【作者】 韩晓霞；

【导师】 南晓红；

【作者基本信息】 西安建筑科技大学 ， 供热、通风与空调工程， 2004， 硕士

【摘要】 近年来，制冷与空调行业中所采用的HCFCs制冷剂的禁用与替代成为研究热点问题，人们努力寻找新的对环境无害或危害小的制冷工质，并对这些新的制冷工质的传热及流动性能进行深入的研究。R22的替代研究表明，对臭氧无害的替代工质的传热性能往往不及R22，采用强化传热技术可以弥补其传热性能的降低。 本课题正是在上述研究背景下提出的。本文对新型环保替代工质R290和R404A在光管、内螺纹强化管内的流动沸腾换热进行了理论分析和计算(编制了C语言程序)，主要内容包括以下几个方面： 1．研究了文献中的几个通用性较好的光管、内螺纹管沸腾换热系数计算关联式，并深入分析了各内螺纹管沸腾换热系数关联式的联系与区别。 2．对R290和R404A，分别根据搜集到的光管、内螺纹管内的沸腾换热系数实验数据，筛选出了相应较好的理论预测模型。Shah关联式对R290和R404A在光管内的沸腾换热系数预测精度最高；Koyama关联式经修正后可较好的预测R290在内螺纹管中的沸腾换热系数；Thome关联式对R404A在内螺纹管中的沸腾换热系数有良好的预测精度。 3．对近共沸混合工质R404A，通过对光管和内螺纹管沸腾换热系数关联式的分析计算得出结论：在计算R404A的光管和内螺纹管沸腾换热系数时可以被作为纯质来处理。 4．对R290和R404A，通过研究Koyama和Thome关联式，分析了内螺纹管齿高、螺旋角等齿型参数对工质沸腾换热性能的影响。此外，还对内螺纹管的强化传热机理进行了分析。 5．研究了通用性较好的Lockhart & Martinelli摩擦压降关联式，同时将R290和R404A的管内沸腾换热压降实验数据与关联式计算值进行了比较，结果显示：此关联式对R404A的光管和内螺纹管沸腾换热摩擦压降有良好的预测精度，而且对于R290的光管沸腾换热摩擦压降有良好预测精度。西安建筑科技大学硕士论文 6.给出了内螺纹管的强化传热性能评价方法，并依据此评价方法研究了R290和R404A在内螺纹管中的强化换热性能，得出结论:R404A在内螺纹管中有良好的沸腾换热强化性能;对于R290，在较小的质量流速下，它在内螺纹管中沸腾换热强化性能较好，但随着质量流速的增大，其沸腾换热强化性能逐渐减弱。更多还原

【Abstract】 In recent years, due to the phase-out of HCFCs in refrigeration and air conditioning industry, refrigerants which do little harm to enviroment are being developed and their thermodynamic characteristics are being studied deeply. Because research on substitutions for R22 shows that the heat transfer abilities of its substitutions are less than that of R22, microfin tubes are applied to augment in-tube evaporation and condensation heat transfer.The objective of this dissertation is to conduct on theorical analysis and calculation upon flow boiling heat transfer inside horizontal smooth and microfin tube of R290 and R404A, which are newly environmental replacements of R22. And the major parts of the dissertation are as follows:1. Some different empirical formulations on predicting the in-tube boiling heat transfer coefficients are examined.2. Based on the experimental data collected, the formulations which can predict accurately in-tube boiling heat transfer coefficients of R290 and R404A are seleted. Shah correlation can predict precisely heat transfer coefficients of R290 and R404A in horizontal smooth tube. Koyama correlation which is modified can predict precisely heat transfer coefficients of R290 inside horizontal microfin tube. Thome correlation has good precison in calculating heat transfer coefficients of R404A inside horizontal microfin tube.3. The analyses on different empirical formulations of in-tube boiling heat transfer coefficients indicate that R404A can be treated as pure refrigerant during calculating its the in-tube boiling heat transfer coefficients.4. The effects of geometrical parameters of microfin tubes on the in-tube boiling heat transfer coefficients is analyzed. In addition, the principles on intensifying heat transfer in microfin tube is also analyzed.5. Lockhart & Martinelli pressure drop correlation is studied, and at the same time, based on theexperimental data collected, the accuracy of this formulation is examined.6. The evaluating method on intensifying heat transfer performance in microfin tube is provided, and by this method the performance of R290 and R404A is investigated.更多还原