Numerical study on heat transfer and pressure drop characteristics of double-row finned-tube heat exchangers with elliptical holes

Based on the methodology of orthogonal experiment, taking the hole diameter and two positions as variable parameters, designs the finned-tube heat exchangers which use elliptical hole fins for air-source heat pump (ASHP). Implements three dimensional (3D) numerical simulation on flat fins and elliptical hole fins by CFD with different Re values, analyses and compares their air-side flow and heat transfer performance. The simulation results are in correspondence with the referenced experiment data, which verifies the correct simulation method. Compared with the results of flat fins, the heat transfer factor (j) values of nine elliptical hole fins are increased by 4% to 25% and the friction factor (f) values vary in the range of -7.5% to 7.9%, within the studied Re scope. The calculation results of performance evaluation index of j/f, j/f12, j/f13 show that comprehensive heat transfer performance of elliptical hole fins is better than that of flat fins under the identical flow rate, pressure drop and pump power. Elliptical hole fins can effectively prevent the boundary layers development of surface temperature and velocity, enhance flow turbulence and strengthen heat transfer performance of fins in a case of the resistance force with a little change. Compared with the positions of elliptical hole, the hole diameter has a greater effect on heat transfer.