Welcome to the course in Heat Transfer (MMV031) L1Martin Andersson & Zan Wu

Agenda

Organisation

Introduction to Heat Transfer

Heat Exchangers (Ex 108)

Course improvement compared to last years

2017: Amount of exercises increased (and consequently the

amount of lectures decreased). Reduced the amount of the theoretical questions Also hints are provided for a fraction of the theoretical

questions. Amount of home assignments decreased (instead we

focus more on a proper methodology 2016: The lectures and tutorial sessions are integrated,

mainly because it is hard for most students to focus on theory (lectures) for 90 minutes.

Contents of the course

Heat Conduction Convection Thermal Radiation Condensation Evaporation, Boiling Heat Exchangers

Organisation

Lectures with tutorials Guest lectures Exercises

Mandatory home assignments

Exam (mandatory)

Organisation

Examiner: Associate Professor Martin Andersson

Teachers: Martin Andersson and Zan Wu (offices at 5thfloor M-building)

Course administrator: Jenny Oldbring (office at 5th floor M-building)

Organisation

Course literature: Introduction to Heat Transfer, SundnB., WIT Press

Examination: 14th March, 8-13 (MA 8) Exam is 50 p + 5 p if all home assignments are delivered in

time

Max 40 % theoretical part + Min 60 % problem solving part

Grade 3 requires 22 p (min 5p on theoretical part)

Grade 4 requires 33 p (min 5p on theoretical part)

Grade 5 requires 44 p (min 5p on theoretical part)

Guest lectures and Study Visit

Guest lecture(s): SWEP Ericsson

Introduction

Heat is energy passing a system boundary due to a temperature difference

Heat is a form of energy in transition.

Heat conduction Heat convection (natural (no pump, fan etc) or forced) Thermal radiation

Introduction

Introduction

Heat conduction

T1 T2

T1 > T2

q

Thickness b

q = (T1-T2)/b

Heat conduction

Solids

Carbon Steel = 15- 50 W/mK

Polymers, = 0.1-0.5 W/mK

Liquids

Water = 0.6 W/mK

Oil = 0.15 W/mK

Gases

Air = 0.025 W/mK

H2 (hydrogen) = 0.2 W/mK

Thermal conductivity (examples)

Convection

q = (TS-T) = h(TS-T)

Tsq

U T Ts > T

How to determine or h

Depends on: Flow velociy Fluid (gas or liquid) Geometry sometimes on temperature Forced convection, Natural convection, Mixed convection

Nu = L/f = function (Re=UL/, Pr=cp/f , geometry) or Nu = L/f = function (Gr=gL3/2, Pr=cp/f , geometry) or Nu = L/f = function (Re, Gr, Pr, geometry)

Thermal Radiation

Qnet = A1F12eff (T14-T24)

q1

q2 T2

T1

Introduction to heat exchangers (ch 15)

What is a Heat Exchanger?

A heat exchanger is a device that is used to transfer thermal energy (enthalpy) between two or more fluids, between a solid surface and a fluid,

or between solid particulates and a fluid,

at different temperatures

and in thermal contact.

Classification of heat exchangers

Transfer process Number of fluids Degree of surface contact Design features Flow arrangements Heat transfer mechanisms

Classification of heat exchangers

Fig. 1 Heat transfer surface area density spectrum ofexchanger surfaces ( Shah, 1981).

Fig. 2 Fluidized-bed heat exchanger.

Fig. 3 (a) Shell-and- tube exchanger with one shell passand one tube pass;

(b) shell-and- tube exchanger with one shell pass and two tube passes.

Fig. 4 Standard shell types and front- andrear-end head types (From TEMA, 1999).

Fig. 5 Gasketed plate-and-frame heat exchanger.

Fig. 6 Plates showing gaskets around the ports (Shah and Focke, 1988).

Fig. 7 Section of a welded plate heat exchanger.

Fig. 9 Spiral plate heat exchanger with both fluids in spiral counter flow.

Fig. 10 (a) Lamella heat exchanger;(b) cross section of a lamella heat exchanger,(c) lamellas

Fig. 11 Printed-circuit cross flow exchanger

Fig. 12 Corrugated fin geometries for plate-fin heat exchangers:(a) plain triangular fin; (b) plain rectangular fin; (c) wavy fin; (d) offset strip fin; (e) multilouver fin; (f) perforated fin.

Fig. 13 (a) Individually finned tubes;(b) flat (continuous) fins on an array of tubes.

