Thermodynamics Lecture Series

email: drjjlanita@hotmail.comhttp://www.uitm.edu.my/faculties/fs

g/drjj1.html

Applied Sciences Education Research Group (ASERG)

Faculty of Applied SciencesUniversiti Teknologi MARA

CombustionCombustion

Review – Steam Power PlantReview – Steam Power Plant

Pum

p

Boiler

Turbin

e

Condenser

High T Res., TH

Furnace

qin = qH

in

out

Low T Res., TL

Water from river

A Schematic diagram for a Steam Power Plant

qout = qL

Working fluid:

Water

qin - qout = out - in

qin - qout = net,out

Review - Steam Power PlantReview - Steam Power Plant

Steam Power Plant

High T Res., TH

Furnace

qin = qH

net,out

Low T Res., TL

Water from river

An Energy-Flow diagram for a SPP

qout = qL

Working fluid:

WaterPurpose:

Produce work,

Wout, out

Composition Summary

Gas Mixtures – Composition by MolesGas Mixtures – Composition by Moles

+

3 kmol

H2 O2

1 kmol+

= = 4 kmol

H2 +O2

Gravimetric Analysis

mix21 mmm

Volumetric Analysis

100% or 1mfmf 21

mix21 NNN

100% or 1yy 21

mix

ii m

mmf where

mix

ii N

Ny where

Dalton’s Law

Gas Mixtures – Additive PressureGas Mixtures – Additive Pressure

PH2

H2 O2

PO2

+

+

= = PH2+ PO2

H2 +O2

The total pressure exerted in a container at volume V and absolute temperature T, is the sum of component pressure exerted by each gas in that container at V, T.

21mix PPP

k is total number of components;)T,(V PPk

1imixmiximix

Amagat’s Law

Gas Mixtures – Additive VolumeGas Mixtures – Additive Volume

The total volume occupied in a container at pressure Pmix and absolute temperature Tmix, is the sum of component volumes occupied by each gas in that container at Pmix, Tmix. 21mix VVV

;)T,(P VVk

1imixmiximix

k is total number of components

VH2

H2 O2

VO2

+

+

= = VH2+ VO2

H2 +O2

Partial Pressure

Gas Mixtures –Pressure FractionGas Mixtures –Pressure Fraction

The pressure fraction for each gas inside the container is

1mix

1

umix

u1

mix

1 yN

N

VT

RN

VT

RN

P

P

mix11 PyP

H2 +O2

Hence the partial pressure is

mixii PyP In general,

;TRNVP mixUmixmixmix Since mixU1mix1 TRNVP

Partial Volume

Gas Mixtures –Volume FractionGas Mixtures –Volume Fraction

The volume fraction for each gas inside the container is

1mix

1

umix

u1

mix

1 yN

N

PT

RN

PT

RN

V

V

mix11 VyV

H2 +O2

Hence the partial volume is

mixii VyV In general,

;TRNVP mixUmixmixmix Since mixU11mix TRNVP

Gas Mixtures –CombustionGas Mixtures –CombustionConverting gravimetric to volumetric

Constituent %

By weight

Mass fraction

mfi = mi/mmix

Mass, kg

mi = mf*mmix

Molar mass

Mi, kg/kmol

CO2 13.3 0.1330 0.13 44

CO 0.95 0.0095 0.01 28

O2 8.35 0.0835 0.08 32

N2 77.4 0.7740 0.77 28

Total 100.00 1.0000 1.00 -

Mixture by weight is: 13.3% CO2; 0.95% CO; 8.35% O2; 77.4% N2. Let the mixture mass be 1 kg.

Gas Mixtures –CombustionGas Mixtures –CombustionConverting gravimetric to volumetric

Constituent # of kilomoles

Ni = mi/Mi

Mole fraction

yi = Ni/Nmix

%

By volume

CO2 0.0030 0.090 9.0

CO 0.0003 0.010 1.0

O2 0.0026 0.078 7.8

N2 0.0276 0.822 82.2

Total 0.0336 1.00 100.0

Mixture by weight is: 13.3% CO2; 0.95% CO; 8.35% O2; 77.4% N2. Let the mixture mass be 1 kg.

Gas Mixtures –CombustionGas Mixtures –CombustionConverting volumetric to gravimetric

Constituent %

By volume

Mole fraction

yi = Ni/Nmix

# of kilomoles

Ni = yi*Nmix

C 85 0.85 0.85

H2 7 0.07 0.07

O2 5 0.05 0.05

S 3 0.03 0.03

Total 100.0 1.00 1.00

Mixture by volume is: 85% C; 7% H2; 5% O2; 3% S. Let the mixture volume be 1 kilomole.

Gas Mixtures –CombustionGas Mixtures –CombustionConverting volumetric to gravimetric

Constituent Molar mass

Mi, kg/kmol

Mass, kg

mi = Ni*Mi

Mass fraction

mfi = mi/mmix

%

By weight

C 12 10.20 0.7907 79.1

H2 2 0.14 0.0109 1.09

O2 32 1.60 0.1240 12.40

S 32 0.96 0.0744 7.44

Total - 12.90 1.0000 100.00

Mixture by volume is: 85% C; 7% H2; 5% O2; 3% S. Let the mixture volume be 1 kilomole.