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The results have been presented of the theoretical and experimental research of the ignition processes of single drops of coal-water coal–water fuel (CWF). Their surface is covered by a water film. The temperature of the environment T e has also been recorded and the main characteristics of the process — the times of complete evaporation of the water film (t e w f )) and the ignition delays (t i g n ). The errors in determining T e have not exceeded 5%. According to the results of the detailed analysis of the video recordings of the investigated process of ignition, the mathematical models have been developed. They describe the interrelated complex of the thermophysical and thermochemical processes. The approximate analytical solutions of the multistage nonlinear problem of ignition of a coal-water coal–water particle have been obtained using the asymptotic procedures. According to the results of the experimental and theoretical studies, it has been established that the thickness of an aqueous film is one of the parameters determining the conditions and characteristics of the CWF ignition. Moreover, under the conditions of the experiments it has been established that the characteristic evaporation time of the near-surface layer can be from 45 to 60% of the total induction period. They depend on the thickness of the film.

This paper presents an investigation into the effect of rock physical parameters on water phase trapping (WPT) damage in tight gas reservoirs. The investigation involved water imbibition and drainage experiments that were performed to simulate the WPT formation process. Gas permeability was measured before and after WPT, and an empirical formula was used to determine water film thickness in order to examine the influence of WPT on effective gas flow channel. Results showed that the average water saturation of 15 tight core samples increased from 19.41% to 44.76% during water imbibition and declined to 38.72% after drainage. Increments in water saturation caused a degree of damage to gas permeability in the 36.03%‐78.10% range with an average value of 59.31%. Comparative analysis showed that the dominant factors affecting WPT were average pore throat radius followed by rock permeability and porosity. Meanwhile, calculations showed that water film thickness in the 21.22‐38.18 nm range correlated to a reduced effective gas flow channel of 20.20‐45.15 nm caused by WPT, which suggests that tight rocks with smaller pore throats may be particularly sensitive to WPT damage. The relative size of the water film filling the pore throat, trapping gas, and reducing the effective gas flow channel together with the size of the pore throat itself were found to be the most common damage mechanisms of WPT and have proven to be fundamentally beneficial in understanding the controlling factors of these damage mechanisms.

In the passive containment cooling system of AP1000, the condensed water is expected to flow down on the inner surface of the steel wall of the containment, and recover to the in-containment refueling water storage tank (IRWST), therefore, to maintain the long-term coolability of the passive residual heat removal system. However, there are attached bulging plates on the inner surface for various engineering needs, such as supporting, and the impingement of condensed water film on these bulging plates can reduce the amount of the recovered water. In this article, a 3-D Eulerian wall film model in FLUENT was used to study a series of flow behaviors when a water film impinged on the bulging plate on a plane surface. The loss ratio of falling film impinging on attached plates of different sizes under different flow rates were calculated and in good agreement with the experiment results. Four stages of the film behavior during the impingement were identified and analyzed; in addition, the influences of the bulging height of attached plate and flow rate were studied. And a correlation between the loss ratio of impinging water film, the bulging height of the attached plate, and the Weber number was obtained.

Mold growth, one of the most severe hazards to soil ruins in humid regions, is often caused by a favorable hygrothermal environment, that is, high relative air humidity (RH) with a suitable temperature and other environmental variables. It was reported that no mold growth occurs in buildings when RH is less than 70%, and mold grows more easily and quickly as humidity increases (Sedlbauer, 2001). The characteristics of mold growth under extremely high humidity conditions remain elusive. In our previous research, samples from the Wenzhou Qiaolou soil ruin were used to estimate the effects of ventilation and lighting modes on mold growth. On that basis, subsequent experiments and analysis were conducted to assess the relationship between mold growth, and RH and lighting modes. In the experiments, six sets of initially wet samples were placed in artificial lighting or dark conditions with different RH to evaluate the characteristics of mold growth under extremely high humidity conditions. We found that extremely high humidity with a condensation environment had a significantly inhibitory effect on mold growth compared with the humidity range (94%–99%) favorable for it. Observations with the microscope conducted to understand the moisture condition of the sample surface confirmed a possibility that the reduction or isolation of oxygen under very high RH conditions with condensation caused this result. This paper provides basic knowledge regarding the characteristics of mold growth in an extremely high humidity environment, and is practically useful for methods of inhibition of mold growth in a high-humidity environment.

Many researchers have revealed that relative permeability depends on the gas-water-rock interactions and ultimately affects the fluid flow regime. However, the way that relative permeability changes with fractal porous media has been unclear so far. In this paper, an improved gas-water relative permeability model was proposed to investigate the mechanism of gas-water displacement in fractal porous media. First, this model took the complexity of pore structure, geometric correction factor, water film, and the real gas effect into account. Then, this model was compared with two classical models and verified against available experimental data. Finally, the effects of structural parameters (pore-size distribution fractal dimension and tortuosity fractal dimension) on gas-water relative permeability were investigated. It was found that the sticking water film on the surface of fracture has a negative effect on water relative permeability. The increase of geometric correction factor and the ignorance of real gas effect cause a decrease of gas relative permeability.

Icing phenomena are one of the hot issues in the aviation field, which has attracted the attention of many manufacturers. The physical process of water film flow determines the position and amount of icing. In this paper, the flow process of water film on a rough surface is studied. An experimental platform was built in a wind tunnel, and the digital image processing (DIP) technology was used to measure the water film flow. The water film flow under different roughness conditions of the plate was obtained in the experiments. The correction model of interfacial shear coefficient is established, and the influence of roughness on water film flow is deduced. The relationship obtained in this paper can provide data support for the study of gas-water coupled flows on rough surfaces.

