四温位吸收式制冷机生态学优化准则

建立不可逆四温位吸收式制冷循环模型,考虑工质与各换热器的热阻损失以及工质内部不可逆损失的影响。应用基于(火用)分析的生态学优化准则对循环(火用)输出率和循环(火用)损率进行协调优化。利用数值方法讨论内不可逆性、外部热源温度对制冷系统最优性能的影响,所得结论可以为实际吸收式制冷机的优化设计和性能改进提供依据。     

开式简单布雷顿制冷循环热力学优化 1.热力学建模

为准确描述开式简单布雷顿制冷循环的热力学性能,根据工质流动机理的一致性,采用与开式布雷顿正循环研究类似的研究方法,建立了考虑压降不可逆性的开式简单布雷顿制冷循环的热力学模型,导出了制冷率和制冷系数等性能参数与压缩机进口相对压降的函数关系,并分析了循环的热力学性能。结果表明,压缩机消耗功率、高温侧换热器换热率、膨胀机输出功率、制冷率和排气损失引起的热流率都与质量流率成正比,存在最佳的压缩机进口相对压降使循环制冷率最大。     

"混合工质脉管制冷法研究及循环分析方法"研究通过鉴定

由浙江大学制冷与低温研究所承担的“混合工质脉管制冷法研究及循环分析方法”科研项目,近日通过浙江省科技厅组织的成果鉴定。该课题组系统论证了各种理论制冷循环与卡诺循环的关系,对现有各种制冷循环进行了合理的分类和比较,提出了用改进的布雷顿循环来分析脉管制冷的新方法。在理论分析的基础上,首次提出了在脉管制冷机中采用混合工质,以提高脉管制冷机制冷量和制冷效率的新方法。通过多年试验,证明了混合工质在提高脉管制冷机性能方面的积极作用。与采用纯He作为工质相比,用He-N2混合工质的脉管制冷机,在80K温区的制冷量和COP可提高…     

单压吸收式制冷技术的发展

介绍了单压吸收式制冷循环的工作原理、技术发展历程、工质组的选取，以及以氨-丁烷-水为工质组的制冷循环运行参数的确定原则。     

热力条件对工质热力循环影响的分析

根据工质是否能达到环境影响小、价格合理、来源丰富、热力学性质满足制冷循环等指标。选择HFCs类制冷剂R245fa,R245ca和R236ea及R134a和碳氢类的制冷剂R600作为热泵新工质进行性能循环分析。并以热泵的制热系数COP,单位容积的制热量qv,压缩机进出口的压力比为工质循环性能评价依据进行具体的理论计算,最后整理、统计数据的计算结果,作出不同热力条件下,各种工质COP、qv压比的比较图,得出不同工质在不同热力条件下的性能特点和各自的适用范围。     

不同制冷剂在喷射式制冷系统中的性能分析

喷射式制冷系统的性能在很大程度上取决于制冷工质的选择。建立了喷射式制冷系统分析的简单模型,并采用EES软件编制程序,分析了7种比较典型的制冷工质对喷射式制冷系统的影响。     

蚕种冷库工艺设计之探讨

文中论述了蚕种冷库制冷工艺设计中最基本的几个问题，确定了冷库设计的技术参数，探讨了制冷工质的选择，压缩机组的选型和机房设备的布置，对制冷工艺的三个循环一氨制冷工艺、盐水循环、冷却水循环系统进行了分析，对蚕种冷库内的冷却排管的布置，保温材料的选用均作了说明。文中还附有冷库设计的技术数据与制冷工艺设备流程图、冷库、平面图、冷库机房平面图。     

高性能吸收式循环与新工质

综述了国外高性能吸收式循环（含制冷与热泵的高ＣＯＰ循环、热变换高温升循环、吸收－－压缩混合循环等）和吸收式新工质研究及其效果，并对发展方向、风冷化与热泵化技术、新制冷剂的新型循环作了分析评述。     

电压缩式制冷循环与吸收式制冷循环的热力学比较分析

采用效率与损失分析方法,计算比较了电压缩式制冷循环与单效吸收式制冷循环的效率及两种制冷循环在典型工况下各环节的损失。结果表明,当采用合适的发生器温度和热源温度时,两种制冷循环的效率基本相同;电压缩式制冷循环的主要损失发生在压缩机环节,吸收式制冷循环的主要损失发生在吸收器和发生器。讨论了两种制冷循环的改进途径。     

对利用低温位热能来驱动的几种制冷装置性能的比较

对利用低温位热能来驱动的几种制冷装置性能进行了比较，以喷射式制冷为基础，以HCFC－123为工质的制冷装置是比较理想的新型空调用制冷装置．     

Performance optimisation for an irreversible variable-temperature heat reservoir air refrigerator

