渗透蒸发的原理和应用（上）

本文介绍一种新的膜分离技术－渗透蒸发的原理和特点，及操作条件对分离性质的影响，并对其关键构件和设备即渗透发膜和渗透池作了专门叙述，结合具体实例从有机溶剂的脱水及水溶液中回收有机溶剂两个方面介绍了该技术在工业上应用的效果。     

An empirical model for estimating evaporative hydrocarbon emissions from canister-equipped vehicles

An empirical model for the estimation of evaporative hydrocarbon emissions from canister-equipped vehicles has been developed from experimental data obtained from repeated tests on a single carbon canister. The model is able to predict canister adsorption and desorption behaviour under different loading and purging conditions and it calculates canister weight and breakthrough emissions for various experimental variables including temperature, mixture concentration and mass flow rate. The model enables the simulation of a full evaporative emission Sealed Housing for Evaporative Determination (SHED) test procedure taking into account vehicle-specific estimations of fuel vapour generation and permeation. Results from measurements conducted on a vehicle equipped with the same canister were used to calibrate the model. Model results were in good agreement with measured evaporative emissions from a number of vehicles.     

Evaporation characteristics of multi-component fuel

The maximum liquid phase penetration and evaporation behavior was investigated by using simultaneous measurement for mie-scattered light images and shadowgraph ones. The objective of this study was to analyze effect of variant parameters and fuel properties on evaporation behavior, and to investigate liquid phase penetration for the single- and multi-component fuels. The experiments were conducted in a constant-volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector. It was observed that: liquid phase length is influenced by fuel properties. High-boiling point fuel within the multi-component fuel controls liquid phase length.     

NUSSELT NUMBER FOR DIRECT CONTACT EVAPORATION OF A MOVING ELLIPSOIDAL DROP IN AN IMMISCIBLE LIQUID

Since Sideman et al.^[1] derived an analytical solution of the Nusselt number for a spherical drop in the direct contact evaporation in an immiscible liquid, many researchers have performed theoretical research on this field under different assumptions [2]-[6]. However drops moving in another immiscible liquid do not take a spherical form, but oblate form, which may be well approximated as an ellipsoid. This paper establishes the mathematical model of heat transfer for a moving ellipsoidal drop in an immiscible liquid, and presents results from numerical calculation. The relationship of the Nusselt number with the Weber number and the Peclet number is given, which is suitable for a relatively large range of We and Pe. The theoretical results for the Nusselt number show good agreement with experimental data. Some important conclusions are obtained.     

采煤工作面局部风流雾化降温效果分析

为分析低温雾化喷淋对高温采煤工作面局部风流的降温效果,采用Eulerian-Lagrangian二相流描述方法,通过液滴与湿空气的双向耦合作用,对高温风流的降温效果进行了数值计算,计算结果表明：1次降温后,风流温度约有4℃的急剧降低,1排喷嘴的有效作用距离为10 m,10 m后,风流温度又逐渐升高1.5℃,总体上,回采面风流的温度呈现出阶跃性的上升趋势;拟合得到的风流降温效果随喷嘴流量呈负指数变化;液滴喷射角在70°~90°范围时,降温效果较明显,而细水雾的高压雾化喷嘴能明显提高降温效果。     

一种增大尾矿库回水量的方法

在分析尾矿库回水量组成的基础上,以内蒙古锡林郭勒盟地区某湿排尾矿库为例,提出了一种采用悬浮球增大回水量的方法。理论分析和对比试验验证表明,该方法能够大大减少蒸发量,增大尾矿库回水量,操作简单,可在缺水地区的尾矿库运行管理中推广应用。     

煤直接液化项目污水处理零排放工艺中蒸发技术的应用

神华煤直接液化项目污水处理以实现“零”排放为标准,蒸发技术在“零”排放工艺中发挥着重要的作用,本文介绍了污水处理引进的GE蒸发器的技术特点,以及在含盐污水处理工艺中的成功应用。     

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循环注气是提高凝析气藏开发效果及凝析油采收率的有效措施，而循环注气能否使已经存在于地层中的凝析油重新蒸发是人们普遍关注的问题。作者以柯克亚凝析气藏Ｘ４２—Ｘ５１层系为例，对循环注气开采过程中注入气对凝析油的再蒸发作用进行了数值模拟研究，并对Ｘ５１（３）循环注气试验区现场注气后的情况进行了具体分析，得出了凝析气藏循环注气可以使地层中的部分凝析油重新蒸发采出地面的结论。建议当地层压力低于露点压力时，采用保持压力循环注气开采，可提高凝析油的回收率。     

A mixture fraction framework for the theory and modeling of droplets and sprays

A mixture fraction is carefully defined for evaporation and combustion of droplets and sprays. The definition is valid at points in either the liquid or gas phases and care is taken to distinguish between definitions based on conserved scalars appropriate for heat transfer and those for mass transfer. Results are presented for Spalding B numbers and values of the mixture fraction at the droplet surface for the fast chemistry case and for the case where the droplet cannot sustain an envelope flame. The classical theory for an isolated droplet with spherical symmetry yields simple formulae when expressed in mixture fraction terms. New results are then readily obtained for several quantities of interest in spray modeling. The formulation provides a seamless unification of droplet evaporation processes with gas-phase mixing and reaction. Mixing in a turbulent spray jet is identified as a model problem that clarifies the role of large scale structures in the overall mixing process. Important constraints on the parameter space for sprays are shown to be greatly clarified when expressed in the mixture fraction framework. It is shown how the classical approach for segregated flow with Eulerian/Lagrangian modeling of dispersion and transfer processes in turbulent sprays can be upgraded to include fluctuations in the temperature and composition surrounding the droplets on top of those coming from the turbulent velocity fluctuations. Such preliminary calculations that assume a simple chemically reacting system can readily be upgraded using flamelet functions derived from counterflow experiments or computations: these can then form the starting point for full chemistry calculations using such approaches as conditional moment closure.     

Numerical study of evaporation by mixed convection of a binary liquid film

This paper deals with a numerical analysis of the evaporation of binary liquid film. The film is falling down on one plate of a vertical channel under mixed convection channel. The first plate of a vertical channel is externally submitted to a uniform heated flux q₁ while the second one (y = d) is dry and isothermal. The liquid mixture consists of water (the more volatile component) and ethylene glycol while the gas mixture has three components: dry air, water vapour and ethylene-glycol vapour. The results concern the effects of the inlet parameters in the gas and in the liquid film on the interfacial pressure, temperature and concentration profiles. The evolutions of the heat fluxes and of the water and mixture evaporation rates have been analysed. Results obtained show, in particular, that it is possible to increase the accumulated evaporation rate of water and of the liquid mixture when the inlet liquid concentration of ethylene glycol (the less volatile component) is less than 40%. This result has been explained by the fact that an increase of the inlet liquid concentration of ethylene glycol has two antagonistic effects on the accumulated evaporation rates of water and of liquid mixture.