Dry fog system controls humidity level in warehouses

Keeping produce ripe and fresh is an ongoing challenge for growers and shippers of fresh produce. When it comes to avocado and citrus, for example, de-greening as well as controlled ripening often requires storage in a controlled humidity environment. Corrigan Corporation of America have developed a humidity system called VaporDry that they say controls the level of humidity in a fine fog, without causing packaging, buildings and floors to get wet.

"The VaporDry system controls the humidity level in various applications including avocado and citrus storage warehouses and distribution centers," explained Emily Corrigan Stavrou of Corrigan, based in Illinois. "The system is comprised of a patent pending design that emits a controlled small particle dry fog that will not make floors, racking or product wet."

"The VaporDry system is used in any application where relative humidity control is critical to the product quality or process efficiency," Stavrou said. "Most importantly, ripening and de-greening operations are a big market for the VaporDry system. Perishable distribution centers, meat processing, barrel fermentation, cheese rooms, concrete curing, and greenhouse operations are some other common applications."

Development and how it works
Using their knowledge of misting systems in the retail environment, Corrigan came up with the specially designed nozzles that emit the dry fog. The system is installed with humidity sensors to automatically apply and maintain the desired humidity level.

"The development of the VaporDry system took many years," Stavrou noted. "It was developed to support the ripening process, the post-harvest storage strategy and to extend the shelf life of stored perishables. The design started with a known nozzle technology Corrigan has used in grocery store service cases for many years. However, we needed to reduce and better control the water particle size to innovate into larger space humidification. Using a diffuser with controlled low water and air pressures, we were able to create the largest volume of dry fog from a single nozzle."

"The VaporDry system works by emitting the exact required amount of dry fog water particles into a space for a designated amount of time," she continued. "Proven, reliable relative humidity sensors are strategically placed throughout the space to provide feedback to the controlling system. This system provides optimal humidity level control by utilizing various set point deviation algorithms."

Practical aspects
Many warehouses and fresh produce storage areas are very large. Controlling the atmosphere in these rooms effectively as well as efficiently is a big consideration when selecting the system to do this task. Stavrou said there is no limit to the size of area that can be treated by the VaporDry system. The number of systems required will be the determining factor when dealing with the size of a building. She also explained the energy requirements of the system.

"The VaporDry system is not limited by the size of the space to be humidified," Stavrou said. "Each system emits a known quantity of dry fog per hour, so if the space is larger we just specify additional systems. Each VaporDry utilizes 3.5 cubic feet (99.1L) of air per minute compressed to 35 psi (241kPa). The compressed air for each system consumes approximately 675 watts. The sensors and controller operate on 120V and consumes less than 100 watts. Compared to an Electrode Boiler the VaporDry requires 89% less electrical energy."

Stavrou also said the system can effectively operate in a wide variety of environments, with only conditions below freezing requiring additional engineering considerations. "The VaporDry system can operate in any conditions from 0 to 100% relative humidity," she explained. "As conditions reach greater than 90% relative humidity, our heated sensor technology ensures that condensation on the sensor surface will not occur. We have installed the system in applications from 32°F (0°C) to over 100°F (38°C). Water freezes at 32°F (0°C), so applications near or below freezing need careful engineering consideration."

Maintenance considerations
According to Stavrou, the VaporDry system itself requires almost no maintenance and the nozzle orifice size allows the system to resist fouling or clogging. Adjoining input requirements such as air and water are also kept to a minimum, with the aim to optimize performance. 

"We believe the VaporDry system is better than other humidification products because it requires little to no maintenance," she said. "It creates a large volume of controlled particle dry fog in a simple, reliable manner. Also, Corrigan’s nozzle technology uses a large orifice size that resists fouling. The water and air pressure requirements are also low, optimizing performance."

"One competing technology uses ultrasonics to humidify," Stavrou continued. "These systems are expensive and are proven to be very maintenance intensive. A recent satisfied customer, the head of Engineering at a major produce warehouse had this to say - “The system has completely changed the way we look at humidity. The most surprising thing is that it requires almost no maintenance. Our old system needed frequent and expensive service to keep it going and we had to manually disassemble and sanitize each unit every single week. The ROI for maintenance labor alone was reason enough to switch.”"

Precise humidity control important for quality product
The importance of proper humidity control cannot be understated. Without a system that works effectively to control the moisture in the produce, it can cause losses both in terms of product and profits. Corrigan claims that the proven reliability of their VaporDry system will lead to a better product in a manner that is consistent and cost effective.

"The VaporDry humidity system helps to prevent product water loss by creating a high humidity environment," Stavrou concluded. "Water loss from improperly stored produce is the biggest contributing factor in weight loss, and for products sold by weight this has major economic consequences. Water loss can also affect shelf life, nutritional quality and the overall aesthetic quality of saleable produce. These factors all contribute to food waste, shrink and profit loss. Here at Corrigan we recognize the importance of precise humidity control and understand that our customers cannot afford any down time. With that in mind, our team of engineers developed the VaporDry system to be simple, robust and innovative."

For more information: 
Emily Corrigan Stavrou
Corrigan Corporation of America
Tel: +1 (800) 462-6478

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