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。     

R134a单元机的绝热毛细管实用关联式研究

对采用(Φ)3.8×0.5mm绝热毛细管的R134a单元式风冷冷风机组进行了试验,改变毛细管的长度,记录机组运行参数并分析机组性能的变化.在此基础之上,采集20个工况点的数据,通过多元线性回归,建立了R134a单元机的绝热毛细管实用关联式.对比试验结果与关联式的计算值,最小相对误差为1.1%,最大相对误差为12.6%,平均相对误差为4.95%.     

制冷系统中毛细管的特性研究

本文分析了制冷剂R12在毛细管流动中出现的堵塞流与闪点的延迟现象,对毛细管在绝热和有内部热交换的两种情况进行了理论计算与比较。计算结果对毛细管长度的选择、制冷系统的设计均有一定的参考价值。     

R22替代物R290的理论与试验研究

从理论上分析了用R290替代R22的可行性。经过热力循环计算的对比，认为R290与R22的各种热力学性质比较接近。对制冷系统的毛细管进行改进后的试验测试结果表明：改进毛细管后用R290替代R22的3种国产家用空调器COP系数分别提高了12．81％、19．03％、14．61％。     

混合工质R22/R152a/R142b用于冰箱替代R12的研究

对在双门冰箱中以非共沸混合工质R22/R152a/R142b替代有害环境的工质进行了热力学分析与实验研究,结果表明,在冰箱结构基本不变的条件下,适当变化毛细管长度,用一定配比的R22/R152a/R142b可以替代R12。     

毛细管内表面粗糙度对除湿机性能影响的试验研究

根据生产过程中除湿机性能散布发生的情况,分析中发现毛细管内表面粗糙度有差异,为了分析粗糙度对性能的影响度;又由于常规氮气流量测试不能准确反映粗糙度的变化,故模拟小型制冷系统毛细管两端冷媒状态,搭建R22毛细管流量测量试验台。通过此实验台对相同规格不同内壁粗糙度的毛细管进行流量测试,其结果对比除湿机性能试验结果,从而分析毛细管内表面粗糙度对除湿机性能的影响。     

节流短管内制冷剂流动的两流体模型

制冷剂在短管内的两相节流过程存在显著的动力学和热力学非平衡特性。建立了描述节流短管内制冷剂两相流的六方程两流体模型,模型中考虑了相间速度滑移和温度滑移。计算表明,制冷剂在短管内比在毛细管(长管)内的闪蒸过程具有更大的相间速度滑移和温度滑移。对R134a在短管内的流量特性进行了预测,与试验数据偏差小于±20％。     

用于光纤传感的非对称法布里-珀罗腔

设计了一种用于光纤传感的新型非对称法布里—珀罗(F-P)干涉腔。干涉腔由固定在石英毛细管的两根镀膜光纤构成,该干涉腔改善了普通F-P腔的反射响应特性,有助于提高传感器的灵敏度和测量范围。基于薄膜干涉理论对该干涉腔的反射率响应关系的计算与分析,得出该非对称F-P腔的结构参数。设计结果表明,这种新型干涉腔具有线性度好、灵敏度高和线性范围宽的优点。     

大面阵彩色CCD航测相机的辐射定标

以大面阵彩色CCD航测相机为研究对象,分析其成像过程,提出了影响相机辐射响应特性的各个因素,并以此为基础,建立了辐射响应特性模型.分别在暗场和使用积分球的条件下进行了辐射响应标定实验,通过组合更改输入辐亮度、曝光时间和CCD增益等因素对相机的辐射响应特性进行测量和分析.结果表明,相机R、G、B颜色通道随输入辐亮度变化的辐射响应特性并不相同,但在工作谱段范围内均呈线性变化趋势.采用最小二乘法对辐射标定数据进行拟合,一次多项式拟合结果的决定系数R2值均可达到0.999以上.当输入辐亮度不变时,相机输出图像灰度值随曝光时间或CCD增益的变化星线性变化趋势,从而为其它工作条件下辐射响应特性曲线的推演奠定了理论基础.将相机辐射响应标定结果应用于相机调光功能,成像结果表明,获得的图像亮度适中,图像平均灰度值满足调光要求.     

