以R134a为工质的OTEC朗肯循环热力计算软件开发

以海洋温差热能转换（OTEC）的热力循环为研究对象，为给循环分析提供方便准确的性能计算工具，采用Python程序设计语言，开发了OTEC朗肯循环热力计算软件。软件可以完成简单朗肯循环、再热朗肯循环、抽气回热朗肯循环等3种循环的热力计算，输出结果包括循环最高限制压力、冷凝压力、工质泵功、膨胀机功、蒸发器热负荷、冷凝器热负荷、循环净功以及循环热效率等朗肯循环性能参数。工质热力性质采用R134a的最新国际标准关联式，计算结果足够精确，在蒸发温度24.34℃、冷凝温度8.14℃，泵效率和透平效率均为1.0的工况下，与采用NIST提供的热物性数据进行循环计算结果对比表明，二者完全一致，循环热效率均为5.15%。软件可作为OTEC发电装置的热工设计参考，也可用于R134a工质的 -103.15℃~426.85℃之间的亚临界朗肯循环、跨临界朗肯循环和超临界循环等领域的应用，软件的成功开发对我国OTEC发电应用领域的发展具有相当程度的技术保障与引领作用。     

中低温热水发电系统循环参数和工质的选择

针对热源为80～150℃热水的有机朗肯循环（ORC）发电系统,以发电功率和效率为评价指标,分别分析了以R134a、R123和R245fa三种工质为循环介质时的系统,确定了最佳循环参数和工质。一般来说,最佳蒸发温度对应着最大的输出电功,且随着热流体温度的升高而升高;当热源温度大于120℃时,R134a的系统不存在最佳蒸发温度,此时输出电功随着蒸发温度的升高而增大。对于80～135℃的热水,工质R245fa的发电功率最大;当热水温度超过135℃时,工质R134a的发电功率最大。工质R245fa的发电效率始终是最大的。     

重型卡车朗肯−朗肯制冷系统热力学研究

本文针对重型卡车发动机冷却液余热工况,采用R245fa作为循环工质建立了朗肯−朗肯制冷系统,剖析了此系统的基本原理和结构特点,根据系统分析建立了数学模型,模拟分析了发生温度、冷凝温度、蒸发温度对系统性能的影响。结果表明：在发生温度85℃、冷凝温度50℃、蒸发温度5℃时,系统COP（coefficient of performance）达到0.254,虽然此系统的效率要低于相同工况下的吸收制冷循环,但是朗肯−朗肯制冷系统相对于吸收制冷系统具有尺寸小、易于控制和快速响应等优点,利用朗肯−朗肯循环回收重型卡车发动机冷却液余热进行制冷是可行的。     

有机朗肯循环与再热式循环低温热源发电系统热力性能研究

针对120℃以下的低温余热热源,探讨了基本有机郎肯循环发电系统和再热式有机朗肯循环发电系统模型的基本原理.从热力学第一定律角度出发,研究了纯工质R245fa和非共沸混合工质R21/R245fa在基本有机郎肯循环系统中,以及纯工质R245fa在再热式有机郎肯循环系统中,三种形式的有机郎肯循环系统热力性能随蒸发温度的变化情况.与纯工质基本有机郎肯循环系统相比,再热式有机郎肯循环最大可提高系统净输出功7.08％,而混合工质对提高整个系统热力性能具有较大的优势,净输出功和热效率最大可提高4.67％和2.91％.     

有机朗肯循环发电系统利用的研究

理想发电循环系统仅与系统热源、冷源的温度相关,而实际低品位有机朗肯循环发电系统效率除与冷热源温度相关外,与工质、系统形式等因素密切相关.但是由于受到热源参数及优化目标等因素影响,尚未优选出合适的工质和系统形式.针对不同热源参数特性,研究相适应的系统形式及工质,为有机朗肯循环发电系统应用提供科学依据,是有机朗肯循环发电系统切实可用的关键.     

