Thermodynamic Cycles for Low- and High-Temperature Waste Heat Recovery from Heavy-Duty Engines
Doctoral thesis, 2021

To reduce the environmental impact of heavy-duty vehicles, it is critical to reduce their CO2 emissions by improving the engine efficiency. A promising way to do this is by extracting waste heat from the engine during operation and converting it into useful work. This thesis presents a comprehensive evaluation of the performance of thermodynamic cycles for waste heat recovery from heavy-duty engines. First, by identifying the combination(s) of heat source, working fluid, and thermodynamic cycle that maximizes the performance. Then, by evaluating the performance of the most promising solutions using experimental investigations and detailed simulations.

The potential for waste heat recovery was investigated with steady-state simulations considering two low-temperature and two high-temperature heat sources, a wide variety of working fluids, and four thermodynamic cycles: the organic Rankine cycle (ORC), the transcritical Rankine cycle, the trilateral flash cycle, and the organic flash cycle. The best overall performance was obtained with the ORC using acetone, benzene, cyclopentane, ethanol, or methanol as the working fluid, or with R1233zd(E), MM, or Novec649 if a non-flammable and non-toxic fluid was preferred. The engine coolant was the best performing low-temperature heat source, recovering 1.5 % of the engine power, and the exhaust gas was the best performing high-temperature heat source, recovering up to 5 %. By combining multiple heat sources in series, almost 8 % was recovered. Using a dual-loop system with the engine coolant and exhaust gas as the heat source, fuel consumption was reduced by over 5 %, rising to 9 % if the engine coolant temperature was increased to 140 C.

Two test setups were constructed to experimentally investigate the performance of the simulated systems. The high-temperature setup consisted of a Rankine cycle with water using the exhaust gases as the heat source while the low-temperature setup recovered heat from the engine coolant using an ORC with R1233zd(E) as the working fluid. Based on the experimental findings, models of both setups were developed to predict their performance over a driving cycle. The low-temperature system was able to recover 0.73 % of the total energy required by the engine, while the high-temperature system could recover 3.37 %.

engine efficiency

low-temperature

organic flash cycle