吸附碳泵循环构建与能耗分析:从热力学角度

从热力学角度审视制约吸附法碳捕集技术推广和工业化应用的能耗问题,其实质是对捕集过程中能量在不同形式之间转换机制的深入认识问题.应用热力学中的"循环"这一成熟概念和衍生工具,对能量转换问题展开专题分析应是恰当的。本文基于热力学碳泵概念,从热力学角度进行吸附碳泵循环的构建与能耗分析,将碳捕集能耗分析模型具化至循环层面。从热力学第一定律角度,基于无限碳源、汇假设,定义工作于碳源、汇之间的吸附碳泵循环,形成抽象模型求解理想功耗及循环COPCO2,与混合气体分离模型(MGS)分析结果进行对比,并分析关键循环参数的影响;从热力学第二定律角度,基于状态点过程解耦方法"白箱化"吸附碳泵循环中具体过程,形成具体模型分析循环中熵增、熵产机制,证实优化传热过程、提升吸附剂性能作为有效降低能耗策略在热力学层面的恰当性。     

热力学碳泵循环构建:以变温吸附碳捕集为例

制约碳捕集技术实用化的重要瓶颈在于捕集能耗过高,而热力学是能源系统效能分析的有力工具。基于将热力学研究方法应用到碳捕集技术效能分析的思想,本文以变温吸附碳捕集为例,按照"物性-过程-冷热源-循环"顺序,完成热力学碳泵循环(TCPC)的构建,进而考察循环参数对总能耗和第二定律效率的影响。结果显示;循环能耗主要受循环温度、吸附剂和吸附相等影响,吸附相显热大约占循环总能耗的2%;第二定律效率区间为13.91%~21.21%,具有较高节能潜力;TCPC作为一种基于热力学思想的"量化规尺",可对碳捕集技术展开效能分析,进而对影响循环总能耗的主要因素进行归纳,并可通过第二定律效率对技术成熟度进行判断,有效挖掘碳捕集技术的节能潜力。     

可再生能源下燃煤电站-碳捕集优化调度

燃煤电站集成碳捕集技术在实现碳减排的同时可以提升电站灵活性,帮助电网消纳风光;而可再生能源网络可以提供富余能量来满足碳捕集的需求,提升电站碳捕集系统的经济性能。为此,本文提出了一种可再生能源背景下超临界燃煤电站-碳捕集系统的整体优化调度方法。该方法将深度学习与启发式计算融合,综合考虑机组运行约束和电网功率平衡约束,以降低运行成本和最大消纳风光为目标,对电站-碳捕集系统整体运行优化。结果表明,碳捕集系统的引入可以消纳51%的弃风弃光量,降低35%的碳捕集成本。通过比较,自由捕集率约束模式具有最好的优化调度空间,而平均捕集率约束模式在满足电网指定碳排放要求的同时能够保证良好的经济性。     

跨临界CO_2热泵性能试验及优化分析

为进一步研究跨临界CO_2热泵的系统性能,针对所设计CO_2热泵系统进行实验。实验结果表明:在风机频率一定时,系统热负荷、压缩机轴功率、系统出风温度均随压缩机频率的增大而增大。蒸发温度从-2℃升至4℃,COP增幅为26%,CO_2在气冷器出口温度降低10℃左右时,系统COP增幅大于30%。实验工况下跨临界CO_2热泵系统出风温度变化范围在50℃-100℃,在获得大于75℃出风温度时,热力学第二定律效率超过30%,CO_2气冷器出口温度、高压侧压力、蒸发温度的升高都会提高系统热力学第二定律效率。     

