Abstract
The present work deals with multi objective optimization of nanofluid based Organic Rankine Cycle (ORC) to utilise waste heat energy. Working fluid considered for the study is R245ca for its good thermodynamic properties and lower Global Warming Potential (GWP) compared to the conventional fluids used in the waste heat recovery system. Heat Transfer Search (HTS) algorithm is used to optimize the objective functions which tends to maximize thermal efficiency and minimize Levelised Energy Cost (LEC). To enhance heat transfer between the working fluid and source fluid, nanoparticles are added to the source fluid. Application of nanofluids in the heat transfer system helps in maximizing recovery of the waste heat in the heat exchangers. Based on the availability and cost, CuO nanoparticles are considered for the study. Effect of Pinch Point Temperature Difference (PPTD) and concentration of nanoparticles in heat exchangers is studied and discussed. Results showed that nanofluids based ORC gives maximum thermal efficiency of 18.50% at LEC of 2.59 $/kWh. Total reduction of 7.11% in LEC can be achieved using nanofluids.
Highlights
With increasing demand of energy in today’s technological world, energy conservation and recovery is one of the major challenge in the field of engineering
In case of conventional Organic Rankine Cycle (ORC) system, maximum thermal efficiency of 18.5% is achieved with a levelised cost of 2.66 $/kWh whereas minimum thermal efficiency of 12.31% was achieved at cost of 2.50 $/kWh
Overall 7.11% reduction in Levelised Energy Cost (LEC) is observed for nanofluids based ORC compared to conventional system
Summary
With increasing demand of energy in today’s technological world, energy conservation and recovery is one of the major challenge in the field of engineering. Conventional fossil fuels are on the verge of depletion and need has arised to develop sustainable energy generation techniques One such technology is Organic Rankine Cycle (ORC) which recovers waste heat energy from different sources and generates electrical energy using organic fluids [1]. Wang et al [3] studied the thermodynamic performance of the ORC system using nine organic working fluids to recover waste heat from internal combustion engines. To enhance the heat transfer characteristics by improvising thermo- physical properties of the conventional fluids, nanofluids have been area of great interest for the researchers [5]. Thermal conductivity, density and specific heat are the important thermos-physical properties which determine the behaviour of nanofluids in a heat transfer system. Thermal conductivity of the nanofluids increases because of the Brownian motion and it results in augmented heat transfer mechanism [9].
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