using computational fluid dynamics in the design of …€œusing computational fluid dynamics in...

“Using Computational Fluid Dynamics

In the Design

of Heat Transfer Rollers”

- A Leap Forward in Thermal Roller Engineering - S

Presented By:

Menges Roller Company

260 Industrial Drive

Wauconda, IL 60084

Main Tel: 847-487-8877

This short technical paper briefly overviews the key point relating

to the utilization of Computational Fluid Dynamics as a tool for

designing liquid-filled heat transfer rollers

for the packaging and plastic converting sectors.

Subjects Covered Include:

Importance of Heat Transfer Rollers & Thermal Transfer to Converters

Challenges Facing Engineers in Designing New Heat Transfer Rollers

Overview of Solutions Provided by Computational Fluid Dynamics

Details on Secondary Applications that Optimize Use of CFD Thermal Models

Menges Roller Company 2014 AIMCAL Technology of the Year Competition

“Computational Fluid Dynamics for Chill Rolls” Category: Metallizing Equipment/Accessories

About Menges Roller:

Menges Roller Company is a leading supplier of industrial rollers to the plastics, film, paper and geosynthetic

material industries. Primary customers include raw material manufacturers as well as those converting the

materials into finished goods. Many top OEMs also rely on Menges to develop and manufacture their rolls.

From multi-layered plastic packaging for the food industry, to sterile linings for the medical sector, or heavy-gage

nonwoven barriers used to protect man from the elements, Menges Roller plays a key role in manufacturing these

important products and optimizing their quality.

Menges’ flagship product line includes high-performance double-shelled spiral-helix-wrapped heat transfer

rollers, sometimes called chill rolls. For converters, heat transfer rolls are one of the most critical components in

the plant. Menges Roller has invested heavily in the equipment and manpower necessary to develop and

manufacture some of the most advanced thermal rollers on the market today.

The company has built its name on embracing innovation, understanding the changing processes of converters,

and delivering products and services that make a real difference in their operations by helping them run faster,

reduce waste, and produce better products. Menges Roller Company serves small specialty plants as well as large

global brands.

Overview of Menges Roller’s New Technology:

Today’s converting industry is very competitive. Engineers are under enormous pressure to innovate – new

products, new processes, new coatings and vapor barriers, and more layers to a laminate – anything to get a

competitive edge. This means diverting from ‘standard’ processes. To accomplish new tasks, engineers are

repurposing and modifying existing equipment, and heat transfer rolls play a key role in this quest to innovate.

But what temperature should my heat transfer roll be to meld a 7 layer laminate if I do 5 now? How big should

my chill roll be if I increase my extrusion laminating line’s output by 30%? My new coating requires a temperature

variance of only +/- 1 degree; can my heat transfer roll perform at that level? Can I get away with simply changing

my fluid velocity? Even veteran process engineers have struggled to answer these questions, until now.

Menges Roller is breaking new ground in the converting industry by bringing science’s most advanced molecular

modeling technology to the converting plant – giving Process Engineers and Plant Managers never-before-seen

images and unprecedented data regarding the chemical, physical and thermal processes taking place in their

plants.

This technology is known as Computational Fluid Dynamics (CFD) and the Menges Roller Engineering

Department is now using this powerful technology for a completely new purpose: simulating converting

processes and modeling thermal roller performance. This is a new use for CFD Modeling, and Menges Roller’s

use of it in converting has the potential to change the industry. Menges Engineers can now accurately see,

design and modify the temperature and performance specifications of heat transfer rollers before they are built.

CFD technology has been used for some time in the aerospace, medical and molecular sciences. Menges Roller is

now applying this advanced modeling discipline toward – for example – visualizing the effects that changes in

fluid turbulence may have on linear BTU measurements across the face of an 84 inch duo-flow heat transfer

roller running modified terphenyl heat transfer fluid at 335F pumped at 135 gallons per minute.



We believe applying CFD technology toward modeling heat transfer roll performance is an innovation onto itself.

The benefits to converters take the form of ultra-accurately-designed heat transfer rolls that perform at a higher

level with more predictable & consistent temperatures; this translates to better converting results , reduced roll

replacement costs, reduced waste, freed-up man-hours, and substantial overall cost savings for the converter.

Problem & Solution Details:

Today’s converting market relentlessly pushes engineers and developers to innovate – via new products and

improved processes. As a result, machines and lines are constantly being upgraded, modified and repurposed.

Heat transfer rolls, cold and hot, are an integral part of all this – but they can be difficult to properly configure,

especially for advanced applications where temperature consistency and control is critical.

