HAT循环饱和器数学模型及实验研究

在分析饱和器内的传热传质过程基础上,建立了一维数学模型,并通过引入广义传质系数CC,简化了饱和器的计算过程。经实验验证表明该模型具有较好的精度,可以比较准确的模拟饱和器内加湿过程,并且对含有填料的饱和器也具有通用性。通过计算得到的饱和器性能曲线图对设计和研究饱和器工作性能和传热传质规律有较大帮助。     

HAT循环中关键部件_饱和器实验台的研制

本文指出了研究ＨＡＴ循环中的饱和器性能的必要性。并初步建立了饱和器性能实验台,为掌握饱和器性能深入研究ＨＡＴ循环作好了实验准备。     

工作压力对湿空气透平循环饱和器性能的影响

饱和器是湿空气透平（HAT）循环的主要部件之一,它的主要作用是加热加湿空气,从而提高整个HAT循环的效率和比功。利用IAPWS-IF97提供的水和水蒸气性质与实际气体状态方程,建立了适用高压条件下饱和器的一维传热传质数学模型;利用该模型计算了不同压力条件下的饱和器工作性能,并分析了饱和器内的传热传质过程中,饱和点的位置、出口性能参数的变化规律,以及能效值的变化,可以供饱和器的设计参考。     

填料式饱和器稳态和动态特性的试验研究

对填料式饱和器进行了稳态及动态特性试验研究,分析了进水流量、进气流量、进水温度对空气加热加湿过程的影响,主要考察了出水温度、出气温度、进出口空气含湿量差、填料段压降和持液量等性能参数的变化规律.结果表明：在相同进水流量下,提高水气比和进水温度,可显著提高加热加湿性能;当气相速度升高时,进出口空气含湿量差减小,填料段压降及持液量升高;在动态工况下,当进口参数发生扰动时,持液量及出水温度比压降需要更长的时间才能达到新的稳定点.     

HAT循环饱和器传热传质过程及相似分析

以HAT循环中饱和器为研究对象,讨论了实验研究的相似条件。在简化条件下建立了饱和器内部多相流的控制方程,并给出了相应的边界条件;对这些方程进行了无量纲化处理．根据微分方程的不变性原理,得到了饱和器实验研究中应遵循的相似准则,并对这些准则在实验中作用进行说明,指出了饱和器实验设计中应注意的主要问题。     

逆流喷雾式饱和器内湿化过程的实验研究

对逆流喷雾式饱和器内部空气的湿化过程进行实验研究,实验中不仅测量了饱和器进出口湿空气的相对湿度、温度和水的温度,而且也测量了饱和器内部几个高度截面上湿空气的相对湿度和气相、液相的温度。根据实验测量的湿空气的相对湿度和温度,计算出了饱和器内湿空气的含湿量和测量高度间湿空气的加湿量。由实验结果可见,随水气质量比的增大,饱和器出口湿空气的温度和温升也相应增大。湿空气的含湿量和水的蒸发量、出口温度随进口水温升高、水气质量比增大而增大。在所有实验工况下,饱和器出口湿空气接近或达到饱和。随空气速度增大水滴逃逸量增大。总体上饱和器内部下部主要是加湿进口空气,上部是加湿和加热空气。     

HAT循环饱和器性能的(火用)分析

饱各器是HAT循环中的关键部件,对其性能的认识关系到整个系统的性能分析。由于饱和器内存在复杂的气液两相流动和相互间的传热质过程,其性能与很多参数有关,因此用一个或多个指标从一个或多个方面来评价饱和器性能问题一直是在研究的问题。本文使用了分析的方法,建立了饱和器衡模型,分析了内部损失,提出了性能评价的方法和4个评价指标:热力学完善度、效率、损系数和流密度变化率,通过这些评定准则可以对饱和器用能水平作出评价,为今后饱和器的设计和性能分析提供了参考。     

HAT循环饱和器性能的炯分析

饱各器是HAT循环中的关键部件，对其性能的认识关系到整个系统的性能分析。由于饱和器内存在复杂的气液两相流动和相互间的传热质过程，其性能与很多参数有关，因此用一个或多个指标从一个或多个方面来评价饱和器性能问题一直是在研究的问题。本文使用了炯分析的方法，建立了饱和器炯衡模型，分析了内部炯损失，提出了性能评价的方法和4个评价指标：热力学完善度、炯效率、炯损系数和炯流密度变化率，通过这些评定准则可以对饱和器用能水平作出评价，为今后饱和器的设计和性能分析提供了参考。     

