HAT循环湿化器内部传热传质实验研究

为了研究湿空气透平(HAT)循环湿化器内部气液两相间的传热传质规律,搭建了高压填料湿化器实验系统,并自主开发了加压气液两相温度和相对湿度测量装置,得到15个工况下湿化器内湿空气温度(气温)、水的温度(水温)以及相对湿度沿湿化器高度的分布规律,研究了水气比、进口水温对湿化器内湿化过程的影响规律。结果表明:气液两相温度分别沿流动方向先降低后升高,湿空气在湿化器底部就已达到饱和状态;水气比对湿化器性能和内部气液参数的影响较大,水气比增大,进口水温升高,同一位置的水温和气温均升高,总体加湿量增大;进口水温升高时,底部湿空气更快达到饱和状态。     

HAT循环后冷湿化过程的传热传质性能研究

为了提升湿空气燃气轮机循环的调控灵活性,自主设计和搭建了后冷湿化器一体化实验系统,通过实验获得不同水气比下后冷湿化器出口空气的温湿度和出口水温,利用实验数据修正表面化学反应速率,基于表面化学反应模型建立了后冷湿化过程三维数值模型,分析了水气比和进口水温对后冷湿化器性能的影响。结果表明：建立的后冷湿化器传热传质模型能高精度模拟后冷湿化过程,空气温度沿流动方向呈逐渐降低的趋势,空气的含湿量和相对湿度沿流动方向逐渐升高;水气比和进口水温均对后冷湿化器的性能有较大影响,随着水气比和进口水温增大出口空气湿度提高,湿化性能提升,而降低水气比有利于提升空气后冷性能。     

泡沫陶瓷填料湿化器加湿性能实验研究

温化器是湿空气透平(HAT)循环的关键部件,其性能优劣对于循环的性能有着重要的影响.对采用新型SiC泡沫陶瓷填料的湿化器在加压条件下的湿化性能进行了实验研究,分析了水气比、进口水温、操作压力以及进口空气温度对湿化过程的影响,研究表明,提高水气比或进口水温会使进出口空气温差、含湿量差相应增加,湿化器节点温差增大.操作压力...     

开式横流热源塔传热传质特性分析

以开式横流热源塔为研究对象,建立塔体内传热传质数学模型,并采用Matlab软件对数学模型编程求解。根据实际工程的测试数据验证数学模型的准确性,进而运用该数学模型分析热源塔冬季传热传质的特性,并通过对空气流量、载冷剂流量、热源塔空气进口干球温度和含湿量、载冷剂进口温度的研究,帮助改善热源塔的换热性能。     

高压水洗沼气净化吸收塔的模拟研究

运用Aspen Plus软件对沼气高压水洗净化工艺中的吸收塔进行了模拟计算。选用RadFrac单元操作模型,采用NRTL热力学性质计算方法,对吸收塔的填料高度和吸收剂用量进行了初步设计,在一定操作条件下考察了塔顶、塔底组成和塔内流量、温度及组成分布的情况、吸收过程中压强、吸收剂用量及吸收塔填料高度对净化后生物甲烷纯度的影响。模拟数据对实际应用具有指导意义。     

焓差法在烟气—水直接接触换热填料塔高度计算的应用

阐述了焓差法在烟气-水直接接触换热填料塔高度计算的应用及方法，并在水侧热负荷和入塔烟气比焓不变的条件下，对使用拉西环的填料塔高度进行了计算，结出塔高度与离塔烟气温度的关系。     

太阳能液体除湿空调再生性能的实验分析

该文中再生器采用逆流式填料塔,并在填料塔设置中间加热器,采用排风进行再生.实验采用氯化锂作为除湿剂,重点分析了中间再热条件下,空气和溶液进口参数以及中间加热器和再生性能的关系,并讨论了再热对单位再生能耗的影响.     

湍球塔内气流分布及除尘性能的试验研究

采用水、空气、填料球作为介质对湍球塔进行烟气除尘实验,重点研究了不同工况下塔内的流速分布及喷淋量、填料静止高度、入口粉尘浓度等因素对除尘效率的影响.实验结果表明填料球具有改善塔内流速分布的作用,添加填料球后,塔内气速稳定在1.5～2 m/s;添加表面活性剂能够显著提高除尘效率,与未加表面活性剂时相比,除尘效率增加超过J％.     