基于化学链燃烧生物质煤互补的天然气动力联产系统研究

针对传统煤制天然气过程存在的能量利用不合理、碳捕集能耗过高等技术瓶颈,本文探索了一种能实现CO_2零排放的基于化学链燃烧的生物质煤互补天然气动力联产系统。生物质与煤互补从气化源头调节了合成气中H_2/CO比例,有利于甲烷化反应过程,化学链燃烧实现了零能耗的CO_2捕集。研究结果表明:系统总能效率(η_(en))为57.03,效率(η_(ex))为54.65,系统能源节约率高达18.6,实现了系统CO_2零排放。分析了关键参数如氧气碳比(O/C)、蒸气碳比(S/C)、生物质煤互补比例和未反应气循环倍率对系统热力学性能的影响。     

结合碳捕集的SOFC-sCO2布雷顿循环集成系统性能分析

固体氧化物燃料电池是将化学能转化成电能的全固态能量转换装置,被认为是极具前景的绿色发电系统。本研究提出了结合碳捕集的固体氧化物燃料电池-超临界二氧化碳布雷顿循环集成系统,通过阳极尾气富氧燃烧实现低能耗碳捕集,并利用s CO₂再压缩布雷顿循环回收燃烧室余热提高系统效率。模拟结果显示,该集成系统在设计工况下的净发电效率为59.74%,二氧化碳捕集量为134.50 kg/h。此外,关键工作参数对系统性能的影响分析结果表明,合理的阳极尾气再循环比、燃料利用率和燃料流量是确保系统安全高效运行的必要前提。     

结合ORC和ARC的中温余热回收系统

中温余热回收过程中传热温差大,系统(火用)效率较低,本文提出一种结合有机朗肯循环和单效吸收式制冷系统的中温烟气余热回收系统。利用热力学第一定律和第二定律对系统建立了数学模型,分析了新系统中有机朗肯循环蒸发温度、冷凝温度等参数对系统性能的影响。同时对系统各主要部件进行了(火用)分析,并与双效溴化锂吸收式制冷系统进行了比较,通过T-Q图分析了新系统及参考系统的换热过程。结果表明新系统的(火用)损失从139.19 kW降低到93.18 kW,(火用)损失减少机理在于换热温差降低。     

水泥窑余热发电辅助碳捕集系统分析

本文提出一种应用于水泥厂的基于余热发电技术的醇胺法碳捕集系统,针对余热发电系统和乙醇胺(MEA)碳捕捉系统建立模型,利用Visual Basic软件编程模拟余热发电系统,利用Aspen Plus软件模拟MEA法CO_2捕集系统。探讨了废气负荷、低压蒸汽温度、压力对余热发电系统性能的影响,废气负荷和解析塔操作压力对MEA碳捕捉系统中解析塔耗能的影响,并分析了系统的耦合和匹配关系。结果表明,该系统碳捕获率范围为8.6%~15.0%。     

不可逆四热源吸收式热变换器的最优性能

在恒温内可逆四热源吸收式热变换器循环模型的基础上,建立了线性(牛顿)传热定律下考虑泵热空间向环境的热漏、工质的内部牦散以及工质与外部热源间的热阻损失的不可逆四热源吸收式热变换器循环模型。导出了在总换热面积一定的条件下,循环泵热率和泵热系数的基本优化关系、最大泵热率和相应的泵热系数、最大泵热系数和相应的泵热率以及最佳工质工怍温度和最佳换热面积分配关系。     

熵与生命科学

 热力学第二定律指出,一切与热现象有关的实际宏观过程都是不可逆的。而直接反映热力学第二定律的是态函数熵,其数学表达式是熵增加原理：ｄｓ≥０。其物理意义是：一个孤立系统的自发过程总是朝着搞增加的方向进行,即从有序走向无序。而生命的发生、演化及成长过程都是从低级到高级、从无序到有序的变化。表面看来,这似乎都与热力学第二定律相矛盾。普里高津的耗散结构理论澄清了这一切。打开了一个从物理科学通向生命科学的窗口。耗散结构理论突破了热力学第二定律只适用于孤立系统的限制,将其适用范围推广到开放系统,并将热力学第二定律的数学表达式改为ｄｓ＝ｄ１ｓ＋ｄｅｓ。     

