微通道换热器在家用分体空调应用的关键问题研究

发布时间：2019-05-17 21:03

【摘要】：家用空调行业氟利昂消费量巨大,制冷剂替代工作任务艰巨。碳氢制冷剂因其良好的环保和热力学性能,被中国政府作为下一代环保制冷剂推广应用。然而,碳氢制冷剂的易燃特性使其存在安全隐患,减少碳氢制冷剂的充注量是提高使用安全性的最有效方法。微通道换热器不仅可减少制冷剂充注量,而且可以提高了换热性能,因此在家用空调行业备受关注。但在实用过程中,微通道换热器也出现了冷凝水排除不畅,造成空调化霜困难,因容易结灰而使系统性能下降等问题。因此,本文针对微通道换热器应用于家用空调的关键问题进行了研究:一、对1.5HP家用分体空调各部件的减少充注量的潜力进行了分析,针对潜力最大的冷凝器进行了微通道换热器直接替代管片式换热器的实验研究。直接替代后,系统制冷剂充注量减少了41.5%,系统能效比提升1.8%。为了进一步优化微通道换热器减少制冷剂充注量的效果,建立了微通道换热器和空调系统模型,研究了微通道换热器集流管直径,扁管孔径等关键参数对于系统制冷剂充注量和性能的影响。研究表明,将集流管直径减小48%,冷凝器内的制冷剂充注量可降低36.2%;扁管内孔水力直径减小50%(增加孔数,保证相同换热面积),冷凝器内的制冷剂充注量可降低23%,且两种减少充注量的方法不会造成系统性能的明显降低。结合理论分析成果,设计了新型的换热器,通过扁管与集流管扭转连接的特殊方式,有效减小了内容积达50%,使1.5HP空调系统制冷剂充注量进一步降低了28.3%。使R290充注量减小到了190g。二、通过图像分割方法,研究了霜层在微通道换热器百叶窗翅片上的生长机理,结合霜层密度分布研究,总结了结霜过程的三个阶段及其霜层生长的特点。研究了换热器表面冷凝水残留对于结霜过程的影响,定量地给出了残水量对于结霜时间、最大换热能力和风阻的关系。通过对于不同放置位置的微通道换热器排水结霜性能的研究,利用扁管竖置有效提高了百叶窗翅片换热器的排水能力,保证了循环结霜过程的稳定性,有效运行时间提高32%。针对百叶窗的排水和结霜性能的缺点,发明了一种新型翅片,在湿工况和结霜工况下进行了实验研究表明,新型样件的排水性能比百叶窗和波纹翅片样件有明显改进,湿工况下换热性能提高了56.7%,结霜工况下有效运行时间增加了78%。三、对微通道换热器的积灰长效特性进行了实验研究。通过比较管片式与百叶窗微通道换热器的积灰过程,研究了微通道换热器表面积灰成核和堆积过程的特点,总结了减少快速成核区域和减缓成核速度的防积灰原则。并基于此原则,提出了波纹翅片加风机反吹的长效解决方案,使三个月后的系统性能衰减从49.5%降低到4.3%,有效抑制了积灰的形成和空调性能的衰减。建立风洞实验台,对7种不同翅片结构参数的波纹翅片微通道换热器的空气侧传热和压降特性进行了研究。利用非线性回归和F显著性检验方法对波纹翅片进行了实验关联式拟合。所获得的波纹翅片换热和压降关联式可对90%以上的数据进行准确预测,其预测误差在15%以内。所开发的波纹翅片关联式已应用于数十款家用空调和工程车用空调冷凝器的产品开发中。
[Abstract]:The consumption of freon in the domestic air-conditioning industry is huge, and the alternative work of the refrigerant is arduous. The hydrocarbon refrigerant is widely used by the Chinese government as the next generation of environment-friendly refrigerant because of its good environmental protection and thermodynamic performance. However, the flammable nature of the hydrocarbon refrigerant makes it a potential safety hazard, and the charge injection quantity of the hydrocarbon refrigerant is the most effective method to improve the safety. The micro-channel heat exchanger not only can reduce the filling amount of the refrigerant, but also can improve the heat exchange performance, so that the micro-channel heat exchanger is of great concern in the domestic air-conditioning industry. However, in the practical process, the micro-channel heat exchanger also has the problems that the condensed water is not smooth, the defrosting of the air-conditioning defrosting is difficult, and the performance of the system is reduced due to the easy-to-fly ash. In this paper, the key problem of the application of micro-channel heat exchanger to the domestic air-conditioning is studied in this paper. The experimental study on the direct replacement of the tube-type heat exchanger with the micro-channel heat exchanger is carried out for the condenser with the largest potential. After a direct substitution, the system refrigerant charge was reduced by 41.5%, and the energy efficiency ratio of the system was increased by 1.8%. In order to further optimize the effect of the micro-channel heat exchanger to reduce the refrigerant charge, a micro-channel heat exchanger and an air-conditioning system model are established, and the influence of the key parameters such as the diameter of the manifold and the aperture of the flat tube on the filling volume and the performance of the system is studied. the research shows that the diameter of the current collecting pipe is reduced by 48%, the filling amount of the refrigerant in the condenser can be reduced by 36.2%, the hydraulic diameter of the hole in the flat pipe is reduced by 50% (the number of holes is increased, the same heat exchange area is ensured), and the filling amount of the refrigerant