提升多联机空调能效的室外机换热器设计

Design of outdoor unit heat exchanger for variable refrigerant flow air conditioner to improve energy efficiency

换热器作为空调产品的主要组成部件之一,对提升能效有重要作用。基于Ф5 mm及微通道等换热器在作为室外机换热器使用时的性能或制作工艺的局限性,提出了新的换热器结构来实现多联机空调能效的提升:通过缩小Ф7 mm铜圆管换热器的管间距来增加单排铜管数量,来同时实现增强管内换热能力(增大管内换热面积)和管外空气换热能力(增大最窄处空气风速来增加空气侧换热系数)的一种高效换热器结构。借助于仿真与测试手段,对该新型换热器进行了全面的分析和验证。对比原型Ф7mm换热器,仿真结果显示:在相同流动压降条件下(13.6 Pa),该Ф7 mm新型换热器的空气侧KA值(KA值表示为换热能力,等于换热系数K与对应换热面积A的乘积)比原型换热器高出20.7%,相应换热器的总KA值分别高出12.02%和9.11%;多联机空调整机性能测试结果显示:该Ф7 mm新型换热器在标准制冷、标准制热及低温制热工况的整机能效分别提升了1.9%、1.8%和1.5%。

As one of the main components of air conditioner,heat exchangers play an important role in improving energy efficiency.Based on the limitation of performance or manufacturing toФ5mm heat exchangers and microchannel heat exchangers used as outdoor unit heat exchangers,a new heat exchanger is proposed to improve the energy efficiency of Variable Refrigerant Flow(VRF)air conditioner.By reducing tube pitch ofФ7 mm copper round tube heat exchangers and thus increasing tubes quantity in each row,the new heat exchanger structure can simultaneously enhance the heat transfer capacity inside the tubes(by increasing the heat transfer area inside the tubes)and the heat transfer capacity outside the tubes(by increasing the maximum air velocity at the narrowest to enhance the air side heat transfer coefficient).Based on simulation and performance testing,a comprehensive analysis and verification were conducted to the new heat exchanger.Compared with the prototypeФ7 mm heat exchanger,simulation shows that at same air flow resistance(13.6 Pa),the air side KA value(which represents heat transfer capacity that equal to the product of heat transfer coefficient K and corresponding heat transfer area A)of the newФ7 mm heat exchanger is 20.7%higher than that of the prototypeФ7 mm heat exchanger,and the correspond total KA value of the heat exchanger is 12.02%and 9.11%higher,respectively;The performance test results of the VRF air conditioner show that the new heat exchanger has improved energy efficiency by 1.9%,1.8%,and 1.5%in the standard cooling,the standard heating,and low-temperature heating,respectively.