The thermofluidic operation of two-phase heat transfer devices is affected by thermally induced fluid oscillations of unknown frequency and amplitude. In line with previous studies, the time-frequency analysis of experimental signals is performed to investigate the existence of local characteristic frequencies. This work applies the wavelet transform to the evaporator fluid pressure signal of a passive two-phase heat transfer which can work as a Thermosyphon or as a Pulsating Heat Pipe, depending on the gravity acceleration. The results, obtained by means of a parabolic flight campaign, shows that the local characteristic frequencies are present only during the microgravity phase and in a frequency range from 0.8 to 2 Hz. Understanding the complex phenomena related to thermally induced oscillation is essential for the development of reliable heat transfer models and robust design tools for Pulsating Heat Pipes.

Time-Frequency Analysis of a Thermally Induced Pulsating Slug Flow

Roberta Perna;Mauro Mameli;Sauro Filippeschi
2019-01-01

Abstract

The thermofluidic operation of two-phase heat transfer devices is affected by thermally induced fluid oscillations of unknown frequency and amplitude. In line with previous studies, the time-frequency analysis of experimental signals is performed to investigate the existence of local characteristic frequencies. This work applies the wavelet transform to the evaporator fluid pressure signal of a passive two-phase heat transfer which can work as a Thermosyphon or as a Pulsating Heat Pipe, depending on the gravity acceleration. The results, obtained by means of a parabolic flight campaign, shows that the local characteristic frequencies are present only during the microgravity phase and in a frequency range from 0.8 to 2 Hz. Understanding the complex phenomena related to thermally induced oscillation is essential for the development of reliable heat transfer models and robust design tools for Pulsating Heat Pipes.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/1019932
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