Consistency of temperature distribution throughout refrigerated cargo space, typically measured as maximum temperature deviation from setpoint across all locations and heights within the space; professional frozen delivery targets ±3-4°C uniformity, while industry-standard equipment commonly exhibits ±8-12°C variation. Why It Matters: Temperature uniformity directly determines frozen food quality and regulatory compliance. A system maintaining -18°C ±10°C means product may experience temperatures from -28°C to -8°C depending on location – the -8°C product is legally and practically compromised for frozen storage. Standard R638 compliance focuses on maintaining -18°C or below but doesn’t address uniformity; operators can pass compliance with temperature sensors in cold zones while ceiling product regularly exceeds -12°C. Physics demands uniform temperatures require adequate capacity, proper airflow design addressing thermal stratification, and elimination of thermal bridges – none of which are priorities in standard bodybuilder practices focused on minimizing construction cost.
Factors Affecting Uniformity:
- Refrigeration Capacity: Undersized systems never overcome natural stratification
- Airflow Pattern: Must address warm air accumulation at ceiling level
- Insulation Quality: Thermal bridges create localized hot spots
- Door Opening Patterns: Frequent openings introduce warm air loads
- Load Configuration: Product blocking airflow creates dead zones
- Altitude Effects: Reduced air density at Johannesburg elevation affects both capacity and convection
Industry Reality: Achieving ±3-4°C uniformity requires:
- 25-30% refrigeration oversizing versus nominal sea-level calculations
- Custom airflow design vs standard roof-mounted evaporator
- Attention to thermal bridging and insulation details
- Additional engineering cost vs standard bodybuilder approach
Result: Industry accepts ±10°C uniformity as “normal” because fixing it costs money suppliers don’t want to spend.
Related Terms: Thermal Stratification, Airflow Pattern, High-Altitude Refrigeration, Door Openings (Thermal Load), Temperature Monitoring System, Cold Chain Integrity