porous esanjor

8/12/2019 Porous Esanjor

1/3

Cilt: 54

Say: 646Mhendis ve Makina 23

Ahmet Ali SertkayaMAKALE

54

46 Mhendis ve Makina22

METAL FOAM HEAT EXCHANGERS

Ahmet Ali SertkayaYrd. Do. Dr.,

Konya Necmettin Erbakan niversitesi,

Seydiehir Meslek Yksekokulu,

Makina ve Metal Teknolojileri Blm

Seydiehir, Konya

Asst. Prof. Dr.,

Konya Necmettin Erbakan University,Seydiehir Vocational School,

Department of Machinery and Metal Technology

Seydiehir, Konya, Turkey

[email protected]

METAL KPK ISI DETRCLER

ZET

Is deitiriciler bir cisim veya ortamdan dier bir ortama s nakletmeye yarayan cihazlardr. Is de-

itiriciler; termik ve nkleer santrallerde, gaz trbinlerinde, stma ve soutmalarda, kimya sanayii

ve dier teknolojilerde yaygn olarak kullanlrlar. Is deitiriciler kullanm maksatlarna gre deiik

isimler alrlar. En yaygn olarak kullanlan s deitiriciler, snn bir akkandan dier bir akkana

kat bir cisim zerinden aktarld ve svlarn karmad s deitiricilerdir. Is deitiricilerde az

bir s transfer yzeyinde en yksek s miktarnn transfer edilmesi ekonomik adan istenilen bir

zelliktir. Bu maksatla son yllarda metal kpk s deitiriciler daha fazla gndeme gelmitir.

Bu almada metal kpk s deitiriciler ele alnmtr.

Anahtar Kelimeler:Metal kpk, alminyum kpk, s deitiriciler

ABSTRACT

Heat exchangers are devices used to transfer heat from one body or medium to another medium. Heat

exchangers are widely used in thermal and nuclear power plants, gas turbines, heating and refrigera-

ting applications, chemical processing industries and in other technologies. Depending on their res -

pective applications, heat exchangers take different names. The most widely used heat exchangers are

those in which heat from one uid is transmitted to another uid by means of a solid body and where

the uids are not mixed with each other. Transferring the highest amount of heat on a small area is an

economic feature sought for in heat exchangers. Under the light of this target, the latest years have

seen an increasing trend in the use of metal foam heat exchangers.

In this study, metal foam heat exchangers have been considered.

Keywords: Metal foam, aluminum foam, heat exchangers

Geli tarihi : 21.08.2013

Kabul tarihi : 27.09.2013

Sertkaya, A. A. 2013. Metal Kpk Is Deitiriciler, Mhendis ve Makina, cilt 54, say 646, s. 22-26.

Sertkaya, A. A. 2013. Metal Foam Heat Exchangers, Engineer and Machinery, vol. 54, no. 646, p. 22-26.

1. GR

Metal kpk, eitli gazlarn metal gvde ierisin -de dalarak boluk oluturduu yapya denmek-tedir. Alminyum, demir, nikel, kurun, inko vetitanyum, metal kpk yapmnda kullanlan malzemelerdir.

Ancak gnmzde alminyum, dk younluu, korozyon

direnci ve dk ergime scakl gibi zellikleri nedeniyle,

metal kpk yapmnda en ok kullanlan metaldir. Bir metal

kpk hcresinde yaklak olarak 12 ile 14 yzey mevcut-

tur. Yzeyler pentagonal ve hegzagonal ekillerden oluurlar.

Her bir yzey ayn veya farkl uzunluklarda 4 ile 6 lamentle

dier yzeylere balanr. ekil 1'de ak hcreli alminyum

kpk ve temsili kpk hcresi grlmektedir.

Metal kpkler, ak hcreli ve kapal hcreli olmak zere

iki yap biiminde retilmektedir. Her iki yap biiminde de

%80-95 oranna varan boluk ve %5-20 orannda malzemeden

oluurlar. Eer gzenekler birbiriyle balantl bir halde bulu-

1. INTRODUCTION*

Metal foam is a structure formed by dispersion ofvarious gases that form air gaps within a metalbody. Aluminum, iron, nickel, lead, zinc and tita -nium are the materials used i n making metal foams. However;

because of it s superior features such as low density, resist-

ance against corrosion and low melting point, aluminum is

the most widely used material in making metal foams. There

are about 12 to 14 surfaces in a metal foam cell. The surfaces

are in pentagonal and hexagonal shapes. Every surface is con-

nected to other surfaces with 4 to 6 laments having same or

different lengths. In Figure 1, open celled aluminum foam and

representative foam cell are shown.

