Exergo-economic analysis of the pinch point temperature difference (PPTD) in both evaporator and condenser of sub-critical organic Rankine cycle system (ORCs) are performed based on the first and second laws of thermodynamics. Taking mixture R13I1/R601a as a working fluid and the annual total cost per net output power
Z as exergo-economic performance evaluation criterion, the effects of PPTD in evaporator Δ
Te, and the PPTD ratio of condenser to evaporator
y, on the exergo-economic performance of ORCs are analyzed. Moreover, how some other parameters influence the optimal PPTD in evaporator Δ
Te,opt and the optimal PPTD ratio of condenser to evaporator
yopt are also discussed. It has been found that the exergo-economic performance of ORCs is remarkably influenced by Δ
Te and
y, and there exists Δ
Te,opt and
yopt. In addition, Δ
Te,opt and
yopt are affected by heat transfer coefficient ratio of condenser to evaporator
ß, the temperature of working fluid at dew point in condenser
T1a, and composition of R13I1/R601a: larger
ß and
T1a lead to lower Δ
Te,opt and
yopt; by contraries, larger mass fraction of R13I1 makes Δ
Te,opt and
yopt increase, and
yopt increases linearly. The effects of the temperature of working fluid at bubble point in evaporator
T3a, mass flow rate of exhaust flue gas
mg, and inlet temperature of exhaust flue gas
Tgi on Δ
Te,opt and
yopt are very slight. For comparison, three additional working fluids, namely R601a, R245fa, and 0.32R245fa/0.68R601a, are also taken into account.
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