Where Dead Zones Form
Dead zones occur predictably in specific locations:
Upper rear corners — Cold air loses momentum before reaching these areas, falling to the floor due to buoyancy effects (Froude number dropping below 1)
Behind dense product stacks — Airflow preferentially routes over and around obstacles rather than through them
Near doors — Areas affected by frequent thermal infiltration during access that receive inadequate circulation to recover
Floor corners — Where cold air accumulates but lacks sufficient velocity for heat exchange
Why Dead Zones Matter
Single-point temperature sensors typically measure return air entering the evaporator—air that successfully completed the circulation loop. Dead zones never contribute to this measurement. A controller can report -15°C compliance while product in dead zones warms to -8°C or higher.
Research from Chungnam National University documented temperature variations exceeding 3°C between different positions in a refrigerated truck body during normal operation, with dead zone positions consistently showing higher temperatures than controller readings indicated.
Mitigation Strategies
Multi-point monitoring — Adding sensors in known problem areas extends visibility beyond the well-circulated zones
Airflow management — Ducted discharge systems, air curtains, and T-bar floor channels can improve circulation to dead zone areas
Loading practices — Positioning temperature-sensitive cargo away from dead zones and maintaining air gaps for circulation
Container design — Using open-sided crates rather than solid containers allows air circulation through product storage
Related Concepts
Dead zones are closely related to
thermal stratification (temperature layering from buoyancy), the
bypass effect (airflow routing around rather than through product), and
return air sensing (measurement bias toward successfully circulated air).
See our technical article:
The Dead Zones in Your Freezer: Why Your Temperature Sensor Is Lying to You]]>