Metal foams are made in two structural shapes open celled

and closed cell types. Each of the two types consists of air

gaps at the rate of 80 to 95% and lling materials at the rate

of 5-20%. If the pores exist in a connected way with each oth-

ekil 1. Ak Hcreli Alminyum Kpk ve Temsili Kpk HcresiFigure 1. Representative of Open-Cell Aluminum Foam and Foam Cell

ekil 2. a) Ak Hcreli Alminyum Kpk [1], b) Kapal Hcreli Alminyum Kpk [2]Figure 2. a) Open-Cell Aluminum Foam [1], b) Closed-Cell Aluminum Foam [2]

* Makalenin ngilizcesi yazar tarafndan salanmtr.


2/3

54

46Cilt: 54

Say: 646Mhendis ve Makina Mhendis ve Makina24 25

Metal Kpk Is Deitiriciler Metal Foam Heat Exchangers Ahmet Ali Sertkaya

nuyorsa, bu tr yapya ak hcreli, hcrelerin her birinin ie-

risinde gaz hapsedilmi ve birbirinden szdrmazlk derecesin-

de duvarlarla ayrlm ise kapal hcreli alminyum kpkler

olarak adlandrlr. ekil 2a'da ak hcreli, ekil 2b'de kapal

hcreli alminyum kpklerin hcre yaps grlmektedir.

2. METAL KPKLERN UYGULAMAALANLARI

Metal kpkler, hcre yapsnn ak veya kapal oluuna gre

deiik kullanm alanlarna sahiptirler. Otomotiv endstrisin-

de; haii, darbe emici zellikleriyle dier metallere gre

tercih edilir. Haf ve salam yapdaki alminyum kpk sand-

vi paneller, elik panellere gre %25 daha haf ve 8 kata va-

ran salamlktadr. Alminyum kpkler, otomotiv sanayinde

arpma emici olarak da kullanlmtr. arpma kutular

darbe tamponu altna konularak arpma annda oluan ener-

jiyi emerek arata meydana gelecek hasar azaltmaktadr[3].

er, the structure is termed as open celled whereas if within

every cell gas has been conned the cells are separated with

walls at a sealing level, then t he foams are known as closed

cell aluminum foams. In gures 2-a open cell and 2-b closed

cell aluminum foams are shown respectively.

2. APPLICATION AREAS OF THEMETAL FOAMS

Depending on their cell structures open or closed form, metal

foams are used in various applications. Due to their lightness

and shock absorbing features, aluminum foams are preferred

in automotive industry over other metals. The light and

strong aluminum foam sandwich panels are 25% l ighter than

steel panels and up to 8 times as durable. Aluminum foams

have had applications as collision suppressors in automotive

industry as well. The collision boxes are placed under thecollision buffer where they absorb the energy generated dur-

Enerji emiciler ayn zamanda rayl sistemlerde de kullanl -

maktadr. Korozyon direnci ve yksek s iletkenlii nedeniyle

ak hcreli alminyum kpkler s deitiricisi olarak kulla-

nlabilirler. Kapal hcreli kpk metaller ise dk s iletken-

likleri nedeniyle termal kalkan olarak kullanlmaktadrlar. Bu

uygulamalara rnek olarak soutma radyatrleri, bilgisayar

ipleri ve g elektronii iin mikro elektronik cihazlar verile-

bilir. Alminyum kpkler, uzay ve havaclk endstrisinde de

yaygn olarak kullanlmaktadr. Alminyum sandvi paneller,

uak gvde ve helikopter kuyruk elemanlarnda tercih edil-

mektedir. Alminyum rnlerin haii nedeniyle gemi ina

sektrnde byk bir kullanm alan bulmaktadr. Modern yol-

cu gemileri, alminyum ekstrzyon rnler, alminyum levha

ve alminyum kpn yaygn olarak kullanld alanlardan

biridir. Alminyum kpkler, haiin esas olduu asansr

kabinlerinde ve inaat yardmc elemanlarnda kullanlabil-

mektedirler. Ses ve grltnn kontrol edilmesi gereken kprve viyadklerin altlarnda, grltl alan (kompresr gibi)

makinelerde susturucu olarak, su artclarda kat paralar gaz

veya svdan ya da iki svy birbirinden ayrmak iin kullan-

labilir. Alminyum kpkler; sanatsal yaplarda, mobilya ve

oturma gruplarnn asi ksmlarnda, bisiklet gibi gnlk kul-

lanlan bineklerden sporcularn dizliine varana kadar olduka

geni bir kullanm alanna sahiptir. ekil 3te metal kpk iin

rnek kullanm alanlarndan baz rnekler verilmitir [4].

