In the study, a new refrigerant piping system was designed for an air conditioner with a capacity of 12 000 BTU. The purpose of designing a new piping system is to eliminate the vibration problem that occurs at low frequencies. This vibration problem causes an undesired sound level in the device acoustically. With the new refrigerant pipe group, the vibration rate has been reduced by 30% on average, in areas where problems were experienced. The pressure, temperature, and velocity distributions in the developed design and the existing design were analyzed numerically with ANSYS 2021 R1 software. At the same time, a new capillary pipe system has been designed for the refrigerant pipe group. By designing the capillary tube, it is aimed to optimize the capacity of the existing system. In addition to numerical studies, experimental studies have also been carried out on which the capillary system is more suitable for the developed system by applying performance tests to both the existing system and different capillary systems. The phase change, pressure, temperature, and velocity distributions in the capillary tubes obtained in the experimental performance tests were used to verify the numerical model. The Volume of Fluids (VOF) model, which is a two-phase flow model, was used in numerical analysis. The lengths of the phase transition in the capillary tube system were also examined within the scope of the study. It has been determined that the phase change zone in the current system with 1.7 mm × 900 mm + 1.7mm × 300 mm capillaries have a shorter distance than the 1.5 mm × 700 mm capillary group. Thanks to the verification of the numerical model results with experiments, a validated numerical model was obtained to be used in future studies. Keywords: Refrigerant pipe system, VOF, Capillary pipe system, two-phase flow, acoustic and vibration performance