Research On Fluid Flow And Heat Transfer Enhancement Performance Of Tubes Equipped With Assembled Rotors

Nowadays China’s energy supply is increasingly intense, and energy demand is growing fast, which contributes to the situation of energy crisis, so it is urgent to accelerate the adjustment of energy structure and promote the clean energy. Under the circumstance of without changing the types of energy consumption, it is of great importance to improve the efficiency of energy usage. Shell and tube heat exchangers are the energy-intensive equipments in chemical production and promoting their efficiency of heat transfer is the crucial step of improving the efficiency of energy utilization. With regard to the problem of heat transfer enhancement of heat exchangers, many techniques as enhanced tubes and inserts have been applied and the technique of assembled rotors is one of them. In this paper, the problems of flow and heat transfer enhancement of assembled rotors are being discussed in depth unceasingly.Firstly, the experimental device of the assembled rotors is designed and built, and the flow field distribution of plain tube and enhanced tube in turbulent flow condition is studied by particle image velocimetry. Experimental results show that velocity field of the tube is changed due to the rotors compared to plain tube; the fluid is presented as rotational state and the turbulent kinetic energy is improved, so the mechanism of heat transfer enhancement of assembled rotors is revealed.Secondly, heat transfer enhancement experiments of combinations of helical two-blade rotors of different diameters are conducted in 70% glycerol solution on the experimental platform. Rotors of diameter 19mm and 22mm are combined in different proportion in the experiment. Experimental results show that when the two rotors are arranged at the proportion of 2:1, the comprehensive heat transfer enhancement performance is the best.Lastly, the flow field and temperature field distribution of tubes fixed with helical two-blade rotor and low flow resistance rotor are numerically simulated with Fluent. Simulation results demonstrate that the fluid flows forward in spiral line; the heat transfers better with the existence of rotors, and at the same axial position, temperature of the cold fluid is higher. At the back of the rotor, axial velocity and K gradually decay.