小型热电站热电联产Yong分析及节能评价

采用Yong平衡分析法,分别对小型热电联产系统和分散锅炉房供热系统进行了Yong流分析,把两者计算所得Yong效率作一对比,从而得出热电联产系统是取代分散锅炉房供热的节能措施之一,同时还对热电联产系统内各环节中的Yong流损失进行计算,得出各热力设备的Yong效率,找出系统用能不合理的主要薄弱环节,为今后设备的工艺过程改进指出了方向。     

小型热电站热电联产分析及节能评价

采用平衡分析法,分别对小型热电联产系统和分散锅炉房供热系统进行了流分析,把两者计算所得效率作一对比,从而得出热电联产系统是取代分散锅炉房供热的节能措施之一。同时还对热电联产系统内各环节中的流损失进行计算,得出各热力设备的效率,找出系统用能不合理的主要薄弱环节,为今后设备的工艺过程改进指出了方向。     

对工业锅炉节能措施的探讨

探讨工业锅炉的节能措施,从蒸汽的有效利用,管道保温,热水供暖,区域锅炉房集中供热,热电联产等几方面来探讨工业锅炉的节能。     

移动式供热装置

自1980年以来,由于国家确定了节约能源的方针,各地热电联产、集中供热,联片供热事业有了较快的发展。热电联产集中供热,热效率高,能大量节约能源,是发展的方向,但由于它的一次投资高、建设周期长、建设难度大,一般黄河以北的北方城市,这种形式的供热量不超过总量的10%,大量采用的还是锅炉房集中供热或联片供热。北京市近年来城市建设中新开发的居民小区,绝大多数是采用联片(锅炉房)供热。居民小区的建筑面积一般在几十万平方米至几百万平方米。由于小区的建筑面积是逐步递增     

积极发展小热电的政策信息

最近能源部向国务院建议制订关于改造小锅炉、大力发展小型热电联产的一些政策。目前我国约有40万台小锅炉,每年耗煤约三亿吨,约占全国煤炭总产量的30%。如将其中10～15%改造为热电联产,相当于1000万千瓦发电容量,既可满足供热,每年又可增加发电量400～500亿度,节约原煤约2000万吨,同时消除这些小锅炉有利于减轻环境污染,经济效益也很好。为此拟在五至七年内更新改造一批工业锅炉,建成1000万千瓦小热电。     

我国热电联产集中供热能发展现状、问题与建议

热电联产集中供热是一种公认的节能环保技术,目前我国的热电联产规模已经位居世界第二位。在回顾分析我国的热电联产集中供热相关政策的基础上,本文研究了我国热电联产集中供热的市场发展现状,并分析了我国热电联产集中供热的市场潜力。分析结果表明,大力发展热电联产集中供热将可在“十一五”期末形成1亿tce以上的节能能力,从而为推动实现我国的节能减排目标做出更大贡献。文章进一步分析了挖掘热电联产集中供热节能潜力面临的主要障碍,并提出了促进我国热电联产集中供热发展的政策建议。     

yong分析在小型热电站热电联产中的应用

本文采用yong平衡分析法,对小型热电站的热电联产系统进行了yong流分析,得出热电联产系统相比于分散锅炉房的供热系统来讲是具有一定的节能效果的,同时还对热电联产系统内各环节中的yong流损失进行计算,得出各热力设备的yong效率,找出系统用能不合理的主要薄弱环节,为今后设备的工艺过程改进指出了方向。     

哈尔滨市王兆小区供热节能改造

目前北方城市居民区的冬季采暖除采用热电厂集中供热外,还在相当多的居民小区采用供热锅炉房供暖。这些小区的供暖面积一般在10万m~2以上,与分散采暖比较,提高了燃料利用率,取得了明显的节能效果,减轻了环境污染。但从能源合理利用角度出发,单纯的集中供热还没有实现能源的梯级利用,节能还有潜力。如在新建的供热锅炉房或对现有的供热锅炉房进行节能改造时实行热电联供,既供热又供电,必将产生明显的节能效果和社会效益。     

