【作者】 朱乐琪；

【导师】 张恩泽；

【作者基本信息】 同济大学 ， 供热供燃气通风及空调工程， 2007， 硕士

【摘要】 变容量多联式空调系统在部分负荷下的节能性较好，近年来其发展迅速。由于其制热性能受气象条件影响，存在结霜问题，热泵的制热能力随着结霜的增加而衰减；并且由于多联机系统的单元室外机可以对多台室内机，单元室外机的装机容量(额定制冷／制热量)不断升级，在增加单元室外机换热面积的同时加大了结霜的可能性，除霜频繁，所以多联机系统单元室外机容量受到冬季运行时结霜除霜的限制。本文深入研究上海地区变容量多联机的除霜性能以及室外机容量与结霜除霜的关系，为更好的设计该系统提供参考依据。多联式空调系统常采用热气逆循环除霜，除霜时室内不制热，除霜时间越长越频繁，机组传热量就会下降越多。除霜时间与盘管上的结霜量有关，而结霜量受室外气象参数、盘管几何尺寸、盘管的几何特性等多种因素的影响，本文应用集总参数法建立多联式空调系统动态除霜模型。实验得出除霜运行时数码涡旋压缩机满负荷运转；单元室外机除霜过程分为4个阶段建立动态模型；室内机并联成一个换热器建立模型，不考虑室内机之间的耦合；由于室内机并联为一个换热器，电子膨胀阀模型也考虑为单个电子膨胀阀模型。在一台数码涡旋多联式空调系统实验台上进行实测研究，验证了本文模型可以预测除霜性能的影响因素。除霜时间随着单元室外机换热面积增大而变长。除霜周期内实际总制热量开始随着单元室外机换热面积增大而增加，当增大到某一限值时，实际总制热量不再上升，反而下降。实验用机组实际总制热量在换热面积增大为2倍时达到峰值为138.19％。随着单元室外机装机容量上升，除霜时间增加，在现有多联机除霜标准下单元室外机装机容量存在上限。更多还原

【Abstract】 Multi air-conditioning system develops quickly these years for its excellent performance under part load. But its heating capacity drops dramatically due to the frosting and defrosting problem under bad weather conditions. The unitary outdoor unit of multi air-conditioning system increase its capacity continually, however, the increment of the heat exchange area increase the possibility of frosting in winter, which in turn restricts the unitary outdoor unit capacity in winter. In this paper, the relationship between unitary outdoor unit capacity and frosting and defrosting performance in Shanghai is studied to optimize the system.Hot gas reverse cycle is commonly used in multi air-conditioning system for defrosting, during which heat will not be brought into the room, so the heating capacity decreases with the frequency of defrosting. The defrosting time is related to the quantity of frost on the tube-fin which is influenced by several factors such as weather conditions, coil dimensions, and the geometric character of coils. According to the test result of a DVM (digital variable multi) air-conditioning system, the digital scroll compressor is found to be on full time load while defrosting. The unitary unit outdoor heat exchanger’s model was set up into 4 stages using the lumped parameter method. All units could be merged as one heat exchanger model without considering their coupling. As the indoor units were merged into one, the EEV(electronic expansion valve) are also considered to be single one.Based on a field test on a DVM air conditioning system, the model was validated. So the model could estimate the influencing factors of defrosting performance. With the rise of heat exchange area of unitary outdoor unit, the defrosting time rises, and the total heat output firstly rises and then goes down. For the DVM system, when heat exchange area of outdoor unit increased to be twice, the actual heat output increased to be maximum 138.19%. It is also analyzed that, the increase of unitary outdoor unit capacity would be limited by defrosting. The defrosting time increases with the unitary outdoor unit capacity, so the capacity is limited by the Standard GB/T18837-2002.更多还原