基于新型S-CO2动力循环的内燃机余热回收

为了有效回收内燃机的废热,基于超临界CO₂(S-CO₂)再压缩循环,提出了一种新型的S-CO₂动力循环,并建立了相应的热力学模型,以分析系统的热力学性能,研究透平入口温度和系统压力对循环性能的影响。结果表明,在设计工况下,系统的净输出功为33.06 kW,热效率和效率分别可以达到35.86%和67.90%,余热回收率为58.70%。随着高压透平入口温度的升高,循环效率增加而净功减少。随着低压透平入口温度升高,循环效率和净功均增加。此外,存在再压缩机出口压力使净功和循环效率达到最大。     

余热型燃气-蒸汽联合循环热力特性参数的最优化

理论和实践证明,各种联合循环均存在有使循环热效率达最高值的热力特性参数最优化组合.寻求这样的最优化组合是十分重要的. 一、最优化数学模型 由热力学知,联合循环发电装置的热效率η是与燃气循环参数及系统、蒸汽循环参数及系统、燃料特性、各组成元件的内效率及压力保持系数、联合循环的型式、燃机与汽机功率比等诸因素有关的多元函数,很难求得解析表达式.本文选取次要影响因素为确定值,     

一种新型余热联产系统的性能优化研究

为满足用户夏季制冷冬季供热的多目标需求,本文提出了一种适用于中低温余热的新型冷电/热电联产系统。考虑经济收益,定义了系统在冷电联产和热电联产两种工作模式下的循环总效率,并以之为目标函数,采用蚁群优化算法,针对系统的关键运行参数,分别进行了自编程优化计算。结果表明:新系统在冷电联产和热电联产时,最优摩尔浓度分别为0.525和0.500,循环总效率分别为19.9%和20.0%;在相同余热工况下,与传统系统或已有联产系统相比,新系统循环总效率更高,是一种适用于低品位热源的多目标能源供应形式。     

注蒸汽燃气轮机循环与燃气-蒸汽轮机联合循环热力性能的比较

一、前言 燃气-蒸汽轮机联合循环(简称联合循环)在现有的技术水平上可使热效率达到40—50％以上。在注蒸汽燃气轮机循坏(简称注蒸汽循环)中,燃气轮机的排气通入补燃或不补燃的余热锅炉,锅炉产生的蒸汽回注到燃气轮机的燃烧室或其它适当部位,同燃气混合加热、膨胀做功,再进入余热锅炉。这一种循环方式也能达到很高的热效率,并可降低NO_x的排放,有利于环境保护。近来它们都有扩大应用的趋势。本文     

内燃机余热利用分流二氧化碳动力循环热匹配研究

二氧化碳动力循环在高效利用内燃机多股余热方面具有很大潜力,基于换热器分流的设计能够显著改善内燃机排气的利用情况。但是,当前研究仍缺少完善的热匹配性及参数分析,来综合权衡基于换热器的分流设计思路带来的热力学性能改变。因此,本文以热源理想匹配过程定义等效比定压热容物性作为出发点,阐述分流设计对于温度匹配机制的影响。结果发现了理想比热具有独特的双峰特性,而分流设计能够有效匹配双峰特性,显著改善外部热源利用率和内部热匹配性,继而提高系统净输出功。     

沼气内燃机烟气余热ORC热电联产系统研究

以青岛市某污水处理厂为例分析了该厂现有沼气热电联产系统存在能源利用率及?效率低的问题,并提出了内燃机烟气余热+ ORC热电联产的余热利用方式.通过对改进后系统经济性、环保性及热工性进行计算分析,得到改进后的系统在满足污水厂中温厌氧发酵需热量的前提下全年发电量可增加60.2万kW·h,预计2.67年可收回初投资成本,相比...     

