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Open AccessArticle

Energy and Exergy Analysis of Different Exhaust Waste Heat Recovery Systems for Natural Gas Engine Based on ORC

1
Programa de Ingeniería Mecánica, Universidad del Atlántico, Carrera 30 Número 8-49, Puerto Colombia, Barranquilla 080007, Colombia
2
Research School of Electrical, Mechanical and Material Engineering, The Australian National University, ACT 2600, Australia
3
Departamento de Energía, Universidad de la Costa, Barranquilla 080002, Colombia
4
Programa de Ingeniería Mecánica, Universidad Pontificia Bolivariana, Medellín 050004, Colombia
*
Author to whom correspondence should be addressed.
Energies 2019, 12(12), 2378; https://doi.org/10.3390/en12122378
Received: 18 May 2019 / Revised: 18 June 2019 / Accepted: 18 June 2019 / Published: 20 June 2019
(This article belongs to the Special Issue Organic Rankine Cycle for Energy Recovery System)
Waste heat recovery (WHR) from exhaust gases in natural gas engines improves the overall conversion efficiency. The organic Rankine cycle (ORC) has emerged as a promising technology to convert medium and low-grade waste heat into mechanical power and electricity. This paper presents the energy and exergy analyses of three ORC–WHR configurations that use a coupling thermal oil circuit. A simple ORC (SORC), an ORC with a recuperator (RORC), and an ORC with double-pressure (DORC) configuration are considered; cyclohexane, toluene, and acetone are simulated as ORC working fluids. Energy and exergy thermodynamic balances are employed to evaluate each configuration performance, while the available exhaust thermal energy variation under different engine loads is determined through an experimentally validated mathematical model. In addition, the effect of evaporating pressure on the net power output, thermal efficiency increase, specific fuel consumption, overall energy conversion efficiency, and exergy destruction is also investigated. The comparative analysis of natural gas engine performance indicators integrated with ORC configurations present evidence that RORC with toluene improves the operational performance by achieving a net power output of 146.25 kW, an overall conversion efficiency of 11.58%, an ORC thermal efficiency of 28.4%, and a specific fuel consumption reduction of 7.67% at a 1482 rpm engine speed, a 120.2 L/min natural gas flow, 1.784 lambda, and 1758.77 kW of mechanical engine power. View Full-Text
Keywords: energy analysis; exergy analysis; organic Rankine cycle; waste heat recovery; natural gas engine energy analysis; exergy analysis; organic Rankine cycle; waste heat recovery; natural gas engine
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Valencia, G.; Fontalvo, A.; Cárdenas, Y.; Duarte, J.; Isaza, C. Energy and Exergy Analysis of Different Exhaust Waste Heat Recovery Systems for Natural Gas Engine Based on ORC. Energies 2019, 12, 2378.

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