Running Hot and Cold
by Lynn Petrak
The latest heat exchanger technologies reflect improvements on a classic design.
Hot things should stay hot. Cold things should stay cold. Perishables should stay safe.
Those are not complex concepts, but in the production of dairy products, controlling the heating and cooling process comes down to the reliability of equipment.
Heat exchangers, including sanitary heat exchangers used during product processing, are critical in dairy processing facilities because of their function in heating, cooling and pasteurizing dairy beverages and foods. As a testament to their function and performance, heat exchangers have been around for decades, with some models in today’s plants dating back decades.
Despite the longevity and proven track record of heat exchangers, equipment manufacturers continue to tweak heat exchanger designs to increase efficiency, help save resources and accommodate for different product types and resulting flow rates. Enhancements have been made for different types of heat exchangers — including plate heat exchangers, tubular heat and scraped-surface exchangers — as well as for gasketed and welded units. Suppliers are updating both sanitary heat exchangers and heat exchangers for utility purposes.
John Bohn, director of engineering, co-owner and founder of AGC Engineering, Bristow, Va., has seen firsthand the evolution in dairy manufacturing and its impact on basic equipment like heat exchangers. “The technology many people have in their plants was developed in the 1950s. When I mean upgrade, I really mean we can help bring them into the 21st century,” he says.
Another supplier who says the time is right for a fresh take on this equipment mainstay is Carl Lemke, business development manager, plate heat exchangers, for the Pleasant Prairie, Wis., sanitary segment group of Alfa Laval Inc. “A lot of our customers are taking a look at new technology to replace things that have been around for 40 years,” he says.
Whether they are replacing aging systems or building new plants with state-of-the-art systems, processors want modern heat exchangers to deliver a multitude of benefits. “All of our clients are concerned with expanding capacity while minimizing capital investment and conserving floor space. The driving forces are the combined demands from expanding business, competitive pricing, and the consolidation of plants,” says Tony Mathis, technical product manager for Waukesha Cherry-Burrell, a unit of Delavan, Wis.-based SPX Process Equipment.
According to Don Bohner, manager, heat exchangers for Vernon Hills, Ill.-based Tetra Pak Inc., plants have the same requirements for heat exchangers as they do for other types of equipment — namely, performance. “Energy, efficiency and flexibility are all important, but when it boils down to what is really important to the processors is, will the heat exchanger process their specific product, at the desired flow rate, at the required temperatures, and do this with little or no breakdowns,” he says, adding that downtime is a luxury that today’s processors cannot afford.
To Bohner’s point, reliability is a key demand of today’s dairy companies, including both large dairy conglomerates that continue to consolidate operations and smaller, regional companies trying to stay competitive and rein in costs. As part of their own R&D process, suppliers of heat exchangers have worked to improve the performance of their respective heat exchanger models.
Tetra Pak, which supplies a range of plate and tubular heat exchangers, has introduced new units and features in response to customer demands for consistency and low maintenance. Recently, the company refined its technology to bring together its Tetra Plex M and Tetra Plex MBasic range of plate heat exchangers into one range. “We combined the low cost of the Tetra Plex MBasic frame with the more robust Tetra Plex M frame into one frame that will not only meet the new 3A Sanitary Standards, but will be a great value with much higher operating pressures,” Bohner explains.
In addition, Tetra Pak is now offering a larger scraped-surface heat exchanger that enables users to reduce the number of required cylinders and hence lower maintenance costs. Processors also can choose from the supplier’s Tetra Plex range of plate heat exchangers with high pressure frames that have a maximum operating pressure of up to 290 psi. “The higher-pressure frame addresses the need for more reliability thus decreasing downtime,” Bohner says, adding that low-carb and lowfat products also tend to create higher pressures.
Alfa Laval, for its part, has pursued what it deems to be the next generation of heat exchangers. Its most recent sanitary heat exchanger is a unit called the AlfaNova. “That is a solid heat exchanger with completely stainless steel construction created using a special fusion process. It is able to handle very high temperatures and is compact and efficient,” explains Lemke, echoing the fact that customers are seeking consistent, high-quality performance. “They want something that is very reliable.”
The R&D team at Waukesha Cherry-Burrell is also driven by manufacturers’ demands for reliability. A year and a half ago, the company upgraded its 4x120 scraped-surface heat exchanger for medium to light-duty applications. “We eliminated the drive coupling, improved the jacket design and changed to a high-performance plastic for the molded scraping blades,” Mathis says.
Waukesha Cherry-Burrell also has enhanced its Votator-II line of scraped-surface heat exchangers, which were developed in 1998 for medium to heavy-duty heating or cooling applications. “We have continuously refined and simplified maintenance items like blades and mechanical seals and improved design of our refrigeration control circuits,” says Mathis, noting that the Votator II series can be used for the injection of viscous variegates into ice cream, process cheese, yogurt, whey concentrates and sour cream.
Meanwhile, as dairies continue to diversify their businesses and introduce new product lines, reliability is just as important for emerging processes. Viscosity, for instance, has been a key variable in the manufacture of many of today’s dairy-based foods and beverages. “We have seen an increase in more viscous products or those with particulates that require processing,” says Damon Wright, who works in heat exchanger projects for Lake Mills, Wis.-based Invensys APV, a division of Invensys plc that supplies plate heat exchangers and tubular heat exchangers for heating as well as for flash cooling.
