This was the problem in three locations of a regional, quick service restaurant chain in a very hot and humid area of the United States — Texas. Many of the chain’s restaurants have experienced significant humidity-related problems that have affected the structure and operation of the restaurants. Traditional methods of controlling humidity through hvac systems were inefficient and costly.
“We used desiccant wheel technology, which did a great job of reducing the latent heat (humidity) but in the process added sensible heat (higher temperatures) to the air. This additional sensible heat load was OK when the air conditioning equipment had enough sensible capacity to remove it. On very hot and humid days, however, we had to shut off the desiccant wheels so the air conditioning system could keep the restaurants cool, which then allowed the indoor humidity to increase,” said Michael Ireland, president and owner of Efficient Systems, the contractor involved with installing a new system for the restaurants. He decided on a new dehumidification system developed by DryKor, Ltd., an Israel-based company, which solves that problem by providing a total solution to humidity-related problems.
New Technology
DryKor, which has its U.S. headquarters near Atlanta, uses a liquid lithium chloride solution. Instead of heating the solution, it is cooled, which allows the solution to absorb humidity and cool the outside air as it passes over the desiccant medium. This design also removes up to 94% of microorganisms and air-borne bacteria and up to 80% of particles larger than 5 microns in the air stream, a significant benefit for maintaining acceptable indoor air quality.
The system does not require an additional heat source for regenerating the desiccant solution, as the system is self-contained. The heat absorbed from dehumidification and cooling is used to regenerate the liquid lithium chloride, which eliminates the need for hot water, hot gas, or gas furnaces to regenerate the desiccant that is required on desiccant wheels, and thus save on total energy consumption. Also, no additional enthalpy wheels, heat transfer wheels, heat pipes, or pre- or post-cooling are required as no additional sensible heat is generated.
“Adding more air conditioning capacity to remove the additional sensible heat was not an option because of space restrictions on the roofs. Further, more tonnage would not help maintain indoor humidity levels on cooler days, since moisture loads are often higher when the outdoor temperatures are in the 80s versus design conditions in the 90s and 100s,” said Ireland.
Immediate Results
The first location was in hot and humid Houston. A DryKor DryTop dehumidification system was added to the Trane 10-ton rooftop unit that served the kitchen, which allowed the introduction of 800 cfm for ventilation and resulted in mitigating the negative pressurization. The dining room was not served by a rooftop unit, so two DryKor D4.0R dehumidification standalone units were installed to treat the air,” said Ireland. “We could measure and feel the difference almost immediately. We also are very pleased with how the DryTop unit saves space as it can sit right on top of the air conditioning unit, a prime consideration for buildings with minimal equipment decks,” he said.“The morning after the DryKor units began operating, several representatives from the restaurant chain visited the restaurant. They were grinning from ear-to-ear. The floor, which had just been mopped, dried very quickly and overall comfort was much improved,” said Tom Krueger, president of DryKor, Inc.
“The second location, in Corpus Christi, TX, is a new building. We installed desiccant wheel technology to address the humidity-related problems we knew of, but building’s unique two-story design plus prevailing winds off Corpus Christi Bay of 20 mph to 30 mph caused more infiltration of outside air than expected. Also, the cooling capacity of the equipment could not compensate for the added sensible heat produced by the desiccant wheels on very hot days,” said Ireland.
A DryKor DryTop unit was installed on top of a Lennox 12-ton package unit that served the building’s second story and processed around 800 cfm of outdoor air.
“As a result, we were able to pressurize the building with outdoor air that was not only dehumidified but also cooled! Better pressurization with conditioned air helped the entire mechanical system in the restaurant,” said Ireland.
The third installation, also in Corpus Christi, had a problem primarily in the dining room. A typical refrigeration system dehumidifier had been tried, but did not remove enough moisture. Two DryKor D4.0R units were installed above the t-bar ceiling and ducted into the dining room. Humidity and comfort conditions were much improved.
