Numerical Simulation And Experimental Research On Convective Heat Transfer In Tube-and-Shell Heat Exchanger By Electrohydrodynamics Effect

With the rapid development of modern industry, focusing on the environmental and ecological issues of energy, "energy crisis" becomes a constraint to the root of human development, therefore, it is imperative to develop energy saving technology. Since the 20th century, heat transfer enhancement, known as the "second generation heat transfer technology" is fully developed and fruitful. Heat exchanger, one of the most widely used heat transfer equipment, application of enhanced heat transfer technology can not only save the environment but also save investment and operating costs. Therefore, the enhanced heat transfer technology has been an important issue, which is attached the importance by scholars from various countries.It is generally believed that the enhanced heat transfer technology can be divided into "active" and "passive". EHD enhanced heat transfer is belong to "active" heat transfer enhancement technology. In this paper, based on the design and manufacture of EHD heat transfer experiment platform, using water as the working fluid, experimental study of the electric field enhanced convective heat transfer process is conducted, while using the experimental model in the numerical simulation of EHD heat transfer enhancement of flow properties and heat transfer properties in the tube side and shell side of single-tube shell heat exchanger to analyze the heat transfer enhancement. The experimental results and numerical results are compared to validate the numerical results..According to the numerical simulation results in the tube-side, it is concluded that there are mutations of rate in the tube inlet and outlet, apart from this the flow distribution uniform. The high voltage electric field had little effect on the flow of fluid. On the other hand, heat transfer performance of tube is researched to get the conclusions that the impact of electric field on the temperature distribution is not uniform in the axial direction, with enhanced electric field ionization degree of the fluid, the electric field can make greater impact on temperature of the fluid in the tube. While according to the numerical simulation results in the shell-side, due to high voltage electrode is arranged in the central of the tube, the radial electric field is gradually weakened, which results in electric field affect insignificantly on the performances of flow and heat transfer.In the experiment, a DC high voltage electrode was set in the central tube-side of the heat exchanger, and the high voltage electrode in the tube-side was adjustable in the range of 0-40 kV. Five different combinations of heat transfer enhancement experiments were conducted under the different voltage and rate of flow. The results indicate that the maximal enhancement coefficient is 1.224 when the flow rate of tube-side inlet is 0.1 m3/h. It is proved that, for the work medium of water, the convective heat transfer can be enhanced by applying high electric field. The performance of EHD-enhanced is sensitive to the variation of flow rate, and in the same flow rate, there exist an optimized voltage in the EHD-enhanced process rather than the monotonic positive-correlation relationship.