Numerical Analysis of Mass Flow Leakage Through Orifices for Supercritical CO2: Two-Phase Flow Effects

2021 ◽  
Author(s):  
Ladislav Vesely ◽  
Akshay Khadse ◽  
Andres Curbelo ◽  
Luca Petrungaro ◽  
Jayanta Kapat
Keyword(s):  
Numerical Analysis ◽  
Mass Flow ◽  
Supercritical Co2 ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Effects

Numerical Analysis of Mass Flow Leakage Through Orifices for Supercritical CO2: Two-Phase Flow Effects

2020 ◽  
Author(s):  
Ladislav Vesely ◽  
Akshay Khadse ◽  
Andres Curbelo ◽  
Jayanta S. Kapat ◽  
Luca Petrungaro
Keyword(s):  
Mass Flow ◽  
Thermodynamic Equilibrium ◽  
Supercritical Co2 ◽  
Two Phase Flow ◽  
Operating Conditions ◽  
Working Fluid ◽  
Great Promise ◽  
Phase Flow ◽  
Computational Domain ◽  
Two Phase

Abstract Supercritical CO2 (sCO2) holds a great promise as a future working fluid for power generating Brayton cycles. One of the challenging research areas in sCO2 power cycles is flow leakage and the design of seals on the compressor side of the cycle. Given the compact nature of sCO2 turbomachinery, even a minimal amount of leakage can lead to a significant power efficiency loss. Hence accurate prediction of mass flow leakage rate becomes important. However, on the compressor side of the cycle, operating conditions across the seal lead to two-phase flow. This makes flow modeling very challenging because conventional one-phase flow CFD models cannot be used. This paper is an attempt to understand the behavior of two-phase sCO2 flow going through circular and annular orifices. The focus is to utilize commercially available CFD scheme for modeling phase change and two-phase flow through constrictions. Since the pressure loss across constrictions is also accompanied with reduction in temperature, the flow becomes two-phase by entering the saturation dome. CFD simulation is performed using commercially available software STAR CCM+. 2D axisymmetric geometry is considered as the computational domain. Eulerian Multi-phase Mixture model is used in conjunction with the Two-Phase Thermodynamic Equilibrium implementation. This model is intended for applications that involve two phases of the same substance that are in thermodynamic equilibrium. Fluid properties are defined over a large range of temperatures and pressures, including both the liquid and vapor phases.

Research on Two-Phase Flow Instability in Evaporator of Refrigeration System

2010 ◽  
Author(s):  
Nan Liang ◽  
Changqing Tian ◽  
Shuangquan Shao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Density Wave ◽  
Phase Flow ◽  
Constant Mass ◽  
Refrigeration System ◽  
Two Phase

As one kind of fluid machinery related to the two-phase flow, the refrigeration system encounters more problems of instability. It is essential to ensure the stability of the refrigeration systems for the operation and efficiency. This paper presents the experimental investigation on the static and dynamic instability in an evaporator of refrigeration system. The static instability experiments showed that the oscillatory period and swing of the mixture-vapor transition point by observation with a camera through the transparent quartz glass tube at the outlet of the evaporator. The pressure drop versus mass flow rate curves of refrigerant two phase flow in the evaporator were obtained with a negative slope region in addition to two positive slope regions, thus making the flow rate a multi-valued function of the pressure drop. For dynamic instabilities in the evaporation process, three types of oscillations (density wave type, pressure drop type and thermal type) were observed at different mass flow rates and heat fluxes, which can be represented in the pressure drop versus mass flow rate curves. For the dynamic instabilities, density wave oscillations happen when the heat flux is high with the constant mass flow rate. Thermal oscillations happen when the heat flux is correspondingly low with constant mass flow rate. Though the refrigeration system do not have special tank, the accumulator and receiver provide enough compressible volume to induce the pressure drop oscillations. The representation and characteristic of each oscillation type were also analyzed in the paper.

scholarly journals Pressure Signal Analysis for the Characterization of High-Viscosity Two-Phase Flows in Horizontal Pipes

2020 ◽  
Vol 8 (12) ◽  
pp. 1000
Author(s):  
Lizeth Torres ◽  
José Noguera ◽  
José Enrique Guzmán-Vázquez ◽  
Jonathan Hernández ◽  
Marco Sanjuan ◽  
...  
Keyword(s):  
Mass Flow ◽  
Two Phase Flow ◽  
High Viscosity ◽  
Flow Rate Ratio ◽  
Phase Flow ◽  
Two Phase ◽  
Local Flow ◽  
Horizontal Pipes ◽  
Pressure Time ◽  
Mass Flow Rates

We study a high-viscosity two-phase flow through an analysis of the corresponding pressure signals. In particular, we investigate the flow of a glycerin–air mixture moving through a horizontal pipeline with a U-section installed midway along the pipe. Different combinations of liquid and air mass flow rates are experimentally tested. Then, we examine the moments of the statistical distributions obtained from the resulting pressure time series, in order to highlight the significant dynamical traits of the flow. Finally, we propose a novel correlation with two dimensionless parameters: the Euler number and a mass-flow-rate ratio to predict the pressure gradient in high-viscosity two-phase flow. Distinctive variations of the pressure gradients are observed in each section of the pipeline, which suggest that the local flow dynamics must not be disregarded in favor of global considerations.

scholarly journals Numerical Analysis of Bed-Load Layer As Solid/Liquid Two-Phase Flow.

1994 ◽  
pp. 11-19
Author(s):  
Hitoshi Gotoh ◽  
Tetsuro Tsujimoto ◽  
Hiroji Nakagawa
Keyword(s):  
Numerical Analysis ◽  
Two Phase Flow ◽  
Bed Load ◽  
Phase Flow ◽  
Two Phase ◽  
Solid Liquid
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