Bring on the heat!

Cost, quality and safety concerns of food processors drive improvements in heat transfer systems.

By Mike Pehanich, Contributing Editor

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The Votator II from Waukesha Cherry-Burrell.

The Votator II Model 6 x 72 is the most popular heat exchanger for SPX. It offers more than 9 sq. ft. of heat transfer area. Because production efficiency is also a product of effective use of the processing floor, it is available in both a horizontal and vertical mount. The vertical offers space advantages but requires higher
ceiling space.

Rapid changeover on flexible lines means that processors are using stronger and more advanced cleaning solutions for quick and efficient clean-in-place (CIP). The demand has forced manufacturers of heat exchangers to employ more corrosion-resistant materials in their equipment, including nickel.

"Many of the scraped surface heat exchangers that we specify today have heat transfer tubes made of 316 stainless steel," says Klusman. "But the thermal conductivity of nickel is about four times greater than 316 stainless, so we enhanced the use of that metal by reducing the wall thickness and applying stiffening rings to the outside of the tube to maintain the high product pressure requirements of the equipment. Depending upon the process and the physical properties of the product, the resulting heat transfer efficiency can be very close to that of pure nickel tubes."

Energy, controls

"Energy costs are going up, and no one expects them to come down significantly in the near future," notes Chuck Sizer, former director of the National Center for Food Safety and Technology (www.iit.edu/), Argo, Ill. "So efficiency is important in heat transfer systems."

That may explain the increase in new plate models. Among the primary categories of heat exchangers, plate systems are the most energy efficient. Tubular types rank next. Scraped surface heat exchangers provide no heat regeneration. Despite that fact, they remain popular and at the high end of the technology because they heat product very quickly and, due to constant scraping action, without fouling.

Heat transfer systems are becoming more automated. This APV Quad-Drive heat exchanger incorporates a PLC.
The incentive of energy efficiency is swaying more processors toward aseptic processing of liquid beverages, Sizer observes.

"Aseptic has very good regeneration rates," he says. "Some of the plate heat exchangers employed are 92- to 94-percent efficient. Compare that with hotfill systems, which have a zero-percent rate. There's no recovery. All the energy is gone."

The ongoing effort to simplify operation and maintenance has nudged processors to select more automated equipment, too.

"Our Quad-Drive heat exchanger incorporates a PLC," says Fryer of Invensys APV. She notes that damage from over-tightened plate packs lead to costly and frequent maintenance calls. "But the Quad-Drive system knows the proper closing dimensions. The operator only has to press a button and walk away."

Advanced automation not only enhances quality and trending data, but can also enable processors to make better use of energy, reducing overall manufacturing and operations costs.

Alfa Laval (www.alfalaval.com), Richmond, Va., is introducing to the American market a new heat transfer system that couples features from both scraped surface and tubular heat exchanger designs. The latest model in the ViscoLine series, sold and manufactured by Alfa Laval in the United States under a licensing agreement with HRS, is the ViscoLine Dynamic Unit.

The unit mounts a bundle of parallel tubes within an outer shell. Product medium flows through the tubes; the service medium flows outside. "This scraped tube heat exchanger with its dynamic
Incorporating features from scraped surface and tubular heat exchanger designs, the ViscoLine series is sold and manufactured in the United States by Alfa Laval under a licensing agreement with HRS.
plunger is an industry first," says Neil Swift, market manager-beverage and viscous foods for the Process Technology Div. of Alfa Laval. He notes its effectiveness in applications involving crystallization and evaporation of high viscosity products, with or without particulates.

Swift says top food industry players are testing its potential not only with the obvious products such as ketchup, dairy desserts and fruit and vegetable purees, pulps and concentrates, but with evaporating applications. "The applications are so varied, from cooking whole chicken to frying onions to freezing orange juice. Wherever you have a heavy heat transfer duty that is subject to fouling, this unit will work."

The alliance will begin manufacturing the units in the U.S. in September.

Low-carb and safety trends

Heightened awareness to the threats of listeria and bioterrorism has made processors more open to alternative technologies. Advanced microwave pasteurization and sterilization systems could provide an alternative to irradiation to address bacterial threats, including anthrax.


"Microwave technology for in-package sterilization has taken off worldwide, but not here," says Sizer, who also sees opportunity for high pressure systems in the marketplace. Nevertheless, he anticipates advances in validating, controlling and monitoring microwave product that could pave the way for more use of the technology in the processing arena.

"Microwave will work," he says. "You just need to be able to control it. You also have a problem with absorption. Different compositions of food heat differently with microwave."

And now there are special considerations for low-carb products and reformulations.

Low-carb foods are driving changes in heat exchanger selection. The reasons illustrate the importance of versatility in today's processing equipment.

"Processors are substituting fiber for carbohydrates and fats in the new formulations," says Alfa Laval's Neil Swift. "This leads to more viscous-type products that require a scraped surface heat exchanger."

Processors need very flexible heat transfer systems in today's competitive and safety-conscious world. Shorter runs with a clean-in-place cycle between are the order of the day.

"Another big development is the plate evaporator system for concentrating products," says Swift of a product introduced by Alfa Laval less than a year ago. "We used shell and tube evaporators in the past. They required a larger surface area to perform the same duty. They were less efficient and, with product spending more time in the evaporator, it was subject to greater heat degradation, which lowers the quality of the product."

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