On the pressure distribution in multi-phase pipelines

The results of investigations and measurements of actual pressure values carried out recently in technological-field pipelines show that the nature of pressure distribution in multi-phase pipelines differs from those in mono-phase ones. The paper analyzes the aspects affecting the pressure distribution in gas-saturated fluids in the presence of phase transformations. Considering the changes in compressibility of gas-saturated mixture, a mathematical model for pressure distribution through the length of pipeline has been developed. It was defined that depending on the compressibility ratio and flow regime, the pressure distribution in multi-phase pipeline decreases steadily at an exponential rate.

Permeability Evaluation of Clay-quartz Mixtures Based on Low-Field NMR and Fractal Analysis

Nuclear magnetic resonance (NMR) technology has been widely used for predicting permeability coefficients of porous medium, such as shales, sandstones, and coals. However, there have been limited studies on the prediction model of clay-quartz mixtures based on NMR technology. In this study, evaporation tests at 40 °C and NMR tests were simultaneously performed on eight clay-quartz mixtures with different mineral compositions. The results show that during the evaporation process, the decay rate of T2 total signal amplitudes was constant at first, and then decreased to 0 after a period of time. Based on the decay rate, the evaporation process was divided into two stages: the constant rate stage and the falling rate stage. Based on the two stages, the T2 cut-offs of eight mixtures were determined. The water in the mixture was divided into two parts by the T2 cut-off: the free water and the bound water. The prediction model of permeability coefficients of clay-quartz mixtures was established based on the Timur-Coates model. In order to simplify the process of predicting the permeability coefficient, fractal analysis was used to develop the relationship between the T2 cut-off and fractal dimension of the T2 spectrum of saturated mixture. A simplified method for predicting permeability coefficients of clay-quartz mixtures based on NMR technology without centrifugal and evaporation experiments was also proposed.

Modeling Shallow Over-Saturated Mixtures on Arbitrary Rigid Topography

In this paper a system of depth-integrated equations for over-saturated debris flows on three-dimensional topography is derived. The lower layer is a saturated mixture of density preserving solid and fluid constituents, where the pore fluid is in excess, so that an upper fluid layer develops above the mixture layer. At the layer interface fluid mass exchange may exist and for this a parameterization is needed. The emphasis is on the description of the influence on the flow by the curvature of the basal surface, and not on proposing rheological models of the avalanching mass. To this end, a coordinate system fitted to the topography has been used to properly account for the geometry of the basal surface. Thus, the modeling equations have been written in terms of these coordinates, and then simplified by using (1) the depth-averaging technique and (2) ordering approximations in terms of an aspect ratio ϵ which accounts for the scale of the flowing mass. The ensuing equations have been complemented by closure relations, but any other such relations can be postulated. For a shallow two-layer debris with clean water in the upper layer, flowing on a slightly curved surface, the equilibrium free surface is shown to be horizontal.

Model Analysis of High-Fogging Effects on the Work of Compression

In recent years, high fogging has received increasing attention as a comparatively simple and cost-efficient means of gas turbine power augmentation. The effects of high fogging on the work of compression are studied in this paper from a fundamental perspective. Considered is a prototype configuration, namely the evaporation of droplets in an initially saturated mixture of air and water, which is exposed to a prescribed pressure rise. Two different approaches are applied: The first approach (‘ideal model’) assumes that thermodynamic equilibrium prevails. In the second approach (‘droplet model’) the finite time of evaporation is taken into account by introducing discrete droplets and modeling explicitly the heat and mass transfer between liquid and gaseous phase. For compression speeds representative of modern gas turbines, it is found that droplets of 1μm in diameter are small enough to allow for approximate equilibrium during compression. The influence of polytropic efficiency on the gains of high fogging is addressed, and it is shown that high fogging is more effective for compressors of lower efficiency.

3He DIMERS IN TWO-DIMENSIONAL 3He-4He MIXTURE FILMS

We have studied the ground state properties of two-dimensional 3 He -4 He mixtures at zero temperature. 3 He atoms with opposite spins form loosely bound dimers in free space and in low concentration mixtures with 4 He . The binding energy of the dimer ranges from milli-Kelvins near the saturation density to micro-Kelvins at the solidification density. The radius of such a weakly bound dimer is tens of Ångstöms. We also calculate the phase diagram of the mixture. The maximum solubility of 3 He ≈7% is determined by comparing chemical potentials in the pure and mixed fluids. The upper stability limit of the super-saturated mixture is obtained from the second derivative of the enthalpy. It becomes negative at the concentration 10-15% depending of the pressure, indicating a softening of the concentration-fluctuation mode. We also find an indication of the phase transition from the dimerized to atomic mixture.

Determination of α-Solanine and α-Chaconine in Potatoes by High-Performance Thin-Layer Chromatography/Densitometry

A high-performance thin-layer chromatographic (HPTLC) method was used to determine the glycoalkaloids α-solanine and α-chaconine in potatoes. α-Solanine and α-chaconine are extracted from dehydrated potatoes with boiling methanol–acetic acid (95 + 5, v/v). The analytes are separated on a Silica Gel 60 F254 HPTLC plate by a saturated mixture of dichloromethane–methanol–water–concentrated ammonium hydroxide (70 + 30 + 4 + 0.4, v/v), which is used for vertical development of the plate up to a distance of 85 mm. For visualization, the plate is dipped 3 times into a modified Carr-Price reagent, 20% (w/v) antimony(III) chloride in acetic acid–dichloromethane (1 + 3, v/v), and subsequently heated on a hot plate at 105°C for 5 min. The glycoalkaloids all appear as red chromatographic zones on a colorless background. Densitometric quantification is performed at 507 nm by reflectance scanning. After determination of the appropriate response function, the proposed method was validated. Good results with respect to linearity, accuracy, and precision were obtained in the concentration range studied.

Analysis of Two-Phase Flow in Cryogenic Damper Seals—Part I: Theoretical Model

Cryogenic fluid damper seals operating close to the liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two-phase flow region which affects the seal performance and reliability. An all-liquid, liquid-vapor, and all-vapor, i.e., a “continuous vaporization” bulk flow model is presented for prediction of the seal dynamic forced response. Continuity, momentum, and energy (enthalpy) transport equations govern the two-phase flow of a homogeneous saturated mixture in thermodynamic equilibrium. Static and dynamic force performance characteristics for the seal are obtained from a perturbation analysis of the governing equations. Theoretical predictions and comparisons to experimental measurements in a liquid and gaseous nitrogen seal are presented in Part II. The effects of two-phase flow regimes on the dynamic force coefficients and stability of an oxygen damper seal are also discussed.

Experimental Study of Two-Phase Propane Expanded through the Ranque-Hilsch Tube

When air or other gases flow through the Ranque-Hilsch vortex tube, the well known temperature separation effect can be produced. This effect has been utilized for many purposes and is especially useful in providing cooling in applications not requiring the higher efficiencies of more sophisticated refrigeration systems. When the inlet fluid to the tube becomes a mixture of saturated liquid and vapor, one intuitively expects the temperature separation to diminish. Experimental data were obtained using propane to quantitatively determine the deterioration of temperature separation when the condition of the inlet fluid becomes a saturated mixture. Observations indicate that temperature separation diminishes rapidly for inlet qualities of less than 80 percent due largely to the decrease in “hot side” temperature. For qualities above 80 percent, significant temperature separation can be maintained.