A REVIEW OF MOLECULAR SIEVES AND ACTIVATED ALUMINA USED IN FILTER DRIERS FOR R134A REFRIGERATION SYSTEMS

Moisture control in R134A refrigerant systems is critical for maintaining system efficiency, preventing corrosion, and ensuring long-term reliability.This comprehensive review examines the role of molecular sieves and activated alumina as desiccant materials in filter driers designed for R134A systems using polyolester (POE) lubricants.The paper synthesizes current research on desiccant characteristics, adsorption mechanism and compatibility with R134A refrigerant and POE oils.Molecular sieves, particularly type 3A,demonstrate superior bulk moisture removal capacity in R134A/POE environments.Activated alumina serves dual functions as both a moisture adsorbent and chemical filter for removing hydrolysis products from hygroscopic POE lubricants.Filter drier design considerations, including cartridge construction and combined desiccant strategies, are analyzed in the context of ASHRAE 97 standard requirements for testing and performance evaluation.Comparative analysis reveals that molecular sieves excel in primary moisture removal, while activated alumina provides essential protection against polar decomposition products.Recent advances emphasize compatibility testing protocols, regeneration strategies, and integrated filter-drier designs.This review provides technical guidance for selecting and implementing desiccant materials in R134A refrigeration systems to meet industry standards and ensure optimal moisture control.