超声场下微细通道内R141b流动沸腾压降特性研究  

Pressure Drop Characteristics of R141b Flow Boiling in Microchannels under Ultrasonic Field

作　　者：罗小平[1] 刘倩 喻葭 廖政标 LUO Xiaoping;LIU Qian;YU Jia;LIAO Zhengbiao(School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China)

机构地区：[1]华南理工大学机械与汽车工程学院,广州510640

出　　处：《农业机械学报》2021年第6期418-426,共9页Transactions of the Chinese Society for Agricultural Machinery

基　　金：国家自然科学基金项目(21776096);广东省自然科学基金项目(2019A1515011053)。

摘　　要：为探究超声波对微细通道内R141b流动沸腾压降特性的影响,设计了带有超声波发生装置的微细通道实验段,以制冷剂R141b为实验工质,在截面尺寸为2 mm×2 mm的矩形微细通道内进行了流动沸腾实验,研究超声波作用下微细通道内R141b的流动沸腾压降特性,并采用高速摄像仪对微细通道内部沸腾情况进行可视化分析。结果表明,在有无超声情况下微细通道压降分量比例大致相同,均以摩擦压降占比最大;在实验段进口处施加超声波会减小微细通道流动沸腾摩擦压降,当质量流率为118.64 kg/(m^(2)·s)、热流密度为17.03 kW/m^(2)时,施加50 W、40 kHz的超声波可使单位长度两相摩擦压降减小12.70%;超声频率越大、功率越小,其减阻效果越好;超声波主要通过影响汽泡运动行为进而影响两相区的压降。可视化分析结果表明,超声波能影响微细通道内汽泡数量及尺寸,并影响通道内的流型。本研究可为超声波在微通道换热器中的应用提供参考。Microchannel heat exchanger is widely used in agriculture due to compact structure and high efficiency.However,the minification of size can lead to the increase in flow resistance of the system,pressure drop and energy consumption,and finally cause lower economic efficiency.Previous work has proved that ultrasound can be applied to microchannel heat exchanger to improve its heat transfer performance,but the effect of ultrasound on flow boiling pressure drop is not clear.To investigate the effect of ultrasound on flow boiling pressure drop characteristics in microchannels,a microchannel experiment section with an ultrasonic transducer was designed.Using the refrigerant R141b as the experimental working fluid,the flow boiling experiment was conducted in rectangular microchannels with the cross-section of each single channel being 2 mm×2 mm to study the pressure drop characteristics of refrigerant R141b in microchannels under the action of ultrasound and a high-speed digital video camera was used to visualize the flow boiling in the microchannels.The pressure of the system was set as 152 kPa,the heat flux density ranged from 10.01 kW/m^(2) to 23.30 kW/m^(2),mass flow rate ranged from 29.67 kg/(m^(2)·s)to 177.96 kg/(m^(2)·s),the applied ultrasonic power ranged from 12.5 W to 50 W and frequency ranged from 23 kHz to 40 kHz.The results showed that the proportions of the pressure drop components of the microchannels with or without ultrasound were approximately the same and the friction pressure drop accounted for the largest proportion,followed by gravity pressure drop and acceleration pressure drop,with the proportion of inlet and outlet pressure drop being the smallest.The ultrasound applied at the inlet of microchannels had a slight reduction effect on the flow boiling pressure drop of the microchannels.When the mass flow rate was 118.64 kg/(m^(2)·s)and the heat flux density was 17.03 kW/m^(2),the application of 50 W and 40 kHz ultrasound could reduce the two-phase frictional pressure drop per unit length by 12.

关 键 词：微细通道 超声波 流动沸腾 压降 可视化 

分 类 号：TK124[动力工程及工程热物理—工程热物理]