Modeling of Electrofusion Coils for Performance Optimization

Modeling of Electrofusion Coils for Performance Optimization Steve Farmer GF Sloane Robert A.. It has been accepted for inclusion in Journal of the Arkansas Academy of Science by an auth

Modeling of Electrofusion Coils for Performance

Optimization

Steve Farmer

GF Sloane

Robert A Sims

University of Arkansas at Little Rock

This article is available for use under the Creative Commons license: Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0) Users are able to read, download, copy, print, distribute, search, link to the full texts of these articles, or use them for any other lawful purpose, without asking prior

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Recommended Citation

Farmer, Steve and Sims, Robert A (2002) "Modeling of Electrofusion Coils for Performance Optimization," Journal of the Arkansas

Academy of Science: Vol 56 , Article 10.

Available at: http://scholarworks.uark.edu/jaas/vol56/iss1/10

GF Sloane

7777 Sloane Drive LittleRock, AR 72206

Applied Science University of Arkansas atLittle Rock

2801 S University LittleRock, AR 72204

""Corresponding Author

Abstract

electrofusion characteristics Finite element incorporate physical parameters and theirinteractions along common boundaries defined withinamodel geometry. The electrofusion of polymeric piping is a widely accepted means of assembling piping systems withzero-leakage integrity The keyparameters inthe fusion process are the coilresistance, thecurrent passing through the coil and the timethecurrent isapplied Modeling the coil and applying current to the model isaccomplished using the MATLABpartial differential equations (PDE) toolbox This paper presents the method of modeling and the results from changing the various fusion parameters such as timeand current. Both the parameters and outputs are illustrated in various configurations

Introduction Electrofusion is a widely accepted means of joining

resistive heating isutilized tochange the state ofpolymers

conductive coilismolded into asocket and amating pipeis

inserted to create apipingsystem. A large current (60-90

resistive heating, melt theplastic near the coil and pipe, and

jointhe twoelements into a system. The heat transferred to

the surrounding polymer changes the state of the polymer

from a solid to a liquid and joins separate pieces into a

common system.

design and development environment where the

parameters of material properties, current and time canbe

simulated for performance optimization

Materials and Methods The piping electrofusion process, shown inFig 1, is

accomplished by first joiningseparate pieces of pipe and

fittings, creating a current loop through the joining region

and creating avoltage droptodrive the current. The voltage

drop is created using a transformer-based fusion machine

designed toprovide a constant potential across the coileven

as theresistive load changes with temperature

Modeling the electrofusion process is begun by

drawing, to scale, the geometry of the pipe joining

components shown inFig 2 The platform for modeling is

the Partial Differential Toolbox (PDE) with MATLAB,

available from TheMathworks, Inc., Natick,Massachusetts The PDE toolbox allows various analysis configurations such as electrostatic, stress and heat transfer The heat transfer mode is used tomodel the electrofusion process since the heat flux between the copper and surrounding

toolbox does not automatically assign units toeach value It

isrecommended that the designer choose a system ofunits,

such as metric or imperial, and maintain those units throughout the modeling process)

The next step, after drawing the geometry of the electrofusion process, is to enter the PDE specification for each material Achoice of ellipticorparabolic FEM ismade Fig 1.Electrofusion process.

Journal of the Arkansas Academy ofScience, Vol.56, 2002

52 Published by Arkansas Academy of Science, 2002

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Fig 2 Geometry inPDE toolbox draw-mode

I Equation rho"C"T'-c»v(k-gio<J|T||-Q»h-(Toxl-T| Trtempeiature PnnnPr

| TypeolPDE Coefficient Value Descriptor.

| r Elplic | ¦ho [5s Density

r | Q |(15558-eKp[ 0001 -III/2113 H»al source

h [o Conveclive heat transfer coefl Text ffl External temperature

Figure 3 PDE specification parameters

equation In this case parabolic is selected to include

material density (rho) and heat capacity (C)intheanalysis

The remainder ofparameters areentered as shown inFig 3

!or the copper coils The copper PDE specification isshown

lue to the unique heat source (Q) property that must be

alculated

The heat source is calculated via data acquisition by

measuring the power output (Watts) of the fusion machine

VIS Excel and a trendline is assigned The trendline

epresents the energy (joules/sec) that is produced by the

usionmachine during the electrofusion process asshown in

7ig.4fora 4-inch coil The energy is then divided by the

volume of the copper wire ineach coil to calculate the

volumetric heat flux generated by the copper

I The mesh is then initiated after the PDE specifications

re complete as shown in Fig 5 After the mesh is

ompleted, the solve parameters of fusion time, initial

smperature (u(tO)), relative tolerance and absolute

Dlerance are entered The plotparameters are selected as

Fig 4.Energy generated by fusion machine

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! u"mu'

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o? -E—j—i—!—c•f -f-j-i-i-+4-j-4"N-i -j-j-j

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0 2 ; ; ¦,.; ;.:.:.;. r-f-J-.;.-¦ •:- j-j-i— l-J -i

01 ;.,. .; '.; ; :.¦ : :.'..:

¦oi ,::.-¦; ¦

-•-.¦':

-0 2 ¦¦• ; -!¦ ;¦ : ¦',-; '; '¦-'¦¦ ;¦-.-,-•¦¦¦¦ ! ¦¦¦ ;¦¦¦-'- i

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Fig 5 Meshing during the FEM process

shown inFig.6and the simulation isexecuted The results

of the simulation are displayed and analyzed for dimensions

of the polymer melt-zones and the maximum polymer

temperature within each zone. As well,each of the fusion

parameters are exactly repeatable and can be varied to

demonstrate the affect of each polymer electrofusion process.

Results The results of simulation are shown inFig 7 fora4-inch pipe, socket and coil The pipe and socket are made of

53 http://scholarworks.uark.edu/jaas/vol56/iss1/10

Plot type: Property: User entry: Plot style

| temperature T] [ | interpolated shad jj

j T Contour

| P Arrows | temperature gradient j»] | | proportional j»]

| r Deformed mesh | temperature gradient T] I

IT Height (3-D plot] | temperature 3] I | continuous T]

| r Plot inx-ygrid Contour plot levels: [20 "

|7 Plot solution automatically

Fig 6 Plot selection parameters

r™-IOS Color I

Fig.7. 4-inch polypropylene electrofusion (105 sec)

casing around each wire The applied potential across the

coilis 16.9 volts for 105 seconds The finaltemperature is

where the polymer bonded isthe red color inthe center of the image where the copper wire reached temperatures

above 300°C

One significant advantage of modeling and simulation

is that some physical parameters can be changed while maintaining exact repeatability of other parameters Thisis demonstrated in the output of a 4-inch polypropylene electro fusion where the fusion time was reduced from 105 sec to75sec as shown inFig 8 Themaximumtemperature reached inthe center of the image isless than 250°C which

is aresult of decreasing the electrofusion timefrom 105 sec

to 75 sees while all other parameters were not changed

Conclusions Modeling and simulation provides a virtual

development environment free from requirements to

change physical parameters indetermining their affect The flexibilityofavirtualenvironment eliminates vast resources traditionally used to create new products and processes while shortening the development cycle

Fig 8 4-inch polypropylene electrofusion (75 sec)

Journal of the Arkansas Academy ofScience, Vol.56,2002

54 Published by Arkansas Academy of Science, 2002