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MARITIME UNIVERSITY OF CONSTANTA

FACULTY: NAVAL ELECTROMECHANICS

UNDERGRADUATE PROGRAMME: ELECTROMECHANICS

DEPARTMENT: ELECTROMECHANICS

STEAM GENERATORS, STEAM AND

GAS TURBINES I, II

PROJECT - APPLICATION

Ph.D. Student Eng. Daniela Elena MITU

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DESIGNING AN AUXILIARY BOILER

PROJECT REQUIREMENT

To achieve thermal and fluid-dynamic calculation of an auxiliary boiler that has the following

parameters:

- Boiler flow: hkg F /.............. ;

- Pressure boiler: bar P ............ ;

- Saturated steam temperature: C t o............ ;

- Feed water temperature: C t o fw ............ ;

- Boiler efficiency ........... ;

- Coefficient of excess air: ........... .

Percentage composition of the fuel is:

- carbon: .........%ic ;

- hydrogen: .........%ih ;

- sulphur: .........%i s ;

- nitrogen: .........%in

- water: .........%iw

%100 iiiii wn shc





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CHAPTER 1.

THERMAL CALCULATION

To achieve the thermal design calculations of marine boiler shall be determined the

furnace size and the evaporator surface, so as to achieve a certain steam production at the

specify parameters.

1. Calculate the amount of air and combustion gases

1.1. Fuel lower caloric power:

kg kJ w sohcQ iiiiii /12,251091030339

1.2. Theoretical volume of dry air needed for combustion:

combkg mo shcV N iiii

o

a ./100

7,0100

6,5100

867,121,0

1 3

1.3. Theoretical mass of air needed for combustion:

combkg kg o shc

Giiii

o

a ./100100100

8100

667,2232,0

1

1.4. Theoretical volume of moist air:

combkg mV xV N o

aum

o

a ./00161,013

07,0 x

1.5. Real volume of dry air needed for combustion:

combkg mV V N o

aa ./3

1.6. Real volume of moist air needed for combustion:

combkg mV V N umo

auma./3

1.7. Theoretical volume of gas triatomic:

combkg mcV N i

o

CO ./100

867,1 32

combkg m sV N

io

SO

./100

375,0867,1

3

2

combkg mV V V N o

SO

o

CO

o

RO ./3

222

1.8. Theoretical volume of gas diatomic:

combkg mnV V N i

o

a

o

N ./100

8,079,0 32

1.9. Theoretical volume of dry flue gas:





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combkg mV V V N o

N

o

RO

o

gu ./3

22

1.10. Theoretical volume of water vapor from flue gases:

combkg mV xwhV N oaii

o

O H ./00161,0100

9244,1 3

2

1.11. Theoretical volume of moist gas:

combkg mV V V N o

O H

o

gu

o

ga ./3

2

1.12. Real volume of dry flue gas:

combkg mV V V N o

a

o

gu gu ./13

1.13. Real volume of flue gas:

combkg mV V V N umo

a

o

ga ga ./13

1.14. Real mass of gas resulted from combustion:

combkg kg V x M oa ga ./306,11

1.15. Density of moist gas content:

3/ N ga

gamkg

V

M

1.16. The percentage composition of the anhydrous flue gas:

%10022 gu

o

CO

V

V CO

%10022 gu

oSO

V

V SO

%100

121,02

gu

o

a

V

V O

%100

179,02

2

gu

o

a

o

N

V

V V N

1.17. The percentage composition of moist flue gas:

%10022 ga

o

COum

V V CO

%10022 ga

o

SOum

V

V SO

%100

121,02

ga

o

aum

V

V O





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%100

179,02

2

ga

o

a

o

N um

V

V V N

%100

100161,02

2

ga

o

a

o

O H um

V

V V O H

Verification: %10022222 umumumumum

O H N OSOCO

CHAPTER 2.

CALCULATION OF THE GASES ENTHALPY AND DRAWING

DIAGRAMS IG - T

2.1. Enthalpy of combustion gases:

kg kJ t I t I t I um

o

a

o

ga ga /)()1()(),(

where:

)(t I o ga - enthalpy of combustion gases from the theoretical combustion;

)(t I um

o

a - Enthalpy of air excess;

t V C V C V C t I o

O H

o

O H

o

N

o

N

o

RO

o

RO

o

ga

222222

)(

]/[)(222222

kg kJ V iV iV it I o O H O H o

N N

o

RO RO

o

ga

where:

]/[,, 3222 N O H N RO mkJ C C C - Medium heat capacity of the triatomic and water vapour are

between 0 and 2000, the values will be taken from the Annex.

t V C I um

o

aumaum

o

a

]/[ kg kJ V i I um

o

aumaum

o

a

where:

]/[ 3 k mkJ C N uma

- heat capacity of humid air;

]/[ 3 N uma mkJ i - specific enthalpy of humid air

.





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CHAPTER 3.

CALCULATION OF THE EFFICIENCY AND FUEL CONSUMPTION

3.1. Variation of the excess air coefficient along the gas channels:

It is choose: 03,002,0

ev

3.2. Boiler efficiency:

exchev qqq 100

where:

qev – Heat loss with flue gases discharged;

qch – Heat loss by incomplete chemical combustion;

qex – heat loss through exterior walls of the boiler.

100i

evev

Q

Qq

100

,,

i

evo gaevev ga

evQ

t I t I q

where:

]/[.........., kg kJ t I evev ga - enthalpy of combustion gases after the last heat exchange;

]/[............., kg kJ t I evo ga - Flue gas enthalpy at the reference temperature and excess

air ratio in the exhaust; Their values will be read from the Annex by oev t t , ( C t o

o 20 the

ambient temperature).

