Ice-free food warehouse relies on desiccants, fabric duct
Teaming up with mechanical engineer Gary Evans, of System Components Corp., Ocala, the duo selected a combination of desiccant equipment and fabric duct air distribution as an energy-saving, maintenance-cutting supplemented to heated freezer entrance doors.
Evans decided on a desiccant system and industrial-grade fabric duct to distribute dehumidified air, a modern solution to an age-old problem. A two-year payback on the $130,000 project now has others interested, and comes from an 80% reduction in costly semi-daily defrost cycles for each of the 21 evaporating coils and dozens of rooftop condensing coils. Defrost cycles on the ammonia refrigeration system have been reduced to once per week.
The payback doesn't include estimates of an additional $50,000 annual savings for ice removal on the 40X360 foot trucking dock that was previously routinely performed by in-house maintenance people, according to Evans. Ice had regularly accumulated on the floor and ceilings as far as 20 feet from each of the four 14X8 foot automatic entry freezer door thresholds.
"With the new desiccant and fabric ductwork system, we reduced relative humidity from worst case scenarios of 90% to a constant everyday 40% RH," said Evans.
Betzel Mechanical installed the 10,000-cfm Model F-30 "FreezAire" desiccant system by Munters, and subcontracted the fabrication of the sheet metal supply and return to Express Metals, St. Petersburg.
The supply duct connects the rooftop desiccant unit to the 140-foot long run of 42-in. dia. fabric duct from Fabric Air Inc. that runs just above the four freezer doors. The project also included 180 feet of 40X24-in. metal return duct with 12 grilles that are spread evenly along the 23 truck dock openings.
Above each freezer door, an eight-foot long section of fabric duct has 120 plastic, narrow-throw air nozzles that bathe the floor and door hardware with dry air.
Aesthetically, the fabric duct matches the company's corporate blue color theme. The fabric duct also springs back to its original shape when bumped by objects such as forklifts or pallets, and can be taken down and cleaned on a routine basis.