade menor que 50 anos e 66,00% ≥ 50 anos. O lado esquerdo foi mais acometido com 56,60% e o direito com 43,39%. Fisioterapia realizada no período pós-operatório imediato em 92,45%; fisioterapia respiratória no pós-operatório imediato em 96,22%; fisioterapia motora em todo período de internação em 96.22%; fisioterapia respiratória em todo período de internação em 94,33%. Não houve relatos de complicações no pós- operatório imediato. Quimioterapia e radioterapia foram realizadas em 43,39% e o encaminhamento para fisioterapia no período de segmento em 13,20%. O estudo confirmou o encaminhamento de pacientes para o serviço de fisioterapia no período de seguimento, porém um percentual considerado baixo em comparação ao tamanho da amostra pesquisada, apontando a necessidade de estudo que justifiquem o baixo número de encaminhamentos

Excitation of pipe bending modes by internal pressure: A phenomenon present in refrigerators with skin condenser

The concept of skin condenser refrigerators has been increasingly explored for its capacity to provide a larger internal cabinet volume. However, the discharge pulsation of the cooling gas has become a significant source of noise because it directly excites the cabinet. This paper analyzes the mechanisms of cabinet vibration excitation by gas pulsation in the condenser tubes. Initial tests were performed with vibration measurements on a refrigerator and on segments of the cabinet excited by pulsation only. The results showed that bending modes of cabinet segments were excited by the pulsation in the condenser tube. A theoretical analysis showed that asymmetry in the condenser tube cross section is responsible for bending moment generation and numerical evaluations confirmed this effect for different types of asymmetries

Dynamic Characterization of Materials from a Refrigerator Compartment

The dynamic properties of materials are important parameters for numerical vibro-acoustics analysis of a household refrigerator. The compartment of a household refrigerator is typically composed by three types of materials: hot rolled steel, polyurethane rigid foam (PUR) and high impact polystyrene (HIPS). In this work, the mechanical properties (dynamical Young‟s modulus and loss factor) of these materials were determinate in order to comprehend its frequency-dependent behavior to use them properly in vibro-acoustic numerical models of household refrigerators. Experimental procedures based in impulsive responses of beams were performed for each material. Moreover, numerical models were used to fit the polyurethane rigid foam properties to experimental data. Finally, a numerical model of “sandwich” beam was built using the obtained properties. The results were compared with experimental tests performed on “sandwich” beam specimen from a refrigerator compartment. Good agreement was found for frequencies between 0 Hz to 600Hz