Frequency characteristics of the noise of R600a refrigerant flowing in a pipe with intermittent flow pattern

Prediction of Flow Velocity from the Flexural Vibration of a Fluid-Conveying Pipe Using the Transfer Function Method

“…The pipe was assumed to be made of aluminium (D = 6241 Nm 2 , ms = 0.5174 kg/m, L = 1 m, E = 70 GPa, ρs = 2700 kg/m 3 , ν = 0.39). The fluid in the pipe was assumed to be water at 4 °C (mf = 2.827 kg/m, ρf = 1000 kg/m 3 The transfer functions of the pipe with varying flow velocities were calculated from Equation ( 7), as shown in Figure 4. As the flow velocity increased, the frequencies of all the mode tended to shift toward zero.…”

“…Flow measurement is crucial to flow control in various application including water supply, fuel pumps, and air conditioning systems [1][2][3]. A common device used to measure flow characteristics is the flow meter.…”

Identification of crack noises in household refrigerators

“…2 where a1, a2 and a3 are the acceleration levels measured on the heater, inside and outside panels, respectively, and p1, p2 and p3 are the sound pressures measured inside the cabinet and at some points close to the evaporator and compressor, respectively. The time signals of both structural acceleration and sound pressure are first recorded with a high sampling rate (fs = 2 15 = 32.8 kHz) and the overall and Fourier analyses of the signals are performed as a post processing phase [16][17] later. The use of exponential averaging (i.e., the use of exponential time weighting) for continuous non-stationary signals is very common in acoustic measurements [18].…”

“…Identification and quantification of the compressor and fan noises is relatively straightforward as the positions and the properties such as rotation speeds, and number of blades of these components are known and the exact contributions of these components can be identified by using the frequency spectrums measured by operating each component separately. However, the crack noises, a serious problem of today's no-frost (modern) refrigerators, have not been identified and the root causes of such noises have not been explored in the literature [13][14][15]. This paper attempts to fill this void with a controlled experimental study and by analyzing a huge number of structural acceleration and sound pressure measurements conducted in a quiet room (representing a kitchen of a typical house) using a few refrigerators and a special test rig under various conditions.…”

Development of noise pattern map for predicting refrigerant-induced noise in refrigerators

“…On the other hand, the pressure drop variation of the bubbly and annular flow was more stable than that of slug and churn flow. According to the research from Han et al [9], the vibration and the noise level of the intermittent flow such as slug flow and churn flow are higher than that of bubbly flow and annular flow. Since the time variation of the pressure drop exerts on the pipe as the external force, the fluctuation of the pressure drop can cause the vibration and noise.…”