Air flow field Testing, simulation and Optimization of CO₂ air-source heat pump outdoor unit arrays

CO₂ air source heat pumps are a pivotal technology in the architectural field for achieving carbon neutrality and transitioning distributed heating system to clean heating technology. In practical engineering applications of distributed heating system, it has been observed that poor layout of outdoor unit arrays leads to disrupted air flow at the inlet, subsequently decreasing the heating efficiency of the heat pump system. This presents a significant engineering challenge in the deployment of CO₂ air source heat pumps. This study focuses on large-scale CO₂ cascade air source heat pumps outdoor units, aiming to examine and optimize the airflow characteristics at the unit inlets through laboratory tests, numerical simulations, and on-site engineering tests. The results show that: (1) The Air Flow Field Parameter Detection, Simulation and Visualization System developed by the team is capable of visualizing the organization of the air flow and detecting and collecting the key parameters of the air flow field. (2) Laboratory tests with two outdoor units indicated that increasing the distance between the inlets to 1.4–1.6 m effectively reduced the interaction of air fluid between the units, which can serve as a reference for similar systems. (3) Numerical simulation of a 6 × 3 outdoor unit array shows detailed velocity distributions and indicates that an outdoor unit spacing of 1.5 m can effectively avoid the impact of air interference within the array. (4) A comparative study of two CO₂ air source heat pump projects shows that COP of the heat pump system can be improved by 11.5 % by increasing the distance between outdoor units form 1.0 m to 1.5 m, which demonstrates that an optimized outdoor unit layout can significantly reduce airflow interference between inlets and improve the heating efficiency of the units.