逆流喷雾式饱和器内两相速度场的实验研究

应用三维粒子动态分析仪(PDA)和二维粒子速度分析仪(PIV)对逆流喷雾式饱和器内湿化过程的气液两相流流场进行了实验测量。通过稳态和瞬态速度场的测量结果,获得了饱和器内各点上水滴的三维平均速度、平均粒径和平均体积流量,以及饱和器中心线上的测量区域内水滴的瞬态速度分布和流线,给出了逆流喷雾式饱和器内液相水滴的三维平均速度、平均粒径和平均体积流量的分布规律,揭示了其内部流动的高紊流特性。图4表1参7     

水膜热阻修正系数对填料饱和器性能的影响

以单膜理论为基础,研究了饱和器内水与空气之间传热传质的过程,引入水膜热阻修正系数K的概念,建立了饱和器传热传质一维计算模型.通过数值模拟计算,分析了K对饱和器性能的影响,并确定了K设计值的取值范围.结果表明:饱和器出口水温、出口气温和出口空气含湿量受K设计值影响明显,K设计值越大,出口气温和出口空气含湿量越高,出口水温则越低;K设计值取得太小,水温和水膜温度相差较大,计算出的空气出口参数会偏小,反之,水膜温度几乎等于水温,计算出的空气出口参数会偏大,K设计值取15～100中的某一个值较为合理.     

Saturator analysis for an evaporative gas turbine cycle

In this paper a thermodynamic assessment and a preliminary cost evaluation are given for an evaporative gas turbine (EvGT) cycle packed humidifier. Both background theory and simulation results are included.Two different approaches were used for the humidifier system modelling: the full integration of the mass-energy balance and mass transfer equations (called SAT model), and an atmospheric cooling tower-based model (called CT model). Both approaches were used to perform component thermodynamic analyses and to determine the humidifier packing design.Within these approaches, two simulation cases are discussed: a test case, with experimental results from the pilot-plant of the University of Lund, and a case study of the saturators for the optimised HAT (humid air turbine) cycles of a plant with a 50 MW power output. The two cases presented consider two different operating conditions for the saturator: the first being a “non-optimised” saturator, and the later the “optimal” configuration with reduced exergetic losses. For the case study, the saturator design and cost evaluation are also included.All simulation results were performed with the in-house SAT (SATurator simulation tool) code.     

喷雾特性对改善柴油机性能的试验研究

本文概括地介绍了为改善CR2柴油机的性能,应用激光全息技术对柴油机的喷雾特性(雾场中不同直径范围油滴的频谱分布、空间分布、时间分布、喷注的贯穿度及锥角)进行了初步试验研究。试验采用了不同喷孔长径比与不同压力室参数的长型多孔式喷油嘴,经与柴油机匹配,获得了比较满意的整机性能指标;为合理选择与进气系统、燃烧室的几何形状达到良好匹配的喷油嘴结构参数及喷孔布置提供了依据。     

Development of new wire mesh packings for improving the performance of zero carryover spray tower

This paper presents the experimental results of chemical dehumidification of air by aqueous CaCl₂ liquid desiccant. A new design of the spray tower for eliminating carryover without increasing the pressure drops has been done. New types of wire mesh packings have also been proposed for improving the performance of the conventional spray tower. Three different configurations of the wire mesh packings have been designed and tested to improve the performance of tower with least cost addition. Experimental results have been presented in terms of ’change in specific humidity’, rate of moisture removal and tower effectiveness. Comparison of the experimental results of towers using these three packings with the conventional spray tower show improvement in the performance of spray tower (∼30%) without mounting air side pressure drop burden. Mass flow rate of liquid desiccant, mass flow rate of air, inlet specific humidity of air, and concentration of desiccant solution are found to have major influence on the performance.     

Comparative Numerical Study of Freeze Drying of Solution and Spray-frozen Particles in Trays and Vials

A prototype spray freeze dryer was constructed to produce microsized porous particles for pulmonary inhalable drugs by incorporating a spray freezing module into a commercial batch-type freeze dryer. A preliminary experiment of the spray freeze drying of an egg albumin solution was conducted and the physical appearance of the produced particles was examined qualitatively. Based on the experimental observation, a numerical model was developed and parametric studies were conducted to investigate the heat and mass transfer characteristics during the freeze drying of spray-frozen particles packed in trays and vials. The simulation results of particle-based products were compared with those of solution-based products to identify the difference in their freeze drying behavior. As a result, particle-based products were predicted to require longer primary drying time than solution-based products, mainly due to the reduction of heat and mass transfer capabilities and the development of a secondary dried layer near heat-supplying surfaces.     

