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Predicting apparent gas permeability (AGP) in nanopores is a major challenge for shale gas development. Considering the differences in the gas molecule-pore wall interactions in inorganic and organic nanopores, the gas transport mechanisms in shale remain unclear. In this paper, gas flow channels in shale, which are separated into inorganic pores and organic pores, are treated as nanotubes. Inorganic pores are assumed to be hydrophilic, and organic pores are assumed to be hydrophobic. In organic pores, multiple bulk free gas and surface adsorbed gas transport mechanisms are incorporated, while the bulk gas and water film are considered within inorganic pores. This paper presents a unified multiple transport mechanism model for both organic nanopores and inorganic nanopores. Unlike the earlier models, the presented models consider the absorption, stress dependence, real gas, and water storage effects on gas transport comprehensively for the entire flow regime. The results are validated with published data which is more in line with the real situation. The results show that (1) the AGP decreases gradually as the pore pressure decreases but that the decrease is sharp in small pores, (2) the AGP decreases dramatically when considering the real gas effect at 50 MPa in a 2 nm pore size, and (3) for a small pore size at the critical high-water saturation, AGP might increase suddenly as the flow regime changes from continuum flow to slip flow. The findings of this study can help for better understanding of the gas transport mechanisms for the entire flow regime in shale.

The capillary spontaneous imbibition length of slick water in confined rectangular cross-sectional nanofractures is investigated in this paper. In the established model, the effective slip length, effective viscosity, wettability and nanofracture size are incorporated into the modified Hagen–Poiseuille equation. The calculated spontaneous imbibition length as a function of time, viscosity, wettability and pore size is qualitatively validated by experimental and previous theoretical Hagen–Poiseuille flow results. Our model calculation results agree well with the published experimental data. The ratio of the effective and bulk water viscosities is higher than one, and increases with an increase in the ratio of the nanofracture width to height and decreasing contact angle. The spontaneous imbibition capacity of confined water is enhanced ∼0.67–1.28 times, as determined by the Hagen–Poiseuille equation without the slip effect for various contact angles and nanofracture dimensions.

It is widely accepted that a fracture can be induced at a wellbore surface when the fluid pressure overcomes the rock tensile strength. However, few models of this phenomenon account for the fluid penetration effect. A rock is a typical permeable, porous medium, and the transmission of pressure from a wellbore to the surrounding rock temporally and spatially perturbs the effective stresses. In addition, these induced stresses influence the fracture initiation pressure. To gain a better understanding of the penetration effect on the initiation pressure of a permeable formation, a comprehensive formula is presented to study the effects of the in situ stresses, rock mechanical properties, injection rate, rock permeability, fluid viscosity, fluid compressibility and wellbore size on the magnitude of the initiation pressure during fracturing of an open-hole wellbore. In this context, the penetration effect is treated as a consequence of the interaction among these parameters by using Darcy's law of radial flow. A fully coupled analytical procedure is developed to show how the fracturing fluid infiltrates the rock around the wellbore and considerably reduces the magnitude of the initiation pressure. Moreover, the calculation results are validated by hydraulic fracturing experiments in hydrostone. An exhaustive sensitivity study is performed, indicating that the local fluid pressure induced from a seepage effect strongly influences the fracture evolution. For permeable reservoirs, a low injection rate and a low viscosity of the injected fluid have a significant impact on the fracture initiation pressure. In this case, the Hubbert and Haimson equations to predict the fracture initiation pressure are not valid. The open-hole fracture initiation pressure increases with the fracturing fluid viscosity and fluid compressibility, while it decreases as the rock permeability, injection rate and wellbore size increase.

The objective of this study was to fabricate anti-gravity heat pipes with a tapering column phase-change chamber and changeable cross-sectional wick structure. The thermal performances of the anti-gravity heat pipes were experimentally investigated. Results show that the thermal resistances of the different heat pipes are less than 0.03 &deg, C/W, except for the sharp conical chamber heat pipe under anti-gravity heating conditions (0.121 &deg, C/W). Start-up times of different types of heat pipes are similar and the temperatures are steady within 3 to 5 min. The heat transfer ability of a conical chamber is always better than that of a cylindrical one. The performance of the sharp conical chamber heat pipe is the best under gravity assistance heating conditions. Contrarily, the blunt conical chamber heat pipe has the best heat transfer ability under anti-gravity heating conditions. Moreover, the heat transfer capability of the blunt conical chamber heat pipe is unaffected by the relative position of the heat and cold sources, which is suitable for constant temperature cooling applications with frequent switching of the heat and cold sources.

