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以水为工质,实验研究了EHD(电场)与脉动流对单管换热器内的传热与阻力特性影响。实验中,电压值设定为0-40 kV,脉动流频率f=1、2、3 Hz,脉动流幅度A=1,脉动流条件下的管内时均流量q=0.1-0.5 m3/h。实验结果表明:管程脉动流单独作用时,同一流量条件下,f增加时传热系数α无明显变化,即脉动流单独作用对圆管传热强化作用不显著;EHD单独作用能显著强化传热,电压相对较小时,α增长缓慢,当电压U>30 kV时α较快增长,但随着电压的继续增加渐趋平缓,α最大提高0.12倍;脉动流和EHD具有一定的复合作用,f对有电场强化条件下的α有较大影响,尤其是当U>30 kV时,f越大,相同电场强度下管程α越大,对应的α最高可提高约0.25倍;EHD/脉动流混合作用时,随着Re的增大,管程阻力系数λ逐渐降低,并且在相同的Re情况下,脉动强化措施下的λ要明显高于无脉动情况;同一Re条件下,同频率工况时,电压的增大与否,对λ的改变并无影响,即阻力损耗主要来源于脉动流的作用,而电场对此的影响较小。
Using water as working fluid, the influence of EHD (electric field) and pulsatile flow on the heat transfer and resistance characteristics of a single tube heat exchanger was experimentally studied. In the experiment, the voltage value is set to 0-40 kV, the pulsating flow frequency f = 1, 2, 3 Hz, the pulsating flow amplitude A = 1, and the in-tube mean flow q = 0.1-0.5 m3 / h under pulsating flow conditions. The experimental results show that heat transfer coefficient α does not change significantly when f increases with the same flow rate under the same flow condition, that is, the effect of pulsating flow alone on the heat transfer enhancement of circular tubes is insignificant. EHD alone can significantly enhance the heat transfer When the voltage and voltage are relatively small, α increases slowly, α increases rapidly when the voltage U> 30 kV, but gradually increases with the increase of voltage, α increases by 0.12 times. The pulsatile flow and EHD have a certain compound effect, f has a great influence on α with electric field enhancement. Especially when U> 30 kV, the larger the f is, the bigger the tube length α is and the corresponding α is increased by about 0.25 times under the same electric field strength. EHD / pulsation Flow mixing, with the increase of Re, the pipe resistance coefficient λ gradually decreased, and in the same Re case, the pulsation enhancement measures λ was significantly higher than the no pulsation; the same Re conditions, the same frequency When the condition increases, the voltage increase or not has no effect on the change of λ, that is, the resistance loss mainly comes from the effect of pulsating flow, and the electric field has less influence on this.