结合燃气-蒸汽联合循环的液化天然气冷能发电利用

提出了结合燃气-蒸汽联合循环的利用液化天然气（liquefied natural gas,LNG）冷能的朗肯循环发电系统,实现LNG冷能梯级利用。朗肯循环蒸发器和燃气-蒸汽联合循环凝汽器换热量匹配一致,循环水系统实现闭式且不受环境温度影响。对系统进行模拟并分析了影响系统的主要参数,结果显示：随着朗肯循环冷凝温度的降低,朗肯循环净输出功率和净效率均有提升;随着循环水温度的提高,朗肯循环的净输出功率和净效率都将提高,而蒸汽轮机输出功率减少,但二者总的输出功率降低幅度不大。     

中低温热水发电系统及效率分析

中低温热水发电通常选用有机朗肯循环系统。本文对ORC系统的特点、工质和参数的选择进行了介绍,并对系统进行效率分析。针对以80℃-150℃热水为热源的有机朗肯循环(ORC)发电系统,以?效率为评价指标,分析了循环工质为R134a、R123和R245fa时的系统。得出,R245fa是较为理想的工质。     

工业余热回收有机朗肯循环工质优选

工业流程中存在大量低于150℃的余热资源,采用这些余热资源驱动有机朗肯循环发电,可以有效地实现节能减排。为了对不同有机朗肯循环工质在工业余热应用过程中的特性进行研究,本文建立有机朗肯循环的性能分析模型,并选取6种工质,利用工程方程解答器(EES)软件分别在不同热源温度与冷源温度条件下,对其发电量、热力学第一定律效率和第二定律效率进行分析与比较。结果表明,不同工质的性能均随着热源温度的上升得到不同程度的提高,并随着冷源温度的上升而下降。在输出功、热力学第一定律效率以及第二定律效率3个方面,R600均表现出最佳特性。     

利用燃气轮机烟气余热的复合有机朗肯循环系统优化分析

本文针对燃气轮机烟气余热设计了一种复合有机朗肯循环系统,对其进行了详细的热力学分析,以某燃驱压气站烟气条件(400℃,26 kg/s)为例,以系统净输出功为目标,利用Matlab和Refprop 9. 0选择了13种工质,并确定了系统最优工况。结果表明,甲苯、R141b、丙酮分别作为3个子系统的工质时,系统可实现最大净输出功为1 587 k W,热效率和火用效率分别可达20. 26%和42. 68%,比单级循环可实现的最大净输出功高23. 33%。对系统各部件进行火用损失分析,发现蒸发器火用损失最大,并提出了改进方案。     

利用气体动力循环的LNG双动力汽车

分析了三种清洁排放汽车--压缩空气汽车、液氮汽车和LNG汽车的特点.提出一种利用气体动力循环的LNG双动力汽车系统,将开式朗肯循环与内燃机循环结合,优势互补.结果表明,LNG双动力汽车系统中的天然气开式朗肯循环输出功远高于液氮汽车.LNG双动力气车系统可用能较普通LNG汽车增加9.82%,且对环境没有污染,节能环保效果明显.     

过冷度对地热发电非共沸工质有机朗肯循环热力性能的影响

有机朗肯循环（organic Rankine cycle,ORC）是利用中低温地热能（< 150℃）发电的主要途径,在实际运行中,非共沸工质往往会冷凝至过冷状态。分析了冷凝过冷度对非共沸工质ORC热力性能的影响,建立了ORC、内回热（internal heat exchanger,IHE）ORC的热力学模型,以净输出功最大为目标函数优化了工质的蒸发压力,并开展了系统的㶲分析。结果表明：过冷度影响了工质与冷源换热流体间的温度匹配特性,受夹点温差的限制,随着过冷度的增加,工质的冷凝压力上升;过冷度亦改变了预热器和蒸发器的热量分摊,随着过冷度的增加,最佳蒸发压力亦上升。混合工质异丁烷/异戊烷的质量配比为0.4：0.6时,净输出功受过冷度的影响最大,当过冷度为2℃时,净输出功下降了4.36%。IHE回收膨胀机排汽的余热,提高了预热器入口温度,可提高过冷ORC系统净输出功0.55%。过冷度增大了冷凝器的㶲损失;采用内回热冷凝器的㶲损失降低了24.7%。     

