利用吸收式热泵的电厂乏汽余热回收性能分析

吸收式热泵回收电厂凝汽余热已得到不少工程应用,但是很多情况下运行效果并不理想。本文分别针对影响吸收式热泵性能的因素,如采暖抽汽压力、背压以及一次网温度参数进行讨论,着重分析这些因素对热源供热能力及供热能耗的影响。分析结果显示,抽汽压力较高可增加热泵的升温幅度,多回收凝汽余热,提高热源的供热能力,但由于抽汽供热份额较大,抽汽压力越高使得热源供热煤耗越高。通过适当提高背压同样能多回收凝汽余热,提高热源供热能力,并降低热源供热能耗。而降低一次网回水温度可通过凝汽器直接换热,提高凝汽供热份额,一方面可提高热源供热能力,另一方面可显著降低吸收式热泵供热系统的能耗。降低一次网供水温度虽然可降低热源的供热能耗,但是热网输送能力可能受限,且会增加热网输配能耗,因此应综合考虑。总的来看,降低一次网回水温度并配合提高背压是降低热源供热能耗的有效途径。

溴化锂吸收式热泵回收循环水余热的模拟研究

循环水的余热造成环境热污染,同时也损失了大量的热能。对此,利用吸收式热泵对其进行回收利用。以某200 MW抽凝机组及其供热系统为例,采用Aspen Plus软件建立单、双效溴化锂吸收式热泵模型,并进行变工况模拟对比分析。研究结果表明:当热泵出口热网水温度升高或热泵驱动汽源汽量增加时,单、双效循环热泵热力系数均降低;在相同热泵出口热网水温度下,双效循环比单效循环节省蒸汽率约30%;当采用多效循环且热泵出口热网水温度高于90℃时,可采用热泵先将热网回水加热到90℃左右,然后采用尖峰加热器加热热网水到需要的温度,以保证系统稳定运行。

PM2.5问题与热电联产行业

由于我国大气污染形势严峻,国务院在2013年9月发布《大气污染防治行动计划》,各地方政府纷纷采取多项措施治理大气污染。总体上看,这些治理措施将对热电联产行业产生正面的影响,但也将不可避免地出现某些负面影响。本文将对此进行探讨,并提出5项具体的研究项目供本行业的行政管理人员和技术人员参考。

基于径向基函数随机响应面法的综合能源系统概率能流计算

该文提出一种基于径向基函数随机响应面法的综合能源系统概率能流计算方法。首先,推导热网节点温度方程,验证并分析混沌多项式随机响应面法和稀疏混沌多项式随机响应面法计算热网节点温度时的局限性;然后,建立径向基函数随机响应面模型并利用线性多项式扩充模型,同时改进其配点方式。在此基础上,提出适用于综合能源系统概率能流计算的径向基函数随机响应面法并给出详细计算流程;最后,采用标准算例和实际算例进行有效性验证和性能评估。算例结果表明,该文所提方法在对含热网的综合能源系统进行概率能流计算时具有良好的计算精度和效率。

Determining heating pipe temperature in greenhouse using proportional integral plus feedforward control and radial basic function neural-networks

Proportional integral plus feedforward (PI+FF) control was proposed for identifying the pipe temperature in hot water heating greenhouse. To get satisfying control result, ten coefficients must be adjusted properly. The data for training and testing the radial basic function (RBF) neural-networks model of greenhouse were collected in a 1028 m2 multi-span glasshouse. Based on this model, a method of coefficients adjustment is described in this article.

Synthesis of Flexible Heat Exchanger Networks with Stream Splits Based on Rangers of Stream Supply Temperatures and Heat Capacity Flowrates

A new superstructure model of heat exchanger networks (HEN) with streamsplits based on rangers of streams supply temperatures and heat capacity flow rates is presented.The simultaneous optimal mathematical model of flexible HEN synthesis is established too. Firstly,the streams with rangers of supply temperatures and/or the streams with the rangers of heat capacityflow rates are pretreated; Secondly, several rules are proposed to establish the superstructuremodel of HEN with splits and the simultaneous optimal mathematical model of flexible HEN; Thirdly,the improving genetic algorithm is applied to solve the mathematical model established at the secondstep effectively, and the original optimal structure of HEN based on the maximum operation limitingcondition can be obtained easily; Finally, the rules of heat exchange unit merged and the heat loadof heat exchanger relaxed are presented, the flexible configuration of HEN satisfied the operationcondition between the upper and down bounds of supply temperature and heat capacity flow rates canbe obtained based on the original optimal structure of HEN by means of these rules. A case studydemonstrates the method presented in this paper is effective

An area method for visualizing heat-transfer imperfection of a heat exchanger network in terms of temperature–heat-flow-rate diagrams

The identification of the imperfection originating from finite-temperature-difference heat transfer is an indispensable step for both the performance analysis and the better design of a heat exchanger network （HEN） with the aim of energy saving. This study develops a convenient area method for visualizing the heat-transfer imperfection of a HEN in terms of temperature-heat flow diagrams （ T-Q diagrams） by combining the composite curves that have already been used in pinch analysis and the re- cently developed entransy analysis. It is shown that the area between the hot and cold composite curves and the hot and cold utility lines on a T-Q diagram is just equal to the total entransy dissipation rate during the multi-stream heat transfer process occurred in a HEN, and this area can be used to graphically represent the total heat-transfer imperfection of the HEN. The increase in heat recovery or decrease in energy requirements with decreasing the minimum temperature difference, ATmin, of a HEN can then be attributed to a lower entransy dissipation rate, quantitatively represented by the decrease of the area between the composite curves and the utility lines. In addition, the differences between the T-Q diagram and the pre-existing energy level-enthalpy flow diagram （12-H diagram） in the roles of visualizing process imperfection and designing HENs are dis- cussed.

Study on the onset temperature of a standing-wave thermoacoustic engine based on circuit network theory

Onset mechanism is one of the most fundamental issues in thermoacoustic field.However,the onset conditions and the phenomena happening in the onset process have not been well explained theoretically.In this paper,a novel model based on the circuit network analogy is proposed to predict the onset temperature of a standing-wave thermoacoustic engine.The activity and instability criteria are proposed to be the onset criteria in the model.The influences of the porosity of the heat exchanger and the stack,and the length of the resonant tube on the onset temperature are analyzed.The calculated results are in agreement with the experimental results,which indicates that the activity and instability criteria can be used to predict the onset conditions of a thermoacoustic engine.