|Title:||Development of a Computer Model for Refrigerant Flow in Small Diameter Tubes
|Abstract:||This report examines the phenomena of flashing fluid flow in small diameter tubes (on the
order of 1 mm). Small diameter tubing is often used as the expansion device in refrigeration
systems. Tubing used as a refrigeration system expansion device is referred to as capillary tubing;
however, these tubes exhibit no appreciable capillarity behavior. Experimental test have shown
capillary-tube flow behaves as any other conduit flow. Emphasis of this study is placed on
refrigeration applications to facilitate ~e use of the proposed model for capillary-tube modeling.
A review of the literature shows that capillary-tube modeling has changed little over the past
40 years. The two-phase flow models used in the fIrst capillary-tube models were homogeneous
models. Homogeneous-flow models are still used almost exclusively today. Experimental
evidence shows, however, that the two-phase flow in capillary tubes is not entirely homogeneous.
The liquid and vapor phases are substantially removed from equilibrium at the inception of
vaporization and near the capillary-tube exit. A model that accounts for the interaction between the
liquid and vapor phases is required for accurate modeling.
A model is presented that treats the liquid and vapor phases separately. In this way, the
effect of phase nonequilibrium can be included in the model. The model is developed so that it will
simplify to the homogeneous model as the phases approach equilibrium. Once the model is
developed, a discussion is given outlining the application of the model to capillary-tube
optimization models, as well as to refrigeration system models.
|Publisher:||Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
|Series/Report:||Air Conditioning and Refrigeration Center TR-27
|Sponsor:||Air Conditioning and Refrigeration Center Project 21
|Date Available in IDEALS:||2009-03-13
|Identifier in Online Catalog:||3557885