空调系统制冷剂灌量与毛细管长度的优化匹配研究

在制冷剂充灌量和毛细管长度对空调系统性能影响进行数值仿真分析的基础上，建立了空调器制冷剂充灌量与毛细管长度的优化匹配模型，确定了以制冷量和EER为优化目标的制冷剂充灌量和毛细管长度的优化区间和制冷量最大以及EER最大时的制冷剂充灌量和毛细管长度，为空调器的优化设计匹配，提高空调器的性能奠定了基础。     

实现房间空调器最佳制冷循环的实验研究

介绍了ＫＣＲ－２２Ａ窗式热泵型空调器的实验研究结果，分析了制冷剂充灌量和毛细管长度（内径一定）之间存在的最佳匹配关系以及制冷剂充灌量对空调器性能的影响。     

确定空调器最佳充灌量的实验研究

提出了一种以小型空调器性能系数ＣＯＰ最大为目标来确定制冷剂最佳充灌量和匹配毛细管的实验方法。这种方法不仅能确定设计工况时的最佳充灌量，还能确定某一工况范围内最佳充灌量的变化量以及毛细管的流量，对于快速、准确确定空调器新品的充灌量和提高空调器的性能指标都有重要意义。     

制冷剂充注量与毛细管长度对家用空调性能的影响

通过试验的方法研究了空调器制冷剂充注量与毛细管长度对制冷系统的影响,得出了相应的试验曲线,找出最佳匹配结果,并根据试验结果分析毛细管长度与制冷剂充注量影响空调性能的规律。     

变径毛细管代替毛细管组件在冷暖空调器上的应用研究

变径毛细管在正向流动和反向流动时其制冷剂流量特性不同,因而可以作为节流元件代替现有冷暖空调器中使用的毛细管组件。为实现这一目的,利用制冷剂流量试验台,先测定原毛细管组件制冷、制热时的制冷剂流量特性,然后通过调整变径毛细管规格尺寸,使变径毛细管制冷、制热时的流量特性与原毛细管组件基本一致,再安装在空调器整机上进行整机性能对比试验。试验表明,在标准工况下,新空调器与原空调器相比,其制冷量减少0.5%,制冷能效比增加0.3%,制热量减少1.1%,制热性能系数增加1.4%。因此可以得出,变径毛细管经过精确匹配,完全可以作为节流元件代替现有冷暖空调器中使用的毛细管组件。     

一种小型工业空调的故障分析与改进

实验分析了制冷剂充灌量、毛细管长度、通风量以及环境温度对冷凝器温度的影响。通过采用优化参数以及一系列改进方案使所使用的小型工业空调排除了故障，实现了正常运转。     

R290替换R22应用于家用空调的试验研究

分析了R290应用于家用空调的优势及可行性,采用某企业生产的R22家用冷风型分体机,直接充注R290制冷剂,在焓差实验室内调整毛细管规格及制冷剂灌注量,使性能达到最佳状态,结果表明:R22系统直接灌注R290制冷剂,灌注量仅为原来的44.7%,但制冷量下降13.64%,能效比稍有提高。为进一步减小灌注量、提高制冷量,采用了平行流换热器作为冷凝器,重新调整灌注量及毛细管规格,结果显示R290灌注量大幅减少,制冷量及能效比显著提高,R290灌注量的减少有利于制冷系统的安全性。     

增设喷雾降温系统的家用空调器性能与特性的试验研究

针对家用空调器夏季运行室外热环境差的问题,提出在其室外机增设喷雾加湿装置以降低冷凝温度进而达到提高空调器性能和制冷量的目的。本文对增设喷雾降温系统地空调器进行了试验研究,分析了增设喷雾降温系统对空调器冷凝器出口空气温度和制冷系统性能的影响。实测研究发现,增设喷雾加湿系统后,冷凝器出口制冷剂压力有所降低,制冷系统性能系数EER可提高2%~7%,效果显著。     

温度对家用空调器制冷性能的影响

在不同的室内外温度情况下,对5台制冷量为2600W热泵型分体空调器进行了实验分析,研究了室内外温度对空调器的制冷能力、显热能力、能耗和能耗比EER等性能的影响规律。总结出:室外温度每上升1℃,制冷量平均下降25.3W,显热量平均下降20.2W,EER值平均下降0.035;室内温度每提高1℃,制冷量平均增加57.6W,显热能力增加26.6W,EER提高0.0515。     

