Developing Adiabatic Two-phase Flow

Developing Adiabatic Two-phase Flow

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In order to understand the characteristics of the adiabatic development of two-phase flow this study was performed using H2FC-CF 3 - 1, 1, 1, 2-Tetrafluoroethane (R134A) as a working fluid in three different transparent tubes. The flow was visualized using a high speed camera. To better (faster and more objectively) analyze the flow, a technique was developed to determine the separation distance using a statistical method known as Change Point Analysis. The distance at which the phases become separated can be an important parameter in design of inlet tubes to evaporators. A method for determining the void fraction from the visualization results was developed and presented. This method allows for a local, instantaneous or time averaged, void fraction determination in Stratified, Intermittent, and Annular flows and could conceivably be implemented into an online void fraction determination. Qualitative examination of these images allowed for the determination of the distinct regions of flow development: Well-Mixed, Separating, Separated but Developing, and Developed regions. Dynamic examples of transitions between flow regimes in the process of flow development were also presented; specifically, transitions from Stratified to Intermittent flow.Specifically, evaporators with parallel channels are known to suffer from maldistribution of the two refrigerant phases. ... an initial tie this back into practical engineering application through the brief analysis of how these characteristics change when the flow studied is at saturation temperatures seen in a typical automotive air-conditioning system with the addition of oil ... (R134a) after an expansion valve and an analysis technique developed especially to study these flow, respectively.

Title:Developing Adiabatic Two-phase Flow
Author:Chad D. Bowers
Publisher:ProQuest - 2009


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