液体CO2在毛细管内的流动特征

提出了液体CO2在毛细管内流动的物理模型,对液体CO2在毛细管内流动时的压降、干度及亚稳态特性等方面进行了分析,并分析了三相点干度突变的原因,推论出两段亚稳态段对液体CO2质量流量总的影响超过了20％,临界流动时液体CO2在毛细管出口处根本没达到当地音速。     

Flow and pressure drop characteristics of R22 in adiabatic capillary tubes

The objective of this study is to present flow and pressure drop characteristics of R22 in adiabatic capillary tubes of inner diameters of 1.2 to 2.0 mm, and tube lengths of 500 to 2000 mm. Distributions of temperature and pressure along capillary tubes and the refrigerant flow rates through the tubes were measured for several condensing temperatures and various degrees of subcooling at the capillary tube inlet. Condensing temperatures of R22 were selected as 40, 45, and 50°C at the capillary tube inlet, and the degree of subcooling was adjusted to 1 to 18°C. Experimental results including mass flow rates and pressure drops of R22 in capillary tubes were provided. A new correlation based on Buckingham π theorem to predict the mass flow rate through the capillary tube was presented considering major parameters which affect the flow and pressure drop characteristics.     

Simulation on refrigerant flow in adiabatic capillary tube

This paper proposes a new mathematical model to calculate flow characteristics of the adiabatic capillary tube, which is aimed at solving problems existing in some earlier models. The Stocker’s model was modified with consideration of various effects due to sub-cooling, area concentration, and rolling diameter. The new model can be used not only for R22, but also for its substitutes such as R410A and R407C. A comparison of simulation results of the modified model with those in literature showed that the errors are within 10%. The flow characteristics are finally analyzed.     

制冷空调系统毛细管和压缩机流量匹配研究

对小型制冷系统毛细管和压缩机的匹配进行理论实验研究,分别建立毛细管和压缩机的流量模型,然后用实验值对压缩机模型进行修正,对Ｒ１２,Ｒ１３４ａ,Ｒ１５２ａ分别进行了计算和实验。     

壅塞流动下绝热毛细管长度的近似解析解

为适应毛细管的工程设计要求，在绝热毛细管积分近似模型的基础上，提出壅塞流动下绝热毛细管长度的近似解析解。对流动壅塞的情况，为解决积分近似模型中长度计算需要迭代的问题，通过长度与压力的变化关系，提出了一种直接判别与计算流动壅塞的方法。实例计算表明近似解满足工程精度要求。基于近似解，对绝热毛细管壅塞流动特性进行了理论分析。     

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.     

微尺度通道内混合物流动沸腾特性研究

对非共沸混合工质R32／R134a(25％／75％)在微尺度管内的流动沸腾换热特性进行了试验研究。试验结果表明,在较高热流密度下,微尺度管内流动沸腾换热与质量干度和质量流量基本无关,热流密度对换热有着很大的影响,在较宽的热流密度范围内,核态沸腾在换热过程中占据主导地位。和细小管道相比,在相同条件下,微尺度管道内的流动沸腾表面传热系数高于细小管道。     

Simulation on refrigerant flow in adiabatic capillary tube

This paper proposes a new mathematical model to calculate flow characteristics of the adiabatic capillary tube, which is aimed at solving problems existing in some earlier models. The Stocker’s model was modified with consideration of various effects due to sub-cooling, area concentration, and rolling diameter. The new model can be used not only for R22, but also for its substitutes such as R410A and R407C. A comparison of simulation results of the modified model with those in literature showed that the errors are within 10%. The flow characteristics are finally analyzed. __________ Translated from Journal of hydrodynamics, Ser. A, 2006, 21(3): 318-323 [译自: 水动力学研究与进展]     

Experimental investigation of the reverse heat transfer of R134a flow through non-adiabatic coiled capillary tubes

This research represents an experimental investigation of the metastable flow and re-condensation phenomenon through non-adiabatic lateral helical capillary tubes and suction tube heat exchanger. The results show that mass flux ratio has a vital role: It affects metastable flow and also reverse heat transfer phenomenon through non-adiabatic helical capillary tube. Therefore, by increasing of the mass flux ratio, the rate of heat transfer between them decreases. In contrast to the strong rate condition of heat transfer between them, reverse heat transfer or re-condensation maybe happen. Moreover, experimental results show that for R134 flow with mass flux ratio more than 57.84, metastable flow exists in non-adiabatic capillary tube with 0.9144 mm inner diameter, 30 mm coil diameter, 6.18 m length, 4 mm inner diameter of compressor suction tube.

     

R717管内流动沸腾传热关系式评价分析

综述了R717管内沸腾传热试验研究;从7篇论文中搜集了1157组R717沸腾传热试验数据;利用试验数据评价了现有的36个管内流动沸腾换热关系式;研究了干度和管径对换热系数的影响;与CO2、N2和水3种自然制冷剂的传热特性进行了比较。文章获得了一些具有使用价值的结论,为R717管内沸腾传热计算公式的选用提供了指导,为R717流动沸腾传热的进一步研究提供了参考。