Plate Fin and Compact Heat Exchanger

Teknik penukar kalor1

TEKNIK PENUKAR KALOR

PLATE FINS HEAT EXCHANGERAND

COMPACT HEAT EXCHANGER

OLEH RANGGA PRATAMA

05171013

DOSEN PEMBIMBING : ISKANDAR .R. MT


Introduction

A heat exchanger is a device built for efficient HE from one medium to another, whether the media are separated by a solid wall so that they never mix, or the media are in direct contact. That have different temperature

Type of heat exchanger

1. Shell and tube HE

2. Plate and panels HE

3. Double pipe HE

4. Plate and frame HE

5. Spiral plate HE

6. Plate fins HE

7. Tube fins HE


plate-fin heat exchanger

plate-fin heat exchanger is a type of Heat exchanger design that uses plates and finned chambers to transfer heat between fluids

It is often categorized as a compact heat exchanger to emphasise its relatively high Heat exchanger surface area to volume ratio. The plate-fin heat exchanger is widely used in many industries, including the aerospace industry for its compact size and lightweight properties, as well as in cryogenics where its ability to facilitate heat transfer with small temperature differences is utilized


Design of plate-fin heat exchangers

A plate-fin heat exchanger is comprised of layers of corrugated sheets separated by flat metal plates, typically aluminium, to create a series of finned chambers. Separate hot and cold fluid streams flow through alternating layers of the heat exchanger and are enclosed at the edges by side bars. Heat is transferred from one stream through the fin interface to the separator plate and through the next set of fins into the adjacent fluid. The fins also serve to increase the structural integrity of the heat exchanger and allow it to withstand high pressures while providing an extended surface area for heat transfer.


Elemen dasar dari plate fins heat exchanger


Sistem aliran fluida


Type of plate fins heat exchanger

1. Plane triangular fin

2. Plane rectangular fin

3. Wavy fin

4. Offset strip fin

5. Pin fin

6. Multilouver fin

7. Round perforated fin


Pin fins

Offset strip fins Multilouver fins

Plain rectangular fins


Wavy fins


Aluminium Plate-Fin Heat Exchanger


Plate-fin heat exchangers have a wide range of applications :

1. Natural gas liquefaction 2. Cryogenic air separation 3. Ammonia production 4. Offshore processing 5. Nuclear engineering 6. Syngas production


The main four type of fins are:

1. plain (Datar), which refer to simple straight-finned triangular or rectangular designs

2. Herringbone(sirip ikan), where the fins are placed sideways to provide a zig-zag pathand

3. serrated (bergigi)

4. perforated (dilobangi) ,which refer to cuts and perforations in the fins to augment flow distribution and improve heat transfer.


Plain fins Herring bone fins

Perforated finsSerrated fins


Kegunaan dari fins (sirip)

1. Untuk memperluas daerah perpindahan panas

2. Untuk media menyalurkan panas antara fluida yang bekerja

Proses penyambungan antara sirip dengan plat antara lain

1. Solderring

2. Braazing

3. pengelasan


Type fluid flow of plate fins HE

1. Paralel flow ( searah)

1. Counter flow ( berlawanan arah)

Teknik penukar kalor

4. cross-counter flow

20

3. Cross flow Heat exchanger


Perpindahan panas yang terjadi ada 2

1. Konveksi, antar fluida pada plat dan sirip

2. Konduksi, antara sirip dengan plat


Efisiensi fins

( )bulk fluid temperature mean surfacetemp

fin eff fbulk fluid temperature base surfacetemp

Efisiensi total


Laju perpindahan kalor pada plate fins HE

Ada 2 metoda yaitu LMTD dan NTU

1. LMTD

ln

(Thi-Tci)-(Tho-Tco)Thi-Tci

lnTho-Tco

T

0 0 lnQ U A T

2.E- NTU


Perbandingan efisiensi plate fin heat exchanger deanagan tube fin dan oil coolers

effisiensi

Aliran fluida


Keuntungan dari plate fins heat exchanger

1. Bisa digunakan untuk fluida yang berbeda fasa, kombinasi gas dan fluida

2. Koefisien perpindahan panas besar, karena luas permukaan panas besar akibat adanya penambahan fins atau sirip.

3. Tidak membutuhkan lahan yang luas untuk instalasi atau pemasangan alat


Kekurangan plate fins heat exchanger

1. Tingkat pengotoran tinggi karena banyak terdapat saluran saluran kecil

2. Membersihkan harus secara kimia dengan mengunakan zat berupa pembersih yang dapat mengikis pengotor dan tidak bisa dibersihkan secara mekanik

