共查询到19条相似文献,搜索用时 207 毫秒
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125MW汽机凝汽器内流体流动和传热特性的数值分析 总被引:4,自引:1,他引:3
利用自行开发的凝汽器数值模拟程序PPOC3.0对125MW汽轮机凝汽器的某试验工况进行了数值计算,将得到的计算结果与试验数据进行了比较。然后,对该凝汽器在设计工况下的壳侧流场的换热情况进行了详细数值分析,并指出其中存在的问题。 相似文献
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首先利用自行开发的凝汽器数值模拟程序对N-36000-1型凝汽器的设计工况热力性能进行了数值分析。然后通过定义凝汽器工程设计方法———“表面式凝汽器标准”中的清洁系数与数值模拟方法中的污垢热阻之间的关系式,分别利用这两种方法计算了该凝汽器在不同的冷却水速度、温度和管侧污垢等一系列对应工况下凝汽器的传热率和蒸汽凝结率。通过对这些计算结果的比较与分析,指出冷却水速度、温度这两种影响因素在这两种计算方法的影响趋势虽然相似,但它们在工程设计方法中的影响更大。 相似文献
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介绍了150MW高背压供热机组,凝汽器高背压供热改造的内容.由机组高背压供热改造后,凝汽器高、低背压运行的试验数据,计算了凝汽器在两种运行状态下的性能指标.高背压供热工况下,凝汽器端差较小,为2.354℃;3个低背压凝汽工况,凝汽器端差为6.535℃、5.358℃、5.148℃,经循环水流量和进水温度修正后的凝汽器端差为8.721℃、7.179℃、6.724C,都高于通常的凝汽器设计端差4℃和改造前的数值,改造后的总体传热系数为2.183kW/(m2·℃),小于改造前的平均值3.388kW/(m2·℃).凝汽器高背压改造后,满足常年安全运行的要求,但性能指标没有达到设计值,也低于改造前的数值,125MW工况下,凝汽器改造后的背压比改造前上升近0.9kPa. 相似文献
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基于汽轮机冷端系统内部协同工作的实际情况,探讨了准确确定凝汽器压力的数值研究方法。以某600MW机组低压凝汽器及其配套的水环式真空泵为研究对象,采用数值计算的方法模拟凝汽器在不同冷却水温下的工作性能,确定了冷却水温变化引起的水环式真空泵抽吸能力的变化;计算了凝汽器抽气口至水环式真空泵入口抽气管道内的流动压损;在考虑冷却水温对凝汽器与水环式真空泵性能影响以及抽气管道流动压损影响的情况下,实施了与凝汽器实际运行情况相符的确定凝汽器压力的数值研究方法。研究结果表明:抽气管道流动压损对凝汽器压力的影响较小,在凝汽器压力确定的过程中可以忽略;真空泵变工况对凝汽器压力的影响较大,当真空泵工作水温低于设计工况下的工作水温,忽略真空泵变工况的影响将会使确定出的凝汽器压力偏高;反之,则确定出的凝汽器压力偏低;而且工作水温高于设计工况越远,确定出的凝汽器压力偏差值越大。以文中的研究对象为例,当真空泵工作水温高于设计工况20℃,考虑真空泵变工况与否确定出的凝汽器压力相差达到213Pa。 相似文献
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基于神经网络和混合遗传算法的凝汽器真空优化控制 总被引:1,自引:0,他引:1
利用人工神经网络进行凝汽器真空建模,然后采用混合遗传算法对运行工况寻优,以获得各种工况下凝汽器的最佳运行方式。通过对某电厂的300MW机组现场热态试验与计算,表明该方法可以指导运行人员进行凝汽器真空的优化调整。 相似文献
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通过数值模拟计算手段对某电厂凝汽器新增一组高效传热管束,用以回收利用凝汽器排放的余热。在满足夏季工况机组真空度考核要求下,在冬季抽汽供热工况下机组背压为4.9kPa和电功率分别为280/250MW时,计算确定在不同环境气温下的机组供热能力并确定相应的凝汽器分区运行方式。电厂试验表明,相对于对现有的凝汽器进行分区改造方式,在凝汽器新增设计高效换热区回收乏汽余热,可以获得较高温度的余热能,运行方式更加灵活,经济和社会效益显著。在非供热工况,凝汽器新增管束的投切对机组真空度的影响不大,可以满足夏季机组真空度考核要求。 相似文献
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《Applied Thermal Engineering》2001,21(10):1049-1065
Analytical and experimental studies were performed on a solar assisted heat pump water heating system, where unglazed, flat plate solar collectors acted as an evaporator for the refrigerant R-134a. The system was designed and fabricated locally, and operated under meteorological conditions of Singapore. The results obtained from simulation are used for the optimum design of the system and enable determination of compressor work, solar fraction and auxiliary energy required for a particular application. To ensure proper matching between the collector/evaporator load and compressor capacity, a variable speed compressor was used. Due to high ambient temperature in Singapore, evaporator can be operated at a higher temperature, without exceeding the desired design pressure limit of the compressor, resulting in an improved thermal performance of the system. Results show that, when water temperature in the condenser tank increases with time, the condensing temperature, also, increases, and the corresponding COP and collector efficiency values decline. Average values of COP ranged from about 4 to 9 and solar collector efficiency was found to vary between 40% and 75% for water temperatures in the condenser tank varying between 30°C and 50°C. A simulation model has been developed to analyse the thermal performance of the system. A series of numerical experiments have been performed to identify important variables. These results are compared with experimental values and a good agreement between predicted and experimental results has been found. Results indicate that the performance of the system is influenced significantly by collector area, speed of the compressor, and solar irradiation. An economic analysis indicates a minimum payback period of about two years for the system. 相似文献
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This paper deals with an experimental study performed to evaluate the condenser geometry effect on the natural circulation loop solar still (NCLSS) performance. Three configurations for the external condenser, namely smooth single-tube condenser, finned-tube condenser, and three-tube condenser, were tested under typical summer conditions. The experimental data show that the obtained daily productivity of the NCLSS for the three condenser designs was 2.057, 2.628, and 3.3 kg/m2, respectively. The comparison shows that adding external annular fins to the smooth single-tube condenser increases the still's daily productivity by about 27%. The increase in both internal and external areas of the condenser increases the freshwater daily productivity by 60.42% than the smooth single-tube design and by 25.57% than the finned-tube design. The calculations show that the daily thermal efficiency of the NCLSS was 16%, 20.8%, and 25.38% for the three test days, respectively. While, the daily exergy efficiency for the three condenser designs was 1.78%, 2.12%, and 2.22%, respectively. 相似文献
