Abstract
The present works deals with waste heat recovery from internal combustion engines using Rankine cycle systems where working fluid are organic liquids (ORC). The first part of the paper presents the ORC technology as one of the most suitable procedure for waste heat recovery from exhaust gas of internal combustion engine (ICE). The particular engine considered in the present work is a turbocharged compression ignition engine mounted on an experimental setup. The working fluids for ORC system are: isobutene, propane, RE245fa2, RE245cb2, R245fa, R236fa, R365mfc, R1233zd(E), R1234yf and R1234ze(Z). Experimental data derived from the experimental setup has been used for 40%, 55% and 70% engine load. This papers focusses on superheating increment, on thermal efficiency and on net power output, obtained with each working fluids in Rankine cycle. Results point out the superheating increment that gives the highest thermal efficiency for each working fluid. The highest thermal efficiency is achieved in case of using R1233zd(E) as working fluid. In case of using R1233zd(E) as working fluid at 40 % load of the engine, the output power of the Rankine cycle is 3.6 kW representing 6.2 %, from the rated power at this load; at 55% load it is 5.7 kW representing 6.7 % the rated power and at 70% it is 6.7 kW representing 6.5 % from the rated power. Future perspectives are given.
Highlights
According to Pereira et al [1], between 1993 and 2011, the world population has increased by 27% while the total energy supply form primary sources, for the same period, has increased with 48%
The ORC operates as a classic Rankine cycle, but instead of water it used organic fluids which enables the exploitation of low grade heat sources, despite of their low thermal efficiency [2]
It has been proved that the use of the Rankine Cycle (RC) and especially ORC is bringing more benefits consisting in brake specific fuel consumption (BSFC) reduction, lower heat exchanger surface and no interaction with the internal combustion engine [9,18]
Summary
The present works deals with waste heat recovery from internal combustion engines using Rankine cycle systems where working fluid are organic liquids (ORC). More recent work shows that the operation of the ORC system could improve by applying several certain methods of the schematic optimization in order to increase the efficiency of the cycle (Optimal Practical - Organic Rankine Cycle – OP-ORC) in terms of waste heat recovery from a Diesel engine. In this case the ORC recovery system consisted in two interconnecting operating loops, one of high temperature, recovering the heat of the engine exhaust gas and one of low temperature, overtaking the heat energy of the engine-cooling agent. Tev [K] stands for the evaporating temperature, c [kJ/(kgK)] is the heat capacity of the working fluid on the dry saturated vapour curve at the given evaporating parameters, Tcr [K] is the critical temperature of the working fluid, hev [kJ/kg] represents the latent heat of evaporation at evaporating pressure and n is an exponent with 0.375 or 0.38 values [27, 29, 30]
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