Fig. 14 Individually fin tubes.

Fig. 15 Heat wheel or a rotary regenerator madefrom a polyester film.

Classification according to transfer process

Indirect contact type Direct contact type

Direct transfer Storage Fluidized bed Immiscible fluids

Gas-liquid Liquid-vapour

Single-phase Multiphase

Classification according to number of fluids

Two-fluid Three-fluid N-fluid (N > 3)

Classification according to surface compactness

Gas-to-liquid Liquid-to-liquid and phase-change

Compact 700 m2/m3

Non-compact < 700 m2/m3

Compact 400 m2/m3

Non-compact < 400 m2/m3

Classification according to design or type

Tubular Plate-type Extended surface Regenerative

PHE Spiral Plate coil Printed circuit

Gasketed Welded Brazed

Double-pipe Shell-and-tube Spiral tube Pipe coils

Cross-flow to tubes

Parallel flowto tubes

Plate-fin Tube-fin

Ordinary Separatingwall

Heat-pipewall

Rotary Fixed-matrix Rotatinghoods

Classification according to flow arrangements

Single-pass Multipass

Counter flow Parallel flow Cross flow Split flow Divided flow

Extended surface

Cross-Counter flow

Cross-parallel flow

Compound flow

Shell-and-tube Plate

Parallel counter flowm-shell passesn-tube passes

split-flow Divided-flow

Fluid 1 m passesFluid 2 n passes

Classification according to heat transfer mechanisms

Single-phase convection on both sides

Single-phase convection on one side, Two-phase convection on other side

Two-phase convection on both sides

Combined convection and radiative heat transfer

Classification according to process function

Condensers Liquid-to-vaporphase-changeexchangers

Heaters Coolers Chillers

Convective heat transfer

vgg

Fluid1

Fluid2

Overall heat transfer coefficient

mm1 t

TRtUAQ ==

Expression for overall thermal resistance

ooFvlw

w

iiFii

1111

oAAA

bAA

TR

+

+

+

+

=

Values of the heat transfer coefficient W/m2K

Air atmospheric pressure 5-75 Air pressurized 100 - 400 Water, liquid 500-20 000 Organic liquids 50 000 Boiling 2 500 -100 000 Condensation 3 000-100 000

Correlations for the heat transfer coefficient

Nu = hL/k = function (flow velocity, physical properties, geometry) = function (Re, Pr, geometry)

General research needs

How to achieve more compact heat exchangers

High thermal efficiency

Balance between enhanced heat transfer and accompanied pressure drop

Material issues especially for high temperature applications

Manufacturing methodology

Fouling

Non-steady operation

Fouling factors - Frsmutsningsfaktorer

Tabell 15-I. FrsmutsningsfaktorerStrmmande medium F/1 [m

2K/W]

Destillerat vatten4101

Sjvatten ( K 325T ) 4102 Matarvatten till ngpannor 4102 Brnsleolja 4109 Industriluft 4105.3

Tabell 15-I. Frsmutsningsfaktorer

Strmmande medium

F

/

1

a

[m2K/W]

Destillerat vatten

4

10

1

-

Sjvatten (

K

325

pT/p

)/p

pdiv class="embedded" id="_1043681052"/

p4/p

p10/p

p1/p

p-/p

p/p

/p

pSjvatten (div class="embedded" id="_1043681078"/

pK/p

p /p

p325/p

p>

T

)

4

10

2

-

Matarvatten till ngpannor

4

10

2

-

Brnsleolja

4

10

9

-

Industriluft

4

10

5

.

3

-

_1043681078.unknown

_1043681172.unknown

_1103026485.unknown

_1043681155.unknown

_1043681165.unknown

_1043681099.unknown

_1043681028.unknown

_1043681052.unknown

_1043680987.unknown

Counter current heat exchanger

t

A

dth

dtcdA

t

th,in

tc,ut

th,ut

tc,in

tb

ta

)(utin hhh ttCQ =

)( inut ccc ttCQ =

ch ttt = ch)( dtdttd =

hph )( cmC = , cpc )( cmC =

h

p

h

)

(

c

m

C

&

=

,

c

p

c

)

(

c

m

C

&

=

_1043690316.unknown

_1103026743.unknown

Counter current Hex

=

hc

11)(CC

Qdtd

=

hc

11)(CC

tdAUtd

=

hc

11)(CC

dAUttd

ccphhp )()( dtcmdtcmtdAUQd ===

-

=

D

h

c

1

1

)

