共查询到20条相似文献,搜索用时 62 毫秒
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在天然气液化技术工程化研究中,LNG分馏工艺较复杂,且设备种类较多,存在热量利用不充分,公用工程消耗量大的问题,为了节约能源需要对换热网络进行改进。先使用HYSYS软件对分馏工艺进行模拟,得出系统工艺参数,分析现有换热网络能量消耗,得到最小换热温差,再运用夹点技术对分馏区换热网络提出了改造方案。通过改进和优化,充分利用脱乙烷塔底物流的冷量,将分馏区热公用工程消耗量降低了15%,冷公用工程消耗量降低了8%,使用夹点技术对系统工艺和设备参数优化的研究得到了良好的节能效果。 相似文献
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水源热泵系统的热力学分析 总被引:3,自引:0,他引:3
本文通过对水源热泵系统进行热力学分析,既评价了水源热泵系统的能质利用和损失状况.又明确了系统能量损失的主要环节和程度,从而为进一步分析系统用能改进的技术措施提供指导。通过对一实例的分析,指出压缩机、蒸发器和冷凝器都是需要技术改进和进一步节能的部分。 相似文献
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在考虑内外缸间辐射换热计算的基础上,用有限元方法分析了某机组中压内缸、高压内缸、高中压外缸的温度场;考虑了内外缸间水蒸汽对辐射换热计算的影响。分析过程包括了汽缸温度场分析简化模型的建立,计算对流换热系数和等效的辐射换热系数,迭代分析温度场。以某机组为例,其中压内缸内表面沿轴向长度平均温度为528.8℃,考虑辐射换热计算后为524.6℃,减少了4.2℃;中压内缸外表面沿轴向长度平均温度为514.6℃,考虑辐射换热后为502.2℃,减少了12.4℃;增加的径向温度差为8.2℃。计算结果表明了考虑辐射换热计算的必要性。 相似文献
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氧燃烧方式是一种能综合控制燃煤污染物排放的新型洁净燃烧技术,有关该方式下煤粉锅炉传热特性的研究对于老机组改造及新机组的重建具有非常重要的意义.以某电厂300 MW燃煤锅炉为例,针对氧燃烧方式下燃烧介质的物理特性发生变化,通过引入循环率的概念,提出并发现了氧燃烧方式下必须考虑CO2、H2O、O2、H2的5种高温分解反应,在此基础上修正并发展了新的适用于氧燃烧方式下绝热火焰温度、锅炉辐射传热的计算方法.结果表明,修正后的辐射传热计算公式在氧燃烧方式下具有良好的通用性,在干、湿两种烟气循环方式下,绝热火焰温度随循环率的增加非线性降低;当干烟气、湿烟气的循环率分别在0.71和0.67附近时,获得与常规燃烧方式相同的烟气平均温度和辐射传热量. 相似文献
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Ertan Buyruk 《传热工程》2018,39(15):1392-1404
In the present study, the potential of rectangular fins with different fin types of inner zigzag-flat-outer zigzag (B-type) and outer zigzag-flat-outer zigzag (C-type) and with different fin angles of 30° and 90° for 2 mm fin height and 10 mm offset from the horizontal direction for heat transfer enhancement with the use of a conjugated heat transfer approach and for pressure drop in a plate fin heat exchanger is numerically evaluated. The rectangular fins are located on a flat plate channel (A-type). The numerical computations are performed by solving a steady, three-dimensional Navier–Stokes equation and an energy equation by using FLUENT software program. Air is taken as working fluid. The study is carried out at Reynolds number of 400 and inlet temperatures, velocities of cold and hot air are fixed as 300 K, 600 K and 1.338 m.s?1, 0.69 m.s?1, respectively. This study presents new fin geometries which have not been researched in the literature for plate fin heat exchangers. The results show that while the heat transfer is increased by about 10% at the exit of a channel with the fin type of C, it is increased up to 8% for the fin angle of 90° when compared to a channel with A-type under the counter flow. The heat transfer enhancements for different values of Reynolds number and for varying fin heights, fin intervals and also temperature distributions of fluids are investigated for parallel and counter flow. 相似文献
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高温、电加热条件下电阻率与导热系数随温度变化明显,因此研究在此条件下的热传导具有十分重要的意义.运用MATLAB中的PDE工具箱,对高温条件下,几种不同材料的发热导体电加热过程中导热系数、电导率变化所引起的导热等问题进行了数值求解.结果表明:当发热导体半径R>5 cm时,温度的变化对发热导体的导热系数和电导率影响显著. 相似文献
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To achieve compact structure, light weight, and high thermal efficiency for the coal-fired boiler, the supercritical CO_2 power cycle has been considered as one of the promising alternatives in the coal-fired power conversion system. One of the major problems concerning fossil fuel powered plants is the safety of the water wall in boiler design. In this work, the heat transfer characteristics of the supercritical CO_2 tube in the combustion chamber were determined through the low Reynolds number k-ε model, the gas real model and the P-1 radiation model. The study covered the supercritical CO_2 tube and the fins, and the annulus flue gas passage was also included. The wall temperature and the heat transfer coefficient were compared against those obtained from the experiments. Based on the examinations of the calculated flow and turbulence fields, the distributions of the velocity and the temperature inside the supercritical CO_2 tube in the combustion chamber were resolved numerically. Moreover, the effects of the heat transfer coefficient on the heat transfer characteristics were also discussed. And it was numerically focused on the influence of the inclined angle on the flow and the heat transfer of the supercritical CO_2 tube. The results show that the heat transfer coefficient keeps namely constant as the increasing inclined angle. It would help to better understand the heat transfer mechanism of unique characteristics of supercritical CO_2 above the pseudo-critical temperature, which may provide the corresponding theoretical basis on the optimization design of the coal-fired boiler. 相似文献
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低温环境下风冷热泵型空调机组应用问题的探讨 总被引:1,自引:0,他引:1
通过分析低温环境下风冷热泵型空调机组制热能力降低的主要原因,提出了在低温环境下提高风冷热泵型空调机组蒸发温度的方法及措施,并通过计算来验证其可行性。 相似文献
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将热阻比拟为等效电阻,采用有限体积元法对超音速燃气喷射管道传热及表面自然对流散热进行数值计算,得到喷射管壁温度分布和表面不同自然对流散热及参数变化对壁温的影响.由于管两端自然对流散热作用,管中部温度高于两端;随着表面自然对流换热增强管壁温度逐渐降低;选用不同材质时,随材质导热系数增大管内外壁温差线性增大. 相似文献
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In this paper, an absorption heat transformer (AHT) with falling film of aqueous LiBr solution inside vertical spiral tubes is installed and tested. The variations of coefficient of performance (COP), thermal efficiency (Eth ), and the heat transfer coefficient of the absorber at different falling film flow rates, hot water flow rates, and operating temperatures are investigated experimentally. The results demonstrated that the coefficient of performance and thermal efficiency of the system decrease with the increase in the flow rate of LiBr solution, and the influence of flow rate of hot water on COP and Eth is insignificant. The available COP in the experiments is higher than 0.4. The heat and mass transfer coefficients of the absorber increase with the increase of the flow rate of LiBr solution, up to 400W/m2/K and 0.013 kg/m2/s (temperature of waste heat is 90°C). The heat transfer coefficient of the absorber increases with the increase of the temperature of waste heat, and decreases with the increase of the cooling water temperature. Meanwhile, the computer code ABSIM (Absorption Simulation) is used to simulate the AHT systems, and the simulated results are compared with the experimental data. 相似文献