Even certified engineers may have difficulty calculating the heat transfer coefficient and its primary inputs, such as

thermal fluid flowrate, viscosity, conductivity and density properties. The roller’s properties add another layer of

complexity, as calculations must consider spiral baffle angles and interior cavity dimensions. Put all that in

linespeed motion, with coatings requiring very specific temperature ranges, and the puzzle becomes exponentially

complex. So it’s easy to see the difficulty Converting Engineers might have in attempting to design a new chill roll.

Our industry’s longstanding inability to develop comprehensive formulae that encompass all the factors

impacting chill roll performance has been costly to plants & converters:

Uneven temperature distribution, the most common result of improperly designed chill rolls, is highly

detrimental to all but the most basic converting processes. Most processes require exact & consistent temps.

In some cases, poorly-designed rolls cannot even reach the desired target temperature (even less acceptable)

Too hot, too cold or uneven temperatures in heat transfer rolls can completely or partially ruin whatever

process application they’re involved in, whether blowing or extruding film, laminating, coating, sealing, etc.

Nobody wants to be responsible for spending $75,000 on heat transfer rolls that foul the laminating process

because of a design flaw, so engineers risk their careers when ordering questionably-designed chill rolls

Re-installing a new heat transfer roll is a disruptive and costly process even under optimal conditions, and if

the plant has to go through the process a second time because the first roll had a bad design, heads will roll

But Menges Roller has solved these issues by bringing Computational Fluid Dynamics to the converting sector.

In the hands of Menges Roller Engineers, CFD Models generate performance simulations that feature accurate

data and imaging on the dynamics of heat transfer originated from rollers and transferred to the web.

Complex yet dependable formulae that consider all the chemical, thermal, physical and reactive factors are the key to Menges’ CFD Models.

This image represents a portion of the data typically found in a final temperature variance report.

These reports require a substantial amount of time and attention for data entry – and high-performance computers must be employed to speed the modeling process – but the results are very accurate.



The data generated by these high-tech models is primarily temperature-related, obviously highly-relevant to

process engineers. Typical data points generated by Menges’ CFD Thermal Modeling Technology include:

Overall peak/maximum potential temperature of the roller (BTU/hr.)

Rollface temperature across hundreds of vector points (temperature variance)

Overall and node-based data on energy transference/temperature change in substrate material

Detailed data on the physical & chemical effects of hot/cold energy has on the web and its coatings

Being able to see how a roller will perform – before it is built – is a colossal advantage for roller manufacturers

and for converters in general. And the accuracy of Menges CFD Modeling Technology is unprecedented. This

can be attributed to the fact that every conceivable variable and input can be worked into our CFD engineering

calculations. By considering every factor, even second-tier and tertiary factors, unknowns are eliminated. This

increases accuracy, as unknown factors are often the root of flawed calculations.

The following is a partial list of the factors & data points integrated into Menges’ Thermal Modeling calculations:

Rollface Width & Diameter

Interior Cavity Volume & Thermal Fluid Capacity

Spiral Baffle Angle & Helix Configuration

In-Feed & Siphon Tube Dimensions

Journal & Collar Dimensions & Heat Sink Specs

Density, Mass & Conductivity of Steel Grades

Rollface Finish Properties (Ni, Chrome, WC, etc.)

Rotary Union Specifications

Linespeed & Roll Rotation Speed

Web Wrap Angle & Contact/Nip Pressure

Thermal Transfer Fluid Chemistry

Thermal Transfer Fluid Temperature

Fluid Volumetric Flowrate & Velocity

Interior Cavity Pressure

Web/Substrate Thermal Properties

Web Chemistry, Dimensions & Density

Station Temp. (entrance, exit, etc.)

Target Temp. / Temp. Change Data

Nodal Temperature Variances

BTU Loss/Gain to Web

Ambient Air Temp. & Humidity

Coating & Adhesive Chemistry

The benefit of Computational Fluid Dynamics technology is the capacity to digest chemical, physical, motion and thermal information. Aerospace and medical sciences use CFD to test complex processes and develop advanced solutions. Menges believes heat transfer technology for converters warrants this level of engineering sophistication.



The Benefits

Now that the temperature and performance of heat transfer rolls can be visualized before being manufactured,

modifications to the roll’s design can be made until optimal characteristics are reached. Menges Roller’s Thermal

Modeling technology ensures the roll will perform as planned for the application for which it was designed.

The benefit chain to people, products and corporate budgets is extensive:

Rollers can be designed to perform with a degree of accuracy never before seen: guaranteeing temperature

profiles accurate to within +/- 1 degree F; this level of accuracy will make tight-tolerance converting

applications run smoother, produce less waste and allow plants to produce higher-quality products.

