Numerical Study On Heat Transfer Performance Of Slitted Circle Fin Surfaces And Analysis With Field Synergy Principle

Heat transfer coefficient can be greatly effectively raised by setting fins on the air side of the smooth tube, besides which, it can be further enhanced by the slots on the fins. Therefore, the issue of slotted circle fin which has played an important role in the heat transfer enhancement of heat exchanger has already become a key research project.In this paper, the heat transfer and resistance characteristics of eleven types of circle fins are simulated under seven different wind speed using FLUENT software. And the heat transfer enhancement mechanism is deeply analyzed combined with field synergy principle. Four of the eleven types is the whole plain plate circular fin, and the other seven ones are of slotted types. The surfaces of all the eleven fins have the same geometry dimension. The slotted fin surfaces have the same number of strips which are produced upward and downward alternatively. One difference of the seven kinds of slotted circular fins is the position of the strips in the surface, two of them is distributed in the rear area and the others are distributed uniformly. And besides, three of the seven types of fins are optimization design model. Three-dimensional steady model is used.It is found that the slotted circle fin's heat transfer surfaces have excellent performance compared with the plain plate circle fin's heat transfer surfaces, the average nusselt number Nu rises by 60% to 90% and the field synergy number rises by 20% to 27%. The performance of rear slotted circle fin is also better than the others. From the viewpoint of field synergy, the velocity and temperature field and resistance characteristic between the two neighboring fin surfaces are analyzed. The results show that the heat enhancement of slotted circle fins is caused by the improvement of the synergy between the velocity field and temperature gradient. After a series of further optimization, a better model which has oval base tube and slotted circle fins densified in the rear part is obtained. The comprehensive performance of this model is much better than the ones with uniform slotted fins, where the average nusselt number Nu rises by 8%, the resistance coefficient f reduces by 30% to 40%, the average field synergy number Fc rises by nearly 10%.