On the occasion of the annual World Refrigeration Day, June 26, we have asked one of our inhouse air engineering experts, Engineering Manager, Michael G. Mortensen, about the essentials of refrigeration applications.
Industrial refrigeration is a group of storage and food processing applications where traditions and requirements differ vastly across national borders. Local knowhow and expertise are thus important in the design phase.
“Generally speaking, industrial refrigeration can be divided into three main subgroups: cool work areas, process cooling and cold storage. Common for all facilities is the need for even air dispersion, proper induction and low temperature gradients across the room. In spaces that occupy people, a draft-free occupant zone is also central.” Says Engineering Manager, Michael G. Mortensen
Cold storage applications offer the highest degree of national differences in terms of the air dispersion system demands.
In China, for example, space restrictions are an important aspect of consideration. Storage facilities are typically very tall buildings (30+ meters) and efficiently packed to the last shelf. Hence, slim duct profiles and precise directional airflows are crucial to the design.
Conventional solutions, such as metal ducting with diffusors, often cause huge temperature gradients across the space due to spot diffusion and an uneven air distribution. An uneven cooling may result in stale air zones or hot spots, causing product degrading and ultimately profit loss.
Conventional solutions also consume more energy, due to a need to over-cool to compensate for the mentioned shortcomings.
With fabric ducting it is not necessary to over-dimension the installation. Even air dispersion with precisely calculated airflows ensures very low temperature gradients across the cooled space.
The diffusion technology in fabric ducting enables the entire duct to function as a diffusor; air dispersion happens throughout the full length of the duct and flow models can be added to the entire circumference of the duct, 360°.
The lower pressure drop, offered by the fabric-based technology, ensures a lower energy consumption compared to conventional solution. Up to 40% savings may be realized.
“As a rule of thumb, we use non-permeable fabrics in cold storage application, because there is no condensation in freezing conditions.” Explains Engineering Manager, Michael G. Mortensen.
Example: ZhangZiDao Cold Logistics Center
The island of ZhangZi in the Yellow Sea is renowned for its seafood industry, where sustainable production methods are gaining ground. The ZhangZiDao Group is the largest producer, managing 70,000 hectares of the Yellow Sea. They see sustainability as an important factor; a line of thought they also applied to their cold logistics facility, which was constructed in 2013.
The six-story ZhangZiDao Cold Logistics Center includes 30,000 m2 of automated CO2 refrigerated cold storage space with a temperature setpoint between -20°C to -25°C [-4°F to -13°F]. They use advanced ammonia-carbon dioxide cascade refrigeration technology, which offers a low energy consumption and emits little carbon.
Dispersing the air through fabric ducting enables an even air distribution, which protects the products. This ensures the product quality and protects against profit loss.
The era of modern fabric ducting began in Denmark in the early 70s to create better conditions for the workers in the meat processing industry. It started as a collaboration between the Danish Meat Research Institute and FabricAir (then known as IPS Ventilation).
Prior to this project there had been scattered attempts at creating fabric ducting. Entrepreneurial employees across the globe had covered air inlets with things like duvet covers, pillowcases or even coffee bean bags to dampen the drafts in cold workspaces. These initiatives were never formalized, and the materials selected were health hazards; a breeding ground for all sorts of bacteria.
When we installed the first modern fabric duct in a slaughterhouse in Denmark in 1973 is became a true gamechanger and instigated a new era for workers in cold rooms across the globe with draft-free, hygienic air dispersion.
The number of employee sick days plummeted, as a result of the newly improved work environment. And the level of hygiene in the production significantly increased with the new technology, that could easily be removed for laundering and re-installed in a matter of minutes.
“Condensation is a significant health hazard and a primary factor in microbial growth. Traditional metal ducts, which were used before our technology was introduced, had a lot of shortcomings in these cold food processing environments. These included issues with condensation, corrosion and general hygienic challenges.” Explains Engineering Manager, Michael G. Mortensen, and continues:
“As an example, the metal ducts cannot be easily cleaned, which means dust, bacteria and other harmful particles accumulate inside the ducting and finds its way into the room atmosphere, where it has a negative impact on product quality and worker safety. A fabric duct can be washed in a regular washing machine and because it’s fiber-based, it doesn’t corrode.”
The innovative air dispersion technology was an instant success that quickly spread across the globe. It has enabled air dispersion engineers to control the airflow and create even air dispersion with a much better air distribution across the space.
Using different permeabilities and perforations in the fabric surface, cooled air is dispersed along the entire length of the duct. This entails a lower air velocity requirement, which minimizes drafts, without compromising product safety.
The targeted airflows produce a homogenous temperature across the production facility without having to use high air velocity or over-cooling the dispersed air. The resulting outcome is a better product hygiene and lower energy consumption, coupled with much higher employee comfort despite the freezing temperatures of the cold workspaces.
“Our rule of thumb in cold workspaces is to use permeable fabrics. They prevent the formation of condensation on the ductwork because there’s the same temperature in the near zone as inside the duct.”, says Engineering Manager, Michael G. Mortensen and expands:
“The condensation point depends on the relative humidity and varies across borders. Condensation will occur when the temperature of the supply air is below the dew point of the room temperature.”
Example: İNAN SÜT Dairy plant
In 2011, one of the leading dairy producers in Turkey established two new production facilities. The company adheres to a strict quality focus and wanted the best suitable air dispersion technology on the market.
They selected a FabricAir dispersion system in order to prevent corrosion and to achieve the highest level of efficiency and hygiene.
Process cooling covers a wide array of food applications, including slaughterhouses, dairy plants and bakeries. Each with their own specific set of unique challenges.
In meat processing it’s of utmost importance to prevent moisture loss in the meat, as a loss of moisture means a loss of value.
In dairy plants it’s crucial to keep a very low temperature gradient, as well as a very high level of hygiene.
In bakeries, process cooling is used to counteract the extreme heat generated by equipment, such as ovens, and to facilities a controlled quick cooling of the baked goods before they moved on to the packaging part of the plant.
“We can also use the airflow to sweep other surfaces, such as production equipment in metal, to prevent condensation from settling on those. This minimizes the risk of bacteria growth” says Engineering Manager, Michael G. Mortensen
Example: Equalizing room at Danish Crown in Denmark
As a natural consequence of the history of our technology, FabricAir was tasked with solving the challenge, when Danish Crown needed a hygienic and efficient process cooling solution for their equalizing rooms.
The aim was to reduce cooling time from 48 hours to 24 hours without sacrificing product quality by losing humidity or weight in the meat.
Using precisely controlled throws, we tailored a solution that was hygienic, ensured against condensation and corrosion, and achieved fast equalization without the loss of humidity and weight.
The solution effectively reduced cooling from 48 hours to 24 hours and as an added bonus also realized significant energy savings due to the higher process efficiency.
Danish Crown has used FabricAir ducting in many room types and applications since the 70s. A lot of the original ducting is still working smoothly despite the ~40 years of running.