Kaltra introduces microchannel coils with axially-graded tube port sizes

Kaltra announces new advancements in microchannel coil technology with the introduction of heat exchangers featuring tubes with axially-graded port sizes. These innovative tubes incorporate ports with progressively increasing/decreasing hydraulic diameters along the direction of airflow.

The port geometry is precisely engineered to achieve uniform refrigerant distribution across all microchannel ports, thereby equalizing local mass flux and heat transfer coefficients among the tube ports. In evaporator coils, this design mitigates the formation of superheated zones, resulting in enhanced thermal uniformity and improved heat transfer performance—particularly under part-load operating conditions.

Heat exchangers equipped with axially-graded port geometry demonstrate even greater performance benefits when operating in evaporator mode, such as in reversible heat pump systems. A significant operational challenge for evaporators under low ambient temperatures and high relative humidity is frost formation, which degrades heat transfer efficiency and reduces system capacity.

Frost accumulation is most pronounced along the leading edge of microchannel tubes due to the greater temperature gradient between the incoming air and the refrigerant at the air inlet side. This phenomenon accelerates fin blockage by ice, leading to a decline in evaporator performance and prolonged defrost cycles.

Tubes with progressively increasing port sizes, where less refrigerant is directed to the leading ports (due to higher pressure resistance), exhibit a more uniform temperature differential along the tube width. This results in more even frost accumulation, thereby extending the time between defrost cycles and reducing the duration required for defrosting.

The integration of axially-graded tube port geometry into microchannel heat exchangers represents a significant step forward in optimizing refrigerant distribution, enhancing thermal performance, and addressing key challenges such as frost accumulation in evaporator applications. Kaltra’s innovative design not only improves overall system efficiency but also extends operational reliability under varying environmental conditions. As testing progresses across diverse applications, these advancements are poised to set a new benchmark in microchannel coil technology, particularly for next-generation evaporation and heat pump systems.