Research On The Effect Of EHD Enhancing Condensation Heat Transfer In The Model Of Power Generation Utilizing Low Temperature Wasted Heat

EHD (Electrohydrodynamics) heat transfer enhancement refers to the active heat transfer enhancement technique in which an electric field is exerted on a dielectric fluid to increase the heat transfer coefficient and heat transfer efficiency greatly by coupling up the flow field and temperature field. In recent years, it has become one of the important topics that attract wide attention and research focus from domestic and international scholars. Applying EHD condensation heat transfer enhancement technique in heat exchanger can decrease heat transfer area,which settles bulk volume issue of heat exchanger. In this dissertation, the experimentation and mechanism of EHD condensation heat transfer enhancement were studied, which based on low temperature wasted heat power generation model of callback low temperature waste heat source, and aimed at overcoming the bottleneck problems about low temperature difference and poor heat transfer capability of heat exchangers existing in low temperature wasted heat power generation.Thorough investigation on national and international studies in relevant fields in terms of the characteristics of low temperature wasted heat power generation, a thermodynamic system experimental model is designed and constructed in this dissertation, which mainly consisted of evaporator, EHD condenser and steam turbine-generator combined with R11 as working fluid. The research of low temperature wasted power generation system indicates that a low temperature wasted heat power generation system can be built using low boiling point dielectrical fluid as working fluid, however the problem of low generation efficiency exists. The experimental results indicate that the condensation heat transfer coefficient increase with the applied voltage on the fluid in condenser under the condition of the same heat transfer surface area and the same flow rate of working fluid. And the increase of the condensation heat transfer coefficient becomes rapid when corona discharge happened.Based on static electric field heat transfer enhancement theory, the models of characterizing thermal field, electric field and fluid force field in the interelectrode of EHD condenser were established. Meanwhile the numerical simulation was made for the distribution of the electric field, the condensation process and the field force distribution in the two-phase flow. The distribution of electric field force were also analysed according to the asymmetry of force in the fluid in this dissertation. The results indicate that the electric field can induce the instability of dielectric liquid and condensating film on the tube wall with bead or quasi-bead, at the same time the electric field also can cause turbulence in gas fluid and result in heat transfer enhancement. Finally the theoretical discussion on EHD condensation heat transfer enhancement and the analysis of experimental results are made from the electric force exerted on fluids. It is concluded that the EHD technique is able to enhance condensation heat transfer obviously.The model of this study not only can be used in low temperature waste heat generation system, but also has very important reference value in terrestrial heat, solar power and sea temperature difference generation. This technique of EHD condensation heat transfer enhancement researched in this thesis is a concrete application in low temperature wasted heat power generation which offers an experimental foundation to the practical application. The theory of EHD heat transfer enhancement in this dissertation not only offers a new technique scheme for active heat transfer enhancement but also it is valuable to extend the theoretical investigation of EHD condensation heat transfer enhancement, and it has a definite promoted effect for bestraddling subject investigation of electromagnetics, hydrodynamics, and thermodynamics theory.