Realization of A Cycle

P M V SubbaraoProfessor

Mechanical Engineering Department

I I T Delhi

How to Create Temperature and Pressure…..?

Power Generation Cycle

Goal: To generate Mechanical Power through from heat input !!!

Question: What is the Upper Limit of Cycle Performance?

Can You Predict?

Is it essential to try and find out using only on the field Test?

A Mathematical Model for (James Watt’s) Steam Engine

expansion

Heat AdditionHeat Removal

Carnot’s Model for Power Cycle

compressorturbinenet WWW

s

1 – 2 : Compressor : Isentropic Compression : s2 = s1

2 – 3 : Boiler: Isothermal Heating : T3 = T2

3 – 4 : Turbines : Isentropic Expansion : s4 = s3

4 – 1 : Condenser: Isothermal Cooling : T1 = T4

Carnot’s Model for Power Cycle

The Carnot Cycle Vs The Natural Cycles

Ecological Nuisance

Abi

lity

to P

erfo

rm

111

nn

b

y

a

x

Realization of A Cycle

• Creation of Parameters of A Cycle

• Resource: Sources of Energy

out

in

out

in

in vdpdhTdsq

inout

out

inout

in

out

ininm ss

vdpdh

ds

Tds

T

,

• Heat Addition in Steam Generator, qin

• Mean Effective Temperature of heat addition : Entropy averaged Temperature.

Analysis of A Cycle

• Net work out put =

• Heat Input =

TdSWnet

max

min

S

S

in TdSQ

outminmnet TTSSw ,,minmax

inmin TSSQ ,minmax

Efficiency, inm

outm

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outminm

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netcycle T

T

T

TT

Q

W

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,

,

,, 1

• The selection of working fluids and operation conditions are very important to system performance.

• The thermodynamic properties of working fluids will affect the system efficiency, operation, and environmental impact.

• Basically, the working fluid can be classified into three categories.

• Those are dry, isentropic, and wet depending on the slope of the T–S curve (dT/dS) to be positive, infinite, and negative, respectively.

• The working fluids of dry or isentropic type are more appropriate for power generation.

• This is because dry or isentropic fluids are superheated after isentropic expansion, thereby eliminating the concerns of impingement of liquid droplets on the turbine blades.

• Moreover, the superheated apparatus is not needed.

Organic Substances must be selectedin accordance to the heat sourcetemperature level (Tcr < Tin source)

Selection of Fluids• RC (Single Componant Working Fluid)

• Evaporation and condensation at fixed temperatures

• Fluid must be selected in accordance to the temperature level of the heat source

• Pinch point is limiting factor for heat transfer

• Environmental impacts and restrictions by using organic substances

• Inflamable and/or toxic and/or GWP (Global Warming Potential) and/or ODP

• (Ozone Depletion Potential)