带膨胀机的CO_2跨(超)临界逆循环的热力学分析

ＣＯ２是一种安全可靠的自然工质,可望在空调和热泵系统中得到应用。根据热力学第二定律,本文提出比较各类循环的统一方法一当量温度法。本文对带膨胀机的ＣＯ２跨临界循环及其系统进行分析和研究。结果显示该循环具有较高的用能效率,在技术上是可行的．     

Geometric heat pump: Controlling thermal transport with time-dependent modulations

The second law of thermodynamics dictates that heat simultaneously flows from the hot to cold bath on average. To go beyond this picture, a range of works in the past decade show that, other than the average dynamical heat flux determined by instantaneous thermal bias, a non-trivial flux contribution of intrinsic geometric origin is generally present in temporally driven systems. This additional heat flux provides a free lunch for the pumped heat and could even drive heat against the bias. We review here the emergence and development of this so called “geometric heat pump”, originating from the topological geometric phase effect, and cover various quantum and classical transport systems with different internal dynamics. The generalization from the adiabatic to the non-adiabatic regime and the application of control theory are also discussed. Then, we briefly discuss the symmetry restriction on the heat pump effect, such as duality, supersymmetry and time-reversal symmetry. Finally, we examine open problems concerning the geometric heat pump process and elucidate their prospective significance in devising thermal machines with high performance.     

带有蓄热装置的直膨式太阳能热泵系统的模拟研究

介绍了一种带有相变蓄热装置的直膨式太阳能热泵系统。以青岛天气为例,对该系统的蓄热模式进行数值模拟,得出蓄热装置进出口制冷剂的温度、蓄热材料的液相率随时间的变化,结果表明在太阳能辐射量变化时,该系统的蒸发温度维持25℃左右,系统能够稳定运行;对系统热力学性质进行理论计算得出系统在冷凝温度为70℃时,系统的COP能维持在5.3左右,系统能够高效运行。     

新型燃煤发电-CO2捕获-供热一体化系统

本文在深入分析燃煤电站CO₂捕获和汽水系统热平衡的基础上,提出一种新型燃煤发电-CO₂捕获-供热一体化系统。该系统通过汽水流程、碳捕获流程及地暖供热流程的有效集成,实现了系统中、低温余热的高效利用,降低了碳捕获对电厂效率的影响。分析结果显示,本文提出的一体化系统,在CO₂回收率90%时,供电效率可达31.32%,供电效率降低8.96%,而传统化学吸收法碳捕获电站效率惩罚普遍在10～12个百分点或更高。同时,该系统可供热350 MW,全厂（火用）效率达34.49%,全厂热效率高达55.88%;该系统以较少的能耗代价实现高效供电、供热与CO₂减排,为燃煤发电机组碳减排提供了独特的学术思路与技术方案。     

Performance and Exergy Analyses of a Solar Assisted Heat Pump with Seasonal Heat Storage and Grey Water Heat Recovery Unit

The main research objective of this paper was to compare exergy performance of three different heat pump (HP)-based systems and one natural gas (NG)-based system for the production of heating and cooling energy in a single-house dwelling. The study considered systems based on: 1. A NG and auxiliary cooling unit; 2. Solely HP, 3. HP with additional seasonal heat storage (SHS) and a solar thermal collector (STC); 4. HP with SHS, a STC and a grey water (GW) recovery unit. The assessment of exergy efficiencies for each case was based on the transient systems simulation program TRNSYS, which was used for the simulation of energy use for space heating and cooling of the building, sanitary hot water production, and the thermal response of the seasonal heat storage and solar thermal system. The results show that an enormous waste of exergy is observed by the system based on an NG boiler (with annual overall exergy efficiency of 0.11) in comparison to the most efficient systems, based on HP water–water with a seasonal heat storage and solar thermal collector with the efficiency of 0.47. The same system with an added GW unit exhibits lower water temperatures, resulting in the exergy efficiency of 0.43. The other three systems, based on air–, water–, and ground–water HPs, show significantly lower annual source water temperatures (10.9, 11.0, 11.0, respectively) compared to systems with SHS and SHS + GW, with temperatures of 28.8 and 19.3 K, respectively.     

