单级混合制冷剂液化循环适应性和调节能力研究

针对在中小型天然气液化装置中广泛应用的单级混合制冷剂液化流程,模拟了环境温度、天然气流量和组分变化时流程参数的变化,以原有设备为约束条件,调节流程参数,使系统能够适应外界变化。结果表明:通过调节制冷剂压缩机的运行压力、工质流量和组成,单级混合制冷剂液化流程能够在较大的范围内适应环境温度和天然气的流量、组成变化,调整后的单级混合制冷剂液化流程能够保持高的效率。     

气体导流装置对微通道蒸发器性能的影响

针对微通道蒸发器制冷剂流量分配不均匀造成的换热性能恶化和干蒸现象,本文搭建了双流程微通道蒸发器性能测试实验台,研究导气装置对蒸发器换热性能及扁管中制冷剂分配均匀性的影响,并与常规的双流程微通道蒸发器进行对比。结果表明：由于入口制冷剂流量不变,液相制冷剂蒸发为气体的最大相变潜热不变,导致二者换热量和传热系数差值较小,最大值仅相差0.5%和6.9%。但加导气装置后流动阻力降低,两相段长度较常规结构增幅为87.3%,过热度显著降低,风速为3 m/s时两种结构的过热度降幅为44.4%。各扁管间制冷剂分布趋于一致,均匀性得到提升,干蒸现象得到缓解。     

带废热回收的家用热泵热水装置实验研究

为回收家庭洗浴废水中的废热,提高能源利用率,本文设计了一种带废热回收的热泵热水装置,并通过搭建实验台研究了该装置制取热水的循环性能。在进水温度为16℃,出水温度为36～46℃时进行实验测试,研究制热量、制热COP、压缩机功率、出水量等参数随出水温度和制冷剂充注量的变化规律。实验结果表明:适当提高制冷剂充注量有利于制热量、制热COP的稳定,在最小的制冷剂充注量为1.4 kg时,获得最大制热量为7.9 k W,制热COP为7.7;在出水温度为36～46℃,随出水温度的升高,压缩机功率增大,出水体积流量下降。该装置能够有效回收废水中的热量,制热量稳定在约7.5 k W,制热COP大于6.0。     

水冷螺杆式冷水机组部分热回收技术研究

为研究冷凝温度和热回收率、制冷能力之间的变化关系,结合试验数据对热回收系统进行理论分析,得出热水进水温度和冷却水流量的变化将对热回收空调系统的热回收率和制冷能力产生一定的影响。同时总结得出采用制冷剂R22的热回收系统热水箱的最佳设定温度为55℃。为今后热回收机组的设计提供了理论和试验依据。     

全封闭制冷设备的制冷剂回收研究

可用物理方法方便、干净地回收全封密制冷设备的制冷剂。本文介绍了该技术原理、装置和回收效果，分析了回收过程，找到了保证安全和回收的制冷剂质量等的条件和途径，回收的制冷剂可再使用。分析表明本文方法同样适用于回收新型无氟制冷剂、适用于非封闭式制冷设备。这种技术为长期沿用的极不合理、造成严重污染的“人工排放”制冷剂的维修工艺提供了一个良好的替代手段。     

制冷剂回收与再生现状分析

制冷剂回收和再生是减少制冷剂排放的推荐方式,但其实施有赖于政策的鼓励及回收再生技术的支持。对于制冷剂的回收,本文总结对比了日本、欧盟、美国和中国在制冷剂回收方面的政策,给出了各自的制冷剂年回收量;介绍了制冷剂回收5种代表性方法的工作原理、优缺点及适用的场合。对于制冷剂的再生,介绍了“简易再生”和“蒸馏再生”这2种再生方法的步骤和应用条件;以及对于不可再生制冷剂进行销毁的7种方法。最后,总结了中国目前在制冷剂回收再生中所面临的主要问题。     

变频两管制热回收多联机的技术研究

介绍多联机尤其是热回收多联机的市场表现和技术意义,阐述可以同时制冷制热技术的变频两管制热回收多联机的实现原理。变频两管制热回收多联机的室外机通过换热器能力无级调节、全逆流无毛细管制冷剂均匀分流可以准确控制室外机输出的高低压和过冷度。其制冷剂流向切换装置MS通过高效气液分离、主路和支路阀体的精细化控制实现气液流量精准分配,满足制冷/制热室内机的需求。通过控制优化使变频两管制热回收多联机不仅可以实现低温制热,而且可以实现高温制冷,并可以实现宽广温度范围下同时制冷制热的热回收。独立式两管制热回收多联机具有室外机占地小、安装简单、材料成本低、所需工时少及安装费用低等优点,市场前景可期。     

汽车空调制冷剂回收与再生方法

本文阐述了汽车空调CFCs-12制冷剂回收与再生的工艺流程、设备装置和操作方法,提出了减少制冷剂排放和保护臭氧层的建议.     

