Void Fraction Measurement System for Steady State Horizontal Two Phase Liquid Nitrogen Flow

Abstract

A cryogenic flow set-up has been designed and realized, that aimed at investigating experimentally the two-phase flow void fraction of liquid nitrogen in horizontal configurations. Various flow void fraction intrinsic to two phase horizontal flow of liquid nitrogen with controllable admixtures of liquid nitrogen fraction and nitrogen gas fractions have been systematically studied in this experimental set-up. The setup comprises of a source of liquid nitrogen, a source connected to the gaseous nitrogen with individual flow measurement devices, thermally insulated connections, a coaxial capacitor is used as void sensing element having a flow equilibrium section with a surrounding vacuum jacket. The capacitance measurement circuit is designed and developed for analyzing the void fraction in the nitrogen flow, inlet/outlet pressure measurement set-ups and Venturi flow meters from where the mass flow rates have been observed and recorded using the Citect SCADA system. The important parameters of temperature, pressure and differential pressures are continuously measured during the experiment in a dedicated data acquisition system. The gas nitrogen (GN2) mass flow rate is kept constant and the liquid Nitrogen (LN2) mass flow rates are controlled using valve, resulting in determination of the void fraction with respect to quality factor. The experimental void fraction is measured and compared with existing two phase flow models. The predictions obtained from various flow models are largely converging in case of two phase flow involving liquid nitrogen. These experimental results are intended to be extended to research towards developing a prototype void sensor that is appropriate to for liquid Nitrogen two phase flow scenarios.

Keywords

• two-phase
• nitrogen
• void fraction
• capacitance
• cryogenics
• void sensor