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电站直接空冷凝汽器变工况计算与特性分析 总被引:12,自引:1,他引:11
对电站直接空冷凝汽器变工况计算进行了研究 ,绘制了空冷凝汽器特性曲线 ,分析了迎面风速、环境气温、凝汽器热负荷对空冷凝汽器性能的影响 相似文献
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空冷岛运行优化中,需要将汽轮机、空冷凝汽器及空冷岛风机的特性综合起来进行分析。在综合直接空冷机组冷端各个组成部分,包括空冷凝汽器、低压缸至空冷凝汽器之间排汽管道及空冷岛风机特性的基础上,建立汽轮机排汽背压与空冷岛风机转速的特性关系,为空冷岛运行优化计算创造了条件。 相似文献
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从六个层面介绍了山西漳山发电有限责任公司1号300MW机组所配三排管直接空冷凝汽器管束冻结的原因,并提及三排管直接空冷凝汽器所存在某些不足及其改进建议,供已投运的三排管直接空冷凝汽器的改造和将来建设三排管直接空冷凝汽器机组的设计参考。 相似文献
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自然通风直接空冷系统凝汽器单元"Λ"型布局和传统翅片结构使得冷却空气流过翅片管束时发生严重转向,从而显著影响空冷凝汽器的流动传热性能。提出了一种新型翅片管束,其翅片通道与基管椭圆长轴方向呈一定夹角,使翅片通道方向与塔浮升力方向平行。通过CFD数值模拟和实验验证,获得了采用新型倾斜翅片管束的自然通风空冷凝汽器的空气流场和温度场,计算得到了不同环境风速下空冷凝汽器总换热量的变化规律,并与现有翅片管束的空冷凝汽器性能进行了对比。研究结果表明,采用倾斜翅片空冷凝汽器可以显著改善自然通风直接空冷系统热力性能,降低机组背压,提高空冷机组运行的经济性。 相似文献
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M. Lucas P.J. Martínez A.S. Kaiser 《International Journal of Heat and Mass Transfer》2010,53(4):594-604
Water drift emitted from cooling towers is objectionable for several reasons, mainly due to human health hazards. A numerical model to study the influence of psychrometric ambient conditions on cooling tower drift deposition was developed as a tool to evaluate liquid droplet dispersion and risk area. Both experimental plume performance and drift deposition were employed to validate the numerical results. This study shows the influence of variables like ambient dry bulb temperature, ambient absolute humidity and droplet exit temperature from cooling tower on the drift evaporation (and therefore deposition) and on the zone affected by the cooling tower. The strongest effect detected corresponds to the ambient dry bulb temperature. When a higher ambient temperature was present, deposition was lower (evaporation was therefore higher) and the zone affected by the cooling tower was smaller. The influence of the other two variables included in the study was weaker than the dry bulb ambient temperature. A high level of ambient absolute humidity increased drift deposition and also the size of the zone affected by the cooling tower. Finally, a high level of droplet exit temperature decreased deposition and increased the zone affected by the cooling tower. 相似文献
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The effect of different earth surface treatments for lowering the subsurface earth temperature has been experimentally investigated. The surface treatments studied include lime covered surface, stone covered surface and tree bark covered surface. The effects of shading and wetting the above treated surfaces on the subsoil temperature have also been investigated. It is found that wetting of the bare surface is most effective for reducing the average value of the subsoil temperature and that the wetted tree bark covered surface is equally effective in reducing the diurnal swings of the earth temperature. The measured subsoil temperature and the measured climatic data (ambient temperature, wet bulb temperature and global radiation) are used to estimate the surface heat transfer coefficient ho and the thermophysical properties of the earth (K, α1 and ρC). 相似文献
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A study is reported of the potential performance of dry cooling on power generation. This is done in the context of a generic trough solar thermal power plant. The commercial power plant analysis code GateCycle is applied for this purpose. This code is used to estimate typical performance of both wet and dry cooling options. Then it is configured to estimate the performance of ideal wet and dry cooling options. The latter are defined as the condenser temperature being at the ambient wet bulb temperature or dry bulb temperature, respectively. Yearly power production of a solar power plant located in Las Vegas is presented for each of the cooling options. To move further toward approaching the possible improvement in dry cooling, the impact of a high-performance heat exchanger surface is evaluated. It is found that higher efficiency generation compared to current dry cooling designs is definitely possible. In fact the performance of these types of systems can approach that of wet cooling system units. 相似文献
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In the current work, a series of experiments are carried out to investigate the degradation behavior of lithium-ion batteries during overcharge cycling, as well as the influence of ambient temperature on the degradation. In which, different charge cut-off voltages (4.5, 4.8, and 5.0 V) and ambient temperatures (0°C, 20°C, 50°C, and 70 °C) are included. During the overcharge process, the batteries demonstrate severe temperature rises, and several key electrochemical parameters such as the charge capacity, energy density, median voltage, and resistances all increase, revealing the deterioration of heat generation and electrode kinetics. Besides that, batteries exhibit serious degradation behavior during the overcharge cycling, which is presented through the evolution of battery temperature curves, charge voltage curves, and internal resistance curves. Moreover, the severity of degradation exacerbates with the increasing overcharge degree. Finally, it is found that deep-overcharged batteries may be more sensitive to the ambient temperature than slight-overcharged ones, where an abusive temperature can significantly aggravate the corresponding degradation. 相似文献
