输气系数对压缩机选型宽余率的影响

利用压缩机的热力性能模拟程序,计算分析陈列柜用低温往复式压缩机变工况运行时输气系数、制冷量及输入功率的变化规律,定量地给出在不同冷凝温度、蒸发温度下输气系数对压缩机性能的影响。由分析得出：冷凝温度的提高和蒸发温度的降低均使压缩机的制冷量和性能迅速降低;蒸发温度对压缩机性能的影响相对冷凝温度的影响要大得多。     

冷凝温度和蒸发温度变化时往复压缩机的变工况特性

通过压缩机的热力性能模拟程序,计算分析了陈列柜用往复式压缩机变工况运行时制冷量、功率和制冷系数的变化规律,定量的给出了冷凝温度、蒸发温度对压缩机性能参数的影响。并使模拟结果与实际测试工况下的实验数据相比较。由分析得冷凝温度的提高和蒸发温度的降低均使压缩机的制冷量迅速降低。蒸发温度对压缩机性能的影响作用相对冷凝温度的影响作用要大一些。     

制冷系统含油量对制冷压缩机工作性能影响的理论分析和实验研究

为研究制冷系统含油量对制冷压缩机工作性能的影响,建立了汽车空调用涡旋式压缩机工作过程数学模型,对压缩过程进行了计算模拟。并在汽车空调压缩机性能测试台上,进行了变含油量、变转速和变工况实验,得到了流入压缩腔内的润滑油量与压缩机容积效率、压缩功率损失、排气温度、制冷量和COP的关系曲线。研究结果表明：理论计算结果和实验结果符合较好;压缩腔内油气质量百分比为7％～9％时,压缩机工作性能较为理想。     

汽车空调用压缩机变转速工况容积效率研究

在变转速工况下进行了压缩机的性能实验,分析了容积系数、压力系数、温度系数和泄漏系数对容积效率的影响以及它们各自在变转速工况下的定义式。容积系数主要与压缩机的结构尺寸和吸、排气压力比有关,压力比的变化对容积系数构成以多变膨胀指数为幂的指数影响;转速变化对压力系数构成二次影响;温度系数和泄漏系数同时受到与压力比和转速的影响。以压缩机的吸、排气压力比和转速为变量,用实验数据拟合了压缩机的容积效率,计算结果与实验数据的平均误差在5％以内,拟合公式具有一定的可信度,适合在压力比为2-10的范围内使用。本文的研究成果可供相关人员在进行压缩机的设计和测试时参考。     

开启式压缩机两种工质变转速工况下容积效率的实验研究

选用某种容积式压缩机在变转速工况下进行了两种工质压缩机的性能实验,得出了不同工况(压缩比)对容积效率的影响以及转速变化的影响,存在一个最佳转速或转速范围使容积效率达到最大值.用实验数据拟合出了两种工质压缩机变转速工况下的容积效率关联式,计算结果与实验数据的平均误差在5%以内,拟合公式具有一定的可信度.     

带经济器的螺杆式压缩机性能试验

为研究带经济器的螺杆式压缩机在不同补气状态下的性能,以压缩机的理论压缩过程为基础,设计不同压比、不同吸气压力和不同补气压差的测试工况,并进行相应试验。结果表明,在吸气压力一定的工况下,压比越大,补气压差增大对于制冷量和性能系数的提升作用越明显;在压比一定的工况下,吸气压力越低,补气压差增大对于制冷量的提升作用越明显;当压比低于2.5时,尽管中间补气可以提升压缩机的制冷量,但压缩机的性能系数呈下降趋势。     

回油量对螺杆式压缩机性能的影响

介绍螺杆式压缩机中冷冻油的作用及回油量的计算和测试方法。在确定的名义工况下，测试回油量与制冷量、功率和压缩机性能系数（COP）的关系，分析回油量对螺杆式压缩机性能的影响，并通过试验确定最佳回油量。该研究对螺杆式压缩机的设计和性能优化具有指导作用。     

压缩机在不同转速下的制冷量和有效功率的确定

活塞式制冷压缩机的制冷量和有效功率与制冷工况、压缩机的汽缸尺寸、活塞行程、汽缸数目、压缩机转速和输汽系数有关。在拥有产品说明书时,可根据制冷工况在压缩机特性曲线图上查得。但是,有时厂家提供的特性曲线图具有一定的局限性。例如,我厂从波兰全套引进的1000T 装配式冷库,高压机10W92SA 的特性曲线图上要求的转速为1460rpm,而目前我们采用的转速为1150rpm,这就无法直接从特性曲线图上查得该机的制冷量及其有效功     