热电厂的经济运行

热电联产、集中供热是一项合理利用能源、大量节约能源的重要措施。建国以来,通过不断的实践、认识,热电联产在节能和改善大气环境等方面的作用,正在广泛深入地被人们所认识和接受。热电厂的节能来自两个方面:一是与分散供热相比,热电厂的锅炉效率一般在90％左右,远比工业小锅炉40～60％的运行效率     

关于我国住宅小区及建筑供暖系统节能途径的探讨

我国城市的供暖将逐步发展热电合产,走集中供热的道路。由于发展热电合产和城市供热管网的初投资较高,不可能在短时期内加以解决,因此,在目前阶段,城区的供暖将基本上通过分区合理规划,首先实现联片供暖的小区锅炉房,减少分散的小型锅炉房,并为大部分居住建筑将来与城市供热管网相连接创造条件。位处郊区的大专院校、医疗单位、军事单位等,其与城市供热管网相连接的可能性比城区或住宅小区更为遥远,因而将长期地由自备的小区锅炉房解决供暖的需要。     

具有热阻和热漏的联合普适和朗肯热机循环性能分析

用有限时间热力学的方法分析联合循环, 导出了存在热阻和热漏损失时,由两个绝热过程、一个加热过程和一个放热过程组成的空气标准普适循环和郎肯循环组成的联合动力循环的性能特性,并由数值计算分析了热阻和热漏对联合循环的输出功率和效率的影响,所得结果包含了顶循环为Carnot、 Otto、 Brayton、 Diesel、 Atkinson和 Braysson循环时联合循环的特性.当热源温度和工质流量相同时,联合热机的最佳功率、效率以及工作范围关系:Carnot和Rankine>Brayton和Rankine>Otto和Rankine;相同条件下如果换热器热导率为定值,联合热机的最佳功率、效率关系:Brayson和Rankine> Brayton和Rankine>Diesel和Rankine>Atkinson和Rankine>Otto和Rankine.     

Mass and heat transfer enhancement of chemical heat pumps

An inert additive, expanded graphite (EG), has been prepared and used to enhance the heat and mass transfer process of chemical heat pumps. The effects of mixing ratio and mixing method on the chemical reaction time are investigated.     

Numerical studies on flow and heat transfer in membrane helical-coil heat exchanger and membrane serpentine-tube heat exchanger

The flow and heat transfer characteristics of synthesis gas (syngas) in membrane helical-coil heat exchanger and membrane serpentine-tube heat exchanger under different operating pressures, inlet velocities and pitches are investigated numerically. The three-dimensional governing equations for mass, momentum and heat transfer are solved using a control volume finite difference method. The realizable k-ε model is adopted to simulate the turbulent flow and heat transfer in heat exchangers. There flows syngas in the channels consisting of the membrane helical coils or membrane serpentine tubes, where the operating pressure varies from 0.5 to 3.0 MPa. The numerically obtained heat transfer coefficients for heat exchangers are in good agreement with experimental values. The results show that the syngas tangential flow in the channel consisting of membrane helical coils is significant to the heat transfer enhancement to lead to the higher average heat transfer coefficient of membrane helical-coil heat exchanger compared to membrane serpentine-tube heat exchanger. The syngas tangential velocity in the membrane helical-coil heat exchanger increases along the axial direction, and it is independent of the gas pressure, increasing with the axial velocity and axial pitch rise and decreasing with the radial pitch rise.     

Boiling heat transfer and critical heat flux in liquid films falling on vertically-mounted heat sources

Boiling heat transfer measurements were obtained for an inert fluorocarbon (FC-72) liquid film injected over a vertical heated wall. Flow visualization revealed that vigorous boiling prior to burnout ruptured the liquid continuum, causing most of the film to separate from the heated wall leaving a thin liquid subfilm which maintained contact with the wall. The critical heat flux (CHF) was accompanied by dryout of the subfilm after total separation of the liquid near the upstream edge of the heater. A higher CHF was achieved by increasing the film velocity or by utilizing a shorter heater. Experimental data correlated favorably with predictions of a CHF model based on the Helmholtz instability and subfilm dryout.     

