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The mathematical model based on conservation of energy, mass and salinity is established to analyse the comprehensive performance of parallel feed multi-effect evaporation system with mechanical vapor compression (MEE-MVC) system. It is found that the efficiency of the MVC evaporation system gradually improves as the number of evaporator effect increases. However, the optimization trend of specific power consumption (SPC) and coefficient of performance (COP) are declining when the number of evaporator effect exceeds 3, which makes the marginal effect of the efforts made to improve the system gradually weakened. Then, the three-effect MVC evaporation system is taken as the main research subject to investigate comprehensive performance of the system. It was found that the SPC of the system increases with the increase of the total heat transfer temperature difference; on the other hand, the COP decreased significantly with the increase of the total heat transfer temperature difference. Furthermore, increasing the evaporation temperature in the last evaporator as well as compressor efficiency can optimize the energy efficiency of the system. In addition, the compressor efficiency has a greater influence on the SPC when the total heat transfer temperature difference is larger, whereas the compressor efficiency has a greater influence on the COP when the total heat transfer temperature difference is smaller. [ABSTRACT FROM AUTHOR]

In the new era of ejector technology entering into system scale from device scale. The methodology of regulation mode of an adjustable ejector has been summarized in this paper. The similarity in characteristics of qualitative and quantitative regulation under different operating modes are researched. The results show that both qualitative and quantitative regulation have the characteristics of 'constant capacity'. Three different 'constant-capacity' phenomena in ejectors have been found, and the similarity indicates that the turbulent flow in ejectors has some statistical invariances in the form of mass flow rate of jetting flow. The ejector has the similar entrainment ability by increasing primary pressure by 43% in the qualitative regulation mode or enlarging the nozzle throat opening by 47% in the quantitative regulation mode under critical mode with similar underexpanded state. The advantages of adjustable ejectors have been promoted, in particular ±5% regulation accuracy or constant regulation ability, discharging improved ability by 80% in flow rate or 10% in pressure lifting ability in subcritical mode or primary flow rate saving ability by 25% or 13% in pressure lifting ability in critical mode. [ABSTRACT FROM AUTHOR]

Based on the pinch theory and energy cascade utilization principle, the performance of a multi-effect shipboard vertical tube climbing film desalination system combined thermal vapor compression with different preheating configuration has been analyzed. The mathematical model is established for thermodynamic simulation, in which various thermodynamic losses caused by boiling point elevation and pressure drop are considered, and the effective heat transfer temperature difference and the hot side temperature difference are used to analyze the influences of heating steam temperature, final effect evaporation temperature, and concentration ratio on thermal performance including gained output ratio (GOR)—specific heat transfer area for different preheating configuration. The results show that the internal average effective heat transfer temperature difference determines characteristics of multi-effect distillation (MED) system. While for system with similar average effective heat transfer temperature, the temperature difference of hot side is the controlling parameter. And the energy cascade utilization principle shows the controlling attribute in MED thermodynamic system, as GOR is improved mainly due to utilization of the secondary energy and residual energy of the heating steam for preheating process. [ABSTRACT FROM AUTHOR]

The effect of surface wettability on droplet impact on spherical surfaces is studied with the CLSVOF method. When the impact velocity is constant, with the increase in the contact angle (CA), the maximum spreading factor and time needed to reach the maximum spreading factor (t max) both decrease; the liquid film is more prone to breakup and rebound. When CA is constant, with the impact velocity increasing, the maximum spreading factor increases while t max decreases. With the curvature ratio increasing, the maximum spreading factor increases when CA is between 30 and 150°, while it decreases when CA ranges from 0 to 30°. [ABSTRACT FROM AUTHOR]

A three-dimensional model is applied to simulate the liquid film spreading process and liquid film thickness distribution. The volume-of-fluid (VOF) method is used to trace the gas–liquid interface. The mutual influences on the liquid film flow behavior between liquid columns are discussed in detail. It is found that the liquid film spreading and the distribution of the liquid film thickness are influenced by liquid column impact and the wave crest formation process. The wave crest forms in the vicinity of the center point of the adjacent liquid column. The Reynolds (Re) number is an important factor in the spread of the liquid film and the distribution of the liquid film thickness, but the tube spacer has almost no influence on it when the Re number is 188. [ABSTRACT FROM AUTHOR]

In this paper, the influence of split-vanes attached to the end of grid spacers on local flow and heat transfer was investigated at a pressure of 25 MPa, a mass rate of 1000 kg/m2s and a heat flux of 800 kW/m2K for the sub-channels of an supercritical water reactor core. The numerical results show that there are obviously different distributions of wall temperature in three regions. The circumferential heterogeneities of the heat transfer are evidently enhanced at the downstream of the grid spacers with split-vanes. Additionally, there is a phenomenon of weakened heat transfer at the downstream of the grid spacers in the large specific heat region. [ABSTRACT FROM AUTHOR]

The process of the impinging of a droplet upon a heated flat solid surface was computationally studied to identify the key process occurring in a liquid droplet. A computational fluid dynamics model, based on the volume of fluid (VOF) approach, was used to simulate the impact of droplet dynamics on the heated flat solid surface. Surface tension and wall adhesion phenomena were taken into account in this model. The model was proved effective by comparing the simulation results with the experimental data in the literature. It could be concluded that the VOF-based model was able to simulate the dynamics of the impinging of a droplet upon a heated solid surface. The key characteristics of droplet evaporation and the interaction between the droplet and the solid surface could be captured. [ABSTRACT FROM AUTHOR]

The present paper was performed to analyze the pyrolysis process of corn straw. Based on the thermogravimetric analysis, the component of pyrolysis gas of corn straw was tested using the gas chromatograph analyzer. Experimental results showed that, as the reaction temperature increases, the component of H2 and CH4 increases, whereas the component of CO and CO2 decreases. Finally, the mechanism of pyrolysis process of corn straw was revealed from the point of view of the molecular structure based on the elemental analysis. [ABSTRACT FROM AUTHOR]

A numerical study on the performance of an adjustable ejector was presented. An axial spindle extending into the nozzle was used to change the throat area of the nozzle to make the ejector adjustable. The re-normalization group (RNG) k-epsilon model reconciled better with experimental measurements than other two turbulence models and was utilized to simulate the flow inside the adjustable ejector. The numerical results indicated that, at the same certain motive and suction operating conditions, the adjustable ejector had higher entrainment ratio and lower discharge pressure. The existence of spindle diminishes the nozzle throat cross-sectional area; as a result, the motive flow rate was reduced. These characteristics of the adjustable ejector provided potential for more economical design and operation. [ABSTRACT FROM AUTHOR]