For purchasing directors, Menges’ new technology makes purchasing heat transfer rolls (and upgrading their

machines in-general) a less-risky act: no more fearing for your job when you the roller will work correctly

Menges’ technology will reduce hot/cold roller rebuilds and “re-rebuilds”: You only have to build it once.

Converters can now spend more time running their chill rolls than monitoring them! Heat transfer rolls

produced using Menges’ Thermal Modeling technology have more reliable performance, so converters can

reduce the time spent monitoring temperatures and compensating for temp variances: this has traditionally

included such time-sapping tasks as tweaking heater/chiller temperatures, monitoring and modifying thermal

fluid flowrates, increasing/decreasing linespeeds and ‘dwell time’ (duration of time the roll contacts the web).

Menges’ technology will promote innovation in the converting industry. Engineers and product developers

will “feel more free to develop” new products & processes, knowing whatever they dream-up can be tested

and modeled in-advance: no more building expensive equipment just for elaborate trial-and-error testing.

CFD Thermal Modeling from Menges can save existing rollers. If a converter is having issues with their

application, it is possible the heat transfer roll is actually not the problem. There may be an issue with low

pump capacity, improper thermal fluid chemistry, or something else related to the converting station:

because Menges’ new technology encompasses all the factors in the chain, it may be able to detect issues

such as these, potentially enabling the converter to make simple adjustments without making a new roll.

With Menges Roller’s new CFD Thermal Modeling Technology, the data and images relating to the roll itself are tremendously useful. But this technology really shines in the fact that we can also see how the roll’s temperature transfers to the web. This is important because, just because a heat-transfer roll reaches a certain temperature, not all that energy is necessarily transferred to the web. Every substrate absorbs heat differently, and Menges’ technology can work different web chemistries into the equation – so converters can see exactly how the roll design will affect their specific web in their specific process.



The Evolution of this Technology:

Menges Roller Company has a long history as a respected designer and manufacturer of heat transfer rolls. We

work daily with well-known extruders, converters and plastic packaging brands. Our decision to develop Thermal

Modeling technology was an informed decision, based on market-driven factors and the unmet needs of our

customers in the converting industry.

Competition among converters in today’s environment has become increasingly fierce, and this has spurred

innovation forward. As plants started reaching for ‘the next groundbreaking thing’ we at Menges Roller started

seeing large numbers of heat transfer roll rebuilds. Upon further inquiry, we noticed two basic trends:

a. Heat transfer rolls were being built and rebuilt to fit new applications, but using existing machines. Rolls

were modified to be larger, hotter, with different finishes, and so on - but it seemed most were going into

machine/line modification projects. The key flaw was that we saw many engineers “guesstimating” on the

size, finish and flow these heat transfer rolls would require to get the job done in these new applications.

Substantial resources were being put toward new components, but nobody knew for sure if they would

actually work properly when complete. Our goal at Menges Roller was to eliminate those questions.

AND

b. We also started seeing a large number “re-rebuilds”. This is where the first roller design did not work

effectively for their “exciting new process” and the engineers had to change the roll’s dimensions (make it

bigger, smaller, with higher fluid flow, etc.) and/or get an entirely new roll manufactured. Again, most of

the time, the first design didn’t work because the engineering team simply didn’t have the capacity and

tools to design the roll to the proper specifications. And again, we sought to eliminate this guesswork. We

simply felt plant managers should have a better way of determining how large their chill roll should be.

Although we admire the “if at first you don’t succeed, try-try again” attitude, the Menges Team knew there had to

be a better approach. We asked ourselves a series of questions: “How hard would it be to develop an algorithm

tying together all the factors that go into chill roll performance…thermal fluid temperature, turbulence and

flowrate, roll dimensions, interior cavity and spiral wrap specs along with their effects on flowrate and

temperature distribution, plus comparative heat conductivity data for the various steel grades, linespeed and

rotation data, etc. Could we develop a formula encompassing all these factors and generate meaningful results?”

It soon became obvious the required calculations would be quite complex. Even with the help of engineering

calculators, spreadsheets and a good amount of industry knowledge, a reliable all-encompassing formula was

elusive. So, after extensive research, the Menges Team concluded the same type of applications used by NASA to

put spacecraft in orbit, monitor chemical reactions in the human brain, and calculate the number of SOx molecules

in power plants could in fact be utilized to model temperature and performance profiles for heat transfer rollers.

We made a trailblazing corporate decision: we would bring Computational Fluid Dynamics to the roller industry.

