403 Flow Visualization and Analysis of Two-phase Gas-liquid Refrigerant Flow passing through a Minute Channel

Abstract

The refrigerant passing through the minute channel in an expansion valve is a gas-liquid two-phase flow. The flow characteristics are complex and remain unclear. The purpose of this study is to analyze the gas-liquid two-phase flow characteristics passing through the minute channel. The experiments are conducted in a flow visualization device that is 0.3-0.5 mm in diameter and 5.0 mm in length, using refrigerant R-134a. The flow characteristics are evaluated concerning the channel diameter and the inlet pressure of the channel, and the phase transition of refrigerant flow is quantitatively analyzed by visualization with a high-speed camera and luminance intensity profile. As a result, the flow characteristics are recognized as bubbly flow, slug flow, annular flow, annular-mist flow and mist flow. It is found that the phase transition and its position are strongly influenced by inlet pressure and minute channel diameter.