Blast furnace slag was used as the main raw material to prepare the alkali activated slag (AAS), a low-carbon binder, for cemented paste backfill (CPB). The optimum parameters for preparing the AAS binders using an orthogonal experiment were obtained. Under the optimum conditions (NaOH content was 3 wt. %, Ordinary Portland cement (OPC) content was 7 wt. %, and gypsum dosage was 4 wt. %), the 28 days compressive strength of the binder was 29.55 MPa. The flow ability of the fresh CPB slurry decreased with solid content due to the increased yield stress, while the flow ability increased when rising the binder dosage. A predictive model for the compressive strength of CPB samples was reached through multivariate analysis and the R2 values were higher than 0.9. Sensitivity analysis showed that the solid content is the most important parameter which influences on the development of the CPB strength with a correlation coefficient of 0.826. From the Toxicity Characteristic Leaching Procedure (TCLP) tests, the leaching concentrations of Pb and Cd were below the threshold. As a result, the AAS has potential application as an alternative binder and cemented paste backfill.

Water films are always formed on the outer or inner surfaces of materials in industrial processes and some key parts of instruments because of complex working environments (moisture and hidden water). This situation may lead to inaccurate measurement results or even unsafety process for instrument operation. Therefore, it is important to reliably detect and quantify the formed water films. A coplanar capacitive sensor and an AD7745-based measurement system were designed for the first stage of this paper. A glass tank and a specific power ultrasonic humidifier were then added to construct the experimental platform. To verify the feasibility of the designed coplanar capacitive sensor, the thickness of the water films was set to change from 0 to 1.5 mm with a 0.1-mm interval. The experimental results based on the self-developed system were compared with the results simulated by COMSOL, and the results derived from Agilent 4294A (an impedance analyzer). The results indicated that the coplanar capacitive sensor could be used to detect and evaluate the thickness of the water film. The resolution of AD7745-based measurement system for water film thickness detection is less than 0.1 mm.

Radiative transfer through a water film was investigated. Films with average thicknesses between 100 and 380 μ m were studied. The film thickness was measured using an optical method based on the attenuation of a near infrared laser beam. The attenuation of infrared radiation on a wide spectral range was determined simultaneously by using a FTIR spectrometer. A high attenuation efficiency was observed even for such small film thicknesses, which demonstrated the shielding effect of water films. Extension of present observations to high temperature sources allows the evaluation of the film absorption, which was predicted in the range 60–95% for films between 100 μ m and 1 mm and for incident radiation from blackbodies up to 1473 K.

International audience; This work is devoted to modeling the evolution of the homogenized solute diffusion coefficient within unsaturated granular materials by means of micromechanics approach. On the basis of its distinct role in solute diffusion, the liquid water within unsaturated granular materials is distinguished into four types, namely intergranular layer (interconnected capillary water), isolated capillary water, wetting layer and water film. Application on two sands shows the capability of the model to accurately reproduce the experimental results. When saturation degree is higher than the residual saturation degree Srr, the evolution of homogenized solute diffusion coefficient with respect to the saturation degree depends significantly on the connectivity of the capillary water. Below Srr, depending on the connectivity of the wetting layer, the homogenized solute diffusion coefficient within unsaturated sands decreases by 2–6 orders of magnitude with respect to that in bulk liquid water. The upper bound of the solute diffusion coefficient contributed by the water films is 4–6 orders of magnitude lower than that in bulk liquid water.

Nanoscopic liquid-like water films were deposited onto silica mesoporous aggregates from vapour phase at 30 °C and at 0.9 P/P0 or from water–paraffin emulsions. The water layers, surround entirely the silica aggregates, reduced their specific surface area from 136 ± 5 m2/g to 80 ± 4 m2/g, and leaved substantially unchanged their meso-porosity. No formation of nano-pores smaller than 1 nm was observed. The dispersions in liquid paraffin of these powders, without applying any shear rate, result different from the correspondent suspensions obtained with dry silica meso-pores aggregates especially when the dispersions reach the gel-like status, i.e. after the percolation threshold θ*, set at 8.2% (v/v). For θ values less the θ* the water films act as insulation to reduce the stability of the dispersions, i.e. to reduce the net attractive forces between the silica surfaces and the paraffin. In the gel-like regime, the adsorbed water molecules play a new and emerging role. As the solid volume concentration is increased the silica aggregates covered with water layers come in to contact and form a “liquid menisci” between neighbouring films that allow the formation of a “pendular state” because of capillary forces. These capillary/viscous forces cause a second generation of gel agglomerates, few millimetres in dimension, that are interconnected between them and somewhat separated by thin voids. By comparison with the gel status formed by the dry silica agglomerate dispersions, it has been derive that the paraffin molecules migrate inside the void spaces created throughout the “pendular state”. Maximum static yield stress and separation energies equal to 2500 Pa and 3 × 10−18 J, respectively, were measured and compared with values of 1190 Pa and 3 × 10−19 J for dispersions without adsorbed water layers.

A study was conducted to demonstrate self-organization of perturbations in fluid films. The flow of such self-organization perturbations in the films considered in the rectangular system of coordinates OXYZ for the Reynolds numbers Re ≤ 20 by the method of multiscale expansions were analyzed to investigate the self-organization perturbations. A computing experiment was carried out for the process of self-organization of perturbations during the flow of a vertical water film to investigate the long-term nonlinear development and the interaction of perturbations on the surface of the nonisothermal fluid film.