The air-cooled direct expansion air conditioning unit revolutionizes the traditional design concept of chilled water systems and combination air handling units, replacing complex water systems with a direct refrigerant evaporation system. This simplifies the system composition, enhances the evaporation temperature of the refrigerant, reduces construction and equipment operation costs, and exemplifies a classic, efficient, and minimalist design philosophy. This unit is specifically designed for purification projects and other HVAC applications, meeting requirements for air conditioning, temperature and humidity control, dust-free and sterile environments, noise reduction, micro-processing programmable automatic control, easy transportation, and simple installation. It solves the issues caused by varying air volume and pressure head requirements for purification and HVAC. It fully showcases the characteristics of direct expansion air conditioning and meets the various process requirements of the purification section, representing an innovative leap in purification HVAC units.