Developing materials that combine passive cushioning protection with active sensory feedback is essential for enhancing safety in outdoor activities like cycling and rock climbing. This study addresses the issue of lo...
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Supercritical water(SCW)fluidized bed reactors convert biomass to fuels without pollutants *** this work,experimental studies were carried out to investigate voidage distribution in an SCW fu-idized bed by capacitance...
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Supercritical water(SCW)fluidized bed reactors convert biomass to fuels without pollutants *** this work,experimental studies were carried out to investigate voidage distribution in an SCW fu-idized bed by capacitance *** sands with different particle sizes were fluidized by SCW under system pressure of 20-27 MPa and temperature of 410-570℃.The effect of operation conditions on voidage distributions of the emulsion phase(*** voidage and probability density)is discussed.A predicting correlation between voidage and superficial velocity in emulsion phase is *** relative error of the correlation is within+25%.These research results provide useful guidance for the optimization of supercritical water gasification technology.
Characterisations of instantaneous mixing behaviours in fluidised beds with binary mixtures has many *** studied the instantaneous mixing characteristics of binary mixtures in a 2-D quasi gas-solid fluidised bed using...
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Characterisations of instantaneous mixing behaviours in fluidised beds with binary mixtures has many *** studied the instantaneous mixing characteristics of binary mixtures in a 2-D quasi gas-solid fluidised bed using a capacitance probe *** method enabled the quantitative assessment of instantaneous mixing behaviours,including mixing index,rate,and *** kinds of binary mixtures of similar size but different density were used for the transient and steady fluidisation experiments in a bubbling fluidised *** mixing curves of initially segregated binary mixtures were acquired,and the instantaneous characteristics for the entire process were *** equation was proposed to describe the mixing process and predict the mixing degree over *** comparing experiments with different working conditions,the effects of superficial gas velocity and density ratio on the mixing in the centre and at the wall of the fluidised bed were *** the stable fluidisation stage,the axial concentration profiles of the mixtures were obtained,and the mechanisms of mixing were *** showed that the mixing level increased logarithmically with time and eventually reached a relatively stable *** the superficial gas velocity and reducing the density ratio promoted mixing and reduced mixing *** superficial gas velocities tended to mix the mixtures well and quickly,regardless of the density ratio of the two components.
Compound droplets surrounded by a gaseous phase with different temperatures widely exist in industrial applications. Previous research has focused on thermally induced non-coalescence or delayed coalescence between tw...
Compound droplets surrounded by a gaseous phase with different temperatures widely exist in industrial applications. Previous research has focused on thermally induced non-coalescence or delayed coalescence between two single-phase droplets or a droplet and a liquid bath. The primary mechanism is the levitated intervening pressure in the lubricating air layer between droplets, which is caused by the thermocapillary convection. In this study, the non-coalescence of two compound droplets in a cold ambient air environment is experimentally investigated. The thermocapillary mechanism manifests three distinct features. First, as the two compound droplets approach each other, the temperature of the contact side of each droplet increases because of reduced heat loss, a phenomenon termed as the contact-side heating effect. This creates a surface temperature gradient, inducing Marangoni stress and subsequent surface convection. Second, owing to the immiscibility of the two phases within each compound droplet, the thermocapillary convection develops independently in each phase, forming independent convection which cannot be observed in single-phase droplets . It was observed that the directions of the thermocapillary convection within the two droplets were correlated and always planar symmetric, which is different from the uncorrelated and opposite convection of two single-phase droplets. Third and most importantly, the thermocapillary convection in the oil phase entrains the air into the lubricating film between droplets, inhibiting their coalescence only when the oil/water interface is adjacent to the contact zone.
flow patterns in upstream and downstream straight tubes of sudden-changed areas in a horizontal straight pipe were experimentally examined. Both sudden-expansion cross-section (SECS) and sudden-contraction cross-secti...
