In an industrial environment, maintaining effective control of humidity is critical to the health of the building and its occupants, and often supports the best performance of the manufacturing process. Explains John Barker of Humidity Solutions.

As we all know, humidity control is the basic element of a healthy environment to maintain good indoor air quality, which is applicable to any space where people live or work. Relative humidity (RH) can also affect the building structure, for example by promoting condensation on cold surfaces, which can lead to corrosion or mold growth (depending on the type of material)-or it can cause a slipping hazard.

In addition, RH can affect the integrity of storage materials and damage the reliability of the machine, leading to interruptions in the manufacturing process.

When there are problems with humidity control in industrial and commercial environments, it is usually because the relative humidity is too low. This can make the eyes dry and itchy, especially for contact lens wearers, and the surface of the respiratory tract begins to dry out, leading to dehydration. Low relative humidity also increases the spread of pathogens such as influenza viruses. The survival rate of this virus is lowest at 40-60% RH and 21°C.

In addition, poor RH control is related to the Sick Building Syndrome and the intensity of chemical pollution caused by gases generated from materials used inside the building. This is because relative humidity affects the distribution speed of these gases, and these chemicals may react with water in the air. Allergic reactions are also affected by RH.

These issues are reflected in the environmental variables identified in HSE Guidance Note 194 (4)-related to maintaining the health, safety and welfare of the workplace. They are climatic and seasonal changes in air temperature, average radiant temperature, ventilation, humidity, air velocity, outdoor temperature, and solar intensity.

Low relative humidity can also cause various materials to dry out quickly. For example, wood tends to shrink, deform and crack when stored in a low-humidity environment.

In addition, low RH makes the occupants feel colder, so they increase the heating to compensate, which increases energy consumption and costs. Increasing the temperature will further reduce the relative humidity, thereby exacerbating the problem. Conversely, RH at the upper end of the acceptable range will make the space feel

The temperature is increased by 2-3°C so that the heating can be turned off.

For all these reasons, it makes commercial sense to include humidity control in any new construction project, and consideration should be given to retrofitting buildings that currently have humidity control.

Good humidity control will keep the RH between 40% and 60%. As mentioned above, humidification systems are usually needed to increase humidity.

In this case, choosing the right type of humidification system is essential to provide the right amount of moisture and maintain the required relative humidity. Other factors must also be considered, such as energy consumption, maintenance requirements, and the location of humidification equipment (especially when the room is limited).

Traditionally, the solution was to heat water to generate steam, and then introduce the steam into the ventilation system-this is still the most suitable option for some projects. However, as discussed in more detail below, high-pressure, low-energy systems that use cold water are becoming more and more popular in industrial applications.

There are many ways to generate humidified steam, and the specific selection needs to be determined according to the specific requirements of the project.

For example, the supply of electrode boilers will not exceed 90 kg/hour. The resistance generator can provide a flow rate of up to 120 kg/h for a single device, while the modular gas humidifier can provide a flow rate of up to 400 kg/h. The ability to use modular configurations for gas humidifiers (such as modular boilers) also means that the system can respond very effectively to different humidification requirements.

Based on experience, 0.73 kilowatts of heat is required to produce 1 kg of steam, but distribution and other losses may increase by another 20%. Therefore, heating methods are an important consideration in today's energy- and carbon-conscious world. In most cases, gas humidifiers will provide higher efficiency and lower carbon footprint compared to utility power.

The installation cost of the gas device may also be lower, because the wiring requirements of the electric humidifier are very high. For example, a 400 kg/hour electrical installation will require 280 kilowatts of power, while a gas installation requires only one gas pipe to provide the same load. When steam is injected into the piping system, the use of a gas system with multiple spray guns will reduce the length of the piping system required for high loads.

Obviously, the cost of ownership must be considered, and there are several issues to consider. In hard water areas, the possibility of scale formation cannot be ignored, and softened water is usually recommended.

For example, we recently cooperated with a professional packaging tester in which the humidity is controlled by an electrode steam boiler. These are experiencing regular fouling and cannot maintain the required humidity without extensive maintenance. It turns out that a more cost-effective alternative is a resistance steam humidifier that uses softened water.

Another consideration is the location of the humidification equipment—especially when room space is at a premium. The area of ​​the gas device is relatively small and can be provided in a skid-mounted configuration for installation outside the building. If rooftop installation is the best solution, electrical installations can also be weatherproof, thereby reducing restrictions.

A lower energy alternative to heating water is to spray water through nozzles to atomize and absorb the water into the air (adiabatic humidification). Water can be sprayed into the piping system at low or high pressure or directly into the space to be humidified. Such systems also need to adopt antimicrobial measures such as ultraviolet disinfection, and can be used in combination with demineralized water or reverse osmosis water.

Despite some differences, all forms of adiabatic humidifiers use less energy than self-generated steam humidifiers. The low pressure nozzle uses compressed air, so the air compressor consumes energy. The high-pressure nozzle obtains energy for atomization from the high-pressure water, so the high-pressure pump here is the main energy consumer, albeit very low.

Achieving effective humidity control while minimizing life cycle costs is a consideration for the custom cardboard tube packaging manufacturer Visitan, because low humidity in warehouses and factories causes paper curling and static electricity issues. The solution proved to be an adiabatic humidification system that introduces water into factories and storage rooms through high-pressure nozzles to maintain a relative humidity of 55%.

A manufacturer of injection-molded plastic beverage bottles adopted a similar solution. The nozzle head was again assisted by a fan to convey water. The configuration of each nozzle head was suitable for the area to be served, and to ensure effective humidification without generating on the machine and the product. Risk of wetting or condensation.

In both cases, the use of adiabatic humidification provides additional benefits through the cooling effect produced by evaporating water, thereby reducing the need for mechanical cooling of the space.

Given all the factors discussed here, it is clear that achieving acceptable humidity control depends on addressing many variables in each project. For this reason, it makes sense to work with companies that have a comprehensive range of different humidity solutions and expertise to apply them to the best results.

For more information, please visit: www.warmitysolutions.co.uk

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