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Ala Hasan 《Applied Thermal Engineering》2010,30(16):2460-2468
Indirect evaporative cooling is a sustainable method for cooling of air. The main constraint that limits the wide use of evaporative coolers is the ultimate temperature of the process, which is the wet bulb temperature of ambient air. In this paper, a method is presented to produce air at a sub-wet bulb temperature by indirect evaporative cooling, without using a vapour compression machine. The main idea consists of manipulating the air flow inside the cooler by branching the working air from the product air, which is indirectly pre-cooled, before it is finally cooled and delivered. A model for the heat and mass transfer process is developed. Four types of coolers are studied: three two-stage coolers (a counter flow, a parallel flow and a combined parallel-regenerative flow) and a single-stage counter flow regenerative cooler.It is concluded that the proposed method for indirect evaporative cooling is capable of cooling air to temperatures lower than the ambient wet bulb temperature. The ultimate temperature for such a process is the dew point temperature of the ambient air. The wet bulb cooling effectiveness (Ewb) for the examples studied is 1.26, 1.09 and 1.31 for the two-stage counter flow, parallel flow and combined parallel-regenerative cooler, respectively, and it is 1.16 for the single-stage counter flow regenerative cooler. Such a method extends the potential of useful utilisation of evaporative coolers for cooling of buildings as well as other industrial applications. 相似文献
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The impact of fouling on performance evaluation of evaporative coolers and condensers 总被引:1,自引:0,他引:1
Fouling of evaporative cooler and condenser tubes is one of the most important factors affecting their thermal performance, which reduces effectiveness and heat transfer capability with time. In this paper, the experimental data on fouling reported in the literature are used to develop a fouling model for this class of heat exchangers. The model predicts the decrease in heat transfer rate with the growth of fouling. A detailed model of evaporative coolers and condensers, in conjunction with the fouling model, is used to study the effect of fouling on the thermal performance of these heat exchangers at different air inlet wet bulb temperatures. The results demonstrate that fouling of tubes reduces gains in performance resulting from decreasing values of air inlet wet bulb temperature. It is found that the maximum decrease in effectiveness due to fouling is about 55 and 78% for the evaporative coolers and condensers, respectively, investigated in this study. For the evaporative cooler, the value of process fluid outlet temperature Tp,out varies by 0.66% only at the clean condition for the ambient wet bulb temperatures considered. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Correlations available in the literature to predict hourly ambient temperature are climate specific. Based on extensive meteorological database, correlations to predict hourly ambient temperature in terms of maximum and minimum temperatures of the day have been developed. The applicability of the present correlation has been examined for a wide range of locations, along with its comparison with other correlations developed earlier for a specific set of locations. The performance of the present correlation has been found to be superior to the performance of the existing correlations. Monthly average hourly ambient temperature values predicted with the present correlation agree with the data values within r.m.s differences of 0·26% when the ambient temperature is in K and the absolute error has been found to be 0·75. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Numerical simulations of a proton exchange membrane fuel cell were carried out for various temperatures ranging from well below the freezing temperature of water to a moderate ambient temperature, and also for various inlet temperatures, to investigate its performance. A three‐dimensional serpentine flow field was used to determine the cell behavior temperature conditions. The saturation of liquid water was considered for various ambient temperatures in order to obtain realistic estimates of cell performance, with special emphasis placed on sub‐cooled temperatures. Results show that both the ambient and the inlet temperature have strong influences on cell performance, although the inlet temperature has much more important influence than the ambient temperature. In addition, liquid water saturation is enhanced at higher inlet temperatures. Moreover, for sub‐cooled ambient temperatures the liquid saturation level is higher in the shoulder region near the inlet section than in the outlet section; this trend is reversed for higher ambient temperatures. There is a high probability that operation of the cell at sub‐cooled temperatures and higher inlet temperatures will result in the formation of ice throughout the system, which may further degrade the cell performance. The model was validated by comparison of predicted polarization curves with those found in the literature. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献