基于燃机废热的超临界二氧化碳布雷顿循环的热力学分析

目的:研究超临界二氧化碳(SCO_2)布雷顿循环布局对回收燃机废热性能的影响。方法:利用Aspen plus软件建立SCO_2布雷顿循环模型,将某F级天然气燃气轮机排气废热作为热源,采用序列二次规划(SQP)优化方法来获得最优系统参数优化。结果:以简单回热循环为基准,间冷循环利用SCO_2的流体特点降低压缩功和初始吸热温度,提升了13.76%净输出功;再压缩循环不能带来净输出功的增加,退化为简单回热循环;双级回热循环利用其分流和多回热器的特点,具有最高的净输出功,较简单循环提升37.21%。结论:通过优化SCO_2布雷顿循环的布局,能够有效提升废热利用率、循环效率和净输出功率。     

有机朗肯循环(ORC)膨胀发电机组设计分析

利用有机朗肯循环回收工业生产废水中的热量进行发电,不但节约能源而且减少废热对环境的热污染,有利于实现节能减排。本文针对某一化工厂95℃的热水作为热源,分析R134a和R245fa在不同蒸发温度下的能源利用效率、净发电功率、工质泵扬程以及单位净发电功率所需的膨胀机排量,并指出在实现利用余热发电可行性的问题上需要考虑设备投资、关键设备(工质泵)、经济效益等问题。     

有机朗肯循环发电系统中换热过程模拟与系统经济性分析

有机朗肯循环发电系统中的能量主要损失在换热设备中。换热设备性能对其发电效率有着直接的影响。为提高有机朗肯循环发电系统的经济性,以最小电力生产成本为目标函数,建立经济性模型,并以实际搭建的有机朗肯循环发电系统对模型进行优化,对安装预热器和过热器的经济性进行分析。研究结果表明:电力生产成本主要受热源介质流量、冷却水流量、系统发电功率、蒸发器节点温差及蒸发温度的影响;在有机朗肯循环发电系统中,尤其是在中大型发电系统中,预热器的安装是经济可靠的;过热器的安装对电力生产成本的增加值较小,而其可提高系统的稳定性、延长系统的使用寿命。     

有机朗肯循环低温余热发电系统的工质选择

有机朗肯循环发电系统对于中低温余热的有效利用发挥了巨大的作用,但是有机朗肯循环系统的工质选择依旧是中低温余热利用中存在的问题。文章提出优选工质的条件,并通过对十种低沸点有机工质的性能对比分析得出R141b最适宜作为此温度的余热回收工质,综合性能高于其他工质,对于有机朗肯循环添加回热会大大提高系统效率。     

包装废弃物热解余热回收用涡旋膨胀机瞬态流动特性研究

目的 为揭示进气压力的变化对涡旋膨胀机内部流动特征及性能参数的影响机制,探究其对膨胀机效率及实际回收功率的影响规律。方法 以余热回收有机朗肯循环中的涡旋膨胀机为研究对象,利用STARCCM+软件,采用重叠网格技术对涡旋膨胀机内部计算流体域进行非稳态离散求解,分析涡旋膨胀机流场变化特性以及性能参数的变化规律。结果 在出口压力不变的条件下,随着进气压力的上升,压力场分布梯度增大;进、出口流量均呈现周期性波动,出口流量的波动幅度明显小于入口流量的波动幅度。填充系数的大小一定程度上反映了膨胀机内部的泄漏程度或流动阻力大小,观察到进气压力为0.75 MPa时填充系数最大,此时工质的流动阻碍相对更小,平均质量流量也最大。涡旋膨胀机等熵效率、输出功率均随进气压力的增大而增大。结论 涡旋膨胀机输出功率的优化与多种因素相关,要综合考虑进出口实际焓差和平均质量流量等因素的影响,只考虑单方面因素缺乏一定的合理性。     

A theoretical study on a novel solar based integrated system for simultaneous production of cooling and heating

An integrated system for simultaneous production of triple-effect cooling and single stage heating is proposed in this paper to harness low grade solar energy. The proposed system combines the heliostat field with a central receiver and the ejector-absorption cycle with the shaft power driven transcritical CO₂ cycle. A parametric study based on first and second laws of thermodynamics is carried out to ascertain the effect of varying the exit temperature of duratherm oil, turbine inlet pressure, and evaporators temperature on the energy and exergy output as well as on the energy and exergy efficiencies of the system. The results obtained indicate that major source of exergy destruction is the central receiver where 52.5% of the inlet solar heat exergy is lost followed by the heliostat where 25% of the inlet exergy is destroyed. The energy and exergy efficiencies of the integrated system vary from 32% to 39% and 2.5%–4.0%, respectively, with a rise in the hot oil outlet temperature from 160 °C–180 °C. It is further shown that increase in evaporator temperature of transcritical CO₂ cycle from −20 °C to 0 °C increases the energy efficiency from 27.45% to 43.27% and exergy efficiency from 2.51% to 2.97%, respectively. The results clearly show how the variation in the values of hot oil outlet temperature, turbine inlet pressure, and the evaporator temperature of transcritical CO2 cycle strongly influences the attainable performance of the integrated system.     

