Abstract

A CFD model to simulate two-phase flow in refrigerant ejectors is described. This work is part of an effort to develop the ejector expansion refrigeration cycle, a device which increases performance of a standard vapor compression cycle by replacing the throttling valve with a work-producing ejector. Experimental results have confirmed the performance benefit of the ejector cycle, but significant improvement can be obtained by optimally designing the ejector. The poorly understood two-phase, non-equilibrium flow occuring in the ejector complicates this task.

The CFD code is based on a parabolic two-fluid model. The applicable two-phase flow conservation equations are presented. Also described are the interfacial interaction terms, important in modelling non-equilibrium effects. Other features of the code, such as a mixing length turbulence model and wall function approximation, are discussed. Discretization of the equations by the control volume method and organization of the computer program is described.

Code results are shown and compared to experimental data. It is shown that experimental pressure rise through the mixing section matches well against code results. Variable parameters in the code, such as droplet diameter and turbulence constants, are shown to have a large influence on the results. Results are shown in which an unexpected problem, separation in the mixing section, occurs. Also described is the distribution of liquid across the mixing section, which matches qualitative experimental observations. From these results, conclusions regarding ejector design and two-phase CFD modelling are drawn.

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List of attached files

File Name	Size (Bytes)
appa.pdf	84,014 Bytes
appb1.pdf	74,370 Bytes
appb2.pdf	90,029 Bytes
back.pdf	63,915 Bytes
ch1.pdf	105,666 Bytes
ch2.pdf	98,247 Bytes
ch3.pdf	123,529 Bytes
ch4.pdf	149,316 Bytes
ch5a.pdf	68,182 Bytes
ch5b.pdf	57,618 Bytes
ch5c.pdf	219,600 Bytes
ch5d.pdf	69,823 Bytes
ch5e.pdf	30,194 Bytes
ch6.pdf	33,052 Bytes
etd.pdf	88,153 Bytes

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