太阳能燃气联合循环系统集成优化研究

太阳能燃气联合循环系统(ISCC)将槽式太阳能与燃气轮机联合循环相结合,充分利用太阳能作为中低温加热热源,是提高太阳能发电效率,降低太阳能发电成本,并减少系统CO_2排放的有效途径。本文针对太阳能直接蒸汽发生系统(DSG)与燃气轮机联合循环(CCGT)集成的系统,研究了太阳能蒸发给水份额对系统性能的影响,寻求最佳的系统集成模式,并对其经济性能做了初步的探讨。结果表明,太阳能蒸发给水份额为75%时,系统性能最优。     

液化天然气CCHP系统的乙烯-丙烷级联动力循环及工艺模拟

文中提出了一种适用于LNG冷热电联产系统的两级乙烯-丙烷级联朗肯动力循环,并采用HYSYS软件对这一级联动力循环进行了工艺模拟,LNG的流量为219kg/h时,共可以产生电力14.06W,并向空调供冷50.24kW.与不采用冷量回收的装置相比,总的能量利用率从83.22％提高到了85.17％.这说明级联式动力循环通过梯...     

褐煤热泵预干燥超临界CO2循环发电系统理论研究

褐煤含水量高,直接燃烧发电存在效率低、投资大的问题。为此,本文提出了一种集成褐煤热泵预干燥的超临界二氧化碳循环发电系统,并建立了超临界二氧化碳循环发电系统和褐煤热泵预干燥系统的耦合计算模型,以某660 MW发电系统为例,对直燃褐煤发电系统和褐煤热泵预干燥发电系统进行对比分析。结果表明：褐煤发电系统通过热泵干燥褐煤可以使系统发电效率提高1.44%,发电标准煤耗率降低8.06 g·(k Wh)^-1;分析发现,预干燥褐煤使得锅炉燃烧损降低高达4.47%,排烟耗散降低0.35%,从而使系统效率提高1.29%,燃烧损和排烟耗散降低是系统节能的主要原因;干燥机效率、褐煤干燥程度和热泵COP越高,褐煤热泵预干燥发电系统节能效果越显著。     

中型直膨式太阳能PVT热泵系统性能实验研究

对一种中型直膨式太阳能PVT(光伏/光热)热泵热电联产系统进行了实验研究。通过对PV(光伏)组件与直膨式集热/蒸发器的合理耦合构建PVT热泵系统,直膨式背板可吸收太阳能电池废热,降低太阳能电池温度,有效提高光伏组件发电效率,同时提高了热泵循环蒸发温度和蒸发压力,改善了热泵系统的运行性能。背板采用新型直膨式集热/蒸发器流道结构,结合PVT组件阵列管路设计,有效提升了冷媒分布均一性和PVT组件工作温度的均匀性。实验结果表明系统在热水模式下的平均COP(Coefficient of Performance)可达6.45,供暖模式的平均COP达4.24。系统所发电量可用于自身压缩机、水泵运行或并入电网,且提供55?C以上的热水,从而实现太阳能PVT热泵系统高效热电联产。     

超临界CO2布雷登循环热电联供系统多目标优化

本文研究了以超临界CO₂布雷登循环为原动机的热电联供系统,对系统主要运行参数进行了分析,得到运行参数对于系统热力学性能和经济性能的影响规律。同时,以一次能源利用率和单位输出成本作为目标函数,采用多目标遗传算法对系统进行了优化;在优化结果的基础上,通过TOPSIS法决策出最优解,并与单目标最优解进行对比。结果表明,透平进口温度、透平进口压力和压缩机进口温度的增大有利于系统效率的提高;作为代价,成本也相应增加。在热电比0~4范围内,尽可能增大热电比能够最大程度上降低系统的单位输出成本,提高能源的利用率。     

Performance Modulation of S-CO2 Brayton Cycle for Marine Low-Speed Diesel Engine Flue Gas Waste Heat Recovery Based on MOGA