基于LNG冷能的低温动力循环研究进展

液化天然气(LNG)是一种应用日趋广泛的清洁能源,构建LNG冷能低温动力循环成为回收冷能的重要途径。本文首先讨论了LNG侧参数、循环工质、设备进出口参数等重要参数对基本LNG冷能动力循环的影响;其次分析和总结了诸多LNG冷能动力循环的结构改进类型,包括朗肯循环、布雷顿循环、卡琳娜循环和复合循环。文章最后指出了参数研究的实际工程意义和循环结构改进的多样性,并指出下一步研究应围绕有机混合工质组分配比、模拟与实验相结合等方面展开。     

带约束条件的CO_2热泵热水系统高压控制方程

系统高压的优化与控制在提升跨临界CO_2系统效率方面至关重要。在CO_2热泵热水系统中,传统的高压控制方程中仅考虑了气体冷却器侧的出口温度而忽略实际应用中对出水温度的要求和温度夹点,导致系统性能大大降低。本文针对温度夹点和进出水温等约束的影响,建立了有约束的气冷器模型,并对系统高压进行了优化。采用实验设计以及统计学方法确定影响最优高压的主要因素,通过最小二乘法回归出最优高压控制方程。使用该高压控制方程的系统平均COP损失1.8%,最大COP损失8.7%,可以更好地满足实际应用。     

A theoretical study on a novel combined power and ejector refrigeration cycle

A new combined power and refrigeration cycle is proposed for the cogeneration, which combines the Rankine cycle and the ejector refrigeration cycle by adding an extraction turbine between heat recovery vapor generator (HRVG) and ejector. This combined cycle could produce both power output and refrigeration output simultaneously, and could be driven by the flue gas from gas turbine or engine, solar energy, geothermal energy and industrial waste heats. Parametric analysis and exergy analysis are conducted to examine the effects of thermodynamic parameters on the performance and exergy destruction in each component for the combined cycle. The results show that the condenser temperature, the evaporator temperature, the turbine inlet pressure, the turbine extraction pressure and extraction ratio have significant effects on the turbine power output, refrigeration output, exergy efficiency and exergy destruction in each component in the combined cycle. It is also shown that the biggest exergy destruction occurs in the heat recovery vapor generator, followed by the ejector and turbine.     

有机朗肯循环的发电系统的实验研究

以低温热蒸汽来模拟废热作为有机朗肯循环(ORC)的热源,建立了以R134a为制冷剂的有机朗肯循环发电系统。通过EES(engineering equation solver)软件对ORC系统进行了数学建模,并将实验与模拟结果进行了比较。结果表明:系统以R134a为工质运行,可以达到8%的发电效率;当膨胀机进口的状态为饱和或者过热时,系统的热效率与发电量都会随着进口压力的增加而增加;系统压力较低的时候,系统的不可逆程度较大,系统效率会有较大损失。     

Optimal design of an absorption chilled water storage air conditioning system driven by waste heat

In order to meet both economic and energy requirements, this study has proposed an optimal design to minimize the sum of the initial and operation energy costs for a 1200 refrigeration ton chiller and 12 water storage tanks in an absorption chilled water storage air conditioning system. Various power consumption calculation methods for the main devices are included to predict the performance of this equipment under different operating conditions. In addition, the performance curves of the water storage tank under the storage and discharge modes are calculated using Fluent software. The article uses five control strategies for a cooling tower along with three hot water inlet temperatures of a generator to simulate the optimal design of a system. The results show that the least power (10,336 kWh) is consumed when the cooling tower’s outlet temperature is 32°C and the generator’s inlet hot water temperature is 105°C.     

Experimental study of a subcritical heat pump booster for sanitary hot water production using a subcooler in order to enhance the efficiency of the system with a natural refrigerant (R290)

This paper presents the experimental results obtained from a new heat pump prototype for sanitary hot water production, in the application of heat recovery from water sources like sewage water or condensation loops (typical temperature condition between 10 °C and 30 °C). The system configuration is able to produce a high degree of subcooling in order to take advantage from the high water temperature glide (typical value for sanitary hot water production is 10 °C to 60 °C). Subcooling is made by using a separate heat exchanger from the condenser (subcooler). The obtained results have shown a high degree of improvement by making subcooling. COP is 5.61 in nominal conditions, which is about 31% higher than the same cycle working without subcooling (Nominal point: inlet/outlet water temperature at evaporator is 20 °C/15 °C and the water inlet/outlet temperature in the heat sink is 10 °C and 60 °C).