(

C

C

Q

d

t

d

&

-

D

=

D

h

c

1

1

)

(

C

C

t

dA

U

t

d

-

=

D

D

h

c

1

1

)

(

C

C

dA

U

t

t

d

_1132136708.unknown

_1132136721.unknown

_1103026816.unknown

Counter current Hex

-

=

D

D

D

D

A

C

C

dA

U

t

t

d

0

h

c

t

t

1

1

)

(

b

a

-

=

D

D

h

c

a

b

1

1

ln

C

C

UA

t

t

-

-

-

D

=

D

D

Q

t

t

Q

t

t

t

Q

t

t

&

&

&

)

(

)

(

ln

ut

in

in

ut

h

h

c

c

m

a

b

a

b

a

b

m

ln

t

t

t

t

LMTD

t

D

D

D

-

D

=

=

D

_1132136752.unknown

_1132136781.unknown

_1103026867.unknown

_1103026870.unknown

_1103026864.unknown

Expression for overall thermal resistance

Parallel flow Hex,Co-Current Hex

)(

)(ln

)()(

utut

inin

ututinin

ch

ch

chchm

tt

tttttt

t

=

a

b

abm

lntt

ttt

=

t

A

dth

dtcdA

t

th,in

tc,in

th,ut

tc,ut

tbta

Arbitrary Hex

LMTDFUAQ =

F korrektionsfaktor som beror av tv parametrar P och R;

F correction factor depending on two parameters P and R

inin

inut

ch

cc

tt

ttP

=

hp

cp

)(

)(

cm

cmR

=

R kan ocks skrivas; R can also be written

inut

utin

cc

hh

tt

ttR

=

F korrektionsfaktor som beror av tv parametrar P och R;

F correction factor depending on two parameters P and R

in

in

in

ut

c

h

c

c

t

t

t

t

P

-

-

=

h

p

c

p

)

(

)

(

c

m

c

m

R

&

&

=

R kan ocks skrivas; R can also be written

in

ut

ut

in

c

c

h

h

t

t

t

t

R

-

-

=

_1103027076.unknown

_1103027083.unknown

_1103027103.unknown

_1103027060.unknown

F vs P och/and R; Shell-and-tube heat exchanger; one shell pass, two tube passes

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10.5

0.6

0.7

0.8

0.9

1.0

P

Kor

rekt

ions

fakt

or, F

R =

6.0

4.0

3.0

2.0 1.5

1.0

0.8

0.6

0.4

0.2

0.1

tc,in

tc,ut

th,ut

th,in

inin

inut

ch

cc

tt

ttP

=

inut

utin

cc

hh

tt

ttR

=

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.5

0.6

0.7

0.8

0.9

1.0

P

Korrektionsfaktor, F

R = 6.0

4.0

3.0

2.0

1.5

1.0

0.8

0.6

0.4

0.2

0.1

t

c,in

t

c,ut

t

h,ut

t

h,in

in

in

in

ut

c

h

c

c

t

t

t

t

P

-

-

=

in

ut

ut

in

c

c

h

h

t

t

t

t

R

-

-

=

_1103027310.unknown

_1103027365.unknown

_1103027383.unknown

_1075193104.unknown

Welcome to the course in Heat Transfer (MMV031) L1Agenda Course improvement compared to last yearsContents of the courseOrganisation Organisation Organisation Guest lectures and Study VisitIntroductionIntroductionSlide Number 11Heat conductionHeat conductionSlide Number 14ConvectionHow to determine or hThermal RadiationSlide Number 18Slide Number 19Introduction to heat exchangers (ch 15)What is a Heat Exchanger?Classification of heat exchangersSlide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Slide Number 30Slide Number 31Slide Number 32Slide Number 33Slide Number 34Slide Number 35Slide Number 36Slide Number 37Slide Number 38Slide Number 39Slide Number 40Slide Number 41Slide Number 42Slide Number 43Convective heat transferOverall heat transfer coefficientExpression for overall thermal resistance Values of the heat transfer coefficient W/m2KCorrelations for the heat transfer coefficientGeneral research needsFouling factors - FrsmutsningsfaktorerCounter current heat exchangerCounter current HexCounter current HexExpression for overall thermal resistance Parallel flow Hex,Co-Current HexArbitrary HexF vs P och/and R; Shell-and-tube heat exchanger; one shell pass, two tube passes