Exergy analysis of a combinded process (gas turbine and steam boiler) runs in a AttributeError

[tub-hofmann]

I create a simple model of a gasturbine and a steam boiler to produce 40 bar steam. Model is solved with starting values. And solved for a second time setting ttd_l at Economizer to 50K.

The exergy analysis runs in a AttributeError. Any ideas?

from tespy.networks import Network
from tespy.components import (Sink, Source, CombustionChamber, HeatExchanger, Drum, Pump, Compressor, Turbine)
from tespy.connections import Connection, Bus
from tespy.tools import ExergyAnalysis
from CoolProp.CoolProp import PropsSI as CP

# fluids
air = {'O2': 0.21, 'N2': 0.79}
fuel = {'CH4': 1}
water = {'H2O': 1}

# network
gtsteamboiler = Network(T_unit='C', p_unit='bar', h_unit='kJ / kg', m_unit='kg / s')

# components
src_air = Source('air-source')
src_fuel = Source('fuel-source')
snk_fluegas = Sink('flue-gas-sink')
src_water = Source('water')
snk_steam = Sink('steam')
cmp_comp = Compressor('air-compressor')
cmp_cc = CombustionChamber('combustion chamber')
cmp_exp = Turbine('expander')
cmp_pump = Pump('pump')
cmp_econ = HeatExchanger('economizer')
cmp_drum = Drum('drum')
cmp_evap = HeatExchanger('evaporator')

# connections
c11 = Connection(src_air, 'out1', cmp_comp, 'in1', label='11 (air)')
c12 = Connection(cmp_comp, 'out1', cmp_cc, 'in1', label='12 (compressed air)')
c13 = Connection(src_fuel, 'out1', cmp_cc, 'in2', label='13 (fuel)')
c14 = Connection(cmp_cc, 'out1', cmp_exp, 'in1', label='14 (hot and compressed fluegas)')
c15 = Connection(cmp_exp, 'out1', cmp_evap, 'in1', label='15 (fluegas)')
c16 = Connection(cmp_evap, 'out1', cmp_econ, 'in1', label='16 (fluegas)')
c17 = Connection(cmp_econ, 'out1', snk_fluegas, 'in1', label='17 (fluegas)')

c21 = Connection(src_water, 'out1', cmp_pump, 'in1', label='21 (water, lq.)')
c22 = Connection(cmp_pump, 'out1', cmp_econ, 'in2', label='22 (water, lq.)')
c23 = Connection(cmp_econ, 'out2', cmp_drum, 'in1', label='23 (water, x=0)')
c24 = Connection(cmp_drum, 'out1', cmp_evap, 'in2', label='24 (drum circulation)')
c25 = Connection(cmp_evap, 'out2', cmp_drum, 'in2', label='25 (drum circulation)')
c26 = Connection(cmp_drum, 'out2', snk_steam, 'in1', label='26 (steam, x=1)')

gtsteamboiler.add_conns(c11,c12,c13,c14,c15,c16,c17,c21,c22,c23,c24,c25,c26)

# parameters

# components
cmp_comp.set_attr(eta_s=0.8, pr=20)
cmp_cc.set_attr(lamb=2.5)
cmp_exp.set_attr(eta_s=0.9)
cmp_pump.set_attr(eta_s=0.8)
cmp_econ.set_attr(pr1=1, pr2=1)
cmp_evap.set_attr(pr1=1)

# connections
c11.set_attr(p=1, T=25, fluid=air)
c13.set_attr(m=3, T=25, fluid=fuel)
c17.set_attr(p=1)
c21.set_attr(m=25, p=1, T=60, fluid=water)
c22.set_attr(p=40)
c23.set_attr(h=CP('H', 'P', 40*1E5, 'Q', 0, 'water')/1E3)
c25.set_attr(x=0.6)

# busses
heat_output = Bus('heat-output')
power_output = Bus('power-output')
fuel_input = Bus('fuel-input')

heat_output.add_comps(
    {'comp': cmp_econ, 'char': -1},
    {'comp': cmp_evap, 'char': -1})
power_output.add_comps(
    {'comp': cmp_comp, 'base': 'bus', 'char': 1},
    {'comp': cmp_exp, 'char': 1})
fuel_input.add_comps({'comp': cmp_cc, 'base': 'bus'})
gtsteamboiler.add_busses(heat_output, power_output, fuel_input)

# solve
gtsteamboiler.solve(mode='design')
gtsteamboiler.print_results()

c13.set_attr(m=None)
cmp_econ.set_attr(ttd_l=50)

gtsteamboiler.solve(mode='design')
gtsteamboiler.print_results()

# exergy analysis
pamb = 1
Tamb = 25
ean = ExergyAnalysis(network=gtsteamboiler, E_F=[fuel_input], E_P=[power_output, heat_output])
ean.analyse(pamb, Tamb)

[fwitte]

Hi and thanks for reaching out!

The issue arises from the fact you are providing the wrong components to the exergy analysis busses.

• Fuel exergy should be represented by the fuel source and not the combustion chamber.
• The power output is missing the substraction of the pump's power
• The heat output is also represented by the steam sink and the water inlet (steam sink with base component, water sink with base bus)
• The flue gas losses are missing, there should be a bus, which passes those to the E_L of the network.

heat_output = Bus('heat-output')
power_output = Bus('power-output')
fuel_input = Bus('fuel-input')
flue_gas_output = Bus('flue-gas-output')

heat_output.add_comps(
    {'comp': snk_steam, 'base': 'component'},
    {'comp': src_water, 'base': 'bus'}
)
power_output.add_comps(
    {'comp': cmp_comp, 'base': 'bus', 'char': 1},
    {'comp': cmp_pump, 'base': 'bus', 'char': 1},
    {'comp': cmp_exp, 'char': 1}
)
fuel_input.add_comps({'comp': src_fuel, 'base': 'bus'})
flue_gas_output.add_comps({'comp': snk_fluegas, 'base': 'component'})

(...)
ean = ExergyAnalysis(network=gtsteamboiler, E_F=[fuel_input], E_P=[power_output, heat_output], E_L=[flue_gas_output])

[fwitte]

Anyway, there is still an issue with definition of E_F of combustion chamber. Will check later.

What specifically?

[tub-hofmann]

E_F_CC = 0, which means exergy destruction of combustion chamber is negative

[tub-hofmann]

Chemical exergy routine must improve. We will talk soon, I guess.

[fwitte]

You forgot to provide the chemical exergy information:

from tespy.tools.helpers import get_chem_ex_lib
(...)
ean.analyse(pamb, Tamb, Chem_Ex=get_chem_ex_lib("Ahrendts"))

I guess, the API and/or documentation on this could be improved

[tub-hofmann]

Yes, let's improve it soon.