A Model of a Plug-Chain System Near the Thermodynamic Critical Point: Connection with the Korteweg Theory of Capillarity and Modulation Equations

1995 ◽  
pp. 419-428 ◽  
Author(s):  
Sergey L. Gavrilyuk ◽  
Denis Serre
Keyword(s):  
Critical Point ◽  
Modulation Equations ◽  
Chain System ◽  
Thermodynamic Critical Point

An Analytical Investigation of Forced Convection Heat Transfer to Fluids Near the Thermodynamic Critical Point

1975 ◽  
Vol 97 (2) ◽  
pp. 226-230 ◽  
Author(s):  
V. S. Sastry ◽  
N. M. Schnurr
Keyword(s):  
Heat Transfer ◽  
Critical Point ◽  
Circular Tube ◽  
Convection Heat Transfer ◽  
Analytical Investigation ◽  
Convection Heat ◽  
Thermodynamic Critical Point ◽  
Constant Wall Heat Flux ◽  
Flow Through ◽  
Implicit Finite Difference

A numerical solution is carried out for heat transfer to fluids near the thermodynamic critical point for turbulent flow through a circular tube with constant wall heat flux. An adaptation of the Patankar-Spalding implicit finite difference marching procedure is used. Agreement of the results with experimental data for water and carbon dioxide show the solution to be quite accurate very near the critical point provided the wall temperature at inlet is less than the pseudocritical temperature of the fluid.

Phase Change Mechanisms in Pulsed Laser-Matter Interaction

2004 ◽  
Vol 850 ◽  
Author(s):  
Xianfan Xu
Keyword(s):  
Phase Change ◽  
Critical Point ◽  
Spinodal Decomposition ◽  
Nanosecond Laser ◽  
Micro Machining ◽  
Laser Micro Machining ◽  
Thermodynamic Critical Point ◽  
Matter Interaction ◽  
Explosive Phase ◽  
Change Mechanisms

ABSTRACTLaser micro-machining is finding many applications in materials processing and manufacturing. Various laser techniques are being used to fabricate micro-electronics, optics, and medical components. This paper will mainly deal with the fundamental issues involved in laser-matter interaction. Our studies are focused on laser induced thermal and thermomechanical phenomena and phase change mechanisms that determine the materials removal process during laser micro-machining. It is shown that during nanosecond laser machining, explosive phase change could occur, during which the liquid is superheated to close to the thermodynamic critical point, followed by an explosive, homogeneous phase transformation. On the other hand, it is observed in the experiment that the time needed for nucleation during laser induced phase explosion is on the order of one nanosecond. Thus, when a laser with a pulsewidth of the order of picosecond or less is used, it is likely that the material can be heated above the critical point, and another type of phase change, spinodal decomposition is possible. Molecular dynamics studies showed that with the use of a femtosecond laser pulse, it is possible to superheat the material to above the critical point, and spinodal decomposition is the dominant mechanism for materials removal.

Heat Transfer to Carbon Dioxide in the Immediate Vicinity of the Critical Point

1969 ◽  
Vol 91 (1) ◽  
pp. 16-20 ◽  
Author(s):  
N. M. Schnurr
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Critical Point ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Reduced Pressure ◽  
Circular Duct ◽  
Heat Transfer Coefficients ◽  
Thermodynamic Critical Point

Local heat-transfer coefficients are measured for carbon dioxide very near the thermodynamic critical point for flow through an electrically heated circular duct. The experiments cover a range of fluid bulk temperatures spanning the transposed critical temperature and of pressure from 1075 to 1110 psia (reduced pressure from 1.003 to 1.03). The data are correlated by the equation Nuz = 0.0266 Rez0.77 Prw0.55 where the Prandtl number is evaluated at the wall temperature and Nusselt and Reynolds numbers are evaluated at a variable reference temperature. The dominant heat transfer mechanism is found to be turbulent forced convection. There is evidence that free convection effects are also present.

Numerical and Experimental Study of Abnormal Thermo-Mechanical Effects in Supercritical Fluid

2021 ◽  
pp. 112-160
Author(s):  
Victor Emelyanov ◽  
Alexander Gorbunov ◽  
Andrey Lednev
Keyword(s):  
Critical Point ◽  
Supercritical Fluid ◽  
Numerical Study ◽  
Mass Conservation ◽  
Coexistence Curve ◽  
Navier Stokes ◽  
Rarefaction Waves ◽  
Thermodynamic Critical Point ◽  
Characteristic Features ◽  
Phase Fluid

At least three regions can be distinguished on the phase diagram where one-phase fluid has abnormal thermo-mechanical properties: (1) the region above the thermodynamic critical point, strictly the supercritical fluid (SCF); (2) the region close to the coexistence curve; and (3) the region where (d2p/dv2)S<0. This chapter is devoted to the experimental and numerical study of abnormal effects in (1) and (3) regions. The calculations are carried out with the use of equations of Navier-Stokes, mass conservation, energy balance, and van der Waals or perfect gas equation of state. Two basic characteristic features of the SCF near the critical point, the accelerated temperature rise in the bulk heated from boundaries (so-called “piston effect”) and very slow relaxation of the generated inhomogeneities of thermodynamic parameters are studied. For region (3) the abnormal regimes of propagation of the shock and rarefaction waves after decay of a discontinuity are found.

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