in the condenser can be reduced by 23%, And the two methods for reducing the filling amount do not cause a significant reduction in the performance of the system. Combined with the results of the theoretical analysis, a new type of heat exchanger is designed, which can effectively reduce the content of 50% by the special mode of the flat tube and the torsion connection of the collecting pipe, and the refrigerant charge of the 1.5HP air-conditioning system is further reduced by 28.3%. The amount of charge of the r290 is reduced to 190 g. Secondly, by means of image segmentation, the growth mechanism of the frost layer on the fin of the micro-channel heat exchanger and the density distribution of the frost layer are studied, and the characteristics of the three stages of the frost formation process and the growth of the frost layer are summarized. The effect of the residual water on the frosting process of the surface of the heat exchanger was studied, and the relation of the residual water quantity to the frosting time, the maximum heat transfer capacity and the wind resistance was given quantitatively. Through the research on the drainage and frosting performance of the micro-channel heat exchanger with different placing positions, the drainage capacity of the louver fin heat exchanger is effectively improved by the vertical installation of the flat pipe, the stability of the circulating frosting process is ensured, and the effective running time is increased by 32%. Aiming at the defects of the water drainage and the frosting performance of the shutter, a novel fin is developed, and the experimental research is carried out under the condition of wet working condition and frosting condition, the water drainage performance of the novel sample piece is obviously improved compared with the louver and the corrugated fin sample piece, and the heat exchange performance of the novel fin is improved by 56.7 percent under the wet working condition, The effective running time in the frosting condition is increased by 78%. 3. The long-term effect of ash deposit on the micro-channel heat exchanger was studied. The characteristics of the surface area ash nucleation and accumulation process of the micro-channel heat exchanger are studied by comparing the ash deposition process of the pipe-piece and the louver micro-channel heat exchanger, and the principle of reducing the ash deposit on the rapid nucleation area and slowing the nucleation speed is summarized. And based on the principle, a long-acting solution for blowing back the corrugated fin and the fan is proposed, the performance of the system after three months is reduced from 49.5% to 4.3%, and the formation of the ash deposit and the attenuation of the air-conditioning performance are effectively suppressed. A wind tunnel experiment table was established to study the air side heat transfer and pressure drop characteristics of the corrugated fin microchannel heat exchanger with different fin structure parameters. In this paper, the non-linear regression and the F-significance test method are used to test the corrugated fin. The obtained corrugated fin heat exchange and pressure drop correlation type can accurately predict the data above 90%, and the prediction error is within 15%. The developed corrugated fin-associated type has been applied to the product development of the air-conditioning condenser for dozens of household air-conditioners and engineering vehicles.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM925.12

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