AA-V5-I1-Mother-of-Invention.pdf

7/31/2019 AA-V5-I1-Mother-of-Invention.pdf

1/3www.a.comANSYS Advantage 2011Ansys, Ic.

Consumer goods

Mother ofInventionsimulatio help to deliver amilk warmer to market two earahead of schedule, saving $54,000i prototpe.

By Jim Shaikh, Founder, yoomi, London, U.K.

The oomi i a combied package of bab bottle ad

warmer. At the touch of a butto, it getl warm liquid

food to the exact temperature of breat milk, quickl ad

afel. The deig challege wa to take freh milk from

5 C to 34 C withi oe miute of activatio acro a full

rage of bab drikig peed.While egieerig a wa to heat the

bottle, IFs egieer looked at a umber

of chemical ad electrical heater ad

decided to ue odium acetate

trihdrate. Thi compoet i ued

i heatig pad ad had warmer

becaue it give off heat whe it

chage phae; i additio, it ca

be eail recharged b boilig. The

chal lege wa that the i i t ia l

prototpe heated the utritioal

fluids to only 17 C, half the needed

temperature.

The egieerig team ued fluid

damic oftware from Ansys

to imulate the multiphae fluid

damic of the propoed deig.

B evaluatig ma imulatio prototpe, the doubled

the performace of the iitial deig cocept while

building only four physical prototypes. IFS saved $54,000

by avoiding the need for 12 additional physical prototypes,ad it delivered the oomi feed warmer to market two

ear earlier tha otherwie would have bee poible.

Whe odium acetate trihdrate crtal are melted

above 80 C and allowed to cool, the aqueous solution

become ubcooled. Clickig a metal dik releae

trapped crtal, cauig the olutio to crtallize ito

olid odium acetate trihdrate ad to releae heat. I the

oomi feed warmer, the milk or formula ru through

chael ad i heated b the olidificatio proce jut

before the bab drik it. The chael are curved to

icreae the amout of urface area icotact with the milk.

The ke to gettig the deig right

wa determiig the geometr ad ize of

the chael where the heat i traferred

to the liquid. Addreig thi challege

require udertadig a complex thermal

tem i which odium acetate trihdrate

goe through a phae chage. It alo

require coideratio of how differet

chael deig might optimize heat

trafer rate to the fluid.

The origial cocept deig wa

created b coductig ver baic

umerical aale baed o imple

geometrie that had bee tudied i

publihed literature, which had bee

developed for heat trafer i lamiar

yoomi warmer on left and bottle on right. The warmer fits

under the bottle cap and liquid is heated as it flows through

the channels of the warmer.

When my first son, Danial, was born, it was my job

to take the expressed milk out of the fridge and heat

it up while he cried to be fed. My wife said, You are

an engineer. Cant you do something useful? To

see what would happen, I assigned my engineering

consulting business, Intelligent Fluid Solutions (IFS)

Ltd., to come up with an easy way to warm liquids

fed to babies. The concept of the yoomi self-

warming baby feeding bottle was thus born. I now

work full time with the company yoomi, which has

sold thousands of bottle warmers.

Prototype 3 design of the yoomi system

Teat

(Nipple)

Outlet

Heatsource

Milk

Inlet

Overmould

Screw cap

Bottle

Plug wall



Consumer goods

flow. The literature deig were retricted to traight

chael ad, therefore, provided reult that did ot

match phical tetig: Whe the IFs egieerig teamdeiged ad rapid prototped the iitial cocept deig,

the milk heated up to ol half the required temperature.

The egieer could have goe back to the drawig

board, chaged the deig ad built aother rapid

prototype. But each prototype cost about $4,500 and took

a week to build. I additio, the propertie of the rapid

prototpe did ot match the productio verio of the

bottle warmer. It probably would have taken 16 prototypes

over four ear to develop a marketable product uig the

prototpig method.

IFs egieer Dr. Adrej Horvat ued Ansys CFX fluiddamic oftware to model the actual chael geometr.

