The increasing adoption of natural refrigerants has intensified the need to better understand refrigerant charge distribution in refrigeration systems, particularly when using flammable hydrocarbons such as isobutane (R-600a). Knowledge of refrigerant distribution during operation and shutdown is essential for accurate safety assessment, charge minimization, and risk analysis related to leakage and ignition. This study presents a systematic experimental methodology for quantifying refrigerant distribution in a refrigeration test rig operating with R-600a. The experimental setup is specifically designed to enable direct measurement of refrigerant mass in different system components. Dedicated shut-off valves divide the refrigeration loop into multiple isolated sections, allowing the refrige ...