Pulsating Heat Pipes are two phase passive heat transfer devices characterized by a thermally induced two phase oscillating flow. The correct detection of the dominant frequencies of such oscillations is fundamental to fully characterize the device thermofluidic operation but the studies available in the literature are very heterogenous and results are often discordant. In this work, the concept of dominant frequency in Pulsating Heat Pipes is thoroughly discussed and defined analytically. The wavelet transform is used to characterize the fluid pressure signal in the frequency domain varying the heat power input at the evaporator and in the condenser zone of a full-scale Pulsating Heat Pipe tested in microgravity conditions. During the slug-plug flow regime, the dominant frequencies falls in the range 0.6–0.9 Hz, showing an increasing trend with the heat load input. The Cross-Correlation reveals that the two signals at the evaporator and at the condenser are very similar. Finally, the instantaneous angle of phase is calculated and lies between 310 and 360 deg. This value can be physically interpreted as a repeatable time shift between the two signals that can be used to evaluate the flow local mean velocity (0.09–0.13 m/s) constituting a valuable alternative to the visualization techniques.

Flow characterization of a pulsating heat pipe through the wavelet analysis of pressure signals

Perna R.
Primo
;
Abela M.;Mameli M.;Mariotti A.;Pietrasanta L.;Filippeschi S.
Ultimo
2020-01-01

Abstract

Pulsating Heat Pipes are two phase passive heat transfer devices characterized by a thermally induced two phase oscillating flow. The correct detection of the dominant frequencies of such oscillations is fundamental to fully characterize the device thermofluidic operation but the studies available in the literature are very heterogenous and results are often discordant. In this work, the concept of dominant frequency in Pulsating Heat Pipes is thoroughly discussed and defined analytically. The wavelet transform is used to characterize the fluid pressure signal in the frequency domain varying the heat power input at the evaporator and in the condenser zone of a full-scale Pulsating Heat Pipe tested in microgravity conditions. During the slug-plug flow regime, the dominant frequencies falls in the range 0.6–0.9 Hz, showing an increasing trend with the heat load input. The Cross-Correlation reveals that the two signals at the evaporator and at the condenser are very similar. Finally, the instantaneous angle of phase is calculated and lies between 310 and 360 deg. This value can be physically interpreted as a repeatable time shift between the two signals that can be used to evaluate the flow local mean velocity (0.09–0.13 m/s) constituting a valuable alternative to the visualization techniques.
Perna, R.; Abela, M.; Mameli, M.; Mariotti, A.; Pietrasanta, L.; Marengo, M.; Filippeschi, S.
File in questo prodotto:
File Dimensione Formato  
PERNA_et_al.pdf

Open Access dal 06/05/2022

Descrizione: documento in Post-print
Tipologia: Documento in Post-print
Licenza: Creative commons
Dimensione 1.87 MB
Formato Adobe PDF
1.87 MB Adobe PDF Visualizza/Apri
Perna_et_al_2020.pdf

solo utenti autorizzati

Descrizione: versione finale editoriale
Tipologia: Versione finale editoriale
Licenza: NON PUBBLICO - Accesso privato/ristretto
Dimensione 8.35 MB
Formato Adobe PDF
8.35 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/1041488
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 17
  • ???jsp.display-item.citation.isi??? 15
social impact