有机朗肯循环在低温余热利用领域的应用分析

本文计算比较了R134a, R245fa, R141b三种典型有机工质在特定传热条件下的朗肯循环热效率情况,最后选择R134a作为系统循环工质。以某化工厂温度为105℃的排空蒸汽余热为案例,提出了有机工质朗肯循环的简化模型,并且在理论上对其进行了热效率和火用效率的分析。依据条件通过计算选择了压比为4的螺杆膨胀机代替了传统的汽轮机,计算出R134a流量以及蒸发器的结构参数,利用软件对蒸发器的传热进行了数值模拟。     

烟气余热驱动复叠式非共沸工质有机朗肯循环系统热力学分析

文章构建了复叠式非共沸工质有机朗肯循环系统模型,并利用该模型对复叠式非共沸工质有机朗肯循环系统的热力学性能进行分析,得到了高温级循环质量流量、低温级循环质量流量、冷却水质量流量、高温级循环净输出功率、低温级循环净输出功率、冷却水泵功耗和系统净输出功率等随工质摩尔组分的变化规律。分析结果表明,高温级循环蒸发泡点温度和高温级蒸发器夹点位置会影响复叠式非共沸工质有机朗肯循环各项性能参数随工质摩尔组分的变化趋势,当高温级循环混合物中环戊烷的摩尔组分为0.8,低温级循环混合物中异丁烷摩尔的组分为0.1时,复叠式非共沸工质有机朗肯循环系统的净输出功率达到最大值,为92.79 kW,比复叠式纯工质有机朗肯循环系统提高了3.83%。     

工质R123和R245fa的有机朗肯循环热力性能

在回收热量一定的条件下,运用热力学第一定律建立了有机朗肯循环热力分析模型,基于蒸发参数法展开了工质R123和R245fa的优选研究。计算结果表明:相同蒸发参数下,工质R123的循环热效率高于工质R245fa;相同蒸发温度下R123具有低压特性,这有利于系统的安全运行。从工质的环保性和热力性能来综合考虑,认为工质R123优于工质R245fa。     

基于有机朗肯循环的低温地热制冷系统热力学分析

为有效利用低温地热资源,本文以有机朗肯–蒸汽压缩制冷系统为研究对象,建立了系统的热力学模型,分析比较了分别以R290、R600、R600a、R601、R601a和R1270为工质时的系统性能,并以系统整体COP和每千瓦制冷量所对应的工质流量为关键指标对工质进行了优选。分析结果表明：当地热水温度为60 ~ 90℃,冷凝温度为30 ~ 55℃,蒸发温度为 –15 ~15℃时,R601是系统的最佳工质。当地热水温度为90℃,其余参数为典型工况值时,工质R601所对应的系统性能系数COP为0.49。     

利用中低温余热的回热有机朗肯循环性能分析

通过选取R227ea、R600和R141b 3种典型有机干流体作为工质,在热源流体进口温度设定为典型工业锅炉排烟温度423.15 K,冷却水进口温度和环境温度分别设定为283.15 K和293.15 K的条件下,分析蒸发温度、过热度和给水加热器出口处工质温度对回热有机朗肯循环性能的影响,比较回热有机朗肯循环与基本有机朗肯循环的性能。结果表明:随着蒸发温度的增大,循环总不可逆损失减小,循环热效率和第二定律效率增大,而循环输出净功率则先增大后减小;随着过热度的增大,循环总不可逆损失和循环输出净功率均减小,而循环热效率和第二定律效率的变化趋势则因工质而有所不同;随着给水加热器出口处工质温度的增大,循环总不可逆损失和循环输出净功率不断降低,而循环热效率和第二定律效率则先增后减;在相同工况下,回热有机朗肯循环的循环热效率和第二定律效率高于基本有机朗肯循环,但对于循环输出净功率和循环总不可逆损失,结果则相反。     

利用低品位热能的有机物朗肯循环的工质选择

工质对低品位热能有机物朗肯循环的安全性、环保性、经济性和高效性具有很大的影响.本文首先对61种工质的热力学、物理、化学、环保、安全和经济特性进行了研究,并从中挑选出11种符合上述特性的候选工质,然后对这些候选工质的干湿性、饱和性质和循环热效率进行了研究,确定了8种适合低品位热能有机物朗肯循环且具有潜力的工质,它们是丙烷...     

低温余热有机朗肯循环发电系统工质选择

对有机朗肯循环系统工质的优化选择已逐渐从单一优化目标向多目标发展,但所选的优化目标及优化方法普遍存在主观性较强的问题.针对上述问题,从环保性、安全性等方面对工质进行初选,得到了R123、R245fa、R245ca和R601等9种工质,然后采用主成分分析法对工质的热效率、循环净功和不可逆损失等7个热力性能指标进行了分析计算,得到了两个较为客观的综合评价指标,并在不同蒸发温度下对工质的综合热力性能进行了分析.结果表明:R601做功能力较强,综合效率较高,是该循环系统较为理想的工质.     