The performance analysis and optimisation of an irreversible air refrigerator with variable-temperature heat reservoirs is carried out by taking the cooling load density, i.e., the ratio of cooling load to the maximum specific volume in the cycle, as the optimisation objective using finite-time thermodynamics (FTT) or entropy generation minimisation (EGM) in this paper. The analytical formulae for the relationships between cooling load density and pressure ratio, as well as between coefficient of performance (COP) and pressure ratio are derived with the heat resistance losses in the hot- and cold-side heat exchangers, and the irreversible compression and expansion losses in the compressor and expander. The influences of the effectiveness of the heat exchangers, the inlet temperature ratio of the reservoirs, and the efficiencies of the compressor and expander on the cooling load density versus and pressure ratio are provided by numerical examples. The cooling load density optimisation is performed by finding the optimum pressure ratio of the compressor, the optimum distribution of heat conductance of the hot- and cold-side heat exchangers for a fixed total heat exchanger inventory, and the optimum heat capacity rate matching between the working fluid and the heat reservoirs. The influences of some design parameters, including the effectiveness of the heat exchangers between the working fluid and heat reservoirs, the efficiencies of compressor and expander, the inlet temperature ratio of heat reservoirs, the heat conductance distribution and the heat capacity rate matching between the working fluid and the heat reservoirs on the maximum cooling load density are provided by numerical examples. Optimisation of refrigeration plant design leads to a reduction in size of the compressor, expander, and the hot- and cold-side heat exchangers.     

Test results of a medium temperature solar engine

The results of a test programme of a completely fluorinated organic fluid solar engine at fluid temperatures around 250°C are Engine design characteristics. as deduced using the particular fluid properties are briefly described problems encountered in the preliminary test phase and relating to fluid losses, heat exchangers reduced performance and minor mechanical disturbances are illustrated together with the actions undertaken to improve the original engine behaviour. Detailed engine overall and components performance, as derived from a series of tests, carried out with a fuel fired heat source (simulating the actual solar heating loop) are presented. Engine efficiency, with reference to the net power output at the high speed shaft proved to be around 21%, at 250°C turbine inlet temperature which can be compared with 22.6% design value at the same temperature and with 23.6% original goal at 280°C top cycle temperature. The analysis of the heat transfer coefficients within the various heat exchangers support the suspicion that available information on working fluid transport properties is not sufficiently accurate.     

集中供暖用地热高温热泵工质研究

介绍了集中供暖用地热热泵的应用工况及使用要求，分析了潜在的高温工质包括纯质和混合物的性能特性，给出了高温热泵工质的筛选原则，实验研究了混合工质R22／R141b在不同配比下的性能特性。     

Numerical analysis on heat transfer characteristics of ionic liquids in a tubular heat exchanger

ABSTRACT

The efficiency of the solar thermal system depends on the performance of the solar collectors. There is a need to operate solar collector at higher possible temperature to attain maximum efficiency limits. However, the performance of the collector system is limited by the heat transfer characteristics of the working fluid called as the heat transfer fluid (HTF). Water is widely used as the HTF in the solar collector, but the major problem of using water as the HTF is its limited operating temperature. The objective of the work is to investigate the heat transfer characteristics of ionic liquids in tubular heat exchanger (HE) suitable for the solar thermal application. The HE was designed for a heat duty of 1?kW based on the thermal transport property of available ionic liquids and the computational fluid dynamics (CFD) analysis was performed. The results indicate that there is only minimal deviation between the assumed and CFD data.     

基于桩土相互作用的嵌岩能源桩传热计算

针对螺旋地埋管嵌岩能源桩传热,提出一种新的计算模型,可考虑基岩温度、大气-地面对流换热、桩顶处绝热处理、流体速度和流体热量损耗对其传热影响。首先求解土体温度自由场;接着考虑桩体运行时系统传热相互作用的影响,得到桩体温度场;然后将土体温度场问题转化为一系列未知系数求解;最后通过边界条件得到土体附加温度场。分析表明:在桩顶和桩底两倍桩径范围内,土的附加温度变化幅度最大;桩土传热系数对能源桩传热性能影响最大,减小桩土传热系数可显著提高能源桩传热性能;流体导热系数及流速对桩的传热效果影响不可忽略;土的导热系数及大气-地面对流传热系数对其传热性能影响很小。     

