Kaltra has introduced a new generation of microchannel evaporator coils designed for reversible operation and improved efficiency in heat pump systems. The coils address key design challenges such as uniform refrigerant distribution and effective condensate drainage, particularly under low-load and frosting conditions.
The innovation features a horizontal arrangement of microchannel tubes — a layout traditionally avoided due to drainage issues. Kaltra's engineers resolved this by using vertical louver-fin plates with leading edges that direct condensate downward and improve de-icing performance. This geometry offers drainage behavior similar to conventional finned-tube coils while preserving the benefits of microchannel technology.
The horizontal tube layout also allows for multi-pass refrigerant circuitry, enhancing heat transfer and efficiency during condenser operation. The coils incorporate newly designed manifolds with internal orifice plates that improve refrigerant mixing and distribution, avoiding superheated zones and ensuring consistent thermal performance.
Circuit geometry has been optimized by adjusting tube counts per refrigerant pass, enabling balanced performance in both evaporator and condenser modes. According to Kaltra, the design supports stable, efficient operation across a broad range of ambient conditions, making it well-suited for modern heat pump systems.
The coils have undergone extensive laboratory and field testing, demonstrating stable performance through repeated frosting and defrosting cycles. Several heat pump manufacturers have already adopted the coils, reporting efficiency improvements.
“The challenge was not only to achieve reversible operation but to make it fully reliable in all real-world conditions — including low-load and frosting scenarios,” said L. Engelhardt, Kaltra’s Business Development Officer.
Dr. Fei Yin Liang, Senior Research Engineer at DTS R&D Center, noted: “Kaltra’s new evaporator coils demonstrated excellent heat transfer characteristics and stable refrigerant distribution across a wide operating range. The improved condensate management proved especially effective under frosting conditions.”
The new microchannel evaporator coils are now available for sampling and specification in heat pump, air-conditioning, and process-cooling applications, with full-scale production underway.