A
vapor compression refrigeration and freezer
system includes a compressor, a condenser, an expansion devise and an
evaporator which includes an
evaporator coil having an inlet and an outlet which coil is in heat exchange relation with an air medium along substantially the entire coil length. The inlet to the
evaporator coil is in flow communication with an outlet of the expansion devise via an evaporator feedline. The expansion device can include a multifunctional valve that cooperates with the evaporator feedline to supply the evaporator coil inlet with a mixture of
refrigerant vapor and liquid at a linear velocity and with relative amounts of vapor and liquid which are sufficient to provide efficient
heat transfer along substantially the entire length of the coil, substantially reducing the build-up of
frost on the evaporator coil and enabling the
system to be operated without requiring a
defrosting cycle over a substantially increased number of operating cycles compared to conventional
refrigeration and freezer systems operating at the same
cooling load and evaporating temperature conditions.