Psychrometrics isn’t just a chart on the wall – it’s the language of air. And for many facility or production issues, speaking that language often means looking beyond refrigeration as the only option available to solve moisture control problems.

Tom Peterson, founder and CEO of Climate by Design International (CDI), has spent more than three decades building custom desiccant dehumidification systems for facilities where dry air needs go beyond what can be accomplished with refrigeration alone. By applying the science of psychrometrics to a few common facility problems, “we’re not just moving air,” Peterson said. “We’re controlling the
environment.”

“Refrigeration can only solve your moisture problem to a certain point, whereas with a desiccant, you can go way beyond what refrigeration alone can do,” said Peterson. Many people don’t think of applying psychrometrics as a solution to the problems they encounter because they’re just not used to a thought process that might involve beyond-the-refrigerant reasoning, he added.

“Not everyone has that experience factor [that would lead them to consider psychrometrics]. They may have been taught to think only in tons of refrigeration, because our industry is so focused on refrigeration alone,” he said. “But there are limits to how dry you can get with just refrigeration before you start dealing with things like frost, sequential defrost, and other problems.”

Peterson applies a desiccant air handling unit to help solve most of these problems. Inside the unit is a wheel filled with desiccant that continually turns, rotating slowly between two airstreams. ” The airstream we are conditioning is moisture filled. That airstream goes into the wheel and the wheel adsorbs that moisture. To then remove the moisture from the wheel it turns into another airstream where the moisture is then ejected to atmosphere.”

Many people don’t know there is a solution to many of their common moisture problems, or generally speaking, they accept the management of moisture issues because they don’t know they have a viable solution to the problem, said Peterson.

“Once people find out what a desiccant is, they start finding many places where dry air can be their friend.” Peterson said there are four main areas where applying psychrometrics can take the guesswork out of solving the moisture related production issues that get the most
attention:

1. WASH DOWN RECOVERY
Wash-down recovery in protein rooms can turn into a significant moisture problem quickly. When wash down occurs in a typical 45 degrees processing room, and 140-degree hot water is used for sanitation, “condensation on cold surfaces is dripping everywhere, and so you have to recover that room and get it back to condition before you can start production again, said Peterson.

“After sanitation, it takes time to get that room back down to temperature and a moisture level below the point where it can condense. Using a desiccant air handling unit can increase by a 4- to 10-fold factor the amount of drying that can be done. You get that room back faster.”

2. LOADING DOCK SAFETY ISSUES
The second most common place moisture related issues can crop up is the cold storage loading dock, said Peterson, where issues come either from a potential safety risk, i.e., slippery floors, or from a maintenance issue when evaporator fans collect frozen vapor and become unbalanced, bearings and motors then fail. Providing a desiccant unit to dry the air in the vestibule – so that moisture from outside air can’t get into a freezer or cooler in the first place – is a preventative solution.

3. PRODUCT ISSUES
A third common area where moisture control can become important is in the more product-related processes, where moisture in the air is an issue that impacts the product itself. Too wet of an environment can cause moisture-regain in the product itself. This issue commonly crops up in applications where a product is meant to be dry. It must be prevented from absorbing moisture, like in pharma applications where moisture can affect the precision of pressing out pills, or in food applications where a crispy texture is needed, where moisture might cause a product to stick to itself or the packaging.

4. IMPROVING ENERGY EFFICIENCY
Sometimes, controlling moisture with a desiccant might simply be an easy way to improve energy efficiency in freezers or coolers, said Peterson. “There can be an energy payoff to paying attention to psychrometrics. Most of the time, the financial rewards come in increased productivity and increased safety, but there can also be operational benefits like improved energy efficiency as well.”

When it comes to applying psychrometrics to solve these problems, “we have to look at all of the factors affecting moisture-in-air as interrelated,” said Peterson. “We need to construct a comprehensive understanding of all of them in a given situation and understanding the psychrometric chart allows us to be able to know any two conditions and then understand all the others..”

Peterson is the presenter of the IIAR Webinar “Psychrometrics, The Science of Moisture in Air,” available to IIAR members through IIAR’s educational resources. During the webinar, he reviews several important principles for decision making including how he uses seven factors to determine an overall picture of a given facility’s psychrometrics, including: 1) vapor pressure; 2) dew point; 3) relative humidity; 4) wet bulb; 5) dry bulb; 6) enthalpy, and 7) the density of air.

Tony Lundell, IIAR’s Senior Director of Standards and Safety, said the webinar covers an often-overlooked strategy for managing moisture. “Where moisture needs to be removed from the air below the freezing point, an air handling unit with a desiccant wheel in it is a great option.”

“Managing moisture so it helps your product, prevents wasted energy, and reduces maintenance, is where the payoff for paying attention to psychometrics comes in – in the science of moisture in air,” said Peterson.