[en] Critical flow is one of the essential parameters in LOCA accident analysis in which pressure different is very high. Void fraction (α), in another term, slip ratio, s, is the key parameter that could effect to critical flow prediction. Henry-Fauske (HF) model is the model for critical flow calculation existing in current computer codes such as MARS, RELAP, TRACE. However, the limitation of this model is slip ratio s=1. By modified the slip ratio correlation, the paper focuses on evaluating the HF model. Among the chosen correlations for slip ratio, Smith correlation is the best option for this purpose. The results in our paper showed that while original Smith correlation with k=0.4 is suggested for horizontal tests, the modified one with k=0.2 could be applied for vertical tests.(author)

[en] The experimental and theoretical study was carried out for the upward gas-liquid two-phase explained reasonably through the analysis of slip ratio of two-phase flow and theoretical analysis using momentum equation of two-phase flow separating model. (authors)

[en] This paper introduces a simple approach for the analysis of tire deformation and proposes a new piezoelectric tire sensor for physically meaningful measurements of tire deformations. Tire deformation measurements in the contact patch can be used for the estimation of slip angle, tire forces, slip ratio and tire–road friction coefficient. The specific case of a wireless tire deformation sensor for the estimation of slip angle is taken up in this paper. A sensor in which lateral sidewall deformation can be decoupled from radial deformation is designed. The slope of the lateral deflection curve in the contact patch is used to calculate slip angle. A specially constructed tire test rig is used to experimentally evaluate the performance of the developed sensor. Results show that the developed sensor can accurately estimate slip angles up to values of 5°

[en] Highlights: • A model was established to investigate the condensation flow. • The characteristics of condensation void fraction in a spiral pipe were analyzed. • 96 existing void fraction correlations were reviewed and evaluated. • Five correlations which can well predict condensation void fraction were recommended. Accurate prediction of void fraction for condensation hydrocarbon refrigerant upward flow in a spiral pipe is very important for the tube-side design of spiral wound heat exchange (SWHE) using in liquid natural gas (LNG) plants. Although scores of void fraction correlations have been developed until now, most of them are focus on two-phase flow in straight tubes and their applicability to spiral pipes needs to be evaluated. In this paper, the condensation void fraction characteristics were numerically investigated based on the verified model. 455 numerical data points of six refrigerants were obtained, under different operating and structural parameters. Based on these data, 96 void fraction correlations were evaluated, which covered the types of homogeneous, slip-ratio, Kα_v,H, Lockhart-Martinelli parameter based, drift-flux, general and implicit, and finally the best five correlations were recommended which can well predict condensation void fraction in a spiral pipe within ±5% error. This study will provide some constructive instructions to predict void fraction for condensation hydrocarbon refrigerant upward flow in a spiral pipe, which is helpful in designing more effective SWHE used in large-scale LNG plants.

[en] The problem of void fraction calculation was studied for a channel containing boiling coolant, when a slip ratio correlation is used. Use of fitting (e.g. polinomial or rational algebraic) for slip ratio correlation and the characteristic method are proposed in this work. In this way we are reduced to some elementary quadrature problem. Another problem discussed in the present work concerns what we must consider as ''initial condition'' in any initial value problem, in order to take into account different error distributions in steady state and in successive time-dependent calculations

[en] This article presents an analytical solution for the creeping flow of steady rotation of a slightly deformed slip sphere. The shape of the particle is slightly varied from that of a sphere and is embedded in a porous medium. Brinkman’s equation is employed to govern the flow in the porous region. The solution was obtained to the first order in terms of the deformation parameter. An application to the present analysis is to evaluate the torque acting on an oblate spheroid (a prolate spheroid) embedded in the porous medium. The graphs and tables envision the effects of permeability, slip and deformation parameters of the particle. In the limiting cases, the hydrodynamic torque acting on the sphere saturated with the porous medium is reduced in no-slip and slip conditions. (author)

[en] When performing calculations on boiling water reactors it is necessary to establish a relation between the average velocity of the steam, Vg, and that of the water, Vf, in the fuel channels. This is usually done through establishing an expression for the slip ratio S=V_g/V_f. In the literature a number of such slip ratio correlations -based on measurements - has been presented. A comparison between some of these correlations has been performed in this paper. While the correlations have some general trends in common, the numerical values of S obtained with the correlations may vary significantly. Further, in spite of the fact that various flow regimes exist in a boiling channel none of the correlations considered take the change of flow regime into account. This raises the question: How reliable is the use of slip correlation? (orig.) (9 refs., 5 figs.)

[en] The results of an experimental investigation concerning the determination of some characteristics of two-component (air-water), two-phase mixtures in vertical downward flow are presented in this article. The experiments were carried out on two pipes, 44 and 90 mm in diameter. Measurements were particularly concerned with void fraction, obtained by the manometric method, in bubble flow regime and for the above mentioned configurations. Firstly, the results were compared with those obtained by other researchers under analogous conditions. Then, the differences in void fraction values from those calculated by means of some well-known correlations for pressure drop by friction were estimated. Experimental data were also dealt with by means of other usual significant correlations for characteristic velocities of the phases, void fraction, slip ratio, in upward flow. Specifically, the models of Wallis, Zuber and Findlay, and Sokolov were considered, and a satisfactory agreement was found

[en] Highlights: • A new drop deposition model is formulated. • Drop turbulence is calculated taking into account its inertia. • The model has capability to predict obstacle effect. -- Abstract: The drop deposition increase due to flow obstruction is usually quantified solely by empirical coefficients. In this work we propose a new way to calculate the drop deposition with the capability to predict the obstacle effect. The model is based on the drop volume fraction, slip ratio and turbulence quantities of the continuous phase obtained from the two-fluid calculations. Additional relations are needed to calculate the fluctuating velocities of the drop phase. These relations are based on the fluid integral time scales. A number of relations are tested, which include the effect of drop inertia and drift parameter. The new model is tested in a number of flow combinations, including air–water and helium–water of 1.5 bar and steam–water at 70 bar pressure, for low and high drop concentration. The high concentration flow shows that further studies are needed to include drop size increase due to coalescence and reduction of velocity fluctuation due to drop collisions. The new model is tested for pipe flow containing an obstacle of steam–water flows of 5, 10 and 15 bar pressure. The new model shows the capability to qualify the obstacle effect. Further improvements are needed to increase the quantitative capability

[en] Anti-lock braking system (ABS) is used on vehicles to keep the wheels unlocked in sudden break (inside braking) and minimalize the stop distance of the vehicle. The problem of it when sudden break is the wheels locked so the vehicle steering couldn’t be controlled. The designed ABS system will be applied on ABS simulator using the electromagnetic braking. In normal condition or in condition without braking, longitudinal velocity of the vehicle will be equal with the velocity of wheel rotation, so the slip ratio will be 0 (0%) and if the velocity of wheel rotation is 0 (in locked condition) then the wheels will be slip 1 (100%). ABS system will keep the value of slip ratio so it will be 0.2 (20%). In this final assignment, the method that is used is Neuro-Fuzzy method to control the slip value on the wheels. The input is the expectable slip and the output is slip from plant. The learning algorithm which is used is Backpropagation that will work by feedforward to get actual output and work by feedback to get error value with target output. The network that was made based on fuzzy mechanism which are fuzzification, inference and defuzzification, Neuro-fuzzy controller can reduce overshoot plant respond to 43.2% compared to plant respond without controller by open loop. (paper)