Abstract
The study presents progress in the development of mixture preparation device (MPD) representing an important part of the larger experimental setup intended for investigation of homogeneous droplet nucleation in CO2-rich systems. MPD allows for accurate adjustment of flow parameters, i.e. temperature, pressure, and flow rate, of CO2 in either superheated vapor or supercritical fluid phases and of other gas components such as argon or nitrogen. Through accurate settings of flow rates of individual components, the mixture composition can continuously be defined. MPD is going to be connected to the expansion chamber, where the droplet nucleation will experimentally be observed. In this work, CO2-branch, i.e. the core part of MPD, was modified and tested. Several components, e.g., pressure transducers and safety valve, had to be calibrated and adjusted to assure well-defined and safe operation. Most attention was paid to the design and performance of throttling capillary tubes installed in thermostatic bath, which define final flow parameters of CO2 coming from the CO2 branch. The flow characteristics of two capillary tubes with lengths of 7.8 and 4.0 m and inner diameter 0.1 mm were measured and compared to the predictions of a numerical model. The 1-D model of isothermal capillary flow was found to provide quite good agreement with the measured data.
Highlights
The present study is a continuation of a long-term research of the team from the Laboratory of Phase Transition Kinetics (LPTK) at the Institute of Thermomechanics of the CAS in Prague focused on investigation of droplet nucleation in CO2-rich systems [1,2]
mixture preparation device (MPD) consists of two main parts: the CO2 branch intended for adjustment of pressure, temperature, and flow rate of either superheated vapor or supercritical fluid CO2 and the gas branch with nitrogen or argon
The CO2 branch representing the core part of MPD was considerably improved
Summary
The droplet nucleation is going to be investigated with the help of a rapid expansion, i.e. a sudden pressure drop, of the superheated vapor or supercritical fluid within an expansion chamber [4,5]. MPD consists of a set of flow controllers, pressure regulating valves, backpressure regulators, supercritical CO2 pump, and other equipment, which allow for fine adjustment of an overall mass flow rate of a given mixture from approximately 65 to 200 g/hour at pressures from 74 to 150 bar. MPD consists of two main parts: the CO2 branch intended for adjustment of pressure, temperature, and flow rate of either superheated vapor or supercritical fluid CO2 and the gas branch with nitrogen or argon. The gas bottle is connected to two other pressure reduction valves, which are used for the set point adjustment on two upstream pressure regulators (UPR) employed in other part of MPD in the expansion chamber section
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