Fractional pressure drops of single-phase water and steam-water two-phase flows were studied in a pressure range of 3.0-3.5 Mpa. Two helical coiled tubes were employed as test sections and their four different helix axial inclinations were examined. It is found that helix axial angles have little influence on the single-phase Frictional pressure drop, while variation of the steam-water two-phase flow frictional pressure drop is enlarged to 70%. For single-phase flow, some previous correlations were quite accurate in predicting the frictional pressure drop for lower Reynolds number conditions, and a modified correlation was obtained from an enlarged Reynolds number range of the present test. For boiling two-phase flow, great deviation was found among the published few empirical equations and their capability of practical utilization is rather poor on account of their complication in structure. A new easily stipulated correlation is deducted from our present data.

A linear instability analysis was conducted firstly on the interface of a stratified gas-liquid two-phase flow in a circular piper employing a two-fluid model. The constitutive equations simulation technique was discussed, and the dispersive equation of interfacial waves was derived. The effects of flow rates of gas and liquid, liquid viscosity, surface tension and tube inclination on the stability of interface were investigated. A set of non-linear hyperbolic governing equations was deduced from the complete two-fluid model equation by omitting the effect of the surface tension and assuming a quasi-steady-state for the gas phase. Using characteristic line and finite difference, the propagation and growth of the interfacial disturbances were investigated in terms of gas and liquid superficial velocities. Then the results of the non-linear stability analysis were compared with those obtained by the linear stability analysis and experimental data. The non-linear stability analysis not only confirms the conclusions reached by the linear instability analysis, but also gives an insight into the growth and propagation of the interfacial disturbances on the interface of a gas-liquid two-phase flow.

A numerical investigation of the flow and heat transfer characteristics in a shuttle kiln is performed using the CFD software FLUENT with non-conformal grids and the standard κ-εturbulence model. The integral and local heat transfer non-uniformities of stacks are evaluated, and furthermore, the formation mechanism of such non-uniformities is analyzed. The results show much greater heat transfer intensity among the peripheral stacks than that among the internal ones, which contributes to the integral non-uniformity. The longitudinal heat transfer non-uniformity is primarily caused by the layer-like nozzle jets and bottom outlet, which form three layer-style surrounding streams converging to outlet. The periodical arrangement of stacks together with the strong impingement of jets, leads to the peripheral heat transfer non-uniformity. Based on the comprehensive understanding of flow and heat transfer, innovative efforts are made to improve heat transfer performance by adjusting flowrate distribution among nozzles.

Thermochemical gasification of biomass has been identified as a possible system for producing renewable hydrogen. A continuous tubular supercritical water gasification system is under development that can be used for solution or slurry materials gasification without drying. A unique feature of this system is its ability to realize the overall high-pressure continuous reaction by operating the valves. By the use of this system, designed for temperatures up to 923.15K and pressures up to 35MPa, glucose, as a model compound of biomass, was gasified in supercritical water at a series of temperature and pressure during different resident times to form a product gas composed of H2, CO, CH4, CO2, and a small amount of C2H4 and C2H6. Glucose at low concentrations (ca. 0.1M) can be completely gasified in 923.15K, 25MPa, and 3.6min resident time and no char or tar was observed. Consequently, we adopted these conditions as baseline reaction conditions for the following glucose concentration, alkali addition and reactor tube diameter effect studies. The raw biomass feedstock of sawdust with some CMC was also gasified in this system, the gasification efficiency in excess of 95% was reached.

The present study is to contribute some knowledge of phase separation phenomena of liquid-solid two-phase turbulent flow in curved pipes and provide a basis for the invention and development of a new type of curved pipe separator. Firstly, the solid-liquid two-phase flows in two-dimensional (2D) curved channels were numerically simulated using a two-way coupling Euler-Lagrangian scheme. Phase distribution characteristics of 2D curved channel twophase flow were examined under conditions of different particle size, liquid flowrate and coil curvature. Based on the numerical results, the dynamic effects and contributions to phase separation of particle-subjected forces, including centrifugal force, drag force, pressure gradient force, gravity force, buoyancy force, virtual mass force and lift force, were exposed by kinematic and dynamic analysis alongparticle trajectories. Secondly, measurement of particle size and concentration profiles in helically coiled tube two-phase flow was conducted usinga nonintrusive Malvern 2600 particle sizer based on laser diffraction. Particle size and concentration distribution characteristics of helically coiled tube twophase flow and the effect of secondary flow on phase separation were analyzed based on experimental data.