How a cold room pulls heat out of produce

Freshly picked produce carries field heat and keeps making heat as it breathes. In a cold room, evaporator fans push chilled air past the crates and the produce temperature falls fast at first and then slower, halving its gap to the room temperature every half cooling time, while the refrigeration system also removes heat leaking in through the walls.

Controls

Labels

Animation speed

Produce loaded

Half cooling time

Short with strong airflow through the boxes, long in still air.

Field temperature

Step through it

Warm crates arriveProduce picked on a hot afternoon can be near 30 °C. Every hour it stays warm it ages faster, so cooling quickly protects shelf life.
Evaporator fansFans blow air across cold coils and through the room. The colder air picks up heat from the produce and returns to the coil.
Half cooling timeEach half cooling time halves the gap between produce and room temperature. Three of them remove seven eighths of the gap, a common target.
Still air is slowIn a plain cold room without forced air through the boxes, half cooling times of many hours are common. The produce stays warm much longer.
Where the heat goesThe condensing unit outside dumps the heat removed from the room. Field heat dominates the load right after harvest.

Newton cooling in halves

Produce cools roughly like any warm object in colder air: the rate is proportional to the temperature gap. That gives exponential cooling, T = room + (start minus room) x 0.5 raised to (time / half cooling time). After three half cooling times, seven eighths of the gap is gone.

The room is held at 2 °C in this model. Real half cooling times depend on package vents, stacking, and airflow, and are measured rather than calculated.

Try it: with 4,000 kg at 30 °C, set the half cooling time to 1 hour. The produce reaches about 2.4 °C in 6 hours but the refrigeration load jumps past 35 kW. Slide it to 6 hours and the load falls under 9 kW while the produce is still near 16 °C.

The load, simplified

Field heat is mass x specific heat x temperature drop; the model uses 3.9 kJ/kg·°C and averages that heat over the seven eighths cooling time. It adds respiration at a flat 0.1 W/kg and wall gains of 0.3 W/m²·°C over 180 m² with 30 °C outside. These are teaching assumptions; real respiration rates vary several fold between crops.

Sources

Chapter 2. Produce Cooling BasicsNC State Extension
Chapter 5. Refrigeration LoadNC State Extension
Numerical Analysis of Air Supply Alternatives for Forced-Air Precooling of Agricultural ProduceSustainability, MDPI (open access)

How to cite this model

Avid Solutions International. (2026, November 11). How a cold room pulls heat out of produce [Interactive 3D model]. Avid Field Lab. https://avidsolutionsintl.com/explore/cold-storage-room

Last updated November 11, 2026

Keep exploring

Livestock & FoodHow a cream separator splits milk Livestock & FoodHow an incubator hatches chicken eggs Livestock & FoodHow a freeze dryer removes water as ice Livestock & FoodHow milk is pasteurized in 15 seconds