Kaltra’s optimized microchannel evaporator

The Kaltra’s research center completes work on the streamlined microchannel evaporator design that displays amplified performance under partial load conditions. Evaporator’s outlet manifold was subjected to optimization to achieve optimum refrigerant distribution between multiport tubes.

The resulting design includes intermediate manifold and outlet manifold – this ensures pressure drop balance within the coil and contributes to uniform distribution of incoming gas/fluid mixture among tubes regardless of load demand (starting from about 15% load). Distributor located inside inlet manifold prevents the gaseous refrigerant from entering microchannel tubes, creating almost single-phase heat exchange. Thus, maldistribution is only due to the asymmetric pressure losses in inlet and outlet manifolds. Large-volume outlet header levels local pressure drops, eliminating uneven, pressure-induced liquid distribution. This novel design is still suitable for large coils having long manifolds and can operate at any installation angle except horizontal or close to it.

Inlet manifold remained unchanged with inbuilt distributor tube with orifices, as well as common coil configuration with vertically-oriented microchannel tubes (ensuring free condensate removal).

The performance of evaporator coils of the present design has been tested in the field, confirming the results of numerical simulations and theoretical expectations. As almost the entire finned surface is used for evaporation, new evaporators demonstrate efficiency not found elsewhere in other designs.