大中间流量四通阀对液击改善的分析与应用

四通阀是热泵型空调采用的冷热换向设备,依靠活塞两端的压力差推动活塞来实现换向。四通阀的可靠换向与系统的制冷剂流量有关。四通阀在制冷剂流量小的情况下,有可能卡在中间,处于中间状态,系统不能正常制冷制热。本文重点分析中间流量对四通阀液击的影响,采用加大中间流量的方式解决四通阀液击的问题。     

四通电磁换向阀液击损坏的预防措施分析

针对四通电磁换向阀(简称"四通阀")液击损坏问题,分析其液动力模型,发现避免四通阀换向时有液体流过、延长四通阀动作时间、减少阀口开度变化及阀口前后压差、增大阀芯材料强度等均可减少四通阀液击损坏。同时,采用楔形螺纹或预涂胶螺钉可以提高四通阀活塞与支架连接的可靠性;合理设置四通阀中间流量能够降低换向过程中的压力峰值。     

显热除霜方式与逆向除霜方式的对比试验研究

显热除霜是针对四通阀换向除霜方式的缺陷而提出的一种新型的除霜方式,它是利用压缩机排出的高温制冷剂的显热对蒸发器进行除霜.显热除霜方式与四通阀换向除霜方式的对比试验表明,采用显热除霜在保证正常除霜效果的同时,可以较大程度缩短除霜时间,避免四通阀换向除霜给制冷系统带来的冲击,消除"奔油"现象,除霜过程中系统供热水温度波动在5℃以内.     

风冷冷(热)水机组四通阀应用分析及实验研究

当前环保冷媒R410A风冷冷(热)水机组逐步大面积用于生产热水,对比此类机组运行条件及系统与普通空调的差异性的变化,研究发现其对四通阀应用存在差异性;本文着重从四通阀材料、结构及控制等方面进行研究并通过实验加以验证,得出在四通阀应用方面的相关结论。     

旁通小孔与环形通道并联型轿车磁流变液减振器

针对磁流变液减振器体积补偿与活塞换向时阻尼力非圆滑过渡问题,提出一种具有串级环形通道、并联旁通小孔、浮动活塞充气补偿的磁流变液减振器结构。依据磁流变液流变学测试数据确定Biplastic-Bingham本构模型参数;建立阻尼通道内磁流变液准稳态流动微分方程,结合本构模型得到流经活塞流量与上下腔压力差的关系;研究活塞旁通小孔节流、导向环状间隙节流、浮动活塞补偿和各部件间摩擦力共同作用下阻尼力的计算方法;依据国产某型号轿车悬架技术参数,设计制作磁流变液减振器样机,并对样机进行示功特性测试。测试结果表明:减振器示功曲线圆润饱满,各种励磁电流下磁流变阻尼器的理论阻尼值与测试值能较好吻合。     

气体微流量标准装置的研制

气体微流量标准是校准同流量的一种装置，可用于传递型和应用型参考漏孔及气体微流旦计的校准。它由恒压式微流量计、流量校准系统、待校流量引入系统和测量与控制系统四部分组成，。恒压式微流量计的变容室采用了活塞液压驱皮纹管结构，活塞的平动由恒力矩测速电机驱动导轨闰支机构完成，活塞的位移用精密光栅尺测量，在流量测量过程中，测量与控制系统将变容室和参考室之间的压力差在工作压力值的０．０１5％之内，该中采用直接测     

气体微流量标准装置的研制

气体微流量标准是校准气体微流量的一种装置，可用于传递型和应用型参考漏孔及气体微流量计的校准。它由恒压式微流量计、流量校准系统、待校流量引入系统和测量与控制系统四部分组成。恒压式微流量计的变容室采用了活塞液压驱动波纹管结构，活塞的平动由恒力矩测速电机驱动导轨平动机构完成，活塞的位移用精密光栅尺测量。在流量测量过程中，测量与控制系统将变容室和参考室之间的压力差控制在工作压力值的0．01％之内。该标准装置可采用直接测量法和比较测量法对气体微流量进行校准，其量程为1．71～1．22×10－5PaL／S，不确定度＜2％。     

一种新型空气源热泵除霜方式的实验研究

提出了一种新型空气源热泵除霜方式,其基本原理是在热汽旁通除霜循环的基础上将室外换热器分为前后两排,中间用毛细管节流,前后排换热管在除霜过程中分别作为蒸发器和冷凝器,利用四通阀换向分别对其进行除霜.对新循环除霜性能进行了实验研究,并与逆循环除霜方式进行了比较.实验结果表明,新型分组节流除霜方式合理地利用了除霜能量,因此除霜时间及除霜损失小于传统逆循环除霜方式.而且在除霜过程中不从室内吸收热量,对其温度波动影响较小.在除霜过程中,新除霜方式的四通阀换向次数与逆循环除霜方式相同,但系统压力的波动幅度远远小于逆循环除霜方式,因此对系统的机械冲击要小得多.     

