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Refrigerant R12, or Freon 12, has been a predominant choice in various refrigeration and air conditioning applications due to its versatility across a broad spectrum of operating conditions. However, R12, a chlorofluorocarbon (CFC) with the chemical formula CCl2F2, poses a significant threat to the ozone layer, contributing to the greenhouse effect. Consequently, the phasing out of R12 is imperative. This study explores viable alternatives to R12, focusing on the impact of external temperature and other parameters on capillary tube length. A detailed comparison between refrigerant R-134a and R-12 is conducted using Engineering Equation Solver (EES) software at Q=366.5 W, d= 1.2 mm, Tconf =45°C and tsurr=35°C. The software utilizes refrigerant thermodynamic and transport properties, including dynamic viscosity, density, thermal conductivity, and specific enthalpy, in the analysis. The research is aimed at understanding the flow dynamics in a capillary tube based on a model that aligns with the requirements of contemporary refrigerator design. Parameters such as operating conditions and tube diameter are scrutinized, with an emphasis on the direct relationship between them. The study also investigates the performance variability of the two refrigerants under identical conditions. A key finding is the superior quality of R-134a over R-12 in the two-phase region, coupled with the observation that the capillary tube length for R-134a is approximately 20% shorter than that for R-12. These results underscore the intricate relationship between refrigerant type, capillary tube dimensions, and overall system efficiency, thereby informing the design and optimization of next-generation refrigeration systems. [ABSTRACT FROM AUTHOR]