变流量双级压缩制冷系统实验研究

为改善变工况条件下,定频双级压缩制冷系统不能达到最佳状态运行的现状,本文搭建变流量双级压缩制冷系统实验台,分析了变工况条件下,调节高压级压缩机频率来改变低高压级压缩机输气量之比,对一次节流中间不完全冷却造成的影响。结果表明：当冷凝温度为30 ℃,蒸发温度为?35~?20 ℃,低高压级压缩机输气量之比由1.25增至3.33时,系统制冷量随着低高压级压缩机输气量之比的增加逐渐减少,性能系数COP最大为2.37;当蒸发温度从?20 ℃降至?35 ℃,每降低5 ℃,最佳COP下的低高压压缩机输气量之比依次增大22.10%、12.52%、14.29%。故实际系统设计时,可参考实验数据,根据不同蒸发温度和制冷量需求,调节合适的低高压级压缩机输气量之比,使系统运行达到最佳状态。     

蒸汽压缩/喷射制冷系统喷射器设计及节能分析

蒸汽压缩/喷射制冷系统是一种有效的节能系统,可以减少节流膨胀损失,降低压缩机压力比,提高制冷系统效率。选择5种计算工况对蒸汽压缩/喷射制冷系统进行计算,研究喷射器结构与蒸发温度和冷凝温度的变化规律,并与普通蒸汽压缩系统对比,从制冷量、压缩机耗功、性能系数三个角度分析新系统的节能效果。计算结果表明蒸汽压缩/喷射制冷系统在低温工况条件下节能效果最优,制冷量最大可提高29%,压缩机耗功最大可降低65%,COP值最大可提高63%。     

Influence of the new refrigerant thermodynamic properties on some refrigerating turbocompressor characteristics

Comparison of the main geometrical and operating parameters of centrifugal compressors working with various refrigerants is realised in this paper. The interdependence between the centrifugal compressor pressure ratio, compression work, impeller peripheral speed, Mach number, compressor capacity, impeller diameter and width, speed of rotation, and refrigerant molecular mass, normal boiling temperature and specific volumetric cooling capacity for various refrigerants are shown and discussed. The flow phenomena in the turbocompressor flow field, caused by high Mach number and high pressure ratio, are analysed. Some theoretical observations for the influence of the substitute of the refrigerant on the turbocompressor performance characteristics are presented. The possibilities for the replacement of the refrigerant in the existing refrigerating machines are discussed.     

用于低温复叠式制冷的CO2螺杆式压缩机组的性能实验

CO2在冷冻冷藏系统中适宜作为低温级制冷剂与其他制冷剂组成复叠式制冷循环。建立采用螺杆式压缩机组的NH3/CO2复叠式制冷实验系统,对低温级的CO2螺杆式压缩机组进行性能测试,并对主要技术参数进行分析,给出机组制冷量、轴功率、容积效率和绝热效率等在不同工况下的变化关系。在相同工况下CO2制冷机组的制冷量约是同型号氨机组的7.5～10.5倍,且在蒸发温度越低时差值越大。对NH3/CO2复叠式制冷机组和NH3单机双级压缩制冷机组的性能系数进行比较,前者在蒸发温度低于-40℃时性能系数更高。     

Thermodynamic analysis on the performance of a variable speed scroll compressor with refrigerant injection

A thermodynamic model for a variable speed scroll compressor with refrigerant injection was developed using continuity, energy conservation and real gas equation. The model included energy balance in the low-pressure shell compressor, suction gas heating, motor efficiency, and volumetric efficiency considering gas leakages as a function of compressor frequency. The developed model was verified by comparing the predicted results for the no injection condition with the experimental data. The deviations of the predicted from the measured values were within 10% for approximately 90% of the experimental data. Based on the model, mass flow rate, suction gas heating, cooling capacity and power consumption of the compressor were estimated and analyzed as a function of frequency. The effects of refrigerant injection on the performance of the compressor were also discussed as a function of frequency, injection conditions, and injection geometry.

Résumé

A thermodynamic model for a variable speed scroll compressor with refrigerant injection was developed using continuity, energy conservation and real gas equation. The model included energy balance in the low-pressure shell compressor, suction gas heating, motor efficiency, and volumetric efficiency considering gas leakages as a function of compressor frequency. The developed model was verified by comparing the predicted results for the no injection condition with the experimental data. The deviations of the predicted from the measured values were within 10% for approximately 90% of the experimental data. Based on the model, mass flow rate, suction gas heating, cooling capacity and power consumption of the compressor were estimated and analyzed as a function of frequency. The effects of refrigerant injection on the performance of the compressor were also discussed as a function of frequency, injection conditions, and injection geometry.     