]/[ kg kJ Qi - lower caloric power of fuel;

][ C t oev - exhaust gas temperature.

3.3. Transmitted useful heat to the boiler water:

]/['3600

skJ ii D

Q aau

where:

]/[' kg kJ i - enthalpy of saturated steam; ]/....[..........' kg kJ i





7/12

7

]/[ kg kJ i aa - enthalpy of feedwater; ]/..[.......... kg kJ ia

a

3.4. Fuel consumption:

]/[

100

skg

Q

Q B

i

u

CHAPTER 4.

FURNACE CALCULATION

4.1. Theoretical temperature of the furnace:

]/[)(100

100),( kg kJ t I

qQt I o

o

ach

it ga

where:

),( t ga t I - combustion gases enthalpy, which corresponds to the theoretical temperature

excess air ratio;

iQ - Fuel lower caloric power;

chq - Heat loss percentage by incomplete chemical burning ;

)( oo

a t I - enthalpy of air theoretically required for burn a fuel unit at ambient temperature;

]/[00161,01)( kg kJ t C V xt I oao

ao

o

a

where:

um

o

aV - Theoretical volume of moist air;

]/.........[ 3 k mkJ C N a - medium heat capacity at p=ct of air;

C t oo 20 - ambiant temperature when ].........[ C t o

t it is determined from the diagram I-t.

4.2. Flue gas temperature at the outlet of furnace:

]/[100

),(),( kg kJ Qq

t I t I i

f

ev f gat ga

ev

f

ev qq 4,0





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f t - it is choose from the I-t Diagram.

4.3. Heat quantity carried out through the cooling gas from t t to f t :

]/[100),(),(1 skJ Q

qt I t I BQ i

f

ev f gat ga

4.4. Heat quantity carried out through the cooling gas from t t to evt :

]/[100

),(),(2 skJ Qqq

t I t I BQ i

f

evevev ga f ga

The condition:

21 QQQu

4.5. Radiant flame thickness:

][6,3 m A

V S

f

f

4.6. Radiation intensity attenuation coefficient caused by soot particles:

]/1[5,01000

6,1203,0 mbar h

ct K

i

i f

f

4.7. Attenuation coefficient of radiation intensity due to flue gas triatomic:

]/1[

100037,011,0

6,178,022

22

2 mbar r r t

p p

r K O H RO

f

s

O H RO

O H

g

][8,1022

barir p p O H O H

][8,1122

barir p p RO RO

18,1 p s

4.8. Emission factor of the flame bright side:

s p K K

fl f g e

)(

11

4. 9. Emission factor darkened part of the flame:

s p K

fl g e

12

4.10. Emission factor of the flame:

21)1( fl fl fl





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4.11. Position coefficient of maximum temperature of the furnace:

ba M

2,054,0 ba

1

1h

H

where:

].........[m H - furnace height ;

].........[1 mh - burner height positioning.

4.12. Dirt coefficient that depends on the furnace refractory weight:

55,0 - for heavy fuel

4.13. Coefficient that takes into account the heat exchange between the furnace

and flue gases: 65,0

4.14. Furnace technical efficiency coefficient:

4.15. Furnace emision factor:

11

1

1 f f

f

f

4.16. Heat quantity by cooling gas from the theoretical temperature to the outlet

temperature of the furnace:

3

2

2

338

1

11

101076,5

f

t

t f f f

calc

t

t

M

M t t AQ

4.17. Calculation error:

100

1

11

Q

QQcalc

%3





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CHAPTER 5

EVAPORATOR CALCULATION

5.1. Convection heat:

]/[100

),(),(2 skJ Qqq

t I t I BQ i

f

evevevev ga f ga

5.2. Temperature medium logaritmic difference:

f t T max

evt T min

min

max

minmax

ln

T

T

T T T m

5.3. Convective heat transfer coefficient from the flue gases from pipe walls, from

the longitudinal flow:

u

S d ech

4

][2

K T T

T ev f

m

)(ech

e

d

l f c

]/[10 smW

ech

ed t echc

d

ccc

V

d W

Pr 023,0

5.4. Heat transfer coefficient by radiation from combustion gases to the walls of the

pipe:

n f r c

952,095,0 f c

]/[265),( 2 K mW t t f no f n

5.5. Heat transfer coefficient from flue gases to the metal wall:

r c 1





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5.6. Global heat transfer coefficient:

21

11

1

real K

]/[0

2

2 K mW

12

11

5.7. Exchange heat surface:

][ 22 mT K

Q A

m

5.8. Pipe number:

' A

A N

][' 2ml d A

CHAPTER 6

HYDRODYNAMIC CALCULATION

6.1. Hydrodynamic calculation

6.1.1. The pressure drop due to frictional resistance:

]/[2

22

m N W

d

e P m

m

i

f f

]/[062,4 3mkg m - fluid medium density

v

d W echRe - Reynolds number

4 Re

316,0 f - friction coefficient


]/[2

22

m N W

P loc f

1loc - local resistance coefficient





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6.1.3. The pressure drop due to fluid acceleration:

]/[0 2m N P acc

6.1.4. The pressure drop due to the level difference:

]/[ 2m N g H P m sh

6.2. Gas-dynamic calculation


][

1

2

2

2

2

bar

T

T

W

d

eh

c

pech

2

ev f

cT T T

T T T c p


T h t htt // t b lt h l i / d t t/ /i tP d ?id d t 1

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