Viewig the imulatio reult, Horvat wa able to

ubtatiall improve heat trafer efficiec b

redeigig the chael to icreae the fluid path. He

adjuted chael width ad depth to improve heattrafer. Uig thi approach, he wa able to icreae

the temperature of the milk comig out of the device to

22 C better but still not good enough.

next, Horvat built a model that imulated the phae

chage of odium acetate trihdrate to better udertad

how the heat i geerated, traferred through the wall

of the chael ad paed to the feedig liquid. Thi

required a accurate model of the olidificatio proce.

He ued a olidificatio model of the behavioral

characteritic of odium acetate trihdrate from the

literature ad calibrated it uig the experimetal data.Horvat the created uer-defied fuctio ad embedded

them ito the Ansys CFX oftware.

The fluid damic tool provided outtadig

performace to obtai covergece uig time tep

large eough to provide meaigful reult for thi

complex aali. With thi accomplihed, the team

wa able to viualize the complete phic, icludig

how the liquid progree through the warmer

chael, how it puhe air i the oppoite directio,

ad how it pick up heat from the phae chage

material.

The multiphae imulatio demotrated that

olidificatio i ot a table proce. A the material goe

from fluid to olid, it releae eerg, but if the eerg i

ot removed, the reactio top. A the team reduced the

umber of chael to improve the efficiec of heat

trafer, there wa a tedec for the liquid flow rate to

var from chael to chael. Thi meat the temperature

wa too cold i ome chael. The team applied fluid

damic to carefull balace the flow betwee chael.

The reult howed that air pla a importat role i

the performace of the oomi warmer. For example, whe

the bottle i tipped upide dow o the bab ca drik,

the air ruhe out of the ipple ad ito the heatig

chael jut a the milk i eterig the thee chael. I

earl deig, imulatio howed that air wa keepig

the feed from flowig ito the ipple. Horvat corrected thi

problem b chagig the chael geometr to adjut the

air ad feed flow ratio o the air could flow i oe

directio ad the milk i the other. It would have take

much loger to udertad ad correct thi problem

without the help of CFD imulatio.

Modelig the multiphae behavior of the heatig

compoud ubtatiall improved the agreemet betweethe imulatio reult ad phical tet reult. Thi

udertadig of how the whole tem work wa critical

to developig a optimized deig i miimal time, ad it

would have bee impoible without fluid damic. Uig

the more accurate imulatio reult, Horvat wa able to

a) b)

a) b)

With each iteration, channel geometry was adjusted to allow for more

consistent liquid flow.

Milk volume fraction in prototype 3: a)t= 39.3 s, b)t= 51.9 s

Milk volume fraction in prototype 4: a)t= 39.3 s, b)t= 51.6 s



Consumer goods

a) b)

Temperature in prototype 3: a)t= 39.3 s, b)t= 51.9 s Temperature in prototype 4: a)t= 39.3 s, b)t= 51.6 s

The design of the feed warmer was iterated to bring the milk at the nipple to an optimal temperature.

a) b)

Temperature of the warmer over a long period of time

Temperature in prototype 3, kplug = 10 W/mK: a)t= 39.3 s, b)t= 60 s, c)t= 120 s, d)t= 600 s

a) b) d)c)

further refie the geometr ad icreae the temperature

of the milk to 28 C, a significant improvement but still far

from the goal.

The team believed the could rapidl improve the

deig if the were able to evaluate a wider rage of

geometrie more quickl. so Horvat performed a erie of

deig tudie uig the imulatio oftware, ad he ued

the reult to build a impler aaltical model that evalu-

ated deig i le time tha full-blow fluid damic

imulatio would take. He applied the aaltical model to

cruch through thouad of poible geometric

alterative, the picked the bet deig ad performed a

full fluid damic aali o thee. Uig thi method,

egieer were able to icreae the temperature to the

target of 34 C.

Fluid imulatio from Ansys aved a huge amout

of time ad moe o thi project. If the egieer had

followed the covetioal approach of build-ad-tet

prototpe, the etimate that the would have pet

$54,000 over four years readying the product for market.Itead, fluid damic imulatio correctl predicted the

phic of the product ad made it poible to meet

deig objective i half the time with ol four prototpe.

Whe the oomi bottle wa lauched o the web, the

iitial productio ru old out i jut four da. Productio

ha bee ramped up to meet demad, ad ditributio

chael are beig expaded to iclude other U.K. ad

iteratioal retailer. n

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AA-V5-I1-Mother-of-Invention.pdf