共查询到20条相似文献,搜索用时 109 毫秒
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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。 相似文献
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焓差法在烟气—水直接接触换热填料塔高度计算的应用 总被引:1,自引:0,他引:1
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。 相似文献
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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。 相似文献
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《Applied Thermal Engineering》2007,27(14-15):2549-2558
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. 相似文献
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《International Communications in Heat and Mass Transfer》2005,32(8):1066-1074
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. 相似文献
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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。 相似文献
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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 Kya was 151.3 g mol/sm3 contact-volume log mean concentration driving force. Spray-only contacting at the higher solution flow rate gave a Kya 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. 相似文献
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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. 相似文献
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《Applied Thermal Engineering》2001,21(11):1119-1135
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. 相似文献
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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. 相似文献
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《Applied Thermal Engineering》2007,27(5-6):910-917
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. 相似文献