ppt klpok 5 kimfis

8/10/2019 Ppt Klpok 5 Kimfis

1/25

CHAPTER 2

THE FIRST LAW OF THERMOYNAMICS

Group 5

1. Riduan

2. Novita Sari3. Putri Eka Nurhikmah Sari


2/25


3/25

SOME BASIC UNDERSTANDING

Some basic understanding of thermoynamics is

much related to:

system and environment,

the state of the system and the equation of

state,

State function, Changes in circumstances,

Heat and work.


4/25

4

system and environment :transfer of energy (E) & materr (m)

System(Focus of attentoin)

environment

environment

environment

An open system Closed System Isolated System

environment

E

&

m E


5/25

5

Open

mass & energyShift:

Closed

Energy

Isolated

Di not happen anything

SYSTEM

ENVIRONMENT

6.2


6/25

6

The State of The System

the state variabel system :

n (the amount of substance)

V (volume)

p (pressure)

T (temperature)

E.g. Gas equation of state:pV = nRT

p = p (n, T, V)


7/25

Condition function

Condition function is each system

characteristic which only concerned with

beginning condition and final condition


8/25

In thermodinamic we know some

condition function :

In energy (u; U)

Entalphy (h; H),

Entropi (s; S),

Gibbs free energy (g; G),

Helmholtz free energy (a; A).


9/25

One of the important characteristic of

differential condition function is total

differential (differential ekstrak),some of total

differrential characteristic are:

2

1. if dz = z2z1, so dz is a

1

Total diferenial

2. If dz = 0, so dz is a total diferential


10/25

3. occurred Euler formula:

if dz = M(x,y) dx + N(x,y) dy so

M N

= (2.1)

y x x y


11/25

Changing condition :

The process which occurred in a system can be

consist of:

1. Reversibel process is a process which

system always in equilibrium condition or

quasy-static

2. Irreversibel process is process which cannt

fulfil reversibel process


12/25

2.1.6 Work

Work is a form of energy that is not ketiap heatexchanged between the system and theenvironment

Figure 2.2. Work exchange between the systemwith its environment

W (+) W(-)

Environment

System


13/25

Sorts of forms of work:

1. electrical work2. mechanical work

3. magnetic work

4. work volume


14/25

work volume

1. Expansion work one step

Expansion work is the work that occurs whenthe system volume swell against pressure

environment.

Work performed by the system: W = mgh


15/25

Expansion work one step

M

M

T.P1.V1

T.P2.V2

S

S

S

S

S

S

S

Sh

(a) Start state (b) Final state


16/25

W=-P1V

W=-P1(V2-V1) (2.5)

W = the total work that accompanies the system

state changes

P1 = pressure outside (environment) caused mass

V2 = volume of the system at the final state

V2 = volume of the system at the initial state

(-) = Adjust system that works


17/25

P1.V1

P2

P1

P2.V2

}rentangP1V1 V2 V


18/25

P1P2

Equation 2.5 is not just for work expansion,

but also the work of compression

In compression, V2


19/25

2. Two-step expansion work

If the state of the system is determined on

the state of his three so-called two-stepexpansion work (2-stroke)

W = W + W first step second step (2.6)


20/25

Expansion work two step

VV2

P1

P1

P1


21/25

The shaded area stating the amount of

work that occurs in a two-step expansion.objec changes to the system with more

steps will be accompanied by greater job.

The shaded area in the two-step systemthat works greater than the work one step.


22/25

P

P

P

P1.V1

P2.V2

V1 V V2 V


23/25


24/25

Pl is the pressure of the environment outside

the detention system can be consideredequal to the system pressure (P), Pl = P, so

that equation (2.6) becomes

dW = -P dV (2.7)


25/25

The total number of workers who produced

the reversible expansion can be obtained byintegrating equation (2.7)

ppt klpok 5 kimfis

Documents