以水为工质的EHD强化管内对流换热实验研究

Experimental Study of the Electrohydrodynamically(EHD)-intensified Convection Heat Exchange Inside a Tube With Water Serving as the Working Medium

以水作为工质,实验研究了EHD(Electrohydrodynamics)对水套管式换热器内对流换热过程的强化作用机理。实验中,在水套管换热器换热管中心设置一直流式高压电极,电极电压DC设置范围为0～40 kV,分别进行了5组不同流量下不同电压值的组合强化实验。实验结果表明:不同管内流量条件下电场对管内传热过程均有不同程度的强化作用,当流量为0.1 m3/h时,其电场强化系数θ最大,为1.224;流量为1.0 m3/h时,电场强化系数θ最小。实验证实了电场对于以水为工质的对流传热过程具有强化作用,但电场强化效果具有对流量变化敏感性的特点,同流量下存在最佳强化电压值而非电压值越高强化效果越大。

With water serving as the working medium,experimentally studied was the EHD(electrohydrodynamics) intensification mechanism controlling the convection heat exchange inside water jacket heat exchanger tubes.During the test,a direct current type high voltage electrode was mounted at the center of the water jacket heat exchanger tubes and the voltage of the electrode was within a range from DC 0~40 kV.A total of five groups of combined intensification test were performed at different flow rates and voltages respectively.The test results show that under the condition of different flow rates inside the tubes,the electric field all played intensification role to various extents on the heat conduction process inside the tubes.When the flow rate is 0.1 m3/h,the intensification coefficient of the electric field θ attains its maximal value,being up to 1.224.When the flow rate is 1.0 m3/h,the above-mentioned coefficient θ attains its minimal value,verifying that the electric field plays an intensification role on the convection heat conduction process with water serving as the working medium.It has also been found,however,that the intensification effectiveness achieved by the electric field enjoys a specific feature,which is susceptible to any change of the flow rate and at an identical flow rate,there exists an optimum intensification voltage value.It is not true that the higher the voltage value the better the intensification effectiveness.