R290空气源热泵蒸发器换热性能分析

利用软件EVAP-COND对采用制冷剂R290的空气源热泵翅片管式蒸发器进行仿真模拟,通过改变制冷剂质量流量和蒸发器进口风量对机组制冷量、压降等进行比较分析。结果表明:制冷量、总传热系数、管路压降随制冷剂质量流量增大而增大,但制冷量增幅逐渐减小;最佳制冷效果下的制冷剂质量流量和风量分别在120 kg/h和25 m~3/min左右;制冷剂质量流量不变时,风量变化对蒸发器制冷剂侧总压降影响不大。     

采用R134a和R600a制冷剂系统毛细管特性分析

建立毛细管模型并通过实验数据验证了模型,给出制冷剂的干度x、温度t、速度W、压力P沿毛细管长度的变化关系,研究了毛细管的内直径、长度、冷凝温度、过冷度等因素对毛细管内R134a、R600a两种制冷剂的质量流量的影响.     

Greencool制冷剂的特点及应用

本文介绍一种具有环保与节能效果的新型制冷剂-Greencool制冷剂,主要介绍这种制冷剂的特点并与传统的氟里昂制冷剂相比较.另外,本文还将介绍Greencool制冷剂的工程应用.     

制冷剂回收再生的碳排放评估及经济性分析

我国已进入HCFCs制冷剂淘汰末期,并即将于2024年启动HFCs的产量和消费量削减。本文以制冷剂的回收再生过程为主要研究对象,基于LCCP气候性能模型,构建了制冷剂回收再生过程的碳排放量评估模型;分析了制冷剂回收再生的经济性;并对所构建模型,以汽车空调制冷剂R134a的回收再生为案例,计算其碳排放量及回收再生经济性。结果表明：本文案例中,对制冷剂进行回收再生处理可以减少当量CO2排放约42％,制冷剂回收再生的经济性能主要与再生后制冷剂单价及工人工资成本有关,工人工资按月最低工资标准时净化后制冷剂售价在11 元/kg（新制冷剂售价的50％）以上可在2年内开始盈利。     

Refrigerant performance evaluation including effects of transport properties and optimized heat exchangers

Preliminary refrigerant screenings typically rely on using cycle simulation models involving thermodynamic properties alone. This approach has two shortcomings. First, it neglects transport properties, whose influence on system performance is particularly strong through their impact on the performance of the heat exchangers. Second, the refrigerant temperatures in the evaporator and condenser are specified as input, while real-life equipment operates at imposed heat sink and heat source temperatures; the temperatures in the evaporator and condensers are established based on overall heat transfer resistances of these heat exchangers and the balance of the system.The paper discusses a simulation methodology and model that addresses the above shortcomings. This model simulates the thermodynamic cycle operating at specified heat sink and heat source temperature profiles, and includes the ability to account for the effects of thermophysical properties and refrigerant mass flux on refrigerant heat transfer and pressure drop in the air-to-refrigerant evaporator and condenser. Additionally, the model can optimize the refrigerant mass flux in the heat exchangers to maximize the coefficient of performance. The new model is validated with experimental data and its predictions are contrasted to those of a model based on thermodynamic properties alone.     

A semi-theoretical model for predicting refrigerant/lubricant mixture pool boiling heat transfer

This paper outlines the framework of a semi-theoretical model for predicting the pool boiling heat transfer of refrigerant/lubricant mixtures on a roughened, horizontal, flat pool-boiling surface. The predictive model is based on the mechanisms involved in the formation of the lubricant excess layer that exists on the heat transfer surface. The lubricant accumulates on the surface in excess of the bulk concentration via preferential evaporation of the refrigerant from the bulk refrigerant/lubricant mixture. As a result, excess lubricant resides in a thin layer on the surface and influences the boiling performance, giving either an enhancement or degradation in heat transfer. A dimensionless excess layer parameter and a thermal boundary layer constant were derived and fitted to data in an attempt to generalize the model to other refrigerant/lubricant mixtures. The model inputs include transport and thermodynamic refrigerant properties and the lubricant composition, viscosity, and critical solution temperature with the refrigerant. The model predicts the boiling heat transfer coefficient of three different mixtures of R123 and lubricant to within ±10%. Comparisons of heat transfer predictions to measurements for 13 different refrigerant/lubricant mixtures were made, including two different refrigerants and three different lubricants.     

非绝热毛细管的数值计算和特性分析

针对非绝热毛细管内制冷剂的流动特性,建立了采用两相流动的漂移流动模型,并开发了非绝热毛细管数值计算程序.利用该模型和程序对非绝热毛细管内制冷剂的流动特性进行了数值计算和特性分析,得到了毛细管内制冷剂干度、空隙率和相对漂移流速3者在毛细管内流动特性上的关系.     

