Humidification Methods for Environmental Chambers

Environmental chambers for insect and plant research
are common applications requiring humidity control.\
Image courtesy Percival Scientific

Many environmental chambers utilized in research or production applications have a requirement to maintain a specified moisture level in the controlled space. Most often, the moisture level is specified as relative humidity. Some moisture levels may require the removal of moisture from the space, but the focus of this article is those instances where moisture must be added to the air in order to maintain the setpoint.

In designing a humidified environmental chamber, or specifying one for your own application, the challenge is to add moisture to the air in a fashion that does not result in detrimental effects on the contained materials or work. Additionally, the humidification system operation must work in concert with, not adversely to, other elements of the system that are tasked with maintaining other environmental conditions, such as temperature. With some awareness of the various methods available for humidification and their potential impact on your work and your budget, you will be better positioned to make an informed selection and achieve your desired outcome.

Several humidification methods are widely available for commercial use, all of which result in the same thing; adding water vapor to the air in the controlled space.

• Steam introduction directly into the space: This direct addition of water vapor using low pressure steam should only be used when the sourced steam is positively known to be suitable for introduction into an occupied space. Any treatment chemicals used for efficient boiler and steam system operation could possibly travel with the steam into the controlled space. If the steam is clean, the main concerns are potential heating of the air by the sensible heat of the steam and the reliability of the steam source. An advantage of this method is that it is very rapid in response to a control signal. The hardware to regulate and control the steam injection can be costly, and present a challenge to some service techs.
• Passive evaporating of water using the chamber air: Water will evaporate into air at differing rates under differing conditions. Directing a flow of air from the space over a water surface or falling stream of water will result in some degree of evaporation, with a corresponding increase in relative humidity. These systems come in many configurations designed to fulfill a range of requirements and available installation space, some with heating of the water to increase the evaporation rate. They are inexpensive and slow to respond. A major issue for some applications is the tendency for the water sitting in the evaporating pan to harbor biological contaminants. Frequent cleaning is a characteristic maintenance item for these systems. Cleaning reduces contamination levels and also removes the accumulated mineral deposits and other debris left behind by the evaporating water. This method of moisture addition will result in a small amount chamber air cooling.
• Evaporating water using electric heat - This humidifier is similar to the passive evaporating method just described, but with the addition of a controlled heating system that can increase the evaporation rate. Consisting essentially of electric heaters immersed in water contained in a comparatively compact unit, these humidifiers can be selected to deliver very large amounts of vapor from a small package. The electric heat is the primary driver of evaporation. Heat applied to the water can be regulated in very fine increments to provide accurate humidity control, with little excursion from the setpoint. It is not uncommon for these units to boil the water contained in the unit, so one concern is the amount of sensible heat that is delivered with the water vapor and its potential impact on room temperature. Cost is moderate. Maintenance levels are low, but a treated water supply is recommended to minimize scale formation. Biological contamination is of little concern with these units due to the temperature at which they operate. Several configurations of this type of humidifier allow for a broad choice of installation options.
• Evaporating water using steam - With essentially the same operation as described above for the electrically heated unit, a steam heated humidifier utilizes steam as the heat source. Precise control of a steam supply is generally more difficult and expensive than a comparable capacity electric heating system. These systems are generally available as larger capacity units.
• Water dispersion devices - Several technologies are utilized to increase the surface area of a water supply and disperse it into the controlled space where it is evaporated by the air. Simple and inexpensive centrifugal atomizers create fog of tiny water droplets that evaporate as they contact the chamber air. Other devices employ compressed air and specialized spray nozzles to create very small water droplets that produce a similar result. Ultrasonic transducers aer also employed to atomize water into a fine mist. Centrifugal atomizers are probably the least expensive option, but may not provide the level of control accuracy needed, since they are not well suited to rapid on/off cycling. Ultrasonic transducers and spray nozzles can be sized or configured to provide better levels of output modulation, but come with a higher cost. Maintenance requirements for water dispersion devices should be considered. Another consideration for this type of humidification is water supply quality. Liquid water is dispersed in the air, then evaporated. Anything contained within the water droplet that is not water will be liberated in the controlled space. Over time, particulates and once dissolved minerals can accumulate on environmental chamber surfaces and require cleaning and removal.

There are many facets of humidification to consider for an environmental chamber or room. The less expensive first cost option may not be the best overall selection. Share your requirements with an environmental chamber specialist and leverage your own knowledge and experience with their application expertise to develop an effective solution.

Does Your Cold Room or Chamber Need a Backup Cooling System? Part Two

The usage pattern of a cold space will determine how
best to reduce the risk from mechanical failure.
Image courtesy of Percival Scientific

In Part One of this series, what may define failure in cold room or refrigerator operation was discussed, giving the reader a starting point in evaluating whether to incorporate a backup refrigeration system into a cold space design. Operational failure can, and does, arise from countless sources. Some can be expected and anticipated, others not. Regardless of the source of failure, though, having a backup plan in place can help avoid damage to cold stored materials in all but the most catastrophic of events.