3. Konstruksi rumit

4. Harga relatif mahal terhadap type lain


PERHITUNGAN PERPINDAHAN PANAS DAN EFESIENSI PADA FIN

• Q fin = A.k.θ0.m.tanh(mL)

= θ0 (PhkA)½ tanh (mL)

• Qideal = PLhθ0

• P = perimeter

• L = length

• A = area• m = (Ph/Ak)½

27


• Θ0 = T0 - T∞

• K = Thermal conductivity• Fin efesiensi = ξ = Q fin / Qideal

= tanh (mL) / mL

28


COMPACT HEAT EXCHANGER


The ratio of the heat transfer surface area on one side of the heat exchanger to the volume can be used as a measure of the compactness of a heat exchanger


1. Tube-fin2. Plate-fin3. Regenerators

Construction Types of Compact Heat Exchangers


1. Tube Fin Heat Exchanger


Tube Layout

1. Inline

if the air stream is laden with dust and

abrasive particles etc., in-line layout is preferred, being less affected and having ease of cleaning.


Tube-fin layout: inline


2. Staggered

The only construction difference between these two is that in the staggered arrangement each alternate row is shifted half a transverse pitch,and the two arrangements differ in flow dynamics.Due to compactness and higher heat transfer, the staggered layouts are mostly used.


Tube-fin layout: staggered.


Aplications

• Tube-fin exchangers are extensively used as condensers and evaporators in air-conditioning

• refrigeration applications, for cooling of water or oil of vehicular or stationary internal combustion engines

• air-cooled exchangers in the process and power industries.


2. Plate Fin Heat Exchanger

Plate-fin heat exchangers are a form of compact heat exchanger consisting of a stack of alternate flat plates called “parting sheets” and fin corrugations, brazed together as a block.


Fin geometry selection

Plate-fin surfaces have• plain triangular, • plain rectangular,• wavy, • offset-strip, • louver, • perforated,• orpin fin geometries.


SURFACE GEOMETRICAL RELATIONS

1. Surface Geometrical Parameters

Hydraulic Diameter, Dh

where A = total heat transfer area,

A0 = free flow area,

L = flow length,

The hydraulic radius rh is given by Dh/4.


Surface Area Density α and σ

The ratio of the total heat-transfer surface area on one side of the exchanger to total volume of the exchanger by α, and the ratio of the free flow area to the frontal area by σ.Thus,


From the definition of hydraulic diameter Dh, the relation between hydraulic diameter,surface area density α, and σ is given by

and


2. Tubular Heat Exchangers

Tube Inside

where L2 = the core length for flow normal to the tube bank

L3 = no-flow dimension

Pt = The lateral pitch

Pl = longitudinal pitch

No = The total number of tubes


The geometrical properties of interest for analysis are

Total heat transfer area A = πd1L1N1

Minimum free flow area A,, = (π/4)d12N1

Hydraulic diameter Dh =d1

Tube length for heat transfer =L1

Tube length for pressure drop =L1 + 2Th


Tube Outside

where L3 = no-flow dimension

Pt = The lateral pitch

No = The total number of tubes

The total heat-transfer area consists of the area consists of the area associated with the tube outside surface, given by


The minimum free flow area A0 frontal area Afr, the ratio of free flow area to frontal area σ, and hydraulic diameter Dh are given by

where A0 = The minimum free flow area

A fr = Frontal area

σ = The ratio of free flow area to frontal area

Dh = hydraulic diameter

Flow length for pressure drop calculation =L2

Heat exchanger volume V =L IL2L3


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Plate Fin and Compact Heat Exchanger

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