低温空气制冷系统中板翅换热器性能实验研究

对低温空气制冷系统中的散热器、回热器性能进行实验研究,测量不同工况条件下两个锯齿形板翅式换热器的换热效率及系统性能,分析了换热器低压侧和高压侧的空气流量对换热器及系统性能的影响。结果表明:(1)散热器低压侧空气流量是影响其效率的主要因素;(2)回热器效率随其低压侧空气流量的增大而增大,随其高压空气流量的增大而减小;(3)高压空气流量是影响制冷量的主要因素;在其它工况参数不变的条件下,高压空气流量增大7.9%,制冷量最大增加14.5%。     

Optimisation thermodynamique en temps fini du moteur de Stirling endo- et exo-irréversible

Finite-time thermodynamics optimisation of an endo- exo-irreversible Stirling Motor. This work deals with the finite time thermodynamic optimization of a Stirling engine. An endo- and exo-irreversible cycle is considered. The internal irreversibilities are due to the internal conductance of the plant and to the non-adiabatic regenerator. Also, the general irreversibilities of the non-quasistatic cycle are taken into account. The external irreversibilities are due to the linear interactions between the heat sources and the working fluids at finite temperature gaps.A sensitivity analysis was performed in order to optimize the operation conditions leading to maximum power output. The results obtained are in good agreement with the experimental data.     

Microcomputer-based design of rotary regenerators

A software package was written in BASIC for the IBM PC based on the ϵ-NTU_o method for counterflow rotary regenerator heat transfer analysis taking into account the effects of longitudinal and transverse heat conduction in the matrix wall together with the influence of fluid bypass and carryover. It was tested for accuracy by comparing the software-generated results with results from case studies in the literature. A comparison with actual operating data of a regenerator used for waste heat recovery in an electric power generation facility showed that the software can predict the regenerator outlet temperatures to within 3.5 percent.     

Reprint of : Thermoelectricity without absorbing energy from the heat sources

We analyze the power output of a quantum dot machine coupled to two electronic reservoirs via thermoelectric contacts, and to two thermal reservoirs – one hot and one cold. This machine is a nanoscale analogue of a conventional thermocouple heat-engine, in which the active region being heated is unavoidably also exchanging heat with its cold environment. Heat exchange between the dot and the thermal reservoirs is treated as a capacitive coupling to electronic fluctuations in localized levels, modeled as two additional quantum dots. The resulting multiple-dot setup is described using a master equation approach. We observe an “exotic” power generation, which remains finite even when the heat absorbed from the thermal reservoirs is zero (in other words the heat coming from the hot reservoir all escapes into the cold environment). This effect can be understood in terms of a non-local effect in which the heat flow from heat source to the cold environment generates power via a mechanism which we refer to as Coulomb heat drag. It relies on the fact that there is no relaxation in the quantum dot system, so electrons within it have a non-thermal energy distribution. More poetically, one can say that we find a spatial separation of the first-law of thermodynamics (heat to work conversion) from the second-law of thermodynamics (generation of entropy). We present circumstances in which this non-thermal system can generate more power than any conventional macroscopic thermocouple (with local thermalization), even when the latter works with Carnot efficiency.     

Thermoelectricity without absorbing energy from the heat sources

We analyze the power output of a quantum dot machine coupled to two electronic reservoirs via thermoelectric contacts, and to two thermal reservoirs – one hot and one cold. This machine is a nanoscale analogue of a conventional thermocouple heat-engine, in which the active region being heated is unavoidably also exchanging heat with its cold environment. Heat exchange between the dot and the thermal reservoirs is treated as a capacitive coupling to electronic fluctuations in localized levels, modeled as two additional quantum dots. The resulting multiple-dot setup is described using a master equation approach. We observe an “exotic” power generation, which remains finite even when the heat absorbed from the thermal reservoirs is zero (in other words the heat coming from the hot reservoir all escapes into the cold environment). This effect can be understood in terms of a non-local effect in which the heat flow from heat source to the cold environment generates power via a mechanism which we refer to as Coulomb heat drag. It relies on the fact that there is no relaxation in the quantum dot system, so electrons within it have a non-thermal energy distribution. More poetically, one can say that we find a spatial separation of the first-law of thermodynamics (heat to work conversion) from the second-law of thermodynamics (generation of entropy). We present circumstances in which this non-thermal system can generate more power than any conventional macroscopic thermocouple (with local thermalization), even when the latter works with Carnot efficiency.     

All-optical 2R regeneration using passive saturable absorption

This paper reports on the regenerative properties and efficiency of an all-optical 2R regenerator based on a tandem of saturable absorber (SA) chips. A new SA structure allowing mark level equalization, which is a complement to the function of extinction ratio enhancement of the classical SA structure, is described. The experimental results at 42.6 Gbit/s show that amplitude fluctuations on both low and high power levels are significantly reduced with the SA tandem regenerator, and the system margin improvements in terms of receiver sensitivity and Q factor are obtained.     

