A common domestic refrigerator consists of medium and low temperature sections. The challenge for the system designer is to find cost-effective solutions to properly control the temperature and humidity for both sections in an efficient manner.
The simplest approach from a refrigeration system design perspective is to use a single evaporator coil. The air that is blown across the evaporator is then directed as needed to one or both sections to maintain desired temperature. This approach is generally not as efficient as a two-evaporator system, and it produces less than desirable humidity control in the medium temperature section by supplying combined air flow to each section.