The development of low-GWP refrigerants (e.g., R1336mzz(Z), R1233zd(E)) for High-Temperature Heat Pumps (HTHPs) focuses on achieving high critical temperatures and thermal stability up to 200°C. However, managing flammability, toxicity, and lower volumetric heating capacity remains a challenge.
To offset high fluid costs and safety risks, falling-film evaporators are implemented to significantly reduce refrigerant charge while maximizing heat transfer coefficient. Current R&D leverages advanced 3D enhanced tubes and CFD modeling to optimize efficiency. The primary engineering hurdles involve preventing localized tube dry-out, ensuring uniform liquid distribution, and modeling complex high-temperature nucleate boiling regimes.