Method of monitoring and measuring seal clearances in a rotary heat exchanger

A new method of measuring and monitoring seal clearances in a rotary heat exchanger is presented. The measuring and monitoring system consists of: a special instrument; linear displacement transducer; digitial display unit and loop oscillograph. The method proposed is described and illustrated by the results obtained during hot and cold rotation. The procedure was carried out for two rotary regenerators, 5.3 and 9.4 m in diameter.     

基于动态故障树的核电站蒸汽发生器液位控制系统可靠性研究

蒸汽发生器作为压水堆核电站一、二回路之间重要的连接设备,蒸汽发生器液位控制系统(Steam Generator Water Level Control System,SGWLCS)的可靠性直接影响核电站的安全性与发电效率.基于蒸汽发生器液位控制系统的系统构成与控制逻辑,本工作采用动态故障树对SGWLCS进行可靠性建模,...     

The advanced steam and gas technology

One of the directions of creating advanced gas and steam power units is usage of new working substances (freons) in the steam turbine stage. This paper presents the authors’ method for estimation (which is the scientific novelty) and results of calculating the efficiency and design-layout parameters of assemblies of a steamand gas power unit (SGU)with the freon technology. It is shown that the use of freons with supercritical parameters in SGU makes it possible to obtain efficiency on a level of 58% and apply more compact (compared to conventional) turbines and once-through recovery boilers, and a regenerator and condenser whose design-layout parameters are comparable with similar conventional designs.     

新型多能源互补系统的热力经济性分析

本文对SOLRGT系统（一种新型的中低温太阳能与化石燃料互补的动力系统）进行了热力经济性分析。该系统基于化学回热循环,通过中低温太阳能品位的间接提升、与先进燃气轮机的集成,实现中低温太阳能的高效、低成本热功转换以及和化石燃料的综合梯级利用。本文将其与同等输入下的两种单输入发电系统进行对比分析,研究表明：基本工况下,SO...     

半导体温差发电过程的模型分析与数值仿真

本文提出一种新型的半导体温差发电模型,在温差发电过程的数值模拟中考虑了热电单元之间封闭腔体内空气传热的影响.同时进一步运用有限元的数值计算方法对不同电臂对数和不同型号温差发电模型的温度场、电压场进行了数值仿真计算,并对仿真结果进行分析.结果表明:采用127对热电单元模型计算的能量转换效率随冷热端温差增大而迅速提高,与采用1对热电单元模型计算的能量转换效率之差从冷热端温差为20℃的0.39%提高到冷热端温差为220℃时的5.16%,能量转换效率比1对热电单元平均高出3.02%.冷端温度恒定在30℃时,温差发电芯片的输出电压、功率以及能量转换效率均随着电偶臂的横截面积的增大而提高,且电偶臂冷热两端的温差越大提高幅度也越大,而温差发电芯片内阻则与电偶臂横截面积成反比关系,当温差为220℃时对应的输出功率最高达28.9 W.     

新型高效汽水分离器的试验研究

汽水分离装置是核电站蒸汽发生器净化蒸汽的重要部件,其性能不仅会影响蒸汽发生器的上筒体尺寸、水循环性能及水位的稳定性,而且还会影响汽轮机的正常运行。由于波形板内的两相流动过程很复杂,目前国外对汽水分离器的研究仍以实验为主。本文则针对冷态条件下新型波形板汽水分离器的分离性能进行了试验研究,验证了二次携带现象的存在,并测量了双钩波形板汽水分离器的分离效率和压降,分析了挡板对分离效率的影响,获得了计算双钩波形板分离效率的经验公式,为波形板分离器的优化设计奠定了基础。     

Energy and exergy analysis of a solid oxide fuel cell plant fueled by ethanol and methane

The method of exergy analysis is presented for a SOFC power plant involving external steam reforming and fueled by ethanol and methane. The optimal operation parameters of the integrated SOFC plant are specified after minimizing the existing energy and exergy losses. A comparison of methane and ethanol as appropriate fuels for a SOFC-based power plant is provided in terms of exergetic efficiency assuming the minimum allowable (for carbon-free operation) reforming factors for both cases. Then, a parametric analysis provides guidelines for practical design. It is concluded that the exergy calculations pinpoint the losses accurately and that the exergy analysis gives a better insight of the system's process. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002.     

Ecological optimization for an irreversible magnetic Ericsson refrigeration cycle

An irreversible Ericsson refrigeration cycle model is established, in which multi-irreversibilities such as finite-rate heat transfer, regenerative loss, heat leakage, and the efficiency of the regenerator are taken into account. Expressions for several important performance parameters, such as the cooling rate, coefficient of performance （COP）, power input, exergy output rate, entropy generation rate, and ecological function are derived. The influences of the heat leakage and the time of the regenerative processes on the ecological performance of the refrigerator are analyzed. The optimal regions of the ecological function, cooling rate, and COP are determined and evaluated. Furthermore, some important parameter relations of the refrigerator are revealed and discussed in detail. The results obtained here have general significance and will be helpful in gaining a deep understanding of the magnetic Ericsson refrigeration cycle.     