单乙醇胺溶液捕集烟气中CO2的传质过程研究

通过建立CO2散装填料(玻璃弹簧)吸收系统,以乙醇胺(Monoethanolamine)溶液为吸收剂,考察了MEA浓度、CO2分压和液气吸收比等对模拟烟气中CO2传质过程的影响。研究结果表明:在实验条件下,随着液气比的增大,CO2脱除率不断增大;液气比过大,将降低吸收液利用率,液气比过小,将导致CO2脱除率太低。此外,在试验条件下,对填料塔气相总体积传质系数KGav进行了分析,试验结果为实际燃煤CO2吸收填料塔的设计及优化提供必要的理论支撑。     

逆流开式发生器内部的热、质传递规律

针对以太阳能加热的空气为携热介质，以LiBr溶液为工作介质的填料塔型开式发生器，建立热质传递数学模型。对2种系统结构形式进行比较，并分别研究太阳能集热板温度、液气比、环境相对湿度以及填料层高度对溶液再生的影响，以揭示此类发生器内热、质传递的规律，为产品开发、设计提供理论帮助。     

Experimental and theoretical studies on air humidification by a water spray at elevated pressure

Humidification of compressed air is important for humid air turbine cycle. In this paper, theoretical and experimental investigations are carried out to analyze and predict the humidification process in spray tower.For predicting the heat and mass transfer in the water droplet–air two-phase flow, a one-dimensional numerical model simulating the conservation of heat and mass of water and humid air was developed. The model considers the effect of droplet motion on the heat and mass transfer. Experimental data were obtained on a pressurized model spray tower at different pressures and water/air ratios, which had been adopted to validate the numerical model. Droplet diameter of the spray was measured and these data were used in the model. Predictions of outlet conditions of air and water for giving input conditions agree well with experimental data, which produces a maximal error of 7.3%. On the basis of the model, distributions of droplet velocity and volumetric heat transfer coefficient over height of the tower are predicted. The effect of droplet diameter on the characteristic performance of spray humidifier is also analyzed in the simulation.     

Study on the heat transfer characteristics of an evaporative cooling tower

In the present study, both experimental and theoretical results of the heat transfer characteristics of the cooling tower are investigated. A column packing unit is fabricated from the laminated plastic plates consists of eight layers. Air and water are used as working fluids and the test runs are done at the air and water mass flow rates ranging between 0.01 and 0.07 kg/s, and between 0.04 and 0.08 kg/s, respectively. The inlet air and inlet water temperatures are 23 °C, and between 30 and 40 °C, respectively. A mathematical model based on the conservation equations of mass and energy is developed and solved by an iterative method to determine the heat transfer characteristics of the cooling tower. There is reasonable agreement from the comparison between the measured data and predicted results.     

直接接触式低温烟气余热回收塔设计参数优化研究

烟气余热回收塔能通过塔内气-水换热过程,回收烟气显热和水蒸气汽化潜热,降低机组排烟温度,并且回收大量冷凝水。本文基于燃机电厂拟开展燃机烟气余热利用工程,对填料式余热回收塔进行换热模型构建,并对填料式余热吸收塔主要参数进行了研究与优化。研究结果表明,随着填料塔塔径的增大,填料层压降随之减小,填料静持液量和总持液量均随之减小。随着冷却水流量的增大,填料层压降随之增大,填料层高度随之减小,填料静持液量和总持液量均随之增大。随着填料比表面积的增大,填料层压降随之增大。     

Solar cooling systems: Mass transfer studies for a liquid desiccant dehumidifier

Liquid desiccant cooling systems have the advantage over conventional compression systems of being able to operate with largely solar thermal energy sources, and of efficiently handling the latent load. The solar energy is used to regenerate the liquid desiccant by removing the water absorbed from air in the dehumidifier. A packed-bed liquiddesiccant (LiBr) dehumidification unit has been operated with varying air conditions and liquid streams and with three levels of packing (0, 28 and 40 cm). Number of transfer units (NTU) values of 2–2.5 were obtained in the best performing configuration; the corresponding height of transfer unit (HTU) values were 0.25–0.31 m. Overall, gas-side mass transfer coefficients calculated for the dehumidifier are made up of contributions from the packed bed and spray sections of the tower. With full packing and a higher solution flow rate, the overall K_ya was 151.3 g mol/sm³ contact-volume log mean concentration driving force. Spray-only contacting at the higher solution flow rate gave a K_ya of 15.7 g mol/sm³ contact-volume log mean concentration driving force. The individual mass transfer coefficients for the two sections have been separated; to the authors' knowledge, this is the first time the separate contributions of spray and packing have been quantified in a composite dehumidifier tower. Spray contributions were found to contribute from 10 to 70% of the mass transfer occurring in the dehumidifier, the higher percentages being found for a very inefficient deep bed and low liquid flow conditions.     

