Numerical Simulation And Experimental Research On Fluid Flow And Heat Transfer Of The Couping Heat Transfer Enhancement Heat Exchanger With EHD And Pulsating Flow

The heat transfer enhancement of electric field is a novel technology which introduced the basic theory of the electric field into heat transfer for heat transfer enhancement with interaction between the flow field, thermal and electric fields. Existing studies suggest that the heat transfer is a very promising enhanced heat transfer technology which has a lot of advantages, such as high efficiency, low power consumption, a wide range of applications. Pulsating flow is a special flow type that velocity or pressure of fluid is in the periodic variation. Existing studies suggest that tube pulsating flow has velocity loop effect, and under certain conditions, pulsating flow can effectively improve the convective heat transfer coefficient.At present, the technology of enhanced heat transfer of the electric field and pulsating flow have been studied as independent ways of heat transfer enhancement, the subject proposes the thought of combination of technologies of two heat transfer enhancement. Combing the electric field enhancement device model and pulsating flow generator which have our own patented technology. The thought of combining heat transfer enhancement is innovative. If it can produce the compound heat transfer enhancement effect, it can open up new areas of heat transfer enhancement and have great significance for the conservation of energy and alleviating energy shortages. Numerical simulation and experimental study are adopted to research on fluid flow and heat transfer of the coupling heat transfer enhancement heat exchanger with EHD and pulsating flow.Experimental data and numerical result show that under the action of pulsating flow separately, the convective heat coefficient has no significant change and convective heat transfer has no obvious enhancement. The heat transfer coefficient has a certain level of growth as the voltage increases under the action of electric field separately and the heat transfer coefficient slowly in the area of low-voltage(0-25kV) while grows rapidly in the area of high voltage(25-35kV).Experimental data and numerical result show that the heat transfer coefficient on the basis of the enhancement effect of the electric field alone will be further improved when the electric field and the pulsating flow take effect simultaneously, the frequency f of the pulsating flow has a greater impact on the convective heat transfer under the conditions of the electric field, the greater the frequency of pulsating flow, the greater the convective heat transfer coefficient of the tube in the same electric field strength, which indicates that pulsating flow and electric field can influence each other, thereby they can achieve a compound enhancement effect in terms of heat transfer.The experimental data shows that when the pulsating flow is applied individually, the pressure drop of the heat transfer tube increases gradually with Reynolds number and is approximately linear relationship, and in the high-frequency pulsating flow conditions (f=3Hz), the pressure drop changs rapidly with the Reynolds number. With pulsating flow and electric field mixing in the same flow rate, the pressure drop increases as the pulsation frequency increases, while the pressure drop approximately tends to be constant as the electrode voltage increases.The experimental data shows that with pulsating flow and electric field mixing, drag coefficient decreases as the Reynolds number(Re) increases, and under the same Reynolds number,the drag coefficient of pulsating flow is significantly higher than the one of no pulsating flow. With pulsating flow and electric field mixing,the evaluation factor of enhanced heat transfer E gradually decreases as Re increases. When Re is above4000, the evaluation factor E of part of frequency begins to be less than1.0.When the frequency f is1Hz(U=30kV, Re=1418), the evaluation factor E is up to2.6.