A Study on the Flow and Heat Transfer Characteristics of Heat Exchanger with Cone-Type Vortex Generators

In order to solve the problem of structural strength of heat exchanger at high Reynolds number, a new type of cone structure is proposed based on the spherical structure with low flow resistance and high heat transfer, and it is applied to cross flow heat exchanger. Experimental and numerical simulation methods are used to study the proposed heat exchanger. The effects of Reynolds number (Re=4 772~38 181), temperature ratio (Th/Tc=4~9) and velocity ratio (Vh/Vc=0.5~4) on the flow and heat transfer characteristics and irreversible loss of the heat exchanger are explored. The flow and heat transfer mechanisms of the cool air side channel of the heat exchanger are analyzed by numerical calculation. Finally, the heat transfer correlation is fitted based on the experimental results. The results show that: in the range of studied parameters, the average Nu and friction coefficient of the cold side channel of heat exchanger increase by 1.67~2.13 times and 5.13~12.16 times, respectively, compared with that of the smooth tube. The temperature ratio and velocity ratio have little influence on the flow and heat transfer in the cold side channel. The windward side of the convex surface has a higher heat transfer coefficient due to the impact of airflow, the concave has a better heat transfer effect at the tail, and the increase of Reynolds number will increase the area of that high heat transfer region. The irreversible loss increases with the increase of temperature ratio, but decreases with the increase of Reynolds number; when the flow velocity ratio is 2, the irreversible loss reaches the minimum value. The correlation obtained by fitting is in good agreement with the experimental results, and the results of this study can provide reference for the structural design of advanced air heat exchangers in the future. © 2021, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.