Structured Media Products
Structured media is one of the many names for the type of heat and mass transfer products that L S Enterprise provides. Depending on the industry and the application, there are different names for this type of media: film fill, cellular fill, packing, filter media, and biofilter media are a few examples. In order to understand the advantages of structured media, it is necessary to know what technology preceded it. As a means of condensing the history of heat and mass transfer products, we will concentrate on the history of water cooling towers since they are the largest users of structured media.
The simplest devices to cool water are known as spray towers. They have no fill and rely on the surface of water droplets to provide the contact area between the water and air. It quickly became apparent that spray towers were very limited in their ability to remove large amounts of heat from water efficiently. The next technology employed was the use of splash fill. Splash bars made from wood were a significant improvement in the use of space and energy to cool water. In a tower with splash bars the surface of the water droplet is still the heat/mass transfer surface. The splash bars improve the efficiency of the system by slowing down the droplets as they fall so that the droplet spends more time in contact with the air. They also renew the surface of the droplets when the droplet contacts the surface of the bar. This allows the hotter water in the middle of the droplet to mix with the colder water at the surface of the drop.
The Evolution of Cooling Tower Fill Media
Cross-Fluted (CF) fills generally provide the highest efficiency per volume of all fill & structured media types. They are also among the oldest designs, having been initially patented by Carl Munters & Co. in 1966. CF fills come in various “densities” where the sheet pitch (spacing) determines the number of sheets per unit width and thus the specific surface area (surface area/volume). Different applications benefit from different specific surface areas and the resultant flow profiles they provide.
The Advantages of Structured Media
The advantages of structured media over splash fills are significant:
- The heat transfer surface changes from droplets to a continuous water film. The velocity of the falling water film is significantly slower than the velocity of a falling water droplet. This leads to a significant reduction in the required air travel distance of the packing, usually by a ratio of about 5 to 1. Instead of 30’ high sections of splash bars in a counterflow tower, structured media only needs to be 6’ deep. This means that the cooling tower structure can be much shorter, which is a big capital cost savings. Shorter towers also mean the water does not have to be pumped as high, so operating costs are also reduced.
- In a properly designed structured media, the water film is turbulent so that the bulk water is constantly mixed with the water on the external water film surface. This increases the heat transfer coefficient between the water and the air. An increased heat transfer coefficient allows structured media to have higher water loadings. (Water loading is the amount of water flow per a given plan area.) The allowance for higher water loadings means that a smaller plan area is required, so again the size of the tower is reduced, and capital costs are lower.
- Structured media is installed in blocks that are high in volume but light in weight. Splash bars are also lightweight, but they have a very low volume per part. They must be installed individually. Thus, the labor to install structured media is significantly lower than that of splash bars.
- Structured media is mechanically strong. This means that the supporting structure is simpler and much less expensive compared to splash bar supporting structures.
Structured Media vs. Random Dumped Media
Structured media is used in several other industries besides water cooling towers. Chemical process industries use several types of media for mass transfer applications, such as distillation columns, strippers, and scrubbers. Prior to the use of structured media, the primary type of mass transfer media was generally referred to as Random Dumped Media (RDM). RDM is composed of small shapes that can vary in size from about 1in3 to about 200in3. Structured media can be cut down to blocks that are about 1700in3, but typically blocks are 10,000in3 or more per piece. There are many hundreds of types of RDM that are produced in different shapes and different materials. One of the few advantages of RDM is that it can be made from many more different materials than structured media.
Examples of Random Dump Media
The mass transfer efficiency of RDM is similar to structured media when comparing types that have similar specific surface areas. (Specific Surface Area = surface area per volume, e.g., in2/in3.) However, there are several significant advantages to structured media. When it comes to performance, RDM has much higher gas flow pressure drops for a given velocity when compared to structured media. Some of the more modern RDM products are only 4 times higher, but some of the older designs may be as high as 10 times higher. Higher pressure drops limit the airflow and corresponding heat/mass transfer. To put it another way, it will require more power and more cost to overcome the higher pressure drop for a given performance of an RDM product vs a structured media product with similar specific surface area. Another disadvantage of RDM is the cost of the media itself. Plastic RDM is produced via injection molding of the parts. Structured media is produced with high-speed thermoforming machines. High-speed thermoforming machines create the surface area for heat transfer at a fraction of the cost of injection molding.
When used in applications where fouling may be a concern or possibility, structured media has inherent advantages over RDM. Structured media that is designed specifically for fouling applications allow higher specific surface areas than RDM. That means smaller vessels for the same performance.
It is important to note that splash bar towers and towers with RDM packing can be designed to accomplish any level of performance. The question becomes: Which system or technology is the most cost effective and has the lowest life cycle cost? Structured media has the clear advantage in almost every application. That is why it dominates in so many industries and applications today.
For information on the various structured media products that we offer, visit our Fill Media page.
Testimonials
L S Enterprise & Industry News
Stay up-to-date on company and industry news and events.
L S Enterprise LLC Proudly Launches a New Website
January 27, 2025, East Earl, PA: L S Enterprise LLC is proud to debut our new website, www.LSEntLLC.com. Our original website biofilters.com launched in 1998. It was an important resource for those who were designing or building Recirculating Aquaculture Systems...
Join Us at the 2025 CTI Annual Conference in Memphis
January 27, 2025, East Earl, PA: L S Enterprise LLC will be attending and participating in the 2025 Cooling Technology Institute (CTI) Annual Conference in Memphis, TN, that runs February 2-6, 2025. Join us in Memphis as we learn about new technologies and goings on...