【作者】 袁玉玲；

【导师】 刘金平；

【作者基本信息】 华南理工大学 ， 工程热物理， 2011， 硕士

【摘要】 能效是表征空调制冷设备质量的重要指标,提高空调设备能效指标的途径主要有:提高压缩机的性能和提高换热器的性能。对空调设备生产厂家来说,提高压缩机性能只能是选用性能比高的压缩机,因此,提高空调设备的能效比的主要途径之一是提高换热器的性能。本文首先建立了翅片管式蒸发器和冷凝器空气侧流动与传热模型以及制冷剂侧流动与传热模型,并基于VB.NET编程语言、Refprop制冷剂物性数据库和空气焓湿图开发了面向对象的蒸发器和冷凝器仿真模拟软件。并通过课题组搭建的翅片管换热性能实验台对蒸发器仿真模拟软件进行了准确性验证。实验结果表明:在相同工况下,仿真计算结果与实验结果基本上吻合,而且变化趋势也相同,证明了本仿真模型和算法是可靠的,计算精度可以满足工程应用上的需要。本文利用作者开发并通过实验验证的蒸发器仿真软件对蒸发器性能进行了仿真模拟计算,研究了管排数对换热性能的影响,管排数在不同迎面风速,不同风机功率下换热性能的影响规律,以及对比分析了管排数对R410A和R22换热器换热性能的影响。研究结果表明:每增加1排管,每排管的平均换热量减少18%左右,增加到7排管时,平均每排管换热量相对于3排管时的平均换热量降低了55%。这说明增加管排数尽管增大了传热面积,但不能使总换热量显著增加,因此并不是一种经济的增加换热量的方式。另外还得出:在相同条件下,制冷剂为R410A的换热量比R22大5%左右,管排数对使用这两种制冷剂的蒸发器换热性能影响趋势一致。本文还利用冷凝器仿真软件对翅片管式冷凝器性能进行了仿真计算研究,由于冷凝器空气侧只有干工况的情况,算法比蒸发器略简单。通过计算得出结论:当管排数增加到一定程度,管排数对压降的影响越来越小;增加管排数后,管后涡流区的范围会扩大,增强了其对换热的恶化作用,导致换热量的增加量越来越小;冷凝液膜所形成的制冷剂侧热阻对换热系数的影响较大,应及时将冷凝液排走,有助于强化管内侧换热性能。管排数增加到一定程度时,换热量变化很小,因此从成本经济性方面考虑,冷凝器设计中管排数一般不超过6排。更多还原

【Abstract】 Energy efficiency is one of the most important indexes of air conditioning and refrigeration equipment. The measure to improve the energy efficiency mainly focuses on two aspects: one step is to enhance the performance of the compressor, and the other is to improve the heat exchanger’s performance. As to manufacturers, the former means to choose efficient compressors only. Therefore, the improvement of the heat exchanger’s performance can be one of the main ways to increase the air conditioning equipment’s energy efficiency ratio.The flow models and the heat transfer models have been firstly established in this paper, both on the air side and the refrigerant side of the fin–tube evaporator and condenser. Then, based on the refrigerants property database of Refprop7.0 and the enthalpy moisture graph of air, the object–oriented simulation calculation software of the heat exchangers was developed with VB.NET. And also, a wind–tunnel experiment apparatus was set up to test the accuracy of the evaporator software. Comparisons were conducted between simulation results and data from experiment. In the same condition, they are almost equal and have identical changing tendency. The results show that the software has a good accuracy. Therefore, the software can meet the needs of engineer applications.The evaporator simulation was conducted with the above software which has been validated by experiment. The influence and its law of number of tube rows on the heat transfer performances of evaporator were respectively analyzed at different head–on airflows and at different fan power. And also, comparative analysis of the above influence was conducted among the heat exchangers using R410A and using R22.The results indicated that the average heat transfer rate of each tube row reduces about 18% for one row added, and the row up to seven, the average value decreases 55%, relatively to three rows of tubes. The results showed that the total heat transfer rate increases indistinctively as number of tube rows increases, though the heat transfer area is enlarged. Therefore, increasing simply the row of tube is not an economic method. Besides, it also concluded that the total heat transfer of the evaporator using R410A is 5% larger than that using R22 in the same condition, but with uniform trend as the tube row increased.Similarly, the Fin–Tube condenser simulation was carried out with the condenser software. Its calculation is simpler than the evaporator, due to dry condition in the air side. The results indicated that the impact of the tube row on pressure drop become smaller and smaller with increase of the tube row, through the emulating calculation. Also, as the row increasing, the area of vortex expanded and led to reinforce the deterioration effect on heat transfer. Therefore, the increment of total heat transfer got less and less. The condensate should be drained off promptly to improve the heat transfer performance of the interior of tubes, since the thermal resistance formed by liquid film has great effect on the heat transfer coefficient. Generally, economy of operation normally requires that the number of tube rows should be less than six in design of condenser.更多还原