润滑油对制冷系统的影响

讨论了润滑油与制冷剂的互溶对制冷系统性能的影响.润滑油与制冷剂的热物理性质相差很大,因而进入循环后必然会引起制冷剂流动、换热系数和压降的变化.分析了制冷剂在制冷系统各部件内循环流动时,含油量对系统性能的影响及机理.总体来讲,少量的润滑油对系统的制冷效果是有利的,但含油量过大则会降低制冷量,并对系统产生许多不利的影响.     

Refrigerant R134a condensation heat transfer and pressure drop inside a small brazed plate heat exchanger

This paper presents the experimental tests on HFC-134a condensation inside a small brazed plate heat exchanger: the effects of refrigerant mass flux, saturation temperature and vapour super-heating are investigated.A transition point between gravity controlled and forced convection condensation has been found for a refrigerant mass flux around 20 kg/m² s. For refrigerant mass flux lower than 20 kg/m² s, the saturated vapour heat transfer coefficients are not dependent on mass flux and are well predicted by the Nusselt [Nusselt, W., 1916. Die oberflachenkondensation des wasserdampfes. Z. Ver. Dt. Ing. 60, 541–546, 569–575] analysis for vertical surface. For refrigerant mass flux higher than 20 kg/m² s, the saturated vapour heat transfer coefficients depend on mass flux and are well predicted by the Akers et al. [Akers, W.W., Deans, H.A., Crosser, O.K., 1959. Condensing heat transfer within horizontal tubes. Chem. Eng. Prog. Symp. Ser. 55, 171–176] equation. In the forced convection condensation region, the heat transfer coefficients show a 30% increase for a doubling of the refrigerant mass flux. The condensation heat transfer coefficients of super-heated vapour are 8–10% higher than those of saturated vapour and are well predicted by the Webb [Webb, R.L., 1998. Convective condensation of superheated vapour. ASME J. Heat Transfer 120, 418–421] model. The heat transfer coefficients show weak sensitivity to saturation temperature. The frictional pressure drop shows a linear dependence on the kinetic energy per unit volume of the refrigerant flow and therefore a quadratic dependence on the refrigerant mass flux.     

Prediction of in-tube condensation heat transfer characteristics of binary refrigerant mixtures

This study presents a prediction model for the condensation heat transfer characteristics of binary zeotropic refrigerant mixtures inside horizontal smooth tubes. In this model, both the vapor-side and liquid-side mass transfers are considered, and the high flux mass transfer correction factor is used to evaluate mass transfer coefficients. The model was applied to the binary zeotropic refrigerant mixture R134a/R123, which has a large temperature glide. Calculation results showed that the heat transfer degradation of R134a/R123 due to gradients in the mass fraction and temperature is considerable, and depends on the mass fraction of the more volatile component and the vapor mass quality of the refrigerant mixture. By comparison with experimental data, incorporating the present finite mass transfer model for the liquid film side into the calculation algorithm was shown to reasonably well predict the condensation heat transfer coefficients of binary refrigerant mixtures with the mean deviation of about 10.3%. In the present calculations, however, it was also found that the high flux mass transfer correction factor had only a slight effect on the condensation heat transfer.     

减压蒸馏中二氯甲烷低温回收试验研究

为了减少实验室中二氯甲烷气体的直接排放,搭建了一套减压蒸馏低温回收试验装置,采用纯二氯甲烷作模拟溶剂回收试验成功后,在乙酰二茂铁制备过程中对二氯甲烷进行回收实验,回收率约90%,比模拟试验偏低;通过对比,两种试验数据规律表现一致,验证了试验方法的准确性。采用改变冷媒温度的方法,改变回收器内温度,对影响回收效果的温度因素进行分析,发现最佳冷媒温度为0℃。试验证明该系统能有效实现二氯甲烷的回收。     

分液冷凝器的管程理论设计及热力性能评价

根据分液冷凝器强化换热思想对其管程理论设计方法进行了研究。依据质量流速和干度来判断每一流程中制冷剂的流型,并依此选取Cavallini换热模型公式的方法求其平均换热系数,同时采用Cavallini两相压降模型和Darcy-Weisbach单相压降模型分别确定冷凝区和过冷段的压降。针对一个案例计算了三种管程设计方案下冷凝器管内冷凝换热系数和端压值,并用惩罚因子PF对其综合热力性能进行了评价。计算结果表明:不同的管程设计方案中管内制冷剂的流量分配均匀性存在较大的差异,均匀性越好,其综合热力性能越优。在质量流速为1200~1500 kg/(m2.s)范围内,与同等换热面积的蛇形管冷凝器相比,其中最好的分液冷凝器的PF值减小了48.5%~54.1%,可见设计优良的分液冷凝器的综合热力性能明显优于蛇形管冷凝器。