The lack of a separate temperature control in some freezers is primarily due to the way modern refrigerators are designed and their operating principles.
In most modern refrigerators, the freezer and the refrigerator compartment share a common cooling system. They are cooled by the same compressor, condenser, and evaporator. The temperature control in these refrigerators typically operates based on the thermostat's setting for the refrigerator compartment.
Here's how it works:
Single thermostat system: Many refrigerators use a single thermostat located in the refrigerator compartment to control the overall cooling system. When you adjust the temperature setting on the refrigerator, you are essentially controlling the compressor's operation and the cooling cycle for both the fridge and freezer.
Airflow and dampers: Inside the refrigerator, there are vents or dampers that regulate the airflow between the freezer and refrigerator compartments. When you adjust the thermostat to a colder setting, it signals the compressor to run longer, cooling both compartments more intensely. As a result, the cold air from the freezer is directed into the refrigerator to maintain the desired temperature.
Temperature difference: The freezer compartment is typically located at the top or bottom of the refrigerator. Since cold air sinks, the freezer will generally be colder than the refrigerator compartment. The temperature inside the freezer is usually maintained at a constant level, while the refrigerator temperature can be adjusted within a certain range.
Lack of separate control: Due to the shared cooling system and the fact that the freezer compartment is naturally colder, there is no separate thermostat or temperature control for the freezer. Adjusting the overall temperature setting will indirectly affect the freezer's temperature, making it colder or warmer along with the refrigerator.
It's worth noting that some higher-end refrigerators or specialty appliances, such as standalone deep freezers or dual-zone wine coolers, may have separate temperature controls for different compartments. However, the vast majority of household refrigerators rely on a single thermostat system to control both the refrigerator and freezer compartments.