Two-Phase Flow Development of R134a in a Horizontal Pipe: Computational Investigation

To improve the performance of vapor compression refrigeration systems that use vertical gravitational flash tank separators, the liquid separation efficiency of the vertical gravitational flash tank separator requires to be approved. To approach this improvement, the two-phase flow development and its behavior after the expansion device need to be investigated and predicted. For thus, this paper presents a three-dimensional computational investigation of the two-phase flow development of R134a after the expansion device in a horizontal pipe. Computational Fluid Dynamic (CFD) was used to predict the two-phase development and its behavior in the horizontal pipe. ANSYS 16.2 program was used to generates the geometry of the three-dimensional horizontal pipe of 2 meters long and 25 mm inner diameter. The hexahedral mesh was generated and it is assessed to obtain the optimum mesh size and number. Eulerian-Eulerian two-phase model was used with k-ɛ turbulence model. R134a was used as a working fluid in the horizontal pipe utilizing four different inlet diameters: 12, 12.5, 25, and 50.0 mm. Mass flux and vapor quality have been changed from 288 to 447 kg/m2.s and from 10 to 20% respectively. Results were validated against experimental results from the literature and revealed that the separation region length is affected by the initial phase velocities, inlet vapor quality, and inlet tube diameter. An empirical correlation to predict the expansion region length is proposed as a function of Froude, Webber, and Lockhart-Martinelli numbers.

Plasticity Autowave Characteristics of Metals and the Periodic Table of Elements

In this paper, the general laws of localized plastic flow development are described for the linear work hardening stages of nineteen metals. The correlations are established and discussed between their element position in the periodic table of elements and the parameters of the autowave process of localized plastic flow in these elements. Patterns of plastic flow are considered for nineteen metals from the 3rd, 4th, 5th, and 6th periods of the periodic table of elements. A conditional characteristic of plasticity is introduced and its relationship with the position of the metals in the periodic table of elements is established. Correlations between the plastic properties and other metal characteristics were analyzed. Some quantitative models are proposed for explaining the observed dependency origin by the drag of moving dislocation by electron gas in metal crystals. Observed correlations indicate the existence of a close bond between localized plastic flow in deforming medium with the lattice characteristics of the elements and their electron structures.