用无量纲等效比分析汽车空调制冷系统的性能

将制冷压缩机排气量、冷凝器风量、蒸发器风量三个参数用无量纲等效比关联起来，提出用无量纲等效比分析汽车空调制冷系统的性能；用算例证明了该方法的有效性；计算分析了无量纲等效比对系统性能的影响关系。分析结果表明：要使系统的制冷量或性能系数最大，压缩机排气量、冷凝器风量和蒸发器风量三者之间存在确定的匹配关系。     

基于正交设计的汽车热泵空调系统参数优化研究

为研究汽车热泵空调在低温时的制热性能及各项参数对系统性能的影响,搭建了热泵系统实验台,研究了汽车热泵空调系统在室外温度为-10～0℃的制热量及制冷系数（COP）,分析了室外换热器风速和室内冷凝器风量对系统性能的影响。基于正交设计,通过一维仿真分析了低温时压缩机转速、电子膨胀阀开度、室内冷凝器风量、室外换热器风速对系统性能指标的影响并确定了最优参数。结果表明：COP随环境温度和室内冷凝器风量的提升而升高,室外换热器风速对COP的影响不大;选择不同的评价指标时,参数对指标的影响及最优参数组合皆有差异。     

EXV开度对纯电动汽车热泵空调性能的影响

基于搭建的电动汽车热泵空调系统性能试验台,详细研究了EXV开度变化对系统的冷凝和蒸发压力、过冷度、热泵出风温度、制热量、压缩机功耗和性能系数COP的影响。结果表明:在压缩机转速、冷凝器进风温度和风量一定的条件下,随着EXV开度增加,冷凝压力减小而蒸发压力变化较小,过冷度、制热量和热泵出风温度均呈减小并当EXV开度增大到一定程度后减小幅度变缓,压缩机功耗先减小后基本维持不变,系统COP先增大后减小;冷凝器出口过冷度较大时,通过改变EXV开度可有效调节热泵出风温度,且在开度较小时增大EXV开度有利于获得较高的COP。研究结果可为纯电动汽车热泵空调系统性能的调节和控制策略制定提供参考。     

氨气回收机组的设计

设计了氨气回收机组,为降低能耗,采用多级压缩方案。按设计工况,对后置压缩机、蒸发式冷凝器、前置压缩机进行了设计选型,给出了真空机组的相关参数。后置压缩机和蒸发式冷凝器风机配备了变频器,可以调节机组的冷凝负荷及配风量,确保机组在最小能耗状态工作。     

风冷冷凝器的计算机设计法

为了提高风冷冷凝器的设计计算精度,防止冷凝器在使用中冷凝压力过高,必须在设计中将压缩机排气的冷凝过程分过热、冷凝和过冷三段计算,同时还要考虑轴流风机风量随冷凝器阻力变化的因素。本文介绍一种用电子计算机设计风冷冷凝器的新方法。采用该方法设计的冷凝面积更符合于实际需要。     

面向多变量控制的制冷系统性能分析

采用仿真的方法研究了控制参数和干扰参数对制冷系统性能的影响，即分别研究了冷凝器风机风速、蒸发器风机风速、膨胀阀开度、压缩机转速、回风温度、环境温度变化对制冷系统性能的影响，为多变量控制器的设计提供依据。     

基于移动边界模型的变频空调系统动态仿真

建立了变频空调系统的动态仿真模型.采用集总参数方法和移动边界模型分别建立蒸发器5阶和冷凝器7阶动态模型;压缩机和膨胀阀由于热惯性小,采用稳态模型求解.系统动态模型以压缩机和膨胀阀模型作为边界条件,通过联立两换热器动态模型,组合成12阶矩阵模型.仿真结果表明,此模型可对压缩机转速、膨胀阀开度、风量等阶跃变化时,系统的动态特性进行有效预测.     