To help manufacturers solve challenges with more viscous products, APV offers its R5 Quad-Drive plate exchanger and is working on a soon-to-be-introduced V plate that can be used for low-flow applications. For dairies that are implementing more ultra-high-temperature (UHT) processes, APV’s tubular units can be used, says Wright. “In higher fouling applications like UHT, then a tubular can provide longer run times and provide flexibility with products with particulates,” he says.
AGC, too, has worked with dairies encountering challenges with products that are more viscous and that contain more particulates “Things like lowfat and low-carb ice cream mixes have high solids and are unpredictable,” explains Bohn. “With our Pro5, you can process varying range of viscous mixes from soft serves that are real light and low solids to something that is 45 percent solids and 15 to 18 percent fat and heavily stabilized.”
Even new products currently in the R&D phase are being processed using heat exchanger technology created to be more flexible and reliable than ever. Microthermics Inc., Raleigh, N.C., offers compact heat exchangers as part of its comprehensive processing systems used to replicate plant conditions in pilot facilities and R&D laboratories.
“With our plates, you can change the amount of heat exchange area in your final heat sections and cooling. It literally gives you an endless set of permutations you can reach,” says company vice president David Miles.
Sizing it Up
In addition to reliability and versatility, another trend impacting heat exchanger technology relates to size. “If anything, capacities are getting larger, which is causing suppliers to look at larger capacity equipment,” Bohner says.
Lemke concurs. “Everything is getting bigger. Companies are consolidating and small dairies are becoming two or three big dairies. They are looking for bigger units to meet demand,” he says.
In response to bigger-is-better movement, providers of heat exchangers are offering models designed to handle a greater volume and range of products. In addition to Alfa Laval’s AlfaNova and Tetra Pak’s latest high-capacity designs, AGC is promoting its Pro5 and Pro5 Plus series of heat exchangers to dairies with greater capacities. “If you have a typical unit running 5,000 gallons an hour, you can go to 6,500 to 7,000 gallons an hour with no piping changes by upgrading the heat exchanger with a Plus plate,” Bohn says, adding that higher flow rates can translate into real bottom-line improvements. “When you talk about production, time is money.”
Waukesha Cherry-Burrell also has altered heat exchanger technology for capacity purposes. Among other upgrades, the company expanded its Votator-II platform into heavy-duty applications, according to Mathis.
Even as heat exchangers are designed to go with a bigger flow, so to speak, dairy processors don’t want units, whether large plates or extensive tubular systems, taking up too much space. According to Lemke, the new Alfa Nova is “a fraction” of the footprint of traditional heat exchanger systems. Other contemporary heat exchangers, including tubular, plate and scraped surface designs, have been created to help processors save on floor space, which is at a premium in most plants.
Energy and Utility Issues
Operational considerations can play into heat exchanger technology as well. The desire to save energy — to both conserve resources and cut costs — is one factor in heat exchanger purchases and upgrades and has been a related topic for years. “Energy concerns have been an issue since the early 1980s and even earlier,” Bohner says, adding that Tetra Pak provides milk pasteurizers with regeneration (regen) efficiencies of up to 96 percent.
Energy issues often vary by region. “In states where water is limited or power consumption issues, like in the Southwest or California, we have seen more requests to maximize regen on a plate heat exchanger,” says Wright, who notes that APV’s plates provides 90 percent regen for most dairy applications. Mathis also points out that incentives also differ based on geography. “There are states or regions where our customers receive discounts from their energy suppliers for the use of high-efficiency electric motors.”
In response to dairies’ desire to conserve energy and reduce utility costs, many of today’s heat exchangers include energy-efficient features. According to Mathis, Waukesha Cherry-Burrell helps customers optimize energy consumption by dividing cooling duty. For example, some Votator units pre-cool the product using a low-cost tower water supply before the final temperature is reached, using Votator units with a less energy-efficient chilled water or direct expansion refrigerant like ammonia. “Often a single extra Votator unit can be added to reduce the required refrigeration compressor duty by 50 percent, compared to doing the entire cooling range with refrigerant,” Mathis explains.
Finally, in addition to sanitary heat exchangers that have been created or upgraded to run as efficiently as possible, utility heat exchangers are also focal points of improvements.
Alfa Laval, for instance, has come out with a TS6 model developed to replace traditional tube and shell systems, according to Lemke. “It takes up a small footprint and is more flexible. The TS6 models are also prepackaged and shipped to the consumer, which reduces fright costs,” he says.
Tetra Pak also has launched a compact tubular heat exchanger for utility functions. The Tetra Spiraflo CIP and Water Heater is used to heat clean-in-place (CIP) solutions and to make hot water that can be mounted off the floor in a vertical or horizontal position. “Maintenance is extremely low,” Bohner says, “and we are now stocked for immediate delivery.”
Lynn Petrak is a freelance journalist based in the Chicago area.$OMN_arttitle="Running Hot and Cold";?>