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Développement d'un écoulement diphasique adiabatique dans un tube de 8 mm après un détendeur.

Developing adiabatic two-phase flow in an 8-mm tube after an expansion valve.

Numéro : 2345

Auteurs : YAO Y., HRNJAK P.

Résumé

Developed two-phase flow has been studied exhaustively in the open literature. However, there is limited research on developing two-phase flow. This paper investigates the developing adiabatic two-phase flow after a thermostatic expansion valve in an 8 mm straight tube with R134a and 1.3% POE 32 as the working medium. The flow patterns are visualized from the exit of the TEV until 595 mm afterward. To cover different types of flow patterns, the mass flux is changed from 100 to 480 kg m-2 s-1, and vapor quality is from 0.002 to 0.5. Based on the observations in our experiments, the developing two-phase flow patterns can be classified into four regions: well mixed, separating, separated but developing, and fully developed flow. At the exit of the expansion valve, liquid and vapor phases are well mixed due to the sudden expansion. The flow structure is similar to homogeneous flow and both phases have similar velocity. As flow progresses along the tube, the liquid velocity will decrease. As a consequence, the gravity/buoyancy force becomes more dominant over inertia and surface tension, resulting in the separating of bubbles/droplets with the main flow. The end of the separating region is characterized by a clear interface between the liquid and vapor phases. However, this does not mean a fully developed flow. The flow characteristics, such as void fraction and flow pattern may still change for a certain distance. This is called the separated but developing region, the last region before fully developed flow. All the flow patterns in developing two-phase flow are shown in a 3D flow pattern map. Compared to the traditional developed flow pattern map, the distance from the expansion valve is added as the third dimension. According to this 3D flow pattern map, as the distance increases, the flow patterns are changing gradually to fully developed flow.

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Pages : 10 p.

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Détails

  • Titre original : Developing adiabatic two-phase flow in an 8-mm tube after an expansion valve.
  • Identifiant de la fiche : 30030671
  • Langues : Anglais
  • Sujet : Technologie
  • Source : 2022 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Date d'édition : 2022

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