变频高温压缩机复叠热泵系统的试验研究

为了研究压缩机频率对复叠式热泵系统的影响,结合复叠式循环技术与压缩机变频技术,搭建变高温压缩机频率复叠热泵实验台。研究分析了压缩机排气温度、压缩机功率、系统制热量及系统COP(以下COP均指系统COP)随高温压缩机频率的变化,试验结果表明:当蒸发温度-30 ℃,冷凝温度46 ℃工况下,随高温压缩机频率增加,高温压缩机排气温度上升,上升速度逐渐加快,最高排气温度99.7 ℃,小于120 ℃,低温压缩机排气温度下降,下降速度逐渐缓慢;高温压缩机功率逐渐增大,低温压缩机功率逐渐减小,系统功率呈增加趋势;系统制热量呈线性增加趋势,COP随高温压缩机频率增加呈先增加后减小趋势,最大COP为2.7。     

基于DCS的进口轴流压缩机控制系统

简要介绍了轴流压缩机组的工艺流程,描述了轴流压缩机控制系统的配置、控制难点。重点介绍了轴流压缩机定风量/定风压控制、防喘振控制和连锁控制的功能实现。该设计实现了国产DCS系统对湘钢1#进口轴流压缩机控制系统的改造。     

侧面叉车空调系统的改进

正1.存在的缺陷根据用户要求,我厂自行设计制造的3t侧面叉车配置了空调系统。该空调系统由冷凝器罩3、冷凝器4、过滤器6、压缩机7、蒸发器8组成,如图1所示。压缩机7由发动机曲轴胶带轮驱动,其通过电信号控制压缩机7离合器的接合与分离来控制空调系统的运行。用户反映该空调系统存在以下缺陷:一是空调系统制冷效果不理想,冷凝器散热效果不良;二是冷凝器散热风向存在缺陷,热风不能及时排出,有部分热风回流,影响散热;三是空调系统与发动机     

A new method for field test of the heating capacity of air source heat pumps

The operation performance measurement of the air source heat pumps in the field, in which conditions are complicated and the accuracy could not be ensured, is very crucial for its performance evaluation and improvement. In this investigation, a novel method for measuring the heating capacity of the air source heat pump is established. An auxiliary electric heater is installed along the pipeline between the compressor and the condenser, and the refrigerant temperature difference caused by the heater is gathered to calculate the refrigerant mass flow rate based on the energy conservation. The heating capacity is calculated with the measured data of the refrigerant enthalpy at the inlet and outlet of the condenser and the refrigerant mass flow rate of the compressor discharge pipe. The validation results in laboratory tests show that the measured heating capacity accuracy is within 9.2%. It is also found that the impact of the novel test method on the heating capacity of the air source heat pumps is below 1.7%, and the power consumption of the tested units is increasing of within 1.8% compared with it when the electric heater is off. The refrigerant enthalpy difference method with an electric heater presented in this research can be applied to measure the heating capacity of different air source heat pump air heaters accurately in the field, which will be much helpful to improve the performance for cleaning heating in northern China.     

Exergy efficiency and irreversibility comparison of R22, R134a, R290 and R407C to replace R22 in an air conditioning system

This work presents an experimental comparison of exergy efficiency (EE), irreversibility at the process 1–2 (evaporator exit to compressor inlet), 2–3 (compressor inlet to condenser inlet), 3–4 (condenser inlet to expansion valve inlet), 4–5 (expansion valve inlet to evaporator inlet) and 5–1 (evaporator), and coefficient of performance (COP) of R22, and its substitutes R134a, R290 and R407C in vapor compression refrigeration system (VCRS) of an air conditioner. In addition, the effects of air temperature in the freezer with reference to environment states on irreversibility and EE have been investigated. At ?18°C air temperature in the freezer, 33°C reference environment state and 42% relative humidity refrigerants R22 and its substitutes R134a, R290 and R407C VCRSs the total irreversibilities are 665.7, 753.5, 582.1 and 677 W, and EEs are 22.9, 14.2, 26.5 and 20.6%, respectively. The refrigerant R290 is the best performer among candidate refrigerants but it suffers from flammability. Thus, R407C can considerably be used to replace R22.     

汽车空调系统电子流量调节问题研究

分析了目前汽车空调器流量控制中存在的一些问题,提出了由发动机转速决定的压缩机转速引起的开环控制与车内蒸发器过热度模糊闭环反馈控制的复合控制系统,介绍了一种具有智能判断和积分功能的自调整模糊控制器的电子膨胀阀流量控制设计,并提出了双过热度控制信号方法。试验结果表明,本文设计电子膨胀阀系统提高了汽车空调的调节品质,同时起到了电磁阀的作用。     

Investigation of domestic air conditioner with a novel low charge microchannel condenser suitable for hydrocarbon refrigerant

