【作者】 李倩侠；

【导师】 张正国；

【作者基本信息】 华南理工大学 ， 化学工程， 2012， 博士

【摘要】 根据蒙特利尔协议，传统的制冷工质R22由于对大气臭氧层具有破坏作用而将禁用。目前，R134a、R410a和R407c作为其替代工质已在制冷空调行业广泛应用。除环保问题外，节能也是制冷空调行业亟待解决的重要问题。冷凝器和蒸发器是制冷空调机组重要的换热设备，其传热性能的高低直接影响到整个机组的效率和能耗水平。节能、节材的重大需求不断推进强化传热技术的发展，并促进了高效冷凝器和蒸发器的开发和应用。过去的几十年，德国、美国及日本公司开发出的不同类型强化传热管已在制冷空调行业广泛应用。其中，代表性的管外冷凝强化管是Turbo C管和管外沸腾强化管Turbo B管。本实验室自主开发出了强化管外冷凝传热的花瓣型翅片管（petal-shaped finned tube，简称PF管）及螺旋槽花瓣型翅片管（helical groove petal-shaped finned Tube简称HGPF管），以及不锈钢微翅片管（micro-fin tube，简称MF管）和强化管外沸腾传热的机械加工表面多孔管（mechanically fabricated porous surface tube，简称MFPS管）。本文对制冷工质R22及其替代工质R134a、R410a和R407c在自主研发强化管外的冷凝与沸腾传热进行了实验和理论研究，主要工作包括：（1）在饱和温度为39°C时，研究了单组分制冷工质R22和R134a及近共沸混合组分制冷工质R410a在单根光滑管、PF管和HGPF管外的冷凝传热性能。实验制冷工质在PF管和HGPF管外的冷凝传热系数都随壁面过冷度的增大而减小。HGPF管为双面强化传热管，既能强化管外制冷工质的冷凝传热系数，又能强化管内水的对流传热系数，且强化冷凝传热性能优于目前文献报道的Turbo C管。在实验范围内，对于R22、R134a和R410a，HGPF管的总传热系数分别是光管管的5.52~6.04倍、5.25~6.21倍和5.15~5.89倍。通过引入表面张力作用系数，建立了HGPF管的冷凝传热系数关系式，该关系式能较好地计算管外冷凝传热系数值。（2）在饱和温度为39°C时，研究了单组分制冷工质R22和R134a及近共沸混合组分制冷工质R410a在三根HGPF管外的冷凝传热性能。对于实验制冷工质，无论是每排管外冷凝传热系数，还是三排管的平均冷凝传热系数，都随壁面过冷度的增大而减小。在相同壁面过冷度条件下，R410a在三排管外的平均冷凝传热系数最大，R134a的平均冷凝传热系数最小。HGPF管存在明显的管束效应影响，基于Nusselt的管束效应公式，建立了HGPF管的管束效应的计算关系式。在相同壁面过冷度条件下制冷工质蒸汽饱和温度为35°C时的管束平均冷凝传热系数高于39°C时的平均冷凝传热系数。（3）在蒸汽温度为39°C时，研究了非共沸混合制冷工质R407C在PF管外（包括单管、三排管束以及螺旋隔板冷凝器）的冷凝传热性能。随着壁面过冷度的增加，管外冷凝传热系数也增加，这与单组分及近共沸混合组分制冷工质的冷凝传热现象相反，其原因是非共沸混合制冷工质冷凝过程中存在传质阻力的影响。单管冷凝传热研究表明，PF管的强化因子为4.6~5.35。对于R407C的冷凝，PF管也存在明显的管束效应。在相同热流密度下，螺旋隔板PF管冷凝器的冷凝传热系数是低肋管（Low finned tube，简称LF管）冷凝器的1.56倍左右。建立了螺旋隔板PF管冷凝器和LF管冷凝器的冷凝传热系数关系式，该关系式与实验结果吻合良好。（4）针对制冷设备在海水等特殊冷却介质中的应用，开发出不锈钢MF管。在饱和温度为39°C时，研究了单组分及近共沸混合组分制冷工质R22、R134a和R410a在单根MF管外的冷凝传热性能。随着壁面过冷度的增加，冷凝传热系数逐渐减小。制冷工质R134a、R22和R410a在MF管的强化因子分别为2.23~2.81、2.4~3.55和2.65~3.55，强化冷凝传热性能大大小于PF管。（5）在饱和（蒸汽）温度为39°C时，研究了制冷工质R22及其替代工质R134a、R410a和R407c在MFPS管束池沸腾传热性能。随着热流密度的增加，制冷工质的沸腾传热系数也增大。在三排管束中，对于制冷工质R22、R134a和R410a，第二排管的沸腾传热最高、其次是第一排管，第三排管最小。对于制冷工质R407c，第二排管的沸腾传热最高、其次是第三排管，第一排管最小。在管束蒸发器中，在相同的热流密度下，R410a沸腾换热传热系数分别是R22和407C的1.25~1.81和6.33~7.02倍。对于R22和R410a，沸腾传热热阻与总热阻的比值分别低于21％和15％，这表明水侧热阻是控制热阻。但对于R407C，沸腾传热热阻与总热阻的比值在55％左右，制冷工质侧热阻比水侧略高。建立了沸腾传热系数与热流密度的关系式，该公式的计算值与实验值吻合良好。在此工作基础上，还完成了双面强化螺旋槽MFPS管满液式蒸发器的性能测试。更多还原

