The Effects of Ambient Temperature on Refrigeration Load Sizing

The key to determining the proper refrigeration load requirement for any box  rests on two general items:

1. Product load or internal heat load. This would include incoming temperature of product being stored, heat of respiration of product being stored, any change of state of the product (freezing), and any heat given off by lights, motors, people, etc.
2. External load. This would include any air infiltration load, radiant load through walls, ceiling, floors, etc.

Ambient temperature or ambient temperature difference from external box temperature to internal box temperature can have a significant impact on the load required.

On walk-in coolers for example, the difference in wall and infiltration loads from an 80°F ambient to a 90°F ambient is approximately 18-20%. From an 80°F ambient to a 100°F ambient that difference increases as much as 30%. See table 1.

Table 1

Data from Russell’s Engineering Manual

Table 2

Data from Russell’s Engineering Manual

In all cases, the refrigeration technician should use proper sizing tools such as the Russell Engineering manual RU-ENG-0313A to determine the proper load requirements.

Source: HTPG Tech Note February 2019