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大港电厂 328 MW 汽轮机凝汽器数值模拟与特性分析 总被引:3,自引:0,他引:3
采用数值方法对大港电厂从意大利引进的328MW汽轮机凝汽器壳侧的流动与传统过程进行了计算,对该凝汽器的设计合理性进行了分析。 相似文献
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The noncondensable gas supported bubbles in an arterial heat pipe are studied. The governing conservation equations are solved to study the growth/collapse of spherical bubbles under different conditions by using the finite element method. The criterion used in the design of the venting pores to prime the artery is explained. The diffusion-limited bubble collapse in the condenser and bubble growth due to the phase change in the evaporator are both studied. A theoretical explanation for the capability of venting bubbles under different scenarios is provided. The experimental results, including rapid startup and condenser cooldown, are also presented to prove the ability of the heat pipes to vent vapor–gas bubbles. 相似文献
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《Applied Thermal Engineering》2007,27(14-15):2592-2599
As CFC (clorofluorocarbon) and HCFC (hydrochlorofluorocarbon) refrigerants which have been used as refrigerants in a vapour compression refrigeration system were know to provide a principal cause to ozone depletion and global warming, production and use of these refrigerants have been restricted. Therefore, new alternative refrigerants should be searched for, which fit to the requirements in an air conditioner or a heat pump, and refrigerant mixtures which are composed of HFC (hydrofluorocarbon) refrigerants having zero ODP (ozone depletion potential) are now being suggested as drop-in or mid-term replacement. However also these refrigerants, as the CFC and HCFC refrigerants, present a greenhouse effect.The zeotropic mixture designated as R407C (R32/R125/R134a 23/25/52% in mass) represents a substitute of the HCFC22 for high evaporation temperature applications as the air-conditioning.Aim of the paper is a numerical–experimental analysis for an air condenser working with the non azeotropic mixture R407C in steady-state conditions. A homogeneous model for the condensing refrigerant is considered to forecast the performances of the condenser; this model is capable of predicting the distributions of the refrigerant temperature, the velocity, the void fraction, the tube wall temperature and the air temperature along the test condenser. Obviously in the refrigerant de-superheating phase the numerical analysis becomes very simple. A comparison with the measurements on an air condenser mounted in an air channel linked to a vapour compression plant is discussed. The results show that the simplified model provides a reasonable estimation of the steady-state response and that this model is useful to design purposes. 相似文献
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The optimum design of a condenser is significant in an organic Rankine cycle to achieve higher waste heat utilization efficiency. Based on the mathematical model of a condenser using plate heat exchanger (PHE), some key geometric parameters on the total heat transfer surface area and pressure drop of the condenser are examined. In order to obtain geometric parameters of a plate heat exchanger, a multi-objective optimization of the condenser in organic Rankine cycle is conducted to achieve the optimal geometry design. The total heat transfer surface area and pressure drop are selected as two objective functions to minimize both total heat transfer surface area and pressure drop under the constant heat transfer rate and LMTD conditions. The plate width, plate length and plant distance are selected as the decision variables. Non-dominated sorting generic algorithm-II (NSGA-II) which is an effective multi-objective optimization method is employed to solve this multi-objective optimization design of PHE. The results show that an increase in channel distance or plate width increases the total heat transfer surface area and decreases pressure drop in the condenser. It is noted that the plate length of PHE has a positive effect on the optimization design of PHE. By multi-objective optimization design of the PHE, a Pareto optimal point curve is obtained, which shows that a decrease in total heat transfer surface area of a condenser can increase the pressure drop through the condenser. 相似文献