并联双U型桩基埋管换热器换热性能研究

本文建立了并联双U型桩基埋管换热器传热问题的三维数学模型,利用江苏某工程现场实测数据验证了所建立模型数值解的准确性。对不同循环液流速,不同桩基长度和不同运停比等工况下埋管出口水温,单位桩深换热量,桩周温度以及桩周土壤温度进行了分析,揭示了出口水温、单位桩深换热量等性能参数在不同工况下的动态变化规律以及桩身和周围土壤温度改变而产生的热堆积现象,提出了单位桩身温度变化换热量β1和单位土壤温度变化换热量β2,评价了不同工况对换热性能影响程度。结果表明,高流速可以增强换热,但高流速工况下为了产生更多的换热量而带来的代价是更高的桩身和土壤温升,不利于长期运行。长桩基长度工况和运停工况可以在有利于长期运行前提下提高埋管换热器的换热量,且运停工况对换热性能的提升更为明显。     

空调热回收热虹吸管换热器工质的试验研究

针对热虹吸管挟热器样机R22和R32两种工质,做了对比试验研究,得到了不同工况下热虹吸管换热器的温度效率,比较分析表明,模拟计算的模型能够较好地反映热虹吸管换热器的能量回收性能,同时试验分析也验证热虹吸管换热器新型工质R32的性能。     

Thermal performance analysis of the glass evacuated tube solar collector with U-tube

In this paper, based on the energy balance for the glass evacuated tube solar collector with U-tube, the thermal performance of the individual glass evacuated tube solar collector is investigated by analytical method. The solar collector considered in this study is a two-layered glass evacuated tube, and the absorber film is deposited in the outer surface of the absorber tube. The heat loss coefficient and heat efficiency factor are analyzed using one-dimensional analytical solution. And the influence of air layer between the absorber tube and the copper fin on the heat efficiency is also studied. The results show that the function relation of the heat loss coefficient of the glass evacuated tube solar collector with temperature difference between the absorbing coating surface and the ambient air is nonlinear. In the different ambient temperatures, the heat loss coefficient of the solar collector should be calculated by different expressions. The heat efficiency factor will be subject to influence of air layer between absorber tube and the copper fin. Specially, the influence is remarkable when the heat loss coefficient of the collector is large. When the synthetical conductance amounts to 5 W/m K, the solar collector efficiency decreases 10%, and the outlet fluid temperature decreases 16% compared with the case which the air thermal resistance is neglected. And the surface temperature of the absorbing coating increases 30 °C due to the effect of air thermal resistance. So the surface temperature of the absorbing coating is an important parameter to evaluate the thermal performance of the glass evacuated tube solar collector.     

基于吸收式制冷沿程加热气泡泵的启动性能

气泡泵是太阳能无泵吸收式制冷的核心部件,其启动性能影响无泵吸收式制冷机的实际工程运用。以水为工质,实验研究了系统初压力,沉浸高度,提升管入口工质温度,加热功率对沿程加热气泡泵启动性能的影响。实验结果表明:当加热功率过低时,气泡泵偶有泵起,但不能正常启动,存在一个最低启动功率。气泡泵正常启动分为三个阶段,延迟阶段:工质温度迅速攀升,但液体提升量为零。过渡阶段:工质温度缓慢上升,液体提升量不断升高。稳定阶段:温度和流量基本保持不变。系统初压力越低,启动时间和最低启动功率减小,提升管内工质温升速度越快。沉浸高度越高,系统越容易启动,但是对提升管出口工质温度的影响很小。系统初压力一定时,随着提升管进口工质温度升高,延迟时间和启动时间减小,当进口温度超过30℃时,其对延迟时间的影响已经很小。启动时间随加热功率的增加而减小。     

Fundamental optimal relation of a generalised irreversible quantum Carnot heat pump with harmonic oscillators

An irreversible quantum Carnot heat pump model working with many non-interacting harmonic oscillator systems is established in this paper. The quantum heat pump cycle is composed of two isothermal processes and two irreversible adiabatic processes. The irreversibilities of heat resistance, internal friction and bypass heat leakage are considered in the model. Based on the quantum master equation, semi-group approach and finite time thermodynamics (FTT), the cycle period, heating load and coefficient of performance (COP) of the quantum Carnot heat pump are derived, and detailed numerical examples are provided. At high temperature limit, the fundamental optimal relations between the heating load and COP of the quantum heat pump are deduced and analysed by using numerical examples. The effects of internal friction and bypass heat leakage on the optimal performance of the quantum heat pump are discussed in detail. The endoreversible, frictionless and without bypass heat leakage cases are discussed. The obtained results are general to the performance optimisation of quantum Carnot heat pumps and can provide some guidelines for optimal design of real quantum heat pumps.