## 1 Introduction
[26] simulated the change of concentration distribution and flammable volume of the leaked R32 in a rooftop air conditioner under different charges, and the results showed that the concentration of R32 in most areas of the air supply duct was in the flammable area, and the leaked refrigerant in the room mainly appeared under the air supply port closest to the leak hole, and the duration of the flammable area in the room was prolonged with the increase in the refrigerant charge. [PERSON] et al. [27; 28; 29] studied the influence of leakage rate, room size, ventilation intensity, and the locations of air inlet and outlet on the concentration distribution of leaked R290 in the multiline air conditioner, and the results found that the volume of the flammable area in the room increased with the increase in the leakage rate, and the mechanical ventilation well reduced the concentration of leaked gas in most areas of the room to below its LFL, and the lower the position of the exhaust port, the faster the refrigerant concentration in the room decreased. [PERSON] et al. [30] simulated the influence of refrigerant charge, leakage rate, leakage friction, leakage height, indoor unit shell, space airflow and obstacles on the concentration distribution of leaked R290 in a commercial refrigeration cabinet. [PERSON] et al. [31; 32] evaluated the risk of refrigerant leakage in the refrigerated transport containers and conducted leakage experiments in different scenarios. [PERSON] et al. [33] studied the leakage characteristics of a portable refrigerated display cabinet, and the results found that the leaked refrigerant was mainly concentrated in the area near the ground below the leak hole, and the cabinet placed in the corners caused the flammable zone to last longer. It can be seen from the above literature review that the refrigerant leakage based on the refrigeration system was approximately simplified to the leakage of refrigerant gas in the pipeline. The hole model was generally used to calculate the leakage process. In the hole model, the pressure and temperature of the gas at the junction of the leakage hole and the outer wall of the pipe were directly assumed, which were equal to the ambient temperature and standard atmospheric pressure in the subsonic flow state; in addition, the influence of the change in the refrigerant thermo-physical parameters on the diffusion process of refrigerant gas leaked from the pipeline to the external space was ignored. Actually, this assumption and ignorance had a certain effect on the concentration field of the leaked gas obtained in the external space, especially for flammable gases. This effect may lead to the inability to accurately determine the scope of the flammable area, which brings potential safety hazards. Based on the current research status, the main goal of this paper was that an improved gas leakage model was proposed and its reliability was discussed; taking R290 as the object, the variation law of field strengths (i.e., temperature field, pressure field, velocity field and concentration field) of the leaked R290 gas was analyzed, and the mutual coupling characteristics between multiple field strengths and the influence of different initial leakage pressures on the leakage gas field strength were further discussed.