3. METAL KPK ISI DETRCLERMetal kpk s deitiriciler, kanatl s deitiricilerle ok

benzer zellie sahiptirler. Tek fark kanatlarda metal kpk

tabakasnn olmasdr. Metal kpkler s deitirici iin ka-

nat grevi grmektedirler. Metal kpkler iin gzenek yo-

unluu, lament kalnl ve kpk malzemesi cinsi hedef

ing collision thereby minimizing the damages imposed on

the vehicle [3]. Energy absorbing devices are also used in rail -

way systems. Because of their corrosion resistance and high

thermal conductivity, open cell aluminum foams can be used

as heat exchangers. As for the closed cell foam metals, they

are generally used as thermal barriers due to their low thermal

conductiviti es. Examples of these applications can be given

as cooling radiators, computer chips and microelectronic de -

vices for power electronics. Aluminum foams have also been

used widely in spacecraft and aircraft industry. Aluminum

sandwich panels are preferred for use in aircraft fuselages and

helicopter tail parts. Ship building sector is another applica-

tion area where aluminum products are used because of their

being light in nature. Besides this, modern passenger ships

also employ extensive use of aluminum extrusion products,

plates and foams. On the basis of their being light, aluminum

foams are used in elevator cabins and as auxiliary materialsin building construction. They can also be used under bridges

and viaducts where noise has to be controlled and as silencer in

noisy operating machines like compressors and also in water

puriers where solid particles need to be separated from gas or

liquid. Aluminum foams have diverse applications from artful

structures, furniture and sofa frames, in daily riding tools like

bicycles to sportsmen knee breeches. In gure 3 some applica-

tion examples of metal foams are given [4].

3. METAL FOAM HEAT EXCHANGERSMetal foam heat exchangers closely resemble nned heat

exchangers in features. The only difference is their having

a metal foam layer on their ns. The metal foams function

as n for the heat exchangers. Porous density, thickness of

lament, type of the foam materials and application areas are

ekil 3. Metal Kpk in rnek Baz Kullanm Alanlar [3,6,7]Figure 3.Metal Foam Sample Some of the Utilization Areas [3,6,7]

ekil 4. Metal Kpk Is Deitiriciler [3,4,8]Figure 4. Metal Foam Heat Exchangers [3,4,8]


3/3

Cilt: 54

Say: 646 Mhendis ve Makina26

Metal Kpk Is Deitiriciler Metal Foam Heat Exchangers

uygulamalar iin ayrt edici zellii oluturmaktadr. Metal

kpk kanatl s deitiriciler, ak hcreli metal kpklerden

ve yaygn olarak alminyum kanatl kpk s deitiriciler-

den yaplmaktadr. Is deitiriciler de yzey alan ile transfer

edilen s arasnda dorusal bir iliki vardr. Metal kpk ka-

natl s deitiriciler, birim hacimde, konvansiyonel kanatl

s deitiricilerden ok daha fazla yzey alanna sahiptirler.

Metal kpk kanatl s deitiricilerde birim hacimdeki y-

zey alan 10,000 m2/m3deerine kadar ulamaktadr [5]. ekil

4'te metal kpk s deitiricilerden baz rnekler verilmitir.

4. SONULAR

Metal kpkler zerine yaplan almalar 1960l yllara da-

yanmaktadr. Son 20 ylda bu almalar hz kazanmtr. Bir-

ok niversite ve aratrma enstitsnde retim yntemlerinin

gelitirilmesi ve maliyetin drlmesi zerine aratrmaya de-

vam edilmektedir. Ticari olarak retilen metal kpkler, genel-

likle eriyik temelli retim esasna dayanmaktadr. Metal kpk

kanatl s deitiricilerin kullanm alanlar olduka eitlidir.

Metal kpklerin birim hacmindeki yzey alan, ayn boyut-

taki konvansiyonel s deitiricilere oranla olduka fazladr.

