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Energy system - Coggle Diagram
Energy system
Pinch Technology
.
heat transfer processes
in the same region
across the pinch point
below = source
above = sink
threshold conditions
on the left
ΔTmin < ΔTth
on the right
composite curves
pinch point
MER conditions
problem table
basic concepts
min value of the cumulated heat transfer
deficit
surplus
.
assumptions
implementation
1) subtracting and adding ΔT/2 to find the PP
2) deficit and surplus of heat
3) cumulated heat transfer
Grand Composites Curve
construction
sink and source + local sink and local source
corrct location of the utilities
rules
fundamental
fulfilling one at a time
second
construction starts from PP
C above the PP
C below the PP
third
stream splitting
fourth
avoiding cyclic
need to split (third rule)
HEN
minimizing costs
minimum number of HEs
including subsystems
higher number of heat exchanger = loop
delete one side and assign it to the other
in a MER HEN
interaction thermal engines (HE) - thermal process (TP)
inclusion of hot and cold streams
positioning of TP vs the PP
heat pump above the PP
heat pump below the PP
heat pump across the PP
matching HE and TP
with GCC
internal heat recovery within thermal systems
possible matching between
hot utilities and thermal process
cold utilities and thermal process
Construction of design and off-design model
off-design model (performance)
design model (size)
Characteristic of energy system model
mass and energy balance
characteristic curves of the components
physical properties
ranges of the operating performance variables
n variables - m equations
sequential way and simultaneous approach
Energy system components
Compressor
Axial
high mass flow rate, low specific energy transfer, limited
pressure ratio of one stage
degree of reaction = 0.5
velocity triangles and thermodynamic processes
Design and Off-Design
dimensional analysis
shape of characteristic curves
equations and variables of both models
centrifugal
low mass flow rate, high specific energy transfer, high pressure ratio of one stage
Turbine
velocity triangles and power generated
characteristic curves
choke situation (ideal and real one)
Stodola's ellipse Law
(turbine behavior = nozzle behavior)
uncontrolled expansion to vacuum
flow coefficient formula and pressure ratio constant
controlled expansion with group of turbine stage having fixed backpressure
derivation of codablele equations from stool's ellipse law
from flow coefficient to "pi"
Design and Off-Design
same as compressor
modelling
transposing graphic in tabular form
high or low speed lines related to the auxiliary lines β
scaling of components maps
Effects of the VIGVs on the compressor maps
relative velocity remains the same
efficiency curves translate and maximum value remains the same
Heat exchangers
LMTD (Logaritmic Mean Temperature Difference)
concentric tubes counter current heat exchanger
evporators and condensers
Design and Off-Design
ε-NTU
efficiency and number transfer units
Combustion model
fuel + oxidizer -> products
conservation of mass
stoichometric combustion
air-to-fuel ratio
excess of defeat of air
heat of reaction
enthalpy of a compound
energy balance and mass balance
heating value
Definition and general features
System boundaries
closed system (fixed mass)
Steps
Understanding the problem
"What?", "Why?" and GANTT chart
Generate and screen alternative concepts
"How?"
Detailed design of processes and equipment
Project Engineering
Startup, operation and retirement
Implementation of models
EES (Engineering Equation Solver)
Matlab-Simulink
Exergetic and exergoeconomic analyses
Exergy analysis
part 1
exergetic efficiency
specific energy associated with a mass stream
standard environment
chemical exergy
Dead State and Restricted Dead State
exergy balance
part 2
exergy balance of the components
guidelines to increase exergy efficiency
design improvement using exergy analysis
improvement of a component may not lead to an overall improvement
exergy picture says where to intervene
SPECO method
taking a record of the exergy addition to and removals
new definitions of
products
fuels
input/output exergy balance-->fuel/product exergy balance
part 3
physical structure and productive structure
chemical reaction
different analysis
combustion chamber
heat exchanger
total or separate exergy forms
boiler
exergoeconomic analysis
part 1
cost balance equation
exergy
monetary
from investment cost to cost flow rate
auxiliary equations
rules
F
P
part 2
examples
cost calculations
turbine
heat exchanger
T>T0
T<T0
cost of fuel
design improvement
influence of energy destruction in the last component
guidelines to improve the cost effectiveness
Construction of new configurations (Synthesis)
Heatsep Method
stages:
1) build the basic system configuration
of one cycle or combined cycle
2) identify all possible heat transfers
thermal cuts
HU-T
CU-C
3) optimize them with other design variables
temperature associated to thermal cuts
black box
4) build the Heat Exchangers Network (HEN)
Pinch Technology
application
Brayton Cycle
1) basic configuration
compressor
combustion chamber
turbine
shaft connecting turbine with compressor
2) thermal links cut
C-CDC
black box
T-CU
3) temperatures included in decision variables
temperatures
from thermal cuts are free to vary
by C and T efficiencies are fixed
by fuel or other constrains are fixed
3a) o.f. is the maximization of the thermal efficiency and Pnet is fixed = no internal regeneration
3b.1) o.f is the minimization of the unit cost of electricity and Pnet is fixed at high value = avoiding internal regeneration
3b.2) Pnet is fixed at a low value = regenerative configuration
construction of HEN with Pinch Technologies
HAT (Humid Air Turbine)
Brayton Cycle + Water Steam Cycle)
saturator = junction
2 compression stages
C2 is cooled in the aftercooler
optimization using simulation runs
Steam injected gas turbine and evolution of the power cycles
gas turbine
advantage and disadvantage
combined plant
advantage and disadvantage
regenerative gas turbine
micro-turbines
interrefrigerated-reheated gas turbine
HAT
Steam Injected Gas Turbine
different % of injected water
efficiency of separated cycles
Base-Line efficiency
comparison with the STIG efficiency
thermal energy
available
recovered
STIG + HPT
efficiency
heat transfer
STIG + HPT + LPT