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%。     

一种新型跨临界CO2冷电联供系统热力分析

提出一种新型跨临界二氧化碳（trans-critical carbon dioxide,TCO₂）再压缩循环和喷射器制冷循环耦合的冷电联供系统。该系统在输出电能的同时,利用低品位热能驱动喷射器工作输出冷量。以输出电量1 MW为设计目标,对比冷电联供系统和再压缩发电系统的性能,研究联供系统各部件（火用）损和主要热力参数对其性能的影响。结果表明：联供系统利用CO₂余热驱动喷射器输出冷量,循环热效率高于单一再压缩系统;加热器（火用）损所占比例最大,回热器次之;透平进口温度、压力和背压对联供系统工质流量、循环效率、输出功率、加热器功率、压缩机耗功及喷射器制冷量等参数影响较大;而冷凝温度和蒸发温度仅对制冷循环制冷量影响较大。在设定条件下,联供系统的循环热效率和（火用）效率可分别达到46.99%和47.21%。     

行波热声发动机的多负载声功输出特性

为进一步提高热声发动机的声功输出能力并为驱动多负载做准备，提出了热声发动机声功的多路引出方案。实验中以氮气为工质，工作压力为2．4MPa，在热声发动机环路压比稳定在1．20的情况下，从环路声容和谐振管处同时引出声功，获得了389．95W的最大声功，11．3％的最大声功输出效率以及16．0％的最大声功输出炯效率，这比单独从环路引出的最大声功和效率分别提高了51．4％，24．6％以及19．4％。     

复叠式低温制冷箱的(火用)分析

根据实验得到的低温箱降温过程和稳定工作过程状态点参数,以R502/R13复叠式低温制冷箱为例对低温箱系统进行了(火用)分析计算.计算得出系统能效系数和(火用)损失随时间变化情况,更好的考察了系统各部件能耗状况,得到其中高低温级压缩机和蒸发冷凝器的(火用)损失所占比重最大,从而为设备改进提供借鉴和参考.     

活塞式压缩机制冷系统启停过程研究

本文研究了具有毛细管节流的活塞式压缩机制冷系统的启停特性。在实验的基础上,分析了启停过程系统参数的变化以及影响启停过程能量转换的因素,研究结果表明,停机后阻止工质迁移能改善制冷系统的启动特性,并减少了启动过程中制冷系统的能量消耗。本文建立了停机过程的数学模型,并由此计算了停机过程工质迁移造成的制冷系统的(火用)损失,这一(火用)损失即为停机过程工质迁移而使启动过程节能的最小值。     

基于PSO算法优化的热水分流式双级ORC系统

以有机朗肯循环的结构优化为基础,建立了热水分流式双级有机朗肯循环数值模型,以粒子群算法为计算方法分析系统设计时最大净输出功,通过理论分析得到了影响系统净输出功的独立变量为热水经过高压蒸发器时换热后的温度和热水出口温度。结果表明热水分流式双级有机朗肯循环可以对热水进行更好的利用,高压循环蒸发温度随着热水入口温度升高更快;热水在进行分流的过程中随着热水入口温度的升高,分流比下降;热水入口温度更高时采用该系统更有优势。     

制冷剂/吸收剂在管内流动及换热过程能耗与(火用)损研究

本文研究分析了水 /二甘醇热泵工质对在管内流动及换热过程 ,建立了描述能量损失与火用损失的数学模型。通过对模型的理论分析、求解和实验研究 ,获得了能耗与火用损失变化规律 ,比较了粘性耗散和导热引起的能耗与火用损     

蒸发器中非共沸混合工质的换热特性

为了阐明非共沸混合工质在制冷、空调系统蒸发器中的换热过程,以及混合工质蒸发时的温度滑移现象为工程实际带来的某些特殊性,运用传热及热力学原理进行了相应的理论分析,发现非共沸混合工质的蒸发过程中蒸发介质存在极限流量的现象,并得到此类工质在可用能角度相比纯工质具有节能效果的结论(一般情况下,相对可用能损失减少40%～55%),最后将理论分析结论应用于几种常用的混合工质上,如R407c、R405a和R414b,并预测了这些工质在实际使用中的极限流量和可用能损失情况.     

过热和过冷对系统[火用]的影响分析

通过对定环境温度条件下的高温冷库中的氨蒸汽压缩系统进行(火用)分析,利用线性拟合的方法对氨的物性进行模拟,并对系统过冷度和过热度变化时,制冷系统的各部件的(火用)损失和系统的(火用)效率进行计算分析,得出在冷库氨蒸汽压缩系统中的蒸发器中的(火用)损失最大,压缩机和冷凝器次之的结果.提出定环境温度条件下,由于过热度越大,对系统越不利,过冷度越大,对系统越有利,提高系统性能可从减少过热度增大过冷度着手.     