Once a decision is made to establish a contingency or backup plan, the form of the backup strategy needs to be addressed.

All backup strategies have a common goal of keeping the cold material cold. A simple clear goal, but with numerous ways it can be achieved, and each option may provide its own array of additional benefits or attributes which make it more suitable for a particular facility, budget, or other constraint.

"Twins" - An obvious backup cooling strategy is to provide a copy of whatever system is required for full range operation of the cold space. While this option offers an easy decision, it is likely to be one of the more costly ways to proceed. Proper design of a cooling system is based upon a load calculation that accounts for all the heat gain to which the cold space will be exposed. The sum of the loads will determine the size of the cooling system. Some applications that require close temperature control, or are subject to excessive door opening time, large warm mass additions, fresh air induction, dehumidifier operation, or a host of other heat sources could have comparatively large cooling systems. Purchasing and installing a full capacity redundant cooling system, in these cases, should be considered only when full operational capability of the space is the only option. When one system fails, the backup can maintain the space conditions without any change needed to the way in which the space is used.

Relocate - When the amount of stored material is manageable and a suitable space can be identified, it may be most effective to maintain unused cold space that is designated for use in the case of equipment failure. This likely will apply best to installations of refrigerated cabinets (refrigerators), where stored materials can be easily moved from the failing refrigerator to the backup space. The backup space should be kept in operation continuously, so its proper operation is confirmed. This backup scheme may be well suited to facilities with numerous refrigerated cabinets in use. The common backup cold space serves multiple users. A challenge specific to this plan is keeping the backup cold space from being used as normal cold space by any user for any number of reasons.

Full Load / Base Load - If a cold space is to have two cooling systems, an alternate to the "Twins" scheme can be considered. An analysis of space usage may reveal patterns that can be adjusted in case of a failure of the primary system. If a change in space usage can be enforced during periods when the primary cooling system is inoperable,  a smaller capacity, lower cost cooling unit can be incorporated as the backup unit. This option can impose some additional control challenges, but also some potential energy saving benefits, which will be discussed in the next installment.

Half Load / Full Load - If there are substantial lengths of time during which the cold space faces a low and stable heat load, another operating scheme may be considered for providing backup cooling. The full heat load component of the design is split evenly between two cooling units. One of the cooling units will be sufficient to maintain cold space temperature during most of the day, with the second unit available to provide additional capacity when needed. The second unit also serves as a backup in case the primary fails. This scheme will require adjustment to room usage in the case of failure, similar to that of the Full Load / Base Load plan previously described.

There are numerous other risk reduction schemes that can be developed to deal with the potential of cooling system mechanical failure. Some schemes may provide energy savings during normal operation, as well. A key element of real risk reduction and maximizing the benefit of the additional equipment cost lies in the control system. The controls need to be capable of detecting failure and taking appropriate action in response to a large matrix of possible conditions. The takeaway from this article is that there is more than one solution to the challenge. Approach the problem with an analysis of how the cold space is utilized, before selecting equipment. The subject can be more complex than it appears, especially to those unfamiliar with control systems. Enlist the help of experienced equipment specialists to help identify the risks, assess cold space usage, and develop an effective plan.

Full Featured Environmental Chamber Control System

The IntellusUltraConnect C9 adds a range of remote
connectivity functions to the operational functions of the
IntellusUltra C8.
Image courtesy Percival Scientific

Percival Scientific has a long history of designing and manufacturing environmental chambers and plant growth chambers for life science industries and institutions. Those years of experience are part of the IntellusUltra series of control units that serve as the user interface and operating unit of the company's line of environmental rooms and chambers.

Ease of use is the hallmark of the controllers. Some applications, especially those for plant studies, can require multi-step profiles that change temperature, humidity, lighting, and other functions. Entering or editing a profile with IntellusUltra is intuitive and simple.

In addition to a plethora of operational features, the "Connect C9" version offers a range of remote connectivity functions that can keep users in touch with their equipment and research anytime and anywhere. From the Percival Scientific website...

• Remote connectivity and monitoring with e-mail notifications.
• On-board USB connection allowing for real time data logging with up to four gigabytes of data storage. Simply use a portable USB stick to download your data to analyze on any other capable device.
• An on-board Ethernet connection allows direct monitoring and analysis of chamber conditions.
• Available remote monitoring software has been optimized to interface with the major web browsers.
• Ability to upgrade to our cloud-based service securely and confidently monitor and backup your research data

Solid control of environmental parameters, plus connectivity that enables access to the system from anywhere. More detail is provided in the document included below. Share your environmental room and chamber plans and challenges with experienced lab equipment professionals, leveraging your own knowledge and experience with their product application expertise to develop effective solutions.

Plant Growth Chamber Environmental Controller from Atlantic Technology Group, Inc.