Analysis Of The Parameter Effect On The Flow And Heat Transfer Characteristics Of A Staggered Circular Tube Bank Fin Heat Exchanger With X-type Arc Slotted Fin

Based on the advantages of the compact structure and the convenient manufacturing processing, the fin-and-tube heat exchanger has been widely used in the fields of chemical industry, refrigeration, air conditioning and cooling system locomotive. The working fluid in outside of the tube for most such heat exchanger is air, however, the heat transfer coefficient of the fin side is low and the thermal resistance is large, which greatly affects the efficiency of heat exchanger. The development of heat transfer enhancement technology can not only improve the utilization rate of energy, but also save the cost and achieve the effect utilizing of energy and emission reduction. Various heat transfer enhancement technologies, such as the slotted fin, including louvered fins, X type slotted fins and the interrupted annular groove fin are widely applied. The interrupted annular groove can reduce the flow resistance, and can improve the heat transfer characteristic at the back of the tube, however, the X type slotted fin can make the flow boundary layer to be discontinuous developed, which destroys the thermal boundary layer. Combined with the advantages of X type slotted fin and interrupted annular groove fin, respectively, X-type arc slotted fin was proposed. However, the current study for the analysis of the parameter effect on the flow and heat transfer characteristics of a staggered circular tube bank fin heat exchanger with X-type arc slotted fin is rare. The purpose of the present paper is to study the effects of parameter on the flow and heat transfer characteristics of a staggered circular tube bank fin heat exchanger with X-type arc slotted fin by numerical simulation in order to the structure optimization of the X-type arc slotted fin.In this paper, a unit that can present the geometry and fluid flow and heat transfer of fin-tube heat exchanger is selected as the computational domain, and the numerical study is carried out for the unit, and then the suitable mesh is generated. In order to ensure the credibility of numerical results, it is necessary to compare the results are obtained from the numerical calculation with the experimental results, the non dimensionless Nusselt number and friction coefficient are compared in the same geometric size. Meanwhile, in order to ensure that the number of the mesh has a little influence on the numerical results, it is necessary to evaluate the grid dependence of the results. The differences of the fluid flow and heat transfer characteristics between the X-type arc slotted fin and the plain fin re compared under various parameters, which includes the velocity field, the flow field and the temperature field in channel cross-section, and the change trend of both Nusselt number and friction coefficient with Reynolds number. Followed the effects of the geometric parameters, such as the slit height of the fin, the slit width W, the fin pitch T_p on the fluid flow and heat transfer characteristics of the fin channel are revealed, and then attention are pied to find some mechanisms of heat transfer enhancement.The results show that the slit height and the fin pitch have greater impact on the Nusselt number and the friction factor, however, the impact of the slit width W is small. By comparing the velocity field and the flow field of the X-type arc slotted fin and the plain fin,it is found that secondary flow is not the main factors that affect heat transfer enhancement.Through the comparison of the local Nusselt numbers of the X-type arc slotted fin and the plain fin, it is found that the local Nusselt number of the X-type arc slotted fin is significantly higher than that of the plain fin. The main reason is that the X-type arc slotted fin can destroy the thermal boundary layer, disrupt the fluid distribution, thus can achieve the purpose of heat transfer enhancement. That is the main factor of heat transfer enhancement. Under identical mass flow rate criteria, identical pressure drop criteria, identical pumping power criteria, the X-type arc slotted fin has a better heat transfer performance than the plain fin.