Numerical Simulation of Heat Transfer Characteristics of Finned Tube Heat Exchanger at Different Flow Velocities

Abstract

A heat exchanger is an important component where high-temperature hot air and normal-temperature water exchange heat. The heat exchange area of the finned tube heat exchanger is calculated by the rated working conditions. However, with the decrease of the heat storage temperature, the hot air temperature at the outlet of the thermodynamic energy storage device changes in a large range, directly affecting the heat exchange capacity and efficiency of the finned tube heat exchanger. This paper’s three-dimensional model is established. The heat exchanger of the finned tube is designed according to the temperature of the outlet section and the return section temperature of the heat storage system. The thermodynamic physical parameter property and characteristics of which heat exchanger’s finned tube in the air’s velocity range of 1∼10 m/s are simulated by fluent software. The velocity, temperature, pressure, and heat exchanger coefficient distribution characteristics at different positions along the airflow direction are obtained. The simulation results show that the mean flow velocity is 2.0 m/s and 5.0 m/s at the inlet cross-section. The average temperature difference between the inlet and outlet is 69.5 K and 100.5 K, respectively. The fin surface temperature difference between the first and eighth rows of finned tubes is 12.5 K and 14.4 K, respectively. The air pressure loss at the air channel inlet’s section and outlet’s section is 16.1 Pa and 69.4 Pa, respectively. When the inlet flow rate change from starting at 1.0 m/s and ending at 10.0 m/s, the tube’s wall coefficient of heat transfer, which is the second level of finned tubes, only increases by 1.8 times. The tube’s wall coefficient of heat transfer of the eighth level of finned tubes increases by the maximum, to 5 times the original, but the heat energy exchange capacity of which the second level of finned tubes is always the strongest.