Fruit Storage

Requirement:

Convert an existing multi thousand crate, aged Refrigerant 12, Direct Expansion multi-room fruit storage facility to a modern system that will maintain 33 degrees in each room, regardless of the time of year or quantity of fruit stored.

The fruit enters at approximately 35 degrees, directly from the hydro-cooler and is not removed until the variable market calls for it. In most cases, this represents a several month storage life. If the storage temperature varies from 33 degrees, the fruit commences to ferment and lose quality and market value.

A structural constraint dictated that the existing R/12 air handling units be reused without dismantling or coil replacement.

Solution:

The solution to that reuse constraint was to reheader in place the R/12 coils to accommodate the use of recirculating Propylene Glycol at velocities that would maximize their heat transfer capability. This meant that each storage room required its own circulating pump for high flow rates coupled to a modulating controlled blending system that made available the necessary glycol temperature flowing in the central system at much lower rates.

The USP grade Propylene Glycol Outdoor Air Cooled Chillers contain multiple compressors for redundancy and variable load capability and with all components identical to the interconnected adjacent Hydrocooler chillers. This arrangement attains the maximum in overall redundancy and year round product inventory protection.

Experience indicates that the cart recorders in each room are drawing perfect circles around the 33 degree level.

Kenneth W. Wicks

ASHRAE Fellow

5/3/99