(1) Background: the shipping industry forced ships to adopt new energy-saving technologies to improve energy efficiency. With the timing modulation for the marine low-speed diesel engine S-CO₂ Brayton cycle, the waste heat recovery system is optimized to improve fuel economy. (2) Methods: with the 6EX340EF marine low-speed diesel engine established in AVL Cruise M and verified by the bench test data, the model of the S-CO₂ Recompression Brayton Cycle (SCRBC) system for the low-speed engine flue gas waste heat recovery was developed in EBSILON, and verified by SANDIA experimental data. On this basis, the effects of injection timing and valve timing parameters on the comprehensive performance of the main engine and the waste heat recovery system were investigated. By optimizing the timing modulation parameters through multi-objective genetic algorithm (MOGA) and evaluating the flue gas waste heat recovery from the perspective of thermodynamic performance and emission reduction, the research on the performance modulation method of the S-CO₂ Brayton Cycle for flue gas waste heat in marine low-speed engines has been completed. (3) Results: the SCRBC with waste heat modulation will further increase the total power and efficiency, which in turn brings about a reduction in the fuel consumption rate. The efficiency of the SCRBC system with the addition of waste heat modulation increases by 2.28%, 1.04% and 2.07% at 50%, 75% and 100%, respectively. After adding the residual heat modulation, the maximum annual CO₂ emission reduction of 748.51 × 10³ kg·a⁻¹ occurred at 50% load; with the exergy analysis, the cooler has the largest system exergy loss of 165 kW, with the exergy loss efficiency of 2.06% under 100% load. (4) Conclusions: the research on the performance modulation method of S-CO₂ Brayton cycle for flue gas waste heat in the marine low-speed engine has been completed, which further improves the efficiency of the system and can be extended to other engines.     

基于热量流法的超临界CO2换热器性能分析

本文基于热量流法,应用进口温差定义的换热器通用热阻,采用分段法考虑超临界CO2的物性变化,结合能量守恒方程,构建了超临界CO2-冷却水换热过程的整体热量流拓扑模型,结合超临界CO2物性库和经验关联式提出了换热器性能分析的流程图,实现了综合考虑物性-结构-运行参数的超临界CO2-冷却水换热器的性能分析,进一步结合(积)耗...     

Evaluation of a Thermosyphon Heat Pipe Operation and Application in a Waste Heat Recovery System

Efficient and economical utilization of industrial waste heat would result in reduced energy use and thereby contribute to reduction of greenhouse gas emissions to the atmosphere. Two-phase thermosyphon technology has demonstrated the potential capability for waste heat recovery, but it has not been yet utilized in large-scale industrial applications. As a part of an industrial project, various types of thermosyphon heat pipes have been designed and tested for extraction of waste heat and process control in aluminum industry. This article presents the heat and mass transfer model, developed to provide a fast and accurate simulation tool for industrial application of thermosyphon heat pipe technology for waste heat utilization. The mathematical model considers the energy, momentum, and mass transfer equations, in their one-dimensional form, to predict output parameters of the thermosyphon and enable parametric and sensitivity analysis. The mathematical model structure is set up in a way that the least numerical cost and time is spent while the model accuracy is kept at acceptable level for the defined application. To provide experimental data for validation of the simulation model, the proposed thermosyphon was tested experimentally using a test set-up instrumented for this purpose. The simulation results are found to be in good agreement with the experimental data. The developed model and code are viable to be used as a simple and fast tool for modeling, design, and optimization of the thermosyphon as an element in a heat recovery module.     

Optimization of a New Design of Molten Salt-to-CO2 Heat Exchanger Using Exergy Destruction Minimization

One of the ways to make cost-competitive electricity, from concentrated solar thermal energy, is increasing the thermoelectric conversion efficiency. To achieve this objective, the most promising scheme is a molten salt central receiver, coupled to a supercritical carbon dioxide cycle. A key element to be developed in this scheme is the molten salt-to-CO₂ heat exchanger. This paper presents a heat exchanger design that avoids the molten salt plugging and the mechanical stress due to the high pressure of the CO₂, while improving the heat transfer of the supercritical phase, due to its compactness with a high heat transfer area. This design is based on a honeycomb-like configuration, in which a thermal unit consists of a circular channel for the molten salt surrounded by six smaller trapezoidal ducts for the CO₂. Further, an optimization based on the exergy destruction minimization has been accomplished, obtained the best working conditions of this heat exchanger: a temperature approach of 50 °C between both streams and a CO₂ pressure drop of 2.7 bar.     