定环境温度下冷库的氨蒸汽压缩制冷系统的火用分析

本文通过对定环境温度条件下的冷库中的氨蒸汽单级压缩系统进行火用分析,利用线性拟合的方法对氨的物性进行模拟,并对定蒸发温度和变蒸发温度时,制冷系统的各部件的火用损失和系统的火用效率进行计算分析,得出在冷库氨蒸汽压缩系统中的蒸发器中的火用损失最大,压缩机和冷凝器次之的结果。提出要对冷库氨蒸汽压缩系统的性能进行改进,必须首先考虑提高其蒸发器、压缩机和冷凝器的火用效率着手;从而提出定环境温度条件下,提高蒸发温度是提高系统火用效率的较好的改进措施之一。     

Working fluids comparison and thermodynamic analysis of a transcritical power and ejector refrigeration cycle (TPERC)

The combined power and cooling cycles driven by waste heat and renewable energy can provide different kinds of energy forms and achieve a higher thermodynamic efficiency. However, only a few researchers have focused on the improvement of temperature matching between the heat source and working fluid. This paper proposes a transcritical power and ejector refrigeration cycle (TPERC) to improve temperature matching between the heat source and working fluid. Based on the modelling of the TPERC system, a comparison of working fluids and the effects of system parameters on the cooling capacity, work output, thermal efficiency and exergy efficiency are discussed. The results show that of the seven working fluids selected, R1234ze has the largest thermal efficiency and exergy efficiency, principally due to having the highest critical temperature. At the identical turbine back pressure, condensing temperature and evaporation temperature, the turbine inlet temperature and its corresponding generation pressure have little impact on thermal efficiency.     

冷前回热式Kalina循环系统(KCS)34g的热力学分析

提出冷前回热式KCS34g,根据热力学第一定律和第二定律,利用EES软件对该循环进行热力性能分析,并与基本KCS34g进行相同条件下的性能对比,研究透平进口压力、氨质量分数和透平出口压力变化对冷前回热式KCS34g性能的影响。研究结果表明:在额定工况下,冷前回热式KCS34g的热效率为11.93%,比基本KCS34g高0.99%;效率为52.26%,比基本KCS34g高4.34%;随着氨质量分数增大和透平出口压力降低,冷前回热式KCS34g热效率、发电量和效率均增大;随着透平进口压力增加,冷前回热式KCS34g热效率逐渐增加,发电量和效率在29 bar时达到最大。     

Methodology for thermal design of novel combined refrigeration/power binary fluid systems

Refrigeration cogeneration systems which generate power alongside with cooling improve energy utilization significantly, because such systems offer a more reasonable arrangement of energy and exergy “flows” within the system, which results in lower fuel consumption as compared to the separate generation of power and cooling or heating. This paper proposes several novel systems of that type, based on ammonia–water working fluid. Importantly, general principles for integration of refrigeration and power systems to produce better energy and exergy efficiencies are summarized, based primarily on the reduction of exergy destruction. The proposed plants analyzed here operate in a fully-integrated combined cycle mode with ammonia–water Rankine cycle(s) and an ammonia refrigeration cycle, interconnected by absorption, separation and heat transfer processes. It was found that the cogeneration systems have good performance, with energy and exergy efficiencies of 28% and 55–60%, respectively, for the base-case studied (at maximum heat input temperature of 450 °C). That efficiency is, by itself, excellent for cogeneration cycles using heat sources at these temperatures, with the exergy efficiency comparable to that of nuclear power plants. When using exhaust heat from topping gas turbine power plants, the total plant energy efficiency can rise to the remarkable value of about 57%. The hardware proposed for use is conventional and commercially available; no hardware additional to that needed in conventional power and absorption cycles is needed.     

First and second law investigation of waste heat based combined power and ejector-absorption refrigeration cycle

In the proposed cogeneration cycle, a LiBr-H₂O absorption refrigeration system is employed to the combined power and ejector refrigeration system which uses R141b as a working fluid. Estimates for irreversibilities of individual components of the cycle lead to possible measures for performance improvement. Results of exergy distribution of waste heat in the cycle show that around 53.6% of the total input exergy is destroyed due to irreversibilities in the components, 22.7% is available as a useful exergy output, and 23.7% is exhaust exergy lost to the environment, whereas energy distribution shows 44% is exhaust energy and 19.7% is useful energy output. Results also show that proposed cogeneration cycle yields much better thermal and exergy efficiencies than the previously investigated combined power and ejector cooling cycle. Current investigation clearly show that the second law analysis is quantitatively visualizes losses within a cycle and gives clear trends for optimization.     

Investigation of an ammonia-water combined power and cooling system driven by the jacket water and exhaust gas heat of an internal combustion engine

An ammonia-water combined power and cooling system is proposed and investigated in this work, in which the waste heat contained in the jacket water and exhaust gas of an internal combustion engine can be recovered efficiently to generate power and cooling energy simultaneously. The proposed system was simulated, and its thermodynamic performance in the base case was calculated based on waste heat data from an actual gas engine with a rated power output of 300 kW. The equivalent heat-to-power efficiency of the combined system is 19.76%, and the total equivalent power output is as high as 92.86 kW. The exergy efficiency of the combined system reaches 33.69%. The effects of the turbine inlet pressure, generation pressure in the reboiler, exhaust gas temperature and cooling water temperature were studied to provide guidance for the system design. The results of an economic analysis indicate that the proposed system has good economic benefit.     

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.     

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。