Compressor efficiency with cylinder slenderness ratio of rotary compressor at various compression ratios

When the air conditioning and heating systems operate in low speed regions, the efficiency of inverter compressor is relatively low, owing to the reduction in motor efficiency. Nevertheless, the annual operating time of compressor is largely occupied by low speed regions. Hence, experimental and numerical analyses were conducted to improve compressor efficiency in these regions, and various pressure conditions were considered. The significant difference in the volumetric efficiency with compression ratios was observed through the experiments. To reduce the decrease in volumetric efficiency at high compression ratio, a geometric combination of the compression part was considered through a numerical analysis. The numerical results showed that the volumetric efficiency at small cylinder slenderness ratio was relatively high and increased by about 6.3% at a compression ratio of 7. Then the cooling capacity increased by 8.77%, while the input work showed a relatively small increase of 2.44%.     

制冷压缩机变工况运行的热力性能研究

制冷系统在实际运行时其工作状况是大幅度变化的,针对压缩机变工况运行时机理模型难以全面反映实际运行的复杂凼素而造成精度不高问题,依据变质量系统热力学理论,采用机理分析和实验拟合相结合的灰箱方法,将控制模型中的主要参数多项式化,提出制冷压缩机的主要热力性能(制冷量和功耗)与热力参数(吸气和排气压力)之间的模型结构和定量关系.理论计算结果与实验测试结果的吻合性较好,证明了该定量关系的可行性和准确性.     

基于高压级活塞排量的双级压缩制冷循环制冷量计算式

为了研究双级压缩制冷循环制冷量简化计算方法,分析了高低压级压缩机活塞排量比、容积效率及指示效率等参数对制冷量的影响,以活塞排量比与中间温度的关系式为基础,作一定的简化处理,理论推导出基于高压级活塞排量的双级压缩制冷循环制冷量简化计算式,并通过实例进行了验证。实例计算结果表明：根据简化计算式以及常规方法计算的结果误差较小,吻合度高,推出的双级压缩制冷循环制冷量计算式是准确的。     

数码涡旋管道机制冷变风量运行的实验研究

对采用数码涡旋压缩机的风管送风式空调(热泵)机组在标称制冷工况下的变风量运行进行了实验研究,得出了机组制冷能力、功耗、机组效率、出风温度、排气压力、排气温度、吸气压力等参数随风量变化的关系,分析了采用数码涡旋压缩机的管道机变风量运行的特点,为风管送风式空调(热泵)机组的节能、稳定运行提供了有价值的实验支撑。     

Comportement dynamique de détendeurs thermostatiques de machines frigorifiques

A good adaptation of refrigerating machine components operating with a variable-speed compressor requires knowledge of the dynamic behaviour of each component, more particularly of the expansion valve. The behaviour of various thermostatic expansion valves (ballast charge, adsorbent charge and maximum operating pressure or MOP charge) has been studied for compressor speed variations (between 20% and 200%) of a refrigerating machine, with R22 as refrigerant, and a cooling capacity of 6kW. This study has shown the disadvantages of these expansion valves, during dynamic operation, without modification of the static superheat. The decrease of the evaporating pressure, consecutive to a step or a ramp of the compressor speed, can lead to the suction of a two-phase fluid in the compressor. This phenomenon takes place particularly either for the low evaporating temperatures or for great variations of the compressor speed, more than 50%. The stable operating limits of different thermostatic expansion valves have been determined as a function of the evaporation temperature and the rotational speed of the compressor during the non-steady state.     

Comportement dynamique de détendeurs thermostatiques de machines frigorifiquesBehaviour of a thermostatic expansion valve in non-steady state for a refrigerating machine

A good adaptation of refrigerating machine components operating with a variable-speed compressor requires knowledge of the dynamic behaviour of each component, more particularly of the expansion valve. The behaviour of various thermostatic expansion valves (ballast charge, adsorbent charge and maximum operating pressure or MOP charge) has been studied for compressor speed variations (between 20% and 200%) of a refrigerating machine, with R22 as refrigerant, and a cooling capacity of 6kW. This study has shown the disadvantages of these expansion valves, during dynamic operation, without modification of the static superheat. The decrease of the evaporating pressure, consecutive to a step or a ramp of the compressor speed, can lead to the suction of a two-phase fluid in the compressor. This phenomenon takes place particularly either for the low evaporating temperatures or for great variations of the compressor speed, more than 50%. The stable operating limits of different thermostatic expansion valves have been determined as a function of the evaporation temperature and the rotational speed of the compressor during the non-steady state.