Today, Computational Fluid Dynamics and CFD Modeling simulations are used daily Menges Roller. We are

coupling our use of CFD Thermal Modeling with Finite Element Analysis, which helps engineers see the strength

and load-bearing capacity of our rollers. After the roll’s design specifications have been finalized and the key

decision makers on the customer-side have approved the roll for production, the Menges Engineering Team

exports the design specifications to a CAD program which generates final fabrication schematics. From there, the

roll goes into production at the Menges Roller Fabrication Facility in northeast Illinois.



Strength Testing:

To ensure a roll’s strength and load-bearing profile is just right, engineers may also utilize a technology known as

Finite Element Analysis (FEA). Often used in direct conjunction with CFD, FEA Simulations generate detailed data

and images to accurately dissect which parts of the roll will incur the most stress when loaded (usually the

shoulder area, where the journal meets the endplate). The engineer can then test and re-test the capacities of

components made from various grades and thicknesses of steel, stainless steel or aluminum until they arrive at

the optimal balance of strength and functionality.

In today’s converting plant, stress testing is actually more important than ever. With faster linespeeds, higher

pressure nip systems, and 24-hour operations, factors such as deflection and centrifugal force represent ever-

present stresses that will breakdown an under-engineered roller in a hurry. On the other hand, every roll cannot

be such a solid steel behemoth that it causes mounting or maintenance issues. We want a balanced design…not

“not enough”…not “too much.” In the hands of a skilled engineer, FEA is useful in finding the proper balance of

size and strength.

After the roll’s design specifications have been finalized and the key decision makers on the customer-side have

approved the roll for production, the Menges Engineering Team exports the final CFD & FEA design specifications

to a CAD program which generates final fabrication schematics. From there, the roll goes into production at the

Menges Roller Fabrication Facility in northeast Illinois.

Conclusions:

At Menges Roller Company, we see our job as delivering more than just rollers: our mission is delivering roller

solutions. This means we don’t just manufacture rollers: we help customers determine which type of roller is best

for their particular process challenge; we help them test different elastomers until the best material handling

rubber is found; we conduct research in an effort to offer informed advice; we track our results so we can offer

solutions that are proven to work; and we work tirelessly to seek out new technologies that will help us design

higher-performing chill rolls & heat transfer rolls - as we did here with acquiring and developing Computational

Fluid Dynamics Thermal Modeling Technology for the converting industry.

As a result of our new and innovative utilization of CFD Thermal Modeling technology, when a converter purchases

a heat transfer roll from Menges, they are purchasing a heat transfer roll that is guaranteed to achieve its target

temperature and meet their predetermined specifications. Additionally, this level of performance and temperature

distribution is stable and capable of being maintained over long production runs. Reliability and accuracy are the

hallmarks of quality when it comes to thermal rollers, and Menges Roller has taken a giant leap toward total

accuracy and total reliability by bringing CFD technology into the roller design realm.

Customers have been thrilled with the results of our thermal models and process simulations, and the

performance of heat transfer rollers designed using this technology has been outstanding. Temperature variations

of 1-2 degrees are regularly delivered, while 7-10 degree variances were common in our customers’ previous rolls.

We believe CFD Technology represents an outstanding solution for this company, our customers, and the

converting industry in general.



Supporting Images:

This is a temperature distribution image generated during one of Menges’ CFD Thermal Modeling projects.

Images and data generated from our CFD system are critically useful, but this technology does not represent a turnkey fix for every roll design challenge.

The knowledge and contribution of Menges Design Engineers as well as Process Engineers on the customer side is very important.

This is a wire-frame still of a heat transfer roll about half-way through the design process. The roll will be modified until the temperature is more consistent and uniform. Each little cell or node in this wire mesh can be dissected and analyzed. Menges Engineers use CFD Models to look at heat transfer in a granular manner, analyzing all the causes and effects, then ultimately delivering very high performing rolls for our customers.

This image illustrates fluid velocity through a duo-flow heat transfer roll. With the duo-flow, thermal transfer fluid is pumped in and out of the same end. This is accomplished with the help of a specially-designed rotary union. The unique design of the duo-flow has a significant effect on temperature distribution, both internally and across the face of the roll. We utilize CFD Models to test design modifications and tweak component specifications – until the converter’s desired temperature and performance profiles are reached.



This is the finished result: a medium-large duo-flow heat transfer roller designed using Menges’ CFD Thermal Modeling Technology.

Although this roller may look basic from the outside, this is a highly-engineered component that is absolutely critical to our customer’s converting operation. The rollface is over 84 inches long and we modeled its internal components and exterior shell to maintain a temperature of 340 degrees Fahrenheit with an allowable variance of +/- two degrees, just as the customer required.

This is a heat transfer roll under a load-bearing stress test. Finite Element Analysis show progressively increasing areas of stress.

Here a Finite Element Analysis simulation is testing the strength of journals in a high-pressure nipping system

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