流体换向装置流量的建模与仿真分析

基于有限元分析、计算流体力学理论,根据换向装置实际结构建立换向装置三维仿真模型,采用滑移网格技术,所用网格划分方案具有网格数量少、网格质量高等特点,仿真分析换向装置换向过程由于喷嘴内部水流流场变化对换向流量误差的影响。仿真结果显示,换入换出同向型换向装置在满足一定的条件下,换向流量零误差,换向装置换向误差与喷嘴内部特性等因素无关;换入换出反向型换向装置在满足一定条件下,换向流量存在误差,这类换向流量误差和喷嘴内流场特性关联。     

液体流量标准装置称重换向系统设计探讨

称重换向系统是液体流量标准装置的重要组成部分,其性能直接影响装置的性能指标。以静态质量法液体流量标准装置为例,简述了称重换向系统设计中的几点体会。     

空调用滚动转子式压缩机内制冷剂泄漏的研究

滚动转子式压缩机内制冷剂泄漏，主要是以溶于润滑油的形式来进行的，通过润滑油流动模型来模拟计算制冷剂的泄漏量。计算结果表明：径向间隙的泄漏量最大，其次是转子通向吸气腔的轴向端面间隙的泄漏量。通过变间隙的性能试验来间接验证泄漏对滚动转子式压缩机的影响。因此合理地设计泄漏间隙值，可以有效地降低滚动转子式压缩机的泄漏损失。     

测量线性压缩机活塞位移和PV功的新方法

提出利用激光三角法测量压缩机的活塞位移,结合压力传感器测得的气体压力,计算得到压缩机的活塞PV功;忽略活塞间隙的漏气损失,可计算得压缩机的输送PV功。设计了适用于激光测量活塞位移的带可视化窗口的压缩机外壳。针对一台特定压缩机,理论计算活塞与气缸之间的漏气量并通过实验验证了漏气量为小量。不同工况下对压缩机活塞位移进行测量,计算得到相应的活塞PV功和输送PV功,并与热线测量的输送PV功进行相互验证。利用激光测活塞位移的方法,观察脉冲管制冷机降温过程中压缩机活塞位移、压力、PV功及相位角的变化,给出相关分析。     

Testing and modelling of an automotive wobble plate compressor

Wobble plate compressors are well used in air conditioning for high-class automobiles. They allow continuous control by automatic adjustment of the piston stroke, to keep the low pressure above a certain limit. Here an externally controlled wobble plate compressor is analyzed experimentally through its isentropic and volumetric effectivenesses and control characteristics. Compressor effectivenesses depend mainly on the compressor speed and pressure ratio: there is obtained, for example, isentropic and volumetric effectivenesses of 0.65 and 0.8 for a pressure ratio of 4 at 1000 rpm and 0.4 and 0.35 for the same pressure ratio at 4000 rpm. This degradation is attributed to the increasing of the supply pressure drop. The “lubricant” (oil + dissolved refrigerant) mass flow rate is obtained by minimization of the residuals of the thermal balances on the compressor, condenser and evaporator. Here an important oil-flow circulation is obtained: between 9.5% and 12.5% of the refrigerant flow rate. A special displacement sensor is used to measure instantaneous piston stroke and to relate it to overall compressor performance. This measurement is then compared with the results obtained with a semi-empirical model, which is able to predict, in part load, the compressor displacement. The model predicts the displacement ratio with deviations that vary between −14.5% and +8.1%.     

