Phase change phenomena, including boiling, melting, and solidification, are crucial in various industries. This discussion focuses on the boiling of natural refrigerants and the melting/solidification of Phase Change Materials (PCM), both vital in building systems, cooling, energy storage, heat pumps, and more. Natural refrigerants like ammonia and CO₂ are sustainable alternatives in refrigeration, while PCM stores and releases thermal energy, enhancing energy efficiency. However, PCM faces heat transfer challenges due to low thermal conductivity, necessitating enhancements like metal foams and advanced studies on convective heat transfer and melting regimes. The ATHT team, with extensive experience in heat exchanger testing, aims to advance measurement techniques and establish heat transfer correlations through high-quality experiments.