自然通风湿式冷却塔加装挡风板优化设计

以湿冷机组自然通风冷却塔相关理论为基础,借助于CFD模拟软件,建立了火电机组湿式冷却塔的传热传质模型,主要的换热区域如填料、雨区和喷淋区采用离散相模型。由于冬季气温较低和塔内的换热不均,在冷却塔的填料下面、进风口处、基环面容易结冰,提出了在进风口处加装挡风板的方案,数值模拟分析结果显示,该方案改善了塔内温度场,有效的防止了塔内结冰。     

Refinement of the Transfer Characteristic Correlation of Wet-Cooling Tower Fills

Transfer characteristic correlations given in the literature for wet-cooling tower fills are generally only a function of the air and water mass flow rates. This is a gross simplification of a very complex heat and mass transfer (evaporative cooling) process. In addition to the effects of the air and water mass flow rates, effects of the inlet water temperature, air drybulb temperature, wetbulb temperature, and fill height on the transfer characteristic, or Merkel number, are investigated in the present study. The accuracy of two different empirical equations is also evaluated. It is found that the transfer characteristic correlations for wet-cooling tower fills are functions of the inlet water temperature and fill height but not of the air drybulb and wetbulb temperatures.     

Coupled heat and mass transfer in a counter flow hollow fiber membrane module for air humidification

Hollow fiber membrane based air humidification offers great advantages over the traditional methods because the liquid water droplets are prevented from mixing with the process air, while water vapor can permeate through the membranes effectively. The novelty in this research is that the coupled heat and moisture transport in a hollow fiber membrane module for air humidification is investigated, both numerically and experimentally. The air stream and the water stream flow in a counter flow arrangement. It is found that the membranes play a key role in humidification performances. For sensible heat transfer, both the liquid side and the membrane side resistance can be neglected, while the total heat transfer coefficients are determined by the air side heat transfer coefficients. In contrast, in mass transfer, only the liquid side resistance can be neglected, while the total mass transfer coefficients are co-determined by membrane properties and the air side convective mass transfer coefficients.     

Experimental and theoretical analysis of air humidification/dehumidification processes using hydrophobic capillary contactors

This paper deals with an experimental and theoretical investigation of air humidification/dehumidification processes carried out in a hollow-fibre membrane contactor.The cross-flow contactor consists of a 1.2 m² total membrane surface of hollow polypropylene capillaries arranged in a staggered array and has a mass transfer area per unit volume of 593 m²/m³.The heat and vapour mass transfer between the liquid phase (water and LiCl saturated solution) and the process air is analysed.During the humidification process, experiments were carried out using three different mass flow rates of water (19, 35, 54 kg/h), while two different mass flow rates of LiCl saturated solution (25, 41 kg/h) were used for air dehumidification. Air flow rates ranging from 30 to 80 m³/h were considered. Variations in the relative humidity of the air and in the temperatures of the air and liquid were measured. Experiments show a high mass transfer efficiency for both humidification and dehumidification.Furthermore, a numerical model to predict heat and mass transfer through the contactor has been developed. Experimental results are in good agreement with theoretical predictions.     

An exergy analysis on the performance of a counterflow wet cooling tower

Cooling towers are used to extract waste heat from water to atmospheric air. An energy analysis is usually used to investigate the performance characteristics of cooling tower. However, the energy concept alone is insufficient to describe some important viewpoints on energy utilization. In this study, an exergy analysis is used to indicate exergy and exergy destruction of water and air flowing through the cooling tower. Mathematical model based on heat and mass transfer principle is developed to find the properties of water and air, which will be further used in exergy analysis. The model is validated against experimental data. It is noted from the results that the amount of exergy supplied by water is larger than that absorbed by air, because the system produces entropy. To depict the utilizable exergy between water and air, exergy of each working fluid along the tower are presented. The results show that water exergy decreases continuously from top to bottom. On the other hand, air exergy is expressed in terms of convective and evaporative heat transfer. Exergy of air via convective heat transfer initially loses at inlet and slightly recovers along the flow before leaving the tower. However, exergy of air via evaporative heat transfer is generally high and able to consume exergy supplied by water. Exergy destruction is defined as the difference between water exergy change and air exergy change. It reveals that the cooling processes due to thermodynamics irreversibility perform poorly at bottom and gradually improve along the height of the tower. The results show that the lowest exergy destruction is located at the top of the tower.