【Abstract】 According to the Montreal protocol, the traditional refrigerant R22will be definitelyprohibited due to the harm to the Ozone layer. At present, R134a, R410a and R407c arewidely used as substitute refrigerants in the refrigeration and air-conditioning industry.Besides environmental protection problem, energy saving is an important issue that must besolved, too. Condenser and evaporator are the crucial heat exchanger equipments in therefrigeration unit, their heat transfer performances will directly affect the refrigeration unitefficiency and energy consumption. The significant demand for energy and material savingwill continue to promote the development of heat transfer enhancement technique and theapplication of high efficient condenser and evaporator.Past several decades, many enhanced heat transfer tubes were developed and used in therefrigeration and air-conditioning industry by some companies in Germany, American andJapan. Turbo C and B tubes were representative condensation and boiling enhanced tubes forheat transfer outside tubes, respectively. Novel condensation heat transfer enhancement tubessuch as petal-shaped finned tube (PF tube), helical groove petal-shaped finned Tube (HGPFtube) and stainless steel micro-fin tube (MF tube) and mechanically fabricated porous surfacetube (MFPS tube) for boiling heat transfer enhancement were autonomously developed by ourgroup. In present work, the experimental and theoretical researches on condensation andboiling heat transfer for refrigerant R22and its substitute refrigerants R134a, R410a andR407c outside novel enhanced tubes were conducted. The main works are summarized asfollowing:（1）At saturation temperature of39°C, the condensation heat transfer performance forsingle component refrigerants R22and R134a and azeotropic refrigerant mixture R410a wereconducted outside single smooth, PF and HGPF tubes. The condensation heat transfercoefficients（HTCs） decrease with increasing wall subcooling. HGPF tube is an inside andoutside enhanced tube, it can enhance both condensation heat transfer outside tube andconvective heat transfer for water flowing inside tube，and the condensation heat transferperformance is superior to Turbo C tube reported in the literature. The overall HTCs of R22,R134a and R410a are5.52~6.04,5.25~6.21and5.15~5.89times HGPF tube outside as largeas those of smooth tube, respectively. By inputting the surface tension coefficient, thecorrelation of condensation HTC HGPF tube was built, it could calculate condensation HTC well.（2）At saturation temperature of39°C, the condensation heat transfer performance forsingle component refrigerants R22and R134a and azeotropic refrigerant mixture R410a wereconducted outside smooth, PF and HGPF tubes. Both condensation HTC on each row andaverage tube bundle decreased with increasing wall subcooling. At the same wall subcooling,the average condensation HTC was the biggest for R410a, and R134a was the smallest. Thetube row effect was obvious for HGPF tube. Based on Nusselt model, the correlation of tuberow effect was produced. At the same wall subcooling, the average condensation HTC atsaturation temperature of35°C was higher than that of39°C.（3）At saturation temperature of39°C，the condensation heat transfer performances onnonazeotropic refrigerant mixture R407c were studied outside single PF tube, three row PFtubes and helical baffle condenser. With increasing the wall subcoolinbg, the condensationHTC increased, this phenomenon was adverse with R134a and R410a, the reason is that themass transfer in vapour phase affected the condensation heat transfer process. The resultshowed that the enhancement factor for single PF tube is4.6~5.35. The tube row effect wasobvious for the PF tube, too. At the same flux, the condensation HTCs of helically baffledcondenser with PF tubes were about1.56times as large as that of helically baffled condenserwith low finned tubes (LF tubes) at the same heat flux. Correlations have been suggested forboth the shell-side condensation HTCs for the two condensers with different tube types andgive very good agreement with experimental results.（4）Aimed at the application of sea water as the coolant in refrigeration unit, the novelstainless steel MF tube was developed. At saturation temperature of39°C，the condensationheat transfer performance of R22、R134a and R410a were researched. The condensation HTCdecreased with increasing wall subcooling. The enhancement factors of R134a、R22andR410a were2.23~2.81、2.4~3.55and2.65~3.55, respectively. They were lower than those PFtube.（5）At saturation or vaour temperature of39°C，the pool boiling HTCs of R22, R410aand R407c were studied on MFPS tube bundle. It is found that the pool boiling HTC increaseswith increasing the heat flux. In three tube rows, the boiling HTC on the second row was thehighest for R22、R134a and R410a, and it was the lowest for the third row. But for R407c, theboiling HTC on the first row was the lowest. For the evaporator with the MFPS tube bundle,it was found that boiling HTCs for R410a are1.25–1.81times and6.33–7.02times higherthan that for R22and R407c, respectively. The experimental correlations for the pool boiling HTCs of R22, R407c, and R410a on the present enhanced tubes bundle were developed. Thethermal resistance analysis reveals that the thermal resistance of the water side was acontrolling factor for the evaporator for R22and R410a. However, for R407c, the thermalresistance of the refrigerant side was slightly higher than that of the water side. The heattransfer performance of the flooded evaporator with helical groove MFPS tubes was tested.更多还原