A numerical study of refrigerant tube diameter effect on enhancing the phase change process

2022 ◽  
Author(s):  
Amrita Sharma ◽  
Parth Patel ◽  
Shobhana Singh ◽  
Bobin Mandal ◽  
Manvendra Sharma ◽  
...  
Keyword(s):  
Phase Change ◽  
Change Process ◽  
Numerical Study ◽  
Tube Diameter ◽  
Phase Change Process ◽  
Diameter Effect

scholarly journals Experimental research on hydrodynamic instabilities during condensation of the pro-ecological refrigerant R1234yf in tubular minichannels

2018 ◽  
Vol 70 ◽  
pp. 02010
Author(s):  
Waldemar Kuczyński ◽  
Aleksander Denis
Keyword(s):  
Experimental Data ◽  
Phase Change ◽  
Experimental Research ◽  
Change Process ◽  
Internal Diameter ◽  
Hydrodynamic Instabilities ◽  
Condensation Zone ◽  
Phase Change Process ◽  
Flow Condensation ◽  
Propagation Velocities

The following paper presents the results of preliminary experimental research on the influence of instabilities of a hydrodynamic type on the condensation phase change process in tubular minichannels. The research was focused on a new pro-ecological refrigerant, R1234yf, intended as a substitute for R134a that currently is being phased out. The flow condensation phase change process was investigated for both steady and un-steady conditions in singular tubular minichannels with an internal diameter d = {1,44; 2,30; 3,30} mm. The scope of the analysis of the experimental data covered an estimation of propagation velocities for both pressure and temperature instabilities as well as the shrinkage of the condensation zone. The results were also compared with the previous results obtained for the flow condensation phase change of R134a refrigerant in tubular minichannels with the same internal diameters.

The Effect of Model Parameters on CFD Simulation of a Thermosyphon

2019 ◽  
Author(s):  
Huiyu Wang ◽  
D. Keith Walters ◽  
Keisha B. Walters
Keyword(s):  
Mass Transfer ◽  
Phase Change ◽  
Change Process ◽  
Flow Behavior ◽  
Density Ratio ◽  
Model Parameters ◽  
Special Focus ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Phase Change Process

Abstract Both numerical and experimental studies have previously been carried out to investigate the heat transfer performance of the two-phase closed thermosyphon (TPCT). This paper investigates the performance of a commercially available computational fluid dynamics (CFD) solver (Ansys FLUENT) to predict the complex flow behavior of TPCTs, with special focus on modeling of the mass transfer phase change process. The present study uses four different sets of mass transfer coefficients for condensation and evaporation within a previously documented phase change model to determine their impact on the simulation results. The mass transfer coefficients effectively control the rate of transfer from liquid to vapor phase during evaporation and vice versa during condensation. The choice of coefficients is assumed to represent a balance between numerical accuracy and stability. A baseline simulation is performed for which both the evaporation and condensation coefficients are equal and set to default values. Three additional simulations vary the magnitude of the coefficients and adopt relative values based on density ratio following a recommended method that has been previously found to be effective for these simulations. Initial results show that the case with the highest coefficient of evaporation and coefficient for condensation based on the density ratio is in good agreement with available experimental data of overall thermal resistance of the TPCT., with predictive capability degrading as the values of the coefficients are reduced. Additionally, the 3D CFD models implemented in this study appear to successfully predict the phase change process and vital flow behavior inside the TPCTs, at least in a qualitative sense.

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