Transcript HYDRO ELECTRIC POWER PLANT

Part II
AGUS HARYANTO
The conservation of energy principle can be
expressed as follows: The net change (increase or
decrease) in the total energy of the system during a
process is equal to the difference between the total
energy entering and the total energy leaving the
system during that process.
Noting that energy can be
transferred in the forms of
heat, work, and mass, the
energy balance can be
written more explicitly as:
Esystem = Ein - Eout
= Qin - Qout + Win - Wout + Emass,in - Emass,out
 Energy
change = Energy at final state –
Energy at initial state
Esystem = Efinal – Einitial = E2 – E1
E = U + KE + PE
U = U2 – U1 = m(u2 – u1)
KE = KE2 – KE1 = 0.5 m(V22 – V12)
PE = PE2 – PE1 = mg(z2 – z1)
stationary systems, KE = 0 and PE =
0), and E = U
 For
 For
a closed system undergoing a cycle, the
initial and final states are identical, thus
Esystem = E2 – E1 = 0. The energy balance
simplifies to: Ein – Eout = 0 or Ein = Eout
 Noting
that a closed system
does not involve any mass
flow across its boundaries, the
energy balance for a cycle
can be expressed in terms of
heat and work interactions as:
Wnet,out = Qnet,in
A rigid tank contains a hot fluid that is
cooled while being stirred by a paddle
wheel. Initially, the internal energy of the
fluid is 800 kJ. During the cooling process,
the fluid loses 500 kJ of heat, and the
paddle wheel does 100 kJ of work on the
fluid. Determine the final internal energy
of the fluid. Neglect the energy stored in
the paddle wheel.
Assumptions :
 The tank is stationary
and thus the kinetic
and potential energy
changes are zero, KE
= PE = 0. Therefore,
E = U.
 Energy stored in the
paddle wheel is
negligible.
Applying the energy balance on the system gives
the final internal energy of the system is 400 kJ:
A fan that consumes 20
W of electric power
when operating is
claimed to discharge air
from a ventilated room
at a rate of 0.25 kg/s at a
discharge velocity of 8
m/s (Fig. 2–48).
Determine if this claim
is reasonable.
Performance = efficiency, is expressed in
desired output by the required input
A
pump or a fan receives shaft work
(from an electric motor) and transfers it
to the fluid as mechanical energy (less
frictional losses).
 A turbine, converts the mechanical
energy of a fluid to shaft work.
= useful pumping =
power
=
Vol ( P2  P1 )
= Power rating x 
 mech , fan 
 E mech , fluid
W shaft , in
1
2

 E mech , fluid  m (V 2 )
2
is the rate of decrease in the mechanical energy of the
fluid, which is equivalent to the mechanical power
extracted from the fluid by the turbine
Q generation  W el , in  W shaft , out
W el , in 
W shaft , out
 motor
1.

Polusi
Merusak lingkunan
dan kesehatan
Smog (asap kota metropolitan) dengan ciri
dark yellow or brown haze in stagnant air
mass and hangs over on calm hot summer
day. Komponen Smog:
 Ground Ozone (O3) : menyebabkan iritasi
mata, merusak paru-paru, dan merusak
jaringan daun tanaman.
 CO : racun mematikan
 VOCs (Benzene, butane, …)
Smog dapat dibawa angin melintasi perbatasan
 persoalan global.
2.
3.



Acid Rain
Fossil fuel contain
sulfur  SOx
SOx and NOx
+ Water + sunlight
 Sulfuric Acid +
Nitric Acid
The acid washed
out by rain water
 Acid Rain
4.
GHG: CO2, CH4, H2O, NOx
 Global Warming