After volume fracturing, shale reservoirs can be divided into nonlinear seepage areas controlled by micro- or nanoporous media and Darcy seepage areas controlled by complex fracture networks. In this paper, firstly, on the basis of calculating complex fracture network permeability in a stimulated zone, the steady-state productivity model is established by comprehensively considering the multi-scale flowing states, shale gas desorption and diffusion after shale fracturing coupling flows in matrix and stimulated region. Then, according to the principle of material balance, a transient productivity calculation model is established with the succession pseudo-steady state (SPSS) method, which considers the unstable propagation of pressure waves, and the factors affecting the transient productivity of fractured wells in shale gas areas are analyzed. The numerical model simulation results verify the reliability of the transient productivity model. The results show that: (1) the productivity prediction model based on the SPSS method provides a theoretical basis for the transient productivity calculation of shale fractured horizontal well, and it has the characteristics of simple solution process, fast computation speed and good agreement with numerical simulation results, (2) the pressure wave propagates from the bottom of the well to the outer boundary of the volume fracturing zone, and then propagates from the outer boundary of the fracturing zone to the reservoir boundary, (3) with the increase of fracturing zone radius, the initial average aperture of fractures, maximum fracture length, the productivity of shale gas increases, and the increase rate gradually decreases. When the fracturing zone radius is 150 m, the daily output is approximately twice as much as that of 75 m. If the initial average aperture of fractures is 50 μm, the daily output is about half of that when the initial average aperture is 100 μm. When the maximum fracture length increases from 50 m to 100 m, the daily output only increases about by 25%. (4) When the Langmuir volume is relatively large, the daily outputs of different Langmuir volumes are almost identical, and the effect of Langmuir volume on the desorption output can almost be ignored.

To improve heat-transfer performance, a novel integral three-dimensional fin-structure on the plat surface was presented to increase the evaporation efficiency. The three-dimensional fin-structure is composed of a spiral micro-groove and multi radial micro-grooves. Both ploughing-extrusion (P-E) and stamping were used to form the integral-fins with a connection between radial and circumferential directions. Based on the SEM results, the relationships among P-E speed vP-E, rotational speed np and feed fp, and among interference length Li, stamping feed angle θc and stamping depth ac were analyzed. The effects of processing parameters on the groove morphology and the matching relationship between parameters were also discussed. The integral finned surface with micro-grooves and cracks can be obtained under such processing conditions: P-E depth ap=0.3 mm, ac=0.3 mm, the interval of helical groove dp=1.24 mm, θc=2° and np=50 r/min.

The soymilk mill is an important food machine, but its volume is too large to be suitable for house using. This study first analyzes some problems in the soymilk mill miniaturization. For these problems, the thinking tools, evolutionary tools and contradiction solving tool of TRIZ theory are used to resolve the conflict in the integration of grinding and boiling and in the keep grinding effect, to tackle the optimization problem in the grinding stria structure and mill plate speed, then the Dwarfs method and substance-field analysis model is used in solving the interference and the conditions water supply problems which are encountered in the design of the global structure and a micro soymilk mill is designed. Finally, the mechanical analysis model about soy granules, soymilk particles in the grinding zone and the computational model of motor starting torque are obtained; they provide the reference data for application of soymilk mill.

In consideration of talent shortage of engineering masters and low quality of engineering education, and in order to effectively strengthen the engineering practice training, this paper elaborates on the significance of creating school-enterprise associate laboratory to train engineering master talents on the base of CDIO engineering education principle. This paper orients towards tutors' research projects and targets at the training of engineering comprehensive abilities, therefore the practice education of engineering masters and actual demand of enterprises can be closely integrated and students' comprehensive qualities can be improved in practice. Meanwhile, this paper discusses the concrete implementation methods and suggestions of creating school-enterprise associate laboratory. The main purpose is to explore the development practice of CDIO engineering education in colleges and universities by virtue of school-enterprise associate laboratory.