Flow-Induced Whistle in the Joint of Thermal Expansion Valve and Suction Tube in Automotive Refrigerant System

Evaluation of flow-induced noise, structure vibration, and flow morphology of R134a flowing through a thermostatic expansion valve

“…According to Koberstein et al (2015) results, TVX pilot suction tube lengths inferior to 9.0 mm, chamfered pilot tubes, and smoothed TXV suction port edges can suppress the noise at 6.18 kHz while the SPL remained similar at other frequencies. Although Koberstein et al (2015) identified a clear relation between the flow-induced noise and the shallow cavity between the TXV and the suction pilot tube, a mechanistic explanation about how this relationship is established was not given by them. Zhang and Elbel (2018) found that increasing the TXV wall thickness by 0.2 mm the natural frequency of the structure increases, therefore the hissing noise that was propagated through the TXV wall around 10 kHz could be mitigated.…”

“…Therefore, these authors were able to verify that for EEV aperture inferior to 200 steps sub-cooled liquid leaves the condenser leading to an inferior SPL than for 300 steps aperture, when two-phase flow leaving the condenser was observed. Koberstein et al (2015) identified an intense whistle noise source at 6.18 kHz in phase with the accelerometer at the suction line of TXV. In order to understand the effect of the inlet TXV geometry on the frequency noise band, Koberstein et al (2015) varied the TVX pilot suction tube length from 8.0 to 12.0 mm (Fig.…”

“…Koberstein et al (2015) identified an intense whistle noise source at 6.18 kHz in phase with the accelerometer at the suction line of TXV. In order to understand the effect of the inlet TXV geometry on the frequency noise band, Koberstein et al (2015) varied the TVX pilot suction tube length from 8.0 to 12.0 mm (Fig. 21a), and the connection geometry between pilot tube and suction TXV port (Fig.…”

“…For the noise evaluated from outside the EEV, Jeong et al (2007), , and Kim et al (2019) found similar mean SPL, despite Kim et al (2019), who pointed out the lowest SPL of 36 dB(A) for vertical layout operational condition for annular flow pattern at the inlet and single-phase vapor at the outlet. Furthermore, only Koberstein et al (2015) mentioned the effect of the connection geometry between the pilot and the TXV suction tube on the flow-induced noise. As a general statement, the SPL evaluated within the expansion devices presented similar values of noise, with mean noise ranging from 132 to 148 dB, regardless the expansion device, fluid and operational condition, except for Boabaid Neto et al (2018) that found the lowest mean noise of 122 dB.…”

“…Additionally, Koberstein et al (2015) identified that even the suction pilot length and its joint geometry with the TXV may result in a unwanted noise. As a passive approach to reduce the noise, Hirakuni et al (2004) came up with porous pieces of metal positioned directly at the EEV inlet and outlet in order to change the flow pattern from slug to bubbly flow, reducing the noise level up to 13 dB.…”