铅基堆超临界CO2复合循环发电系统热力学分析

本文对比了再压缩超临界CO2 (S-CO2)循环、蒸汽朗肯循环、He布雷顿循环分别应用于铅基堆的最优热学性能,明确了S-CO2循环与铅基堆结合较传统循环的热力学优势。为进一步提高再压缩S-CO2循环的效率,以跨临界CO2 (T-CO2)循环为底循环构建了再压缩S-CO2/T-CO2复合循环,探讨了不同顶循环透平入口温度、压力和压缩机入口温度条件下系统性能的变化规律,对比了S-CO2/T-CO2复合循环和S-CO2循环的热学性能。结果表明:铅基堆再压缩S-CO2循环发电系统较传统循环形式具有更高的热效率;构建的S-CO2/T-CO2复合循环能够有效提高S-CO2循环的效率,在所研究参数范围内,S-CO2/T-CO2复合循环的热效率和效率比S-CO2循环分别最大可提高约4.8%和8.3%;再压缩S-CO2循环和S-CO2/T-CO2复合循环热学性能随顶循环关键参数变化规律具有一致性。     

Thermodynamic Analysis and Optimization of a Novel Power-Water Cogeneration System for Waste Heat Recovery of Gas Turbine

A power-water cogeneration system based on a supercritical carbon dioxide Brayton cycle (SCBC) and reverse osmosis (RO) unit is proposed and analyzed in this paper to recover the waste heat of a gas turbine. In order to improve the system performance, the power generated by SCBC is used to drive the RO unit and the waste heat of SCBC is used to preheat the feed seawater of the RO unit. In particular, a dual-stage cooler is employed to elevate the preheating temperature as much as possible. The proposed system is simulated and discussed based on the detailed thermodynamic models. According to the results of parametric analysis, the exergy efficiency of SCBC first increases and then decreases as the turbine inlet temperature and split ratio increase. The performance of the RO unit is improved as the preheating temperature rises. Finally, an optimal exergy efficiency of 52.88% can be achieved according to the single-objective optimization results.     

Modeling and Performance Optimization of an Irreversible Two-Stage Combined Thermal Brownian Heat Engine

Based on finite time thermodynamics, an irreversible combined thermal Brownian heat engine model is established in this paper. The model consists of two thermal Brownian heat engines which are operating in tandem with thermal contact with three heat reservoirs. The rates of heat transfer are finite between the heat engine and the reservoir. Considering the heat leakage and the losses caused by kinetic energy change of particles, the formulas of steady current, power output and efficiency are derived. The power output and efficiency of combined heat engine are smaller than that of single heat engine operating between reservoirs with same temperatures. When the potential filed is free from external load, the effects of asymmetry of the potential, barrier height and heat leakage on the performance of the combined heat engine are analyzed. When the potential field is free from external load, the effects of basic design parameters on the performance of the combined heat engine are analyzed. The optimal power and efficiency are obtained by optimizing the barrier heights of two heat engines. The optimal working regions are obtained. There is optimal temperature ratio which maximize the overall power output or efficiency. When the potential filed is subjected to external load, effect of external load is analyzed. The steady current decreases versus external load; the power output and efficiency are monotonically increasing versus external load.     

乳品行业低温余热回收系统性能分析

针对乳品行业排风风量大但品位低的特点,本文提出利用排风余热代替蒸汽来预热干燥空气的余热回收系统.在构建预热器、回热器和主加热器等部件热量流模型的基础上,建立了不包含中间节点参数的系统整体热量流模型.结合某奶粉厂运行数据对模型进行求解,结果表明,该系统将排风温度由90℃降低到42.58℃.在给定热负荷下,通过匹配中间回路...