耦合太阳能和地热能的冷热电联供系统优化

天然气和可再生能源互补是一种并行解决环境污染和克服可再生能源不稳定的有效方式,本文提出一种耦合太阳能和地热能的混合冷热电联供(CCHP)系统。基于以电定热(FEL)和以热定电(FTL)运行策略,提出了地源热泵出力比依照逐时电价和季节而变化的运行模式;以一次能源节约率、费用年值节约率以及二氧化碳减排率为目标函数,建立CCHP系统优化模型,运用多目标遗传算法对系统配置及运行策略进行了寻优求解。结果表明:该混合CCHP系统在FEL模式能够实现最优的综合性能.     

Quantum heat engines, the second law and Maxwell's daemon

We introduce a class of quantum heat engines which consists of two-energy-eigenstate systems, the simplest of quantum mechanical systems, undergoing quantum adiabatic processes and energy exchanges with heat baths, respectively, at different stages of a cycle. Armed with this class of heat engines and some interpretation of heat transferred and work performed at the quantum level, we are able to clarify some important aspects of the second law of thermodynamics. In particular, it is not sufficient to have the heat source hotter than the sink, but there must be a minimum temperature difference between the hotter source and the cooler sink before any work can be extracted through the engines. The size of this minimum temperature difference is dictated by that of the energy gaps of the quantum engines involved. Our new quantum heat engines also offer a practical way, as an alternative to Szilard's engine, to physically realise Maxwell's daemon. Inspired and motivated by the Rabi oscillations, we further introduce some modifications to the quantum heat engines with single-mode cavities in order to, while respecting the second law, extract more work from the heat baths than is otherwise possible in thermal equilibria. Some of the results above are also generalisable to quantum heat engines of an infinite number of energy levels including 1-D simple harmonic oscillators and 1-D infinite square wells, or even special cases of continuous spectra.     

Thermodynamic characteristics of a Brownian heat pump in a spatially periodic temperature field

This paper has studied the thermodynamic performance of a thermal Brownian heat pump,which consists of Brownian particles moving at a periodic sawtooth potential with external forces and contacting with the alternating hot and cold reservoirs along the space coordinate.The heat flows driven by both potential and kinetic energies are taken into account.The analytical expressions for the heating load,coefficient of performance(COP) and power input of the Brownian heat pump are derived and the performance char...     

Comparative Assessment of Various Low-Dissipation Combined Models for Three-Terminal Heat Pump Systems

Thermally driven heat pump systems play important roles in the utilization of low-grade thermal energy. In order to evaluate and compare the performances of three different constructions of thermally driven heat pump and heat transformer, the low-dissipation assumption has been adopted to establish the irreversible thermodynamic models of them in the present paper. By means of the proposed models, the heating loads, the coefficients of performance (COPs) and the optimal relations between them for various constructions are derived and discussed. The performances of different constructions are numerically assessed. More importantly, according to the results obtained, the upper and lower bounds of the COP at maximum heating load for different constructions are generated and compared by the introduction of a parameter measuring the deviation from the reversible limit of the system. Accordingly, the optimal constructions for the low-dissipation three-terminal heat pump and heat transformer are determined within the frame of low-dissipation assumption, respectively. The optimal constructions in accord with previous research and engineering practices for various three-terminal devices are obtained, which confirms the compatibility between the low-dissipation model and endoreversible model and highlights the validity of the application of low-dissipation model for multi-terminal thermodynamic devices. The proposed models and the significant results obtained enrich the theoretical thermodynamic model of thermally driven heat pump systems and may provide some useful guidelines for the design and operation of realistic thermally driven heat pump systems.