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Cold storage cooling that holds the room at the number.
A cold store is judged on one thing: the product temperature at the back of the rack on the busiest day. The unit coolers have to throw air the full aisle, defrost without warming the room and keep running while the doors open all shift.
Cold storage warehouses use ceiling-mounted industrial unit coolers inside the room and condensers or a central plant outside. Freezers usually run at -10 to -20°F with 2 to 4 fins per inch to manage frost, and coolers at 33 to 40°F with 4 to 6 fins per inch.
What makes it hard.
The problems we size against.
Frost chokes the coil.
Every door opening brings in moist air that freezes on the fins. Wide fin spacing and the right defrost keep capacity up between cycles.
Air has to reach the far end.
Tall racks and long aisles need air throw sized to the room, or the back pallets run warm.
Refrigerants are changing.
The AIM Act is phasing down high-GWP HFCs. New plants move to CO2, ammonia or low-GWP blends, and the coils have to match.
How the system works.
From the load to the air, in four steps.
- Product and doors add heat.
Stored product, people, lights, forklifts and every door opening load the room.
- Unit coolers pull it out.
Ceiling-mounted unit coolers move room air across a cold coil fed by the refrigeration plant.
- Defrost keeps them clean.
Electric, hot gas or water defrost clears frost on a schedule so capacity holds.
- Condensers reject it.
The heat leaves through air-cooled condensers or gas coolers outside the building.
Industrial Unit Coolers
Dual Discharge Unit Coolers
CondensersQuestions about cold storage
What fin spacing should a freezer unit cooler have?
Low-temperature rooms frost heavily, so freezer coils use wide spacing, typically 2 to 4 fins per inch. Coolers above freezing can use 4 to 6 fins per inch for more capacity in the same size.
How is a cold storage unit cooler sized?
From the room load in MBH, the room temperature, the refrigerant and the TD, the difference between room air and saturated suction. US ratings are given at 10°F TD.
Which defrost is best for a freezer?
Electric defrost is simple and common on HFC systems. Hot gas defrost is faster and common on larger and ammonia systems. Water defrost suits some process rooms. The choice follows the plant design.
Can the unit coolers run on CO2 or ammonia?
Yes. The published tables cover HFC, CO2 pumped, ammonia pumped and glycol versions.
Send the heat load.
Loop temperatures, flow and site. A sized selection comes back.