Duty Free Americas, Inc. (DFA) reduced electricity costs 25% and eliminated moisture-related damages to goods by installing DuCool desiccant cooling and dehumidification systems. The installation of two DuTreat model DT800/4 desiccant cooling systems alongside two existing conventional air conditioning units made it possible to maintain constant conditions of 76oF (24.4oC) and 52% relative humidity even in the hot Miami summer when the outdoor temperature and humidity are extremely high and loading dock doors are frequently opened. Energy costs have been reduced because the DuCool systems are more efficient in handling the heat load and the air conditioning rarely operates. ‘Since the DuCool units were installed, the indoor air is cool and dry, we haven’t seen any humidity related product spoilage and we feel much more comfortable,’ said Duty Free Americas operations manager Lorenzo Lorenzo.
DFA operates stores in major international airports that sell items without duties or taxes to passengers who are leaving the country for a minimum period of time. The company’s warehouse in Miami stores goods sensitive to temperature and humidity levels such as tobacco, watches, candy, chocolate and cosmetics. The large doors in the loading dock area are frequently opened to load and unload products. In the past, the two existing air conditioning systems were set to 60oF (15.5oC) and operated nearly continuously, consuming large amounts of electricity. The air conditioning units reduced temperature and humidity but could not effectively handle the significant latent load. The high humidity levels and the water dripping off the air conditioners caused damage to expensive products, causing management to take action and find an alternative solution.
DFA evaluated several alternatives and selected the DuTreat system, which uses an innovative liquid desiccant process to cool and remove humidity from the air using minimal energy. In the DuTreat unit the liquid desiccant is cross flowed with the air from the building, absorbing the humidity from the air while cooling it. The moisture collected from the air is then ejected to the outdoors in vapor form. An embedded heat pump is used to cool the air and the liquid desiccant. The heat extracted in the cooling process is then used for ejecting the moisture collected from the air. Using both the evaporator and condenser sides of the heat pump significantly improves the overall energy efficiency of the system.
Two DuTreat units each process 800 cubic feet per minute (CFM) of air. Moving the air from the DuTreat units through the existing air conditioning systems made it possible to utilize the existing ductwork, reducing the cost of the installation. The DuTreat units cool and remove the humidity from the air, providing comfortable conditions while allowing the air conditioning thermostat to be set to 82oF (27.8oC) so that it rarely operates. The DuTreat units take in return air at a temperature of 76oF (24.4oC) and 52% relative humidity and provide treated air at 71oF (21.7oC) and 29% relative humidity.
The workers in the warehouse are very happy about the improved indoor air quality and say that the air inside the warehouse feels like ‘mountain air.’ The DuTreat units keep ducts dry to eliminate fungus and bacteria growth. The lower humidity level in the warehouse reduces moisture-related damages and prevents growth of mold and mildew.