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flow patterns in upstream and downstream straight tubes of sudden-changed areas in a horizontal straight pipe were experimentally examined. Both sudden-expansion cross-section (SECS) and sudden-contraction cross-section (SCCS) were investigated. The flow pattern maps upstream and downstream were delineated and compared with those in straight tubes with uniform cross-sections. The effects of the SECS and SCCS on flow patterns were discussed and analyzed. Furthermore, flow pattern transition mechanisms resulting in occurrences of different flow patterns were simply discussed and some transition criteria for the flow pattern transitions were deduced by using the non-dimensionlized analysis method.
Phase change flow boiling heat transfer in microchannel is a very efficient thermal management mode for high-power electronics/devices cooling. However, achieving comprehensive enhancement of flow boiling heat transfe...
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Underground in-situ pyrolysis of tar-rich coal is an effective approach to expand the supply channels of oil and gas while ensuring energy security, and it has currently aroused wide attention in the academic communit...
Underground in-situ pyrolysis of tar-rich coal is an effective approach to expand the supply channels of oil and gas while ensuring energy security, and it has currently aroused wide attention in the academic community. The coupling of multiple interdependent physical fields causes the in-situ pyrolysis process and related phenomena. However, existing studies usually only have focused on a single process. The study proposed a three-dimensional (3D) model for the in-situ pyrolysis of tar-rich coal employing external high-temperature fluids. Numerical simulation was used to achieve the transient calculation of the coupling model of chemical reaction, fluid flow, and heat transfer. The impacts of medium type, medium temperature, inlet rate, well patterns, and the number of horizontal fractures were investigated by characterizing the temperature and concentration fields. The results indicate that, under the basic working condition, the pyrolysis reaction of tar-rich coal in the formation has been completed after ∼28.5 months of heat injection. Both N 2 and CO 2 are heat carriers with greater advantages in heat transfer as compared to H 2 O (g). The threshold of injection rate is 5 m·s −1 . The heat transfer effect of coal seams with 4 injection wells is obviously better than that of 1 and 2 injection wells. The number of 3 horizontal fractures is superior to 1 and 2 fractures, which can effectively enhance heat transfer and promote the thermal decomposition. The present study has emphatically investigated the evolution of characteristic fields of tar-rich coal seams under thermo-fluid-chemical coupling conditions during the in-situ pyrolysis process, providing substantial reference significance to guide the in-situ conversion mining.
Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 ( columns × rows) finned-tube heat exchanger w...
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Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 ( columns × rows) finned-tube heat exchanger with rectangular fins was investigated experimentally in a wind tunnel with constant wall temperatures condition. The air flow velocity based on the minimum flow cross-section area over flow channel ranged from 13.8 to 50. 2 m/s, the heal transfer rate ranged from 21.8 to47. 1 kW, and the air temperatures increase ranged from 10. 9 to 19. 8 ℃. The present results were compared with results calculated from correlations proposed by CSPE. For air flow velocity less than 25 m/s, these two results of heat transfer agreed well with each other, whereas for larger velocity, our test data disagreed with the CSPE correlations. For the friction factor, present data are much higher than the predicted results in the whole range. Finally, correlations for friction factors and heat transfer coefficients are DrODosed based on the experimental results.
Helical tube is one type of once-through stream generators in integrative nuclear device. The thermal-hydrodynamic instabilities in helical tubes of a once-through steam generator (HTOTSG) with exit-steam superheated ...
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Helical tube is one type of once-through stream generators in integrative nuclear device. The thermal-hydrodynamic instabilities in helical tubes of a once-through steam generator (HTOTSG) with exit-steam superheated were studied by using multi-variable liner-frequency-domain theory. Based on the drift-flux model, a small perturbation method, as well as Laplace transformation theory, was empolyed to linearize the system of partial differential equations. A computer code called HTOTSGM-D was developed to investigate the influences of inlet flow rate, inlet subcooling, heat flux, and system pressure on oscillations. The calculated results showed that the above factors must be considered comprehensively in once-through steam generator design and operation, even though the installation of the entrance throttles was still an effective way to stabilize the system.
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