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。     

混合工质HCFC—22／HFC—152a汽车空调系统中泄漏性能分析

对采用HCFC-22/HFC-152a混合制冷剂的汽车空调的泄漏性能进行了分析;说明了HCFC-22/HFC-152a混合制冷剂不会因泄漏引起制冷系统性能的显著变化,它可作为现有的汽车空调系统的过渡替代工质。     

绝热毛细管内制冷剂质量流量的特性研究

运用绝热毛组管的均相流模型，数值模拟了毛细管内制冷剂的质量流量，并进行了实验验证；分析了R12、R134a两种制冷剂在毛细管内的流动特性，讨论了过冷度、毛细管长度、入口压力、出口压力等参数对制冷剂质量流量的影响。     

变频空调器中工质分布实验研究

以系统中制冷工质充注量守恒为原则 ,通过实验 ,研究了变频空调器工作过程中系统内制冷工质的分布规律     

Numerical simulation of the effects of a suction line heat exchanger on vapor compression refrigeration cycle performance

Most modern refrigerators incorporate heat transfer between the refrigerant in a capillary tube and the refrigerant in a suction line. This heat transfer is achieved by a non-adiabatic capillary tube called a capillary tube-suction line heat exchanger and is supposed to improve the performance of the small vapor compression refrigeration cycle by removing some enthalpy of the refrigerant at the evaporator entrance. To investigate the effects of this heat transfer on the refrigeration cycle, a computer program was developed based on conservation equations of mass, momentum, and energy. The non-adiabatic capillary tube model is based on a homogeneous two-phase flow model. The simulation results show that both the location and length of the heat exchange section influence the coefficient of performance (COP) as well as the cooling capacity. It is noteworthy that the influence was not monotonic; that is, the performance may be deteriorated under certain conditions.     

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.

     

Performance investigation of capillary tubes for machine tool coolers retrofitted with HFC-407C refrigerant

The machine tool coolers are the best managers of coolant temperature in avoiding the deviation of spindle centerline for machine tools. However, the machine coolers are facing the compressed schedule to phase out the HCFC (hydro-chloro-floro-carbon) refrigerant and little attention has been paid to comparative study on sizing capillary tube for retrofitted HFC (hydro-floro-carbon) refrigerant. In this paper, the adiabatic flow in capillary tube is analyzed and modeled for retrofitting of HFC-407C refrigerant in a machine tool cooler system. A computer code including determining the length of sub-cooled flow region and the two phase region of capillary tube is developed. Comparative study of HCFC-22 and HFC-407C in a capillary tube is derived and conducted to simplify the traditional trial-and-error method of predicting the length of capillary tubes. Besides, experimental investigation is carried out by field tests to verify the simulation model and cooling performance of the machine tool cooler system. The results from the experiments reveal that the numerical model provides an effective approach to determine the performance data of capillary tube specific for retrofitting a HFC-407C machine tool cooler. The developed machine tool cooler system is not only directly compatible with new HFC-407C refrigerant, but can also perform a cost-effective temperature control specific for industrial machines.     

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.     

A study of signal noise reduction of the mass air flow sensor using the flow conditioner on the air induction system of heavy-duty truck

The mass air flow meter is a critical sensor that works based on thermal hot wire technology, used to determine the fuel to be injected into the cylinder and calculate the fuel-air ratio. In order to measure the airflow rate accurately, the flow should be uniform and smooth upstream of the sensor. The flow disturbance with a short straight length upstream of the flow meter results in the noise of the sensor signal. This noise causes unstable mass flow measurement on the system. Flow conditioners can be used to smooth the velocity profile of the flow. In this study, experimental and numerical methods were used to characterize the performance and operating accuracy of the mass flow meter used in heavy-duty truck applications. The flow conditioners were implemented to smooth the velocity profile around the mass flow meter that was disrupted by bends. The flow structures with and without flow conditioner were examined using Particle Image Velocimetry (PIV) to measure the time-averaged velocity. As well as the validated computational fluid dynamics (CFD) model provides data to understand the flow uniformity effect of the conditioner on the mass airflow (MAF) sensor. The optimization study was performed using a full factorial design of experiment (DOE) for flow conditioner design. A robust methodology was developed for the flow conditioner characteristics and mass airflow sensor implementation on the air induction system.