1. Basic Principle & 1st Law.pptx

7/25/2019 1. Basic Principle & 1st Law.pptx

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TKM-307

Termodinamika Teknik Kimia I

Basic Principles & First Law


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The Scope of Thermodynamics

Thermodynamics deals with transformations of energy of all ki

nds from one form to another.

The general restrictions within which all such transformations

are observed to occur are known as the first andsecond la

w of thermodynamics. These laws cannot be proved in themathematical sense. Rather, their validity rests upon experi

ence.

The universal applicability of thermodynamics is shown by thefact that it is employed alike by physicists, chemists, and en

gineer. The basic principles are always the same, but the ap

plications differ.


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Chemical Engineering Thermodynamic

s

The chemical engineer must be able to cope a wide variety of

problems vi. the determination of heat ! work re"uirement

s for physical ! chemical processes! the determination of

e"uilibriumconditions for chemical reactions and for the tra

nsfer of chemical species between phases.

Thermodynamic consideration alone are not sufficient to allo

w calculation of therates of chemical or physical processes

, because rates depend on both driving force ! resistance.#riving forces are thermodynamic variables, resistances ar

e not.


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Chemical Engineering Thermodynamic

s

Thermodynamics is a macroscopic$property formulation. %t ca

nnot reveal the microscopic &molecular' mechanisms of ph

ysical or chemical processes. (ut, on the other hand, know

ledge of the microscopic behavior of matter can be useful i

n the calculation of the thermodynamic properties.

Such property values are essential to the practical application

of thermodynamics) numerical results of thermodynamic ar

e accurate only to the extent that the re"uired data are acc

urate.The chemical engineer must deal with many chemical specie

s ! their mixtures, and experimental data are often unavail

able.


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*pplying Thermodynamics

The application of thermodynamics to any real probl

em starts with the identification of a particular body o

f matters as the focus of attention. This "uantity of m

atter is called thesystem, and its thermodynamic state is defined by a few measureable macroscopic pro

perties+

orce

Temperature

-olume+ specific volume, molar volume, density

ressure+ gauge pressure, absolute pressure


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ressure

The reading on a mercury manometer at /0 o &open

to the atmosphere at one end' is 12,31 in. The loc

al acceleration of gravity is 41,154 ft6s1. *tmospher

ic pressure is 78,93 in:g. ;hat is the absolute pressure in &psia' being measured< The density of m

ercury at /0 o is 74,254 g6cm4.


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=nit Conversion

Convert of physical parameters below+

200

o

> ?.. @ > ?..

o

C > ?.. R

R> 9,475 A6mol.@ > ?.. (tu6lbmol.R > ?.. cm:g.cm46mol.@ > ?.. ka.m46mol.@

5200 k; > ?.. (tu6Bam > ?..lbf.ft6detik > ?.. kgf.m6

detik


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Thermodynamics -ariable+ ;ork, Energy ! :eat

;ork ; is done whenever a force acts through a distance. Th

e "uantity of work done is defined by the e"uation+

is the component of the force acting in the direction of the dis

placement dl.

%n engineering thermodynamics an important type of work is th

at which accompanies a change of volume of a fluid, i.e. com

pression or expansion.

dlFdW=

dVPW2

1

V

V


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1

* gas is confined in a 0.5/$m$diameter cylinder by piston, onwhich rest a weight. The mass of the piston and weight together is 720 kg. The local acceleration of gravity is 8.974 ms$1, and atmospheric pressure is 707.2/ ka.

a. ;hat is the force in newton exerted on the gas by atmosphere, the piston and the weight, assuming no friction between the piston and cylinder

b. ;hat is the pressure of the gas in ka

c. %f the gas in the cylinder is heated, it expands, pushing the

piston ! weight upward. %f the piston ! weight are raised 72 cm, what is the work done by the gas in kA

d. ;hat is the change in potential energy in kA of the piston! weight


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;ork ! Energy

;ork done on a body in accelerating it from an initial velocity

u7to a final velocity of u1is e"ual to the change of kinetic e

nergy of the body mu161

;ork done on a body in raising it through the distance 1$7is

e"ual to the change in the "uantity of potential energy mg

%f the work done on a body in accelerating it or in elevating itcan subse"uently be recovered, then the body by virtue of

its velocity or elevation must contain the ability or capacity

to do this work.

Energy is the capacity of a body for doing work


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;ork

*n automobile having a mass of 7,120 kg is travelin

g at 50 m s$7. ;hat is its kinetic energy in kA< :ow

much work must be done to bring it to a stop RT with b > $0,000

77 m46mol


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roblem 1.78

The path followed by a gas during a particular mechanically reversible process is described by the e"uation+

;here a ! c are constants. %n the initial state, 7 > 30 bar and

-t7>0.001 m4. %n the final state, 1> 10 bar and -

t1> 0.005

m4. #uring the process, heat in the amount of 2000 A is tran

sferred to the gas. #etermine ; and H=tfor the process.

!VP t=

Constant -olume rocess ! Constant ressure roces


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%onstant olume %onstant Pressure

2

1

PdVQU

Constant -olume rocess ! Constant ressure roces

s

=

2

1

+dVP

VPUH

VPQU

UQ HQ

:eat capacity+ :eat capacity+

V

V"

U#

=

P

P"

H#

=

2

1

"

"

V d"#UQ

2

1

"

"

P d"#HQ


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:eat Capacity

ive moles of nitrogen at 90o

C is contained in a rigid vessel. :owmuch heat must be added to the system to raise its temperature t

o 400oC if the vessel has a negligible heat capacity

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1. Basic Principle & 1st Law.pptx