The Fin Side Flow And Heat Transfer Characteristics Of A Louvered Fin And Tube Exchanger

Fin and tube bank heat exchanger has been widely used in industry, transportation, refrigeration, air conditioning and other fields due to the advantages of compact structure and convenient operating. Evaporator and condenser are the main part of the air conditioning system, and their heat transfer performance has a direct impact on the efficiency of air conditioning system. The fin side of fin and tube heat exchanger has large heat transfer resistance. Therefore, improving the heat transfer coefficient of the fin side surface significance.Punching louvered fin on the fin surface of the circular tube bank fin heat exchanger is an efficient method to enhance heat transfer, and which is widely used in the field of air conditioning. When fluid flows through the channel formed by tubes and the louvered fins, the louvers on the fin surface discontinue the development of fluid flow and thermal boundary layer, and then enhance heat transfer. At the same time, fluid flow resistance also increases. To further optimize the louvered fin, a numerical method is used to study the fluid flow and heat transfer characteristics in the channel formed by the circular tubes bank louvered fins.This paper selects the channels which formed by the tube bank and the louvered fins as the computational domain. A reasonable grid system of the computational domain is obtained, and the independence of the numerical results on the grid size is strictly examined. In order to prove the rationality of the numerical method and the validity of the numerical method, the numerical results are compared to the experimental results. After performing above processes, numerical method is used to obtain the fluid flow and heat transfer characteristics in the channels formed by the louvered fins and the channel formed by the plain fin with the same configurations.The various characteristics such as the flow fields on the transversal sections and vertical sections, local heat transfer characteristics on the fin surfaces, the Nusselt number Nu and the pressure drop Δp along the main flow direction are compared. Under different flow rate, comparisons of the flow field and the temperature field and the pressure field between the cases of the louvered fin and the plain fin are performed. Through changing the geometry parameters of the louvered fin such as the louvered angle θ, the louvered pitch Lp, the fin pitch Fp, the length of louvered reversing area Ld, the number of louvered units N, the transversal and the longitudinal tube pitch S, the effects of these parameters on the heat transfer performance in the channel are obtained.The results show that compared the plain fin, the louvered fin destroyed the fluid flow boundary layer, effectively improves the performance of heat transfer, and then heat transfer enhancement are obtained. The geometric parameters of the louvered fin have obvious its fluid flow and heat transfer characteristics. With increasing the louvered pitch, the number of the louvered units, and decreasing the tube pitch, Nusselt number increase. With increasing the louvered angle, the louvered pitch, and decreasing the tube pitch, the friction coefficient increase. According to the overall performance factor JF, the region of the parameters studied in this paper: the factor JF of the 1.2 mm fin pitch is the best; when the louver angle is 19°, the louvered pitch is 1.2 mm, the length of the louver direction reversing area is 1.95 mm and the number of the louvered units are 12, the heat transfer performance is better with 1.28 mm fin pitch; when the louver angle is 19°, the heat transfer performance is better with 1.68 mm fin pitch; when the louver angle is 27°, the length of the louver direction reversing area is 1.3 mm and the number of the louvered units are 12, the heat transfer performance is better with 2.10 mm fin pitch. The correlations of the heat exchange factor and the friction factor with Re, the louvered angle θ, the louvered pitch Lp, the fin pitch Fp, the length of louver direction reversing area Ld, the transversal and longitudinal tube pitch S, the number of the louvered units N are provided and are compared with the experimental correlations for using in the design conveniently.