Study of oscillating flow inside a matrix regenerator: impact of internal scale on the operating frequency
Description
The pulse tube cryocooler is one of the key technologies in cryogenic satellite cooling systems. Although compact, there is a real interest to reduce its size to optimize the payload of space missions. The regenerator is at the heart of the pulse tubes technology. A promising miniaturization method lies in the use of micro fabrication techniques to design reticular-type exchangers with controlled porosity. In this context, this thesis work focuses on the study of micro-fabricated diamond-shape arrays in oscillating flows at frequencies between 20 and 150 Hz. In the steady state, the hydraulic performance of these devices is a function of the friction factor that can be expressed as a function of the pressure drop across the device and the flow rate. In the oscillating regime (where the pressure and flow conditions vary sinusoidally), a similar relationship can be derived. A careful study performed during this work shows that the phase shift between the pressure drop and the flow rate, that increases with frequency, also plays a role. The microstructure also plays a role on the friction factor. As an analytical study would be too complex, we set up an experimental bench dedicated to the measurement of the Poiseuille number associated to the friction factor through the measurement of the flow rate and of the pressure drop between the device's ends. We manufactured samples with a network of diamonds-shape pillars of different characteristics (sizes and angular opening) and different porosities. These samples were then measured in the stationary and oscillating regimes. Similar to the stationary regime, the results in the oscillating regime show an increase in the Poiseuille number with the angle of the diamond and the porosity of the device. The measurements also seem to corroborate the effect of the phase shift on the Poiseuille number. However, this remains to be confirmed, as the phase shift range swept by our samples is not large enough. (author)
Abstract (French)
Le refrigerateur a tube a gaz pulse est une des technologies cles des chaines de refroidissement cryogeniques des satellites cryogeniques. Bien que deja compacte, il y a un veritable interet a reduire la taille de ces refrigerateurs afin d'optimiser la charge utile des missions spatiales. Le regenerateur est au coeur de la technologie des pulse tubes. Une methode de miniaturisation prometteuse reside dans l'utilisation des techniques de micro fabrication pour concevoir des echangeurs de type reticulaire de porosite controlee. Dans ce contexte, ce travail de these porte sur l'etude de reseaux de losanges micro-fabriques dans des ecoulements oscillants a des frequences entre 20 et 150 Hz. En regime stationnaire, les performances hydrauliques de ces dispositifs sont fonction du coefficient de frottement qui peut etre exprime en fonction de la perte de charge au borne du dispositif et du debit. En regime oscillant (ou les conditions de pression et de debit varient de facon sinusoidale), une relation semblable peut-etre derivee. Une etude soigneuse menee durant cette these montre que le dephasage entre la perte de charge et le debit qui augmente avec la frequence joue egalement un role. La microstructure joue egalement un role sur le coefficient de frottement. Une etude analytique etant trop complexe, nous avons mis en place un banc experimental dedie a la mesure du nombre de Poiseuille associe au coefficient de frottement au travers de la mesure du debit et de la perte de charge au borne du dispositif. Nous avons fabrique des echantillons comportant un reseau de piliers en forme de losanges de differentes caracteristiques (dimensions et ouverture angulaire) et de differentes porosites. Ces echantillons ont ensuite ete mesures en regimes stationnaire et oscillant. De facon similaire au regime stationnaire, les resultats en regime oscillant montrent une augmentation du nombre de Poiseuille avec l'angle du losange et de la porosite du dispositif. Les mesures semblent egalement corroborer l'effet du dephasage sur le nombre de Poiseuille. Cela reste toutefois a confirmer, la plage de dephasage balayee par nos echantillons n'etant pas assez etendue
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Additional details
Additional titles
- Original title (French)
- Etude des ecoulements oscillants a l'interieur d'un regenerateur de type reticulaire: impact des dimensions internes sur la frequence de travail
Publishing Information
- Imprint Title
- Study of oscillating flow inside a matrix regenerator: impact of internal scale on the operating frequency
- Imprint Pagination
- 146 p.
- Report number
- FRCEA-TH--17205
INIS
- Country of Publication
- France
- Country of Input or Organization
- France
- INIS RN
- 56008259
- Subject category
- S42: ENGINEERING;
- Resource subtype / Literary indicator
- Thesis
- Descriptors DEI
- CRYOGENICS; FRICTION FACTOR; LAMINAR FLOW; MICROSTRUCTURE; MINIATURIZATION; POROSITY; REGENERATORS; SATELLITES; SIZE
- Descriptors DEC
- DIMENSIONLESS NUMBERS; FLUID FLOW
Optional Information
- Notes
- 29 refs.; Available from the INIS Liaison Officer for France, see the INIS website for current contact and E-mail addresses