Abstract: The connecting pipe is the main component that connecting the outdoor unit and the indoor unit, make the freezing medium forms a closed cycle in the whole air-conditioning system. At present, most of the materials used in the connection pipes are copper pipes. Due to the special material properties, the connection pipes are prone to scratch and deformation on surface during the connection process, which leads to leakage. Through simulation experiments, it is found that the maximum stress position is where the bell mouth contacts the boss under the thread of the pipe joint, and the other is where the bell mouth contacts the bottom of the pipe joint. Increasing the thickness of the position to improve the sealing properties. With the applying of the finite element analysis software, analysis the mechanics property of different structures of the bellmouthing, confirming the optimized double-layer bellmouthing structure and increasing the tightening torque allows the connecting pipe to fully squeeze and mesh to improve the sealing performance of the connecting pipe.

Key words: Connecting pipe, Double-layer bellmouthing, Sealing, Finite element analysis