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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Heat! Its application to a mix of ingredients creates a critical control point, a vital stage where issues of quality, safety and, ultimately, cost come to a head.

This heat juncture is often the focal point in the product stream, the defining point where raw ingredient becomes processed product. How carefully and hygienically you move heat from one medium into another may determine the quality and safety of your product.

Heat exchangers enable heat to pass from one medium to another without allowing them to mix. The evolution in heat exchanger technology has been a quest for the perfect tailoring of equipment design and materials to specific processed foods and beverages. Today, that quest encompasses process efficiency as well, namely lower cost and energy consumption and, equally important, running more product through the system.

Note to R&D

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."
"When you're designing a system, each process has certain requirements, such as throughput and rate of heat exchange," explains Carlos del Sol, vice president of global engineering systems for Campbell Soup Co., Camden, N.J. "Any equipment you buy for that system must meet those requirements.

"A lot of questions come into play with your selection," he continues. "Will the system be able to do what it's intended to do? What are the energy costs of running it? And then there are issues of maintainability: How long will it run before we have to change a part? How quickly can you clean it? What is the equipment's projected life?"

Cost has long been of paramount concern in the product development lab where pennies saved on ingredients convert to dollars on the profit ledger. For a few years now, food processors have been taking equal issue with the cost components on the processing side of the business. The goal may seem simple: produce more and more product at lower and lower cost. But in the real world, notes del Sol, decisions on systems and equipment must strike a balance between product, equipment life, maintainability and overall cost.

Yet cost considerations are never far from a food processor's mind.

"Every manufacturer is trying to get more throughput," says del Sol. "Virtually every manufacturer has a program of cost improvement. Yes, that entails consideration of line speed, but it is also influenced by the uptime of your system. It's not always a matter of how fast your equipment can run. Downtime can take that away. It's what you end up with at the end of the day. Throughput is the name of the game."

Throughput, indeed, factors seriously into the selection of heat transfer equipment these days. It is one of several key factors in the cost/quality equation.

Bigger is better

Manufacturers of heat exchangers are facing a good news/bad news scenario. The bad news is food processors still have a stranglehold on their moneybags. The good news is some heat transfer equipment, particularly in the dairy industry, is old enough to draw attention from antique collectors.

Above: Heat exchanger plates from API Schmidt-Bretten.
But another basic need is driving processors into the heat exchanger market. They need "bigger and better" to get the most out of their manufacturing network, bigger heat exchangers, bigger ports, larger surface areas to heat product.

"Processors need to accomplish bigger duties than in the past," says Jeff Ceier of API's Schmidt-Bretten division (www.apiheattransfer.com/), Buffalo, N.Y. "Some food equipment is simply not big enough. That's certainly been the case in much of the dairy industry. The duties of evaporators are getting bigger all the time. The food industry is not in the habit of investing now for results later. But the purse strings are opening."

Melissa Fryer, senior applications engineer for Invensys APV (www.apv.com/), Tonawanda, N.Y., reiterates the theme: "Higher flow rates. Longer run times."

Processors hunting for new equipment are finding more versatile heat transfer systems in their crosshairs.

"Processors want equipment to work with a large variety of products," says Fryer, whose company finds plate and frame heat exchangers its biggest sellers. "Sales of corrugated tubular heat exchangers are on the rise. They tend to be a bit more versatile (than plate and frame heat exchangers)."

"Our Votator II (scraped surface heat exchanger) was designed to be efficient with several process options so that it could be adapted to most heating and cooling applications," says Ray Klusman of SPX Process Equipment/Waukesha Cherry-Burrell (www.gowcb.com), Delavan, Wis. He links the introduction of new food products and ongoing plant consolidation to the expansion of scraped surface heat exchanger use.

"It also had to be easy to maintain," Klusman continues. "For example, the product heads are held in place by a bayonet ring, which does not require bolts. An integral gear motor drive eliminates the traditional drive shaft and motor coupling, and it reduces the overall length or height of the unit by almost two feet."

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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