Yzey alannn artmas Fourier s iletim kanununa gre daha

yksek s iletiminin salanmas anlamna gelmektedir. Bu

avantajna ramen alminyum kpkl s deitiriciler, en-

dstride henz istenilen seviyede yaygnlaamamtr. Bunun

en byk nedeni alminyum kpk retimindeki zorluklar ve

maliyetinin yksek olmasdr. Ayn boyuttaki konvansiyonel

kanatl s deitiricilerin etkenlii alminyum kpk kanatl

s deitiricilerden daha yksektir. Metal kpkl s deiti-

ricilerinin etkenliinin dk kmasnn bir nedeni de, scak

akkann getii borularla, kanat grevi yapan alminyum

kpk lamentlerinin tam temas salayamamasndan kaynak-

lanmaktadr. Her ne kadar birim hacimdeki yzey alan fazla

da olsa borularla lamentler arasnda noktasal bir temas sz

konusudur. Birim hacimdeki yzey alannn byk olmasna

ramen s kaynayla temas eden lamentlerin noktasal olma-

s, s transferini azaltmaktadr. Noktasal temasn artrlmas et-

kenlii artracaktr. Bu balantlarn retim aamasnda yapla-

bilecek baz proseslerle iyiletirilmesinin metal kpk kanatl

s deitiricilerin etkinliini artraca umulmaktadr [4].

distinctive features for the metal foams. Metal foam n heat

exchangers are generally made by using open cell aluminum

foams. There is a linear relationship between the surface area

and the amount of heat transferred on heat exchangers. Metal

foam and nned heat exchangers have wider surface areas per

unit volume than their conventional nned counterparts. It is

known that the surface areas per unit volume for the metal

foam heat exchangers can reach values of up to 10,000 m2/m3

[5]. In gure 4, some metal foam heat exchangers are shown.

4. CONCLUSIONSStudies conducted on metal foams are dated back to 1960s. In

the latest 20 years, these studies have recorded an increasing

trend. A number of universities and research institutes continue

to conducting researches on improving production methods

and lowering costs. Metal foams produced commerciallygenerally rely on melting base production principles. There

are various application areas of metal foam nned heat

exchangers. When compared with the conventional nned

heat exchangers, metal foams exhibit large surface areas per

unit volume. According to Fourier heat transfer theory, an

increase in surface area leads to increasing the amount of heat

transferred. Regardless of all these advantages they possess,

aluminum foam heat exchangers have not yet been able to

achieve a required level of use in industry. The main reason

for this is the higher costs involved in production of aluminum

foams due to difculties encountered in the process. The

effectiveness of a conventional nned heat exchanger is higher

than that of an aluminum foam heat exchanger of the samesize. The reason for the low effectiveness value in metal foam

heat exchangers is the insufcient contact existing between

the tubes carrying hot uid and the foam laments that act

as ns. Although the metal foam heat exchangers exhibit

wider surface areas per unit volume, there is a point-wise

type of contact between the tubes (heat source) and laments

which hinders the heat transferring process. Increasing

the point-wise contact will improve the effectiveness. It is

hoped that, by using some processes, improvements made on

these connections during production phase will increase the

effectiveness of the metal foam heat exchangers.

KAYNAKA/REFERENCES 1. Sertkaya, A. A., Altnsk, K., Dincer, K. 2012. Experi-

mental Investigation of Thermal Performance of Aluminium

Finned Heat Exchangers and Open-cell Aluminium Foam

Heat Exchangers, Experimental Thermal and Fluid Science,

vol. 36, p. 8692.

2. http://commons.wikimedia.org/wiki/File:Closed_cell_me-tal_foam_with_large_ cell_size.JPG, son eriim tarihi:

10.04.2013.

3. Girlich, D. 2006. Open Pore Metal Foam Description and

Applications, GmbH Enderstrasse 94(G), 01277 Dresden,

Germany.

4. Sertkaya, A.A.2008. The Production of Aluminium Foam

As Heat Exchanger & Heat Transfer Modelling, Ph.D. The-

sis, Department of Mechanical Engineering, Graduate School

of Natural and Applied Sciences, Seluk University, Konya.

5. Boomsma, K., Poulikakos, D., Zwick F.2003. "Metal Fo-ams as Compact High Performance Heat Exchangers," Mec-hanics of Materials, vol. 35, p. 1161-76.

6. www.porvairadvancedmaterials.com/metalfoamhome.htm,son eriim tarihi: 22.03.2013.

7. Banhart, J. 2003. "Aluminium Foams for Lighter Vehicles,"International Journal of Vehicle Design, p.1-19.

8. http://www.ifam-dd.fraunhofer.de/en/Energy_and_thermal_management/leistungen_ und_methoden.html, son eriim

tarihi: 03.05.2013.

porous esanjor

Documents