Abstract:

The non-uniform distribution of wind velocity generated by the axial fan on the outside of the window air conditioner will lead to non-uniform distribution of refrigerant in the condenser and thus deteriorate the heat transfer performance, so it is necessary to analyze the characteristics of the wind velocity distribution and adjust the design of the flow path to match with it, so as to realize the performance improvement of the condenser. This paper takes the window air conditioner condenser as the research object, establishes the numerical model of non-uniform wind velocity contour of axia fan, and carries out three-dimensional numerical simulation of non-uniform wind velocity distribution. The wind velocity simulation results are discretized into a grid distribution of 18×10 and substituted as boundary conditions into CoilDesigner software to analyze the effect of the axial blowing wind velocity distribution on the performance of the condenser, and the accuracy of the model is verified by experiments, and the deviation of the model's heat exchanger calculation results is less than 2%. The simulation results show that the non-uniformity of the wind velocity distribution increases with the increase of the fan speed, and when the speed is increased from 1200 r/min to 2000 r/min, the extreme deviation and variance of the wind velocity increase by 1.95 m/s and 0.460 m²/s², respectively; furthermore, the effect of the non-uniform wind velocity distribution on the heat exchange performance of the condenser is analyzed, and it is found that the heat exchange coefficient of the condenser in the central static zone of the axial wind contour is smaller while in the bottom accelerated zone, the heat exchange coefficient is smaller than in the bottom accelerated zone. It is found that the heat transfer coefficient of the condenser in the center static zone of the axial wind field is small and the heat transfer coefficient in the bottom accelerated zone is large, and in the process of flow path design, it is necessary to increase the heat transfer area of the branch arranged in the center static zone, so as to make the heat load of the different branches equal, and to match the bottom accelerated zone with the pipeline of the refrigerant flow rate that is large to have a larger heat transfer coefficient, so as to enhance the performance of condenser. Finally, 20 flow path arrangement schemes are designed and simulated to investigate the influence of piping configuration on condenser performance under the non-uniform wind velocity distribution of axial fan, and the simulation results show that, compared with the original flow path, extending the length of the center static zone pipe, placing the convergence section in the bottom acceleration zone, and placing the convergence point of the branch in the leeward side, the heat exchange capacity can be increased by 1.8%, and the pressure drop can be reduced by 26.1%.

Key words: window air conditioner, non-uniform wind velocity, heat transfer, optimal design, numerical simulation

摘要：

窗式空调器室外侧的轴流风机产生的风速分布不均匀会导致冷凝器内制冷剂分布不均，从而恶化换热性能，需分析风速分布特性并调整流路设计与之相匹配。以窗式空调器冷凝器为研究对象，建立了轴流风机非均匀风场的数值模型，对非均匀风速分布进行了三维数值模拟。将风速仿真结果离散为18×10的网格分布，作为边界条件代入CoilDesigner软件中分析风速分布对冷凝器性能的影响，实验验证模型的换热量偏差小于2%。仿真结果表明，风速分布的不均匀性随风机转速的增大而增大，转速从1200 r/min增至2000 r/min时，风速的极差与方差分别增加了1.95 m/s与0.460 m²/s²。通过分析非均匀风速分布对冷凝器换热性能的影响，发现冷凝器在轴流风场的中心静区传热系数较小而在底部加速区传热系数较大，在流路设计过程中需要增大布置在中心静区的支路换热面积，使不同支路热负荷相当，并用制冷剂流量较大的管路匹配传热系数更大的底部加速区。最后，设计并仿真了20种流路布置方案来探究轴流风机非均匀风速分布下管路配置对冷凝器性能的影响规律。与原流路相比，延长中心静区管长，并将汇合段置于底部加速区，支路汇合点置于背风侧，换热量可以提升1.8%，压降可以降低26.1%。

关键词: 窗式空调器, 非均匀风速, 传热, 优化设计, 数值模拟