基于动态透平效率的有机朗肯循环性能分析及优化

常规有机朗肯循环(ORC)中透平效率多假设为定值,而实际上透平效率因工质种类和运行参数的不同而有较大差异。因此,采用向心透平效率计算模型,将动态透平效率与ORC系统耦合,分析透平效率随蒸发温度与冷凝温度的变化规律,比较固定透平效率与动态透平效率ORC系统热效率的差异。综合考虑热力性与经济性,采用多目标优化算法,对固定透平效率与动态透平效率ORC系统进行工质筛选及参数优化,并对优化结果进行分析比较。结果表明:透平效率随蒸发温度的下降或者冷凝温度升高而增大;不同工质及不同蒸发冷凝温度条件下,透平效率差异较大,最大达0.148。固定透平效率ORC系统与动态透平效率ORC系统的热效率随蒸发温度的变化规律有较大差异,尤其在高蒸发温度区间更为明显。对于固定透平效率ORC系统,R245ca和R236ea为最佳工质;而对于动态透平效率ORC系统,R114为最佳工质。在引入动态透平效率前后,各工质的最佳蒸发温度与最佳冷凝温度也有较大变化。     

不同工质对太阳能有机朗肯循环系统性能的影响

循环工质的特性是影响有机朗肯循环系统性能的重要因素之一,在不同的蒸发温度条件下,选取R600、R600a、R245fa、R236fa、R236ea、R601、R601a、RC318及R227ea共9种有机工质,基于热力学第一定律和第二定律对其热力循环特性进行了计算分析,并对各有机工质的蒸发压力、热效率、功比和不可逆损失等进行了比较.结果表明：R245fa作为太阳能低温热发电朗肯循环系统的循环工质具有较高的热效率和效率,并且产生的系统总不可逆损失较小,是一种较理想的有机工质;其次,R236fa和R236ea作为系统循环工质也具有较为良好的性能.     

余热驱动的有机朗肯循环-复叠式制冷系统?分析

针对余热的有效利用,建立了有机朗肯循环-复叠式制冷系统的热力学模型,其中:有机朗肯循环系统分别采用R123、R1234ze、R245fa、R600a、RC318、R141b等六种工质;复叠式制冷系统分别采用R22/R23、R404/R23、R290/R744、R717/R744等四种工质对。选择系统?效率作为性能评价指标,运用热力学第二定律研究系统运行参数对系统?效率的影响,分析了系统各部件的?损失,并指出了能量利用的薄弱环节,提出了有效提高系统性能的建议,为系统的优化提供参考。结果表明,对系统?效率而言,R141b和R717/R744是最佳工质。系统主要部件按?损失大小依次为凝汽器、膨胀机、高温级冷凝器、发生器、高温级压缩机、低温级蒸发器、蒸发冷凝器。尽可能提高压缩机的等熵效率,优化设计换热器的结构,减小传热温差,才能减少不可逆损失,提高换热器的?效率。     

Energetic and exergetic analysis of CO2- and R32-based transcritical Rankine cycles for low-grade heat conversion

Transcritical Rankine cycles using refrigerant R32 (CH₂F₂) and carbon dioxide (CO₂) as the working fluids are studied for the conversion of low-grade heat into mechanical power. Compared to CO₂, R32 has higher thermal conductivity and condenses easily. The energy and exergy analyses of the cycle with these two fluids shows that the R32-based transcritical Rankine cycle can achieve 12.6–18.7% higher thermal efficiency and works at much lower pressures. An analysis of the exergy destruction and losses as well as the exergy efficiency optimization of the transcritical Rankine cycle is conducted. Based on the analysis, an “ideal” working fluid for the transcritical Rankine cycle is conceived, and ideas are proposed to design working fluids that can approach the properties of an “ideal” working fluid.     

