Performance Assessment of a Recuperative Helium Gas Turbine System

Abstract

Helium is considered an ideal working fluid for closed cycle gas turbines powered by the heat of nuclear reactors or solar concentrators. Energetic and exergetic based thermodynamic analyses are applied to an actual 120 MW recuperative closed gas turbine operating with helium with two compression stages. The maximum pressure and temperature of the plant are taken as 70 bar and 850 °C at the turbine inlet. Parametric studies are performed to investigate the effects of different parameters on the plant performance and the irreversibilities associated with the system operation. In the exergy analysis, internal and external irreversibilities are considered. At the optimal pressure ratio, the energy and exergy efficiencies obtained here are found as 45.5 and 60.5 % at the base case. Also, various exergetic parameters are calculated for the exergy assessment of the gas turbine plant. Furthermore, gas turbine exergetic performance map is introduced.

Nomenclature

c _p :

Specific heat capacity, kJ/kg K

E :

Energy, kJ

$\dot{ Ex}$ :

Exergy rate, kW

${\dot{ Ex}}_d$ :

Exergy destruction rate, kW

Ex _R :

Exergy destruction ratio, %

h :

Specific enthalpy, kJ/kg

IP :

Improvement potential, kW

k :

Constant

$\dot{m}$ :

Mass flow rate, kg/s

N _c :

Number of compression stages

P :

Pressure, kPa

(ΔP/P):

Pressure loss coefficient

$\dot{Q}$ :

Heat rate, kJ/s

r _c :

Pressure ratio

R :

Gas constant, kJ/kg K

s :

Specific entropy, kJ/kg K

$\dot{S}$ :

Entropy rate, kW/K

SI :

Sustainability index

t :

Time, s

T :

Temperature, K

w :

Specific work, kJ/kg

$\dot{W}$ :

Power, kW

y _D :

Exergy destruction percentage, %

β :

Temperature ratio

ε :

Heat exchanger effectiveness, %

η :

Energy efficiency, %

ψ :

Exergy efficiency, %

ϒ :

Specific heat ratio

a :

Adiabatic

c :

Cold stream

C :

Compressor

ex :

Exit flow

f :

Fuel

gen :

Generation

h :

Hot stream

H :

Highest

HE :

Heat exchanger

in :

Inlet flow

IC :

Intercooler

L :

Lowest

p :

Polytropic

PC :

Precooler

R :

Recuperator

T :

Turbine