蒸发盘管内制冷剂喷射蒸发的制冷系统研究

制冷剂高压能的利用对改善制冷系统运行有重要意义。基于场协同理论,提出了一种利用制冷剂在蒸发管内进行喷射的新型制冷系统,理论上分析了协同角随毛细管管径和喷射孔直径的变化规律,并进行了相关的可视化实验。理论分析结果表明:协同角随着喷射孔直径的增大而增大;随着毛细管管径的减小而减小,但是随之减小的速率降低。实验结果表明:和传统的毛细管节流制冷系统相比,开孔实验的制冷剂的充注量减少70%以上,COP提高了9%,系统达到稳定的时间减少了70%。     

Foaming of refrigerating oil in a rolling piston type rotary compressor

This paper is concerned with foaming of refrigerating oil in a rolling piston type rotary compressor for an air conditioner. Factors causing foaming during the starting operation were investigated experimentally. It was proved that foaming was caused by the stirring of the refrigerant-oil mixture with a motor rotor, a vane and a discharge refrigerant flow. The foaming was correlated with the solubility of refrigerant in oil and with the amount of refrigerant contained in the stirred region of the liquid mixture.     

制冷用大容量交叉式电磁四通换向阀设计改进

制冷用大容量交叉式电磁四通换向阀作为大型风冷热泵、热泵热水机组的核心部件，采用大流道活塞、交叉式结构，摆杆阀片控制方式，耐磨金属材料，可拆式螺纹联接及法兰密封等设计，使制冷剂流经阀体的流程短、阻力小、动作可靠、使用寿命长和维修保养方便。采用改进的信号管位置结构、单向阀座、活塞端面气室与接管封帽等后，更有力地提高了产品的可靠性。     

Effect of the header pressure drop induced flow maldistribution on the microchannel evaporator performance

This paper presents an experimental and numerical investigation of the flow maldistribution caused by the pressure drop in headers and its impact on the performance of a microchannel evaporator with horizontal headers and vertically oriented tubes. Experimental results show that the flash gas bypass method almost eliminates the quality induced maldistribution. However, refrigerant flow maldistribution caused by the header pressure drop still exists. This is mainly because the pressure drop along the headers results in uneven pressure difference and therefore non-uniform liquid refrigerant mass flow rate across each microchannel tube. A microchannel evaporator model validated by experimental results is employed to quantify header pressure drop induced flow maldistribution. Parametric analysis reveals that such maldistribution impact is significantly reduced by enlarging the outlet header size, increasing heat exchanger aspect ratio, or reducing the microchannel size while other parameters are kept constant. When ratio of outlet header to the total evaporator pressure drop is less than 30%, the cooling capacity reduction is limited below 3%.     

补气增焓低温多联机制热性能实验研究

低温空气源热泵产品普遍采用中间补气技术解决空气源低温多联机在低温环境中能力衰减严重的问题。本文研究了低温多联机中间补气增焓系统,通过多联机性能实验测试对系统压力、温度等参数进行测试,并对测试数据进行拟合分析,确定了补气增焓技术的控制要素:流经室外换热器的制热主路制冷剂的质量流量与状态是多联机补气增焓控制中的主要因素;中间补气增焓支路制冷剂干度越接近1,制热效果越好,因此保证压缩机补气口制冷剂饱和蒸气态可以作为低温多联机制热控制的重要参数;而由吸排气压力计算的理论最佳增焓压力不具有普适性,不能作为低温多联机补气增焓的有效输入项参数控制。     

浅析水源热泵空调系统的调试

水源热泵空调系统的性能主要受水系统和制冷剂充注量的影响,通过调节循环水温度和流量以及制冷剂的压力可以使机组在最佳状态下运行,减少故障率,为设备生产企业节约售后服务费用。     

Influences of miscible and immiscible oils on flow characteristics through capillary tube—part I: experimental study

A capillary tube is widely used as an expansion device for small refrigeration cycles. In a practical refrigeration cycle, some amount of refrigeration oil is discharged from a compressor and refrigerant/oil mixture flows through the capillary tube. This study investigated experimentally the influence of mixing of the refrigeration oil with the refrigerant on the flow through the capillary tube. The experiments are carried out with not only a miscible combination of refrigerant and oil but also an immiscible combination. In both cases, the mass flow rate through the capillary tube and temperature and pressure distributions along the tube are measured under several conditions of subcooled degree and oil concentration. In the case of miscible combination, the mass flow rate of refrigerant decreases with increasing the oil concentration because the viscosity of liquid phase increases by the mixing of viscous oil. Even in the case of the immiscible combination, the oil droplet is so small that it mixes homogeneously in the liquid phase in the capillary tube and the refrigerant mass flow rate decreases by the mixing of immiscible oil. There is no significant influence of the oil concentration on the underpressure, which means pressure difference between saturation pressure and flash inception pressure, in both miscible and immiscible combinations.