Performance analysis of cogeneration systems based on micro gas turbine (MGT), organic Rankine cycle and ejector refrigeration cycle

In this paper, the operation performance of three novel kinds of cogeneration systems under design and off-design condition was investigated. The systems are MGT (micro gas turbine) + ORC (organic Rankine cycle) for electricity demand, MGT+ ERC (ejector refrigeration cycle) for electricity and cooling demand, and MGT+ ORC+ ERC for electricity and cooling demand. The effect of 5 different working fluids on cogeneration systems was studied. The results show that under the design condition, when using R600 in the bottoming cycle, the MGT+ ORC system has the lowest total output of 117.1 kW with a thermal efficiency of 0.334, and the MGT+ ERC system has the largest total output of 142.6 kW with a thermal efficiency of 0.408. For the MGT+ ORC+ ERC system, the total output is between the other two systems, which is 129.3 kW with a thermal efficiency of 0.370. For the effect of different working fluids, R123 is the most suitable working fluid for MGT+ ORC with the maximum electricity output power and R600 is the most suitable working fluid for MGT+ ERC with the maximum cooling capacity, while both R600 and R123 can make MGT+ ORC+ ERC achieve a good comprehensive performance of refrigeration and electricity. The thermal efficiency of three cogeneration systems can be effectively improved under off-design condition because the bottoming cycle can compensate for the power decrease of MGT. The results obtained in this paper can provide a reference for the design and operation of the cogeneration system for distributed energy systems (DES).     

Thermo-economic analysis and optimization of a combined Organic Rankine Cycle (ORC) system with LNG cold energy and waste heat recovery of dual-fuel marine engine

A combined Organic Rankine Cycle (ORC) system with liquefied nature gas (LNG) cold energy and dual-fuel (DF) marine engine waste heat utilization was proposed. Engine exhaust gas and engine jacket cooling water were adopted as parallel heat sources. Thermo-economic analyses of the proposed system with 32 working fluids combinations were performed. Two objective functions covering thermal efficiencies and economic index were employed for performance evaluation. Afterward, the effects of operation pressure on the objective functions were investigated. Finally, the optimal conditions were obtained from the Pareto front with the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) method. The results show that the proposed ORC system has better energy recovery performances than the parallel ORC system. R1150-R600a-R290, R1150-R601a-R600a, and R170-R601-R290 are determined as the three most promising working fluids combinations. Under optimized conditions, the output power range is 199.97 to 218.51 kW, the energy efficiency range is 13.64% to 15.62%, and the exergy efficiency range is 25.29% to 27.3%. The payback period ranges from 8.36 to 8.74 years. The working fluids selection helps to reduce the exergy destruction of intermediate heat exchanger, which could be up to 30.59%.     

Effect of working fluids in a novel geothermal-based integration of organic-flash and power/cooling generation cycles with hydrogen and freshwater production units

One of the essential steps to design energy conversion-based systems is choosing an efficient working fluid under the design goals to access stable products with high efficiency and overcome environmental issues. In this regard, the current paper is motivated to devise and evaluate a novel geothermal-driven multigeneration system under the effect of various working fluids. The proposed system consists of a flash-binary geothermal power plant, an organic flash cycle (OFC), a power/cooling subsystem (an organic Rankine cycle (ORC) and a thermoelectric generator incorporated with a compression refrigeration cycle), and freshwater and hydrogen production units utilizing a humidification-dehumidification desalination unit and a low-temperature electrolyzer. Considering the design potential of the OFC and ORC, four different environmentally-friendly working fluids, i.e., R123 and R600 in the OFC and R1234yf and R1234ze(e) in the ORC are selected and classified in four groups to introduce the best one, under the energy, exergy, and economic (3E analysis) approaches. Also, the whole system is optimized through a genetic algorithm, respecting the optimal solution for the energy efficiency and unit exergy cost of the products. According to the results, R123/R1234ze(e) shows the highest cooling, hydrogen, freshwater production rates, and energy efficiency. Likewise, the maximum power generation and exergy efficiency belong to R600/R1234ze(e). Moreover, R600/R1234yf has the lowest unit exergy cost of products.     

低温地热发电有机朗肯循环的优化

采用(火用)分析方法及PR状态方程,建立了低温地热发电有机朗肯循环的工质优选及主要参数优化热力学方法.比较计算了以10种干流体有机工质为循环工质的低温地热发电有机朗肯循环的输出功率、(火用)效率及其余主要热力性能.结果表明,低温地热发电有机朗肯循环的性能极大地受工质的物性及蒸发温度的影响.总体来看,随着工质临界温度的升...