A review on packed bed solar energy storage systems

Because of intermittent nature of solar energy, storage is required for uninterrupted supply in order to match the needs. Packed beds are generally used for storage of thermal energy from solar air heaters. A packed bed is a volume of porus media obtained by packing particles of selected material into a container. A number of studies carried out on packed beds for their performance analysis were reported in the literature. These studies included the design of packed beds, materials used for storage, heat transfer enhancement, flow phenomenon and pressure drop through packed beds. This paper presents an extensive review on the research carried out on packed beds. Based on the literature review, it is concluded that most of the studies carried out are on rocks and pebbles as packing material. A very few studies were conducted on large sized packing materials. Further no study has been reported so far on medium sized storage elements in packed beds.     

Effect of geometrical and thermophysical characteristics of bed materials on the enhancement of thermal performance of packed bed solar air heaters

In this experimental investigation, a packed bed solar air heater has been designed, fabricated and tested under the local weather conditions of Roorkee, India. Data were obtained from May to June 1992. Tests were conducted to cover a wide range of influencing parameters,including the geometrical and thermophysical characteristics of absorber matrices, mass flow rates and input solar energy fluxes under actual outdoor conditions. The effects of these parameters on the thermal performance have been investigated, and the results have been compared with those of flat plate (plane) collectors. Based on thermal performance, the woven screen of different geometry (having the lowest values of bed thickness to element size ratio, bed porosity and extinction coefficient) and the copper woven screen (having highest value of thermal conductivity) have been found to be the best absorber matrices for packed bed solar air heaters. It is observed that the performance of the collector improves appreciably as a result of packing its duct with blackened absorber matrices, and this improvement is a strong function of the bed and operating parameters.     

闪急沸腾喷雾规律的试验研究

本文通过采用特殊的高温、高压喷雾罐,可从三个垂直方向的石英玻璃窗口,用高速摄影记录喷雾发展的全过程,探索了各种不同燃料和在不同条件下对闪急沸腾喷雾规律的影响,并在实机做了试验。     

Application of spray impingement technique for characterisation of high pressure sprays from multi-hole diesel nozzles

An attempt has been made to study and characterise the performance of two multi-hole nozzles of different nozzle hole geometry using the impingement technique. The technique was able to characterise the nozzle geometry and the near nozzle spray characteristics. The transients of the needle motion, dynamics of the pressure fluctuations were all reflected in the momentum flux measurements. The impingement distance had no significant effect on the derived injected fuel mass and the nozzle discharge coefficient. The momentum of the spray was observed to be strongly dependant on the fluctuations of the injection pressure but the average nozzle discharge coefficient for an orifice was not significantly influenced by different injection pressures. Numerous transients were observed to occur in the spray parameters over a single injection cycle and the transients in the spray were unique for an orifice and varied from one orifice to another in the same nozzle. This technique proves to be a vital tool for predicting the transient performance of high pressure nozzle flows.     

CFD study on local fluid-to-wall heat transfer in packed beds and field synergy analysis

To reach the target of smaller pressure drop and better heat transfer performance, packed beds with small tube-to-particle diameter ratio (D/d _p<10) have now been considered in many areas. Fluid-to-wall heat transfer coefficient is an important factor determining the performance of this type of beds. In this work, local fluid- to-wall heat transfer characteristic in packed beds was studied by Computational Fluid Dynamics (CFD) at different Reynolds number for D/d _p=1.5, 3.0 and 5.6. The results show that the fluid-to-wall heat transfer coefficient is oscillating along the bed with small tube-to-particle diameter ratio. Moreover, this phenomenon was explained by field synergy principle in detail. Two arrangement structures of particles in packed beds were recommended based on the synergy characteristic between flow and temperature fields. This study provides a new local understanding of fluid-to-wall heat transfer in packed beds with small tube-to-particle diameter ratio.     

Performance study of thermosyphonic circulation solar water heaters using packed bed collectors

In the present investigation the performance behaviour of thermosyphonic circulation solar water heaters using packed bed collectors has been analysed. Iron chips, gravels and stones have been used as packing materials. Average tank water temperature, collector as well as system efficiency and mony pay-back for these packed bed solar water heaters are compared with those for solar water heater using a plane collector. Experimental results reveal that the performance of solar water heater improves appreciably by packing its collector with packing material. Among the packed-bed solar water heaters tested the iron chips packed-bed solar water heater gives the overall best performance.