Regenerative Organic Rankine Cycle as Bottoming Cycle of an Industrial Gas Engine: Traditional and Advanced Exergetic Analysis

Javier Cardenas Gutierrez,Guillermo Valencia Ochoa,Jorge Duarte-Forero

doi:10.3390/app10134411

Javier Cardenas Gutierrez, Guillermo Valencia Ochoa + Show 1 more

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https://doi.org/10.3390/app10134411

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Abstract

This investigation shows a traditional and advanced exergetic assessment of a waste heat recovery system based on recuperative ORC (organic Rankine cycle) as bottoming cycle of a 2 MW natural gas internal combustion engine. The advanced exergetic evaluation divides the study into two groups, the avoidable and unavoidable group and the endogenous and exogenous group. The first group provides information on the efficiency improvement potential of the components, and the second group determines the interaction between the components. A sensitivity analysis was achieved to assess the effect of condensing temperature, evaporator pinch, and pressure ratio with net power, thermal efficiencies, and exergetic efficiency for pentane, hexane, and octane as organic working fluids, where pentane obtained better energy and exergetic results. Furthermore, an advanced exergetic analysis showed that the components that had possibilities of improvement were the evaporator (19.14 kW) and the turbine (8.35 kW). Therefore, through the application of advanced exergetic analysis, strategies and opportunities for growth in the thermodynamic performance of the system can be identified through the avoidable percentage of destruction of exergy in components.

Highlights

Given the current high energy demand, improvements of waste-to-energy conversion systems are necessary to promote the rational use of energy and environmental preservation
Organic Rankine cycle (ORC) systems are appropriate for this type of use, due to their ability to recover heat in low-temperature applications and the option of implementing them in lower capacity decentralized power plants [3], as well as, if widely applied in industry, ORC systems should contribute to the global trend in energy efficiency and greenhouse gas emissions
All the equipment in the cycle are thermally insulated; To ensure that the recuperative organic Rankine cycle (RORC) studied works under steady state conditions, it is assumed that the coupling flow in the oil cycle compensates for the temperature changes in the combustion gases; Pressure changes in the heat exchangers are considered as a function of the geometry and hydraulic characteristics of the fluid, whereas in the pipes they are not considered as pressure changes

Summary

Introduction

Given the current high energy demand, improvements of waste-to-energy conversion systems are necessary to promote the rational use of energy and environmental preservation. The human population is growing, and as a consequence, the energy sector needs to meet the increasing demand. Some waste heat recovery systems such as bottoming cycles have been studied to increase the global energy efficiency of the power generation process [2]. Organic Rankine cycle (ORC) systems are appropriate for this type of use, due to their ability to recover heat in low-temperature applications and the option of implementing them in lower capacity decentralized power plants [3], as well as, if widely applied in industry, ORC systems should contribute to the global trend in energy efficiency and greenhouse gas emissions. According to the energy consumption trend, by 2050, an increase of 70% in worldwide energy demands and an increase of 60%

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