For environmental protection, flammable hydrocarbon refrigerants have been applied to domestic refrigerator and air conditioners. How to reduce refrigerant charge is the main problem for the safety use of hydrocarbons. A novel low charge microchannel condenser was proposed and investigated experimentally and numerically in domestic air conditioner system. Experimental results show that in comparison with normal microchannel condenser, cooling capacity of the novel condenser system increased by 1.6%, system refrigerant charge decreased by 28.3%. The optimum charge for R290 was reduced to 190 g, which meet the safety requirement of China National Standard GB 4706.32-2012. A numerical model of domestic air conditioning system (3.2 kW) with this new condenser was established. Parametric analysis of the new condenser and its impact on the system performance was studied. It was found that the reasonably reducing header inner diameter and flat tube hole diameter can cause more refrigerant charge reduction in condenser (−6.9% and −45.5% respectively) and almost no energy efficiency attenuation. Flow pass arrangement and its impact on refrigerant charge were also studied in this paper. If the novel condenser are fully optimized or other components of the air conditioning system (like compressor) are improved, the system charge may be reduced to 150 g, so as to meet IEC safety charge requirement.     

近共沸混合制冷剂充灌量对冰箱性能的影响

研究了近共沸混合制冷剂充灌量与冰箱性能及运行参数间的关系。这些参数包括冷却速度、耗电量、冷藏室温度、冷冻室温度、冷凝器温度、压缩机吸气温度和排气温度等。为进一步提高替代工质冰箱性能提供了依据，并为近共沸混合制冷剂充灌量优化模型的验证提供了基础数据。     

蒸发冷凝式冷水机组设计及应用

蒸发冷凝式冷水机组,即采用蒸发冷凝器作为机组的冷凝器。该机组由压缩机、平衡管、蒸发冷凝器、贮液器、节流装置、蒸发器、电器控制箱、变频系统等构成。就如何保证机组在全天候运行状况下其高压和排气温度维持在一个安全的范围内,以及实际使用中存在的诸如电子膨胀阀、平衡管、变频系统、蒸发冷凝器水质问题、运行效率等方面提出解决方案。     

Refrigerant charge prediction based on start-up characteristics of an air conditioner using a gray box model

The refrigerant charge is one of the important parameters that determines the performance and power consumption of an air conditioner. Refrigerant charge fault occurs because of refrigerant leakage as well as initial charge fault. Since refrigerant charge loss resulting from a leakage is a gradual process, it is difficult to detect it in an early stage of leakage. In this study, the refrigerant charge of an air conditioner was estimated using predictions of its start-up characteristics obtained from a gray box model. The dynamic characteristics of heat exchangers were assumed to vary with the refrigerant charge as well as operating conditions. Furthermore, the moving boundary method was used to determine the transient behavior of the refrigerant in the condenser and evaporator. Additionally, correction factors were employed in the heat exchanger model. The correction factors were correlated under training conditions of the air conditioner, and the accuracy of the model was verified by comparing its predictions with experimental results under test conditions. The condensation temperature was selected for estimating the refrigerant charge amount. The refrigerant charge could be estimated within a prediction error of 5 % by minimizing the differences between simulation and experimental data. The proposed method can be used for predicting the refrigerant charge and detecting faults in air conditioners during refrigerant leakage on the basis of the start-up characteristics of the air-conditioners.

     

制冷系统变工况性能数值模拟与实验研究

采用分布参数的方法建立了制冷系统的数学模型,在建立冷凝器和蒸发器两相区模型时采用了分相流模型,并考虑了流型变化对制冷剂流动换热过程的影响。利用所建模型,计算分析了冷凝器进口空气温度、蒸发器进口空气温度等参数变化对系统性能的影响,在焓差实验室对一台风冷热泵空调器性能进行了实验研究,得出了冷凝器和蒸发器进口空气温度随冷凝压力、蒸发压力、过冷度和过热度的变化曲线。将理论计算结果与实验结果进行对比分析,结果证实了所建仿真模型是合理的。     

冬季工况下R32热泵性能的试验研究

以一台变转速热泵空调器为研究对象,测试其在冬季用R32做制冷剂时机组的能效及换热器的传热性能,以研究制热工况下空调系统中用R32作为替代制冷剂的可行性。试验测量参数包括蒸发器(室外机)和冷凝器(室内机)的传热系数、换热量、总压力降以及整机制热工况下的COP。通过结构匹配的室内、外侧两换热器在系统运行中同步测量,结果表明:冬季名义制热工况下,R32空调系统的制热能力比用R410A高出约3.0%,蒸发器、冷凝器的传热系数也有所提高,其中蒸发器的传热性能提高约6.0%,冷凝器传热性能提高约6.7%,而压降对比则变化不大。