电站中液化天然气可用冷能的回收利用

液化天然气（ＬＮＧ）具有大量可用冷能。本文提出一种高效回收ＬＮＧ可用冷能的方法,即以蒸汽动力循环中气轮机排出的乏气为热源,结合天然气直接膨胀和二次冷媒动力循环。并对该循环进行了详细分析,对其参数进行了优化。利用这种方法,ＬＮＧ可用冷能的回收效率可达５５％左右。     

Optimization Modeling of Irreversible Carnot Engine from the Perspective of Combining Finite Speed and Finite Time Analysis

An irreversible Carnot cycle engine operating as a closed system is modeled using the Direct Method and the First Law of Thermodynamics for processes with Finite Speed. Several models considering the effect on the engine performance of external and internal irreversibilities expressed as a function of the piston speed are presented. External irreversibilities are due to heat transfer at temperature gradient between the cycle and heat reservoirs, while internal ones are represented by pressure losses due to the finite speed of the piston and friction. Moreover, a method for optimizing the temperature of the cycle fluid with respect to the temperature of source and sink and the piston speed is provided. The optimization results predict distinct maximums for the thermal efficiency and power output, as well as different behavior of the entropy generation per cycle and per time. The results obtained in this optimization, which is based on piston speed, and the Curzon–Ahlborn optimization, which is based on time duration, are compared and are found to differ significantly. Correction have been proposed in order to include internal irreversibility in the externally irreversible Carnot cycle from Curzon–Ahlborn optimization, which would be equivalent to a unification attempt of the two optimization analyses.     

Influence of thermomechanical processing on shear bands formation and magnetic properties of a 3% Si non-oriented electrical steel

The effect of thermomechanical processing on the formation of shear bands and on the magnetic properties of a 3.0 wt% silicon non-oriented steel was investigated by hot rolling samples with different thicknesses at different temperatures, in order to obtain a variation in hot band grain size and cold strain. All the samples were processed in a single-stage cold rolling and finally annealed at 1020 °C. It was found that the increase of the hot band grain size decreases the γ fiber volume fraction and increases the η fiber volume fraction after the final annealing. The increase of the cold strain strongly contributed to this result. A good combination of intense generation of shear bands, and proper crystallographic texture, due to higher nucleation of grains with favorable orientations to magnetization in these bands, can be obtained for the samples hot rolled at 1000 and 1120 °C and submitted to cold strain of 64.3% and 72.2% respectively. However the best combination of B₅₀, W_15/60 and μ_r can be obtained by hot rolling the samples at 1000 °C to the thickness of 1.4 mm, corresponding to 64.3% of cold strain.     

S-CO2布雷顿循环转化效率分析

以超临界二氧化碳简单回热型布雷顿循环为研究对象,以核电站为应用背景,详细论述了系统循环模型与关键器部件的效率模型建立方法,并利用该模型初步分析了各类工程因素对布雷顿循环效率、系统体积的影响,分析结果表明,循环效率、系统体积对温度、压力、涡轮机械效率、回热器等参数的敏感性存在较大差异,其中增加透平入口温度对缩减系统总体积最为有效,需要建立完善的系统分析模型以进行S-CO₂系统的优化设计。     

高频线性斯特林制冷机的性能测试和分析

线性压缩机 SL 4 0 0用于红外探测器及超导应用的高频同轴式脉管制冷机的研制。在不同的输入功率、不同的工作频率下 ,测试了 SL 4 0 0型压缩机驱动 SL 2 0 0型及 SL 10 0型斯特林制冷机冷指的制冷性能。输入功率在 10 W～ 10 0 W范围内调整 ,输入功率为 5 0 W时 ,在 4 0 Hz～ 6 0 Hz变化压缩机的工作频率 ,测试和计算制冷机的 COP系数及压缩机的效率。对制冷机冷指不同放置方向时的制冷性能作了测试 ;比较了散热片风冷及水冷情况下制冷机的性能 ;得出了 SL4 0 0型压缩机的工作特性。     

Development and Analysis of the Novel Hybridization of a Single-Flash Geothermal Power Plant with Biomass Driven sCO2-Steam Rankine Combined Cycle

This study investigates the hybridization scenario of a single-flash geothermal power plant with a biomass-driven sCO₂-steam Rankine combined cycle, where a solid local biomass source, olive residue, is used as a fuel. The hybrid power plant is modeled using the simulation software EBSILON^®Professional. A topping sCO₂ cycle is chosen due to its potential for flexible electricity generation. A synergy between the topping sCO₂ and bottoming steam Rankine cycles is achieved by a good temperature match between the coupling heat exchanger, where the waste heat from the topping cycle is utilized in the bottoming cycle. The high-temperature heat addition problem, common in sCO₂ cycles, is also eliminated by utilizing the heat in the flue gas in the bottoming cycle. Combined cycle thermal efficiency and a biomass-to-electricity conversion efficiency of 24.9% and 22.4% are achieved, respectively. The corresponding fuel consumption of the hybridized plant is found to be 2.2 kg/s.