石墨烯-PFA复合材料换热器与金属换热器的传热性能对比

氟塑料换热器以其耐腐蚀、耐磨损等优点而备受关注,但氟塑料热导率较低,换热能力差,限制了其广泛应用。石墨烯-PFA复合材料兼具石墨烯优异的导热性和可熔性聚四氟乙烯(PFA)良好的耐酸碱腐蚀性,是新一代的换热器材料。搭建了余热回收测试实验台,对石墨烯-PFA复合材料换热器和金属换热器的传热性能进行对比。研究了不同烟气流速、不同进口烟气温度以及不同石墨烯配比对复合材料传热性能的影响。结果表明:对于金属换热器和复合材料换热器,当烟气流速从2.0增加到4.0 m/s时,传热系数分别增加到原来的1.19和1.34倍;随着进口烟温的升高,两种材质的传热系数分别降低了15.6%和14.7%;随着石墨烯含量增加,复合材料的导热系数以及传热系数均增加。     

“制冷、制热、卫生热水”型空气源热泵系统及分析

提出一种小型中央空调用“制冷、制热、卫生热水”型空气源热泵系统设计方案,能够利用空调部分冷凝热提供生活用卫生热水,该系统可与家用中央热水系统连接。     

Temperature Distribution and Heat Saturating Time of Regenerative Heat Transfer

In this paper, heat transfer of the ceramic honeycomb regenerator was numerically simulated based on the computational fluid dynamics numerical analysis software CFX5. The longitudinal temperature distribution of regenerator and gas were obtained. The variation of temperature with time was discussed. In addition, the effects of some parameters such as switching time, gas temperature at the inlet of regenerator, height of regenerator and specific heat of the regenerative materials on heat saturating time were discussed. It provided primarily theoretic basis for further study of regenerative heat transfer mechanism.     

Comparison of heat storage systems employing sensible and latent heat

This study makes an evaluation of the performances of heat storage systems destined for power plants with a discontinuous power source such as nuclear fusion. Two classes of heat storage systems are investigated: heat storage systems based on first sensible heat storage and second latent heat storage. Both classes of heat storage systems are evaluated both from a thermodynamic point of view, inquiring whether the irreversibility of the system stays limited or not, and from an economic point of view, examining whether the system makes proper use of the heat storage capacity present. It is shown that an unambiguous conclusion that one is superior to the other is not possible and that the operating conditions and the configuration of the phase‐changing materials play an important role. Copyright © 1999 John Wiley & Sons, Ltd.     

Fluid flow and heat transfer characteristics of cross-cut heat sinks

In this study, effects of cross-cuts on the thermal performance of heat sinks under the parallel flow condition are experimentally studied. To find effects of the length, position, and number of cross-cuts, heat sinks with one or several cross-cuts ranging from 0.5 mm to 10 mm were fabricated. The pressure drop and the thermal resistance of the heat sinks are obtained in the range of 0.01 W<P_p < 1 W. Experimental results show that among the many cross-cut design parameters, the cross-cut length has the most significant influence on the thermal performance of heat sinks. The results also show that heat sinks with a cross-cut are superior to heat sinks containing several cross-cuts in the thermal performance. Based on experimental results, the friction factor and Nusselt number correlations for heat sinks with a cross-cut are suggested. Using the proposed correlations, thermal performances of cross-cut heat sinks are compared to those of optimized plate-fin and square pin-fin heat sinks under the constant pumping power condition. This comparison yields a contour map that suggests an optimum type of heat sink under the constraint of the fixed pumping power and fixed heat sink volume. The contour map shows that an optimized cross-cut heat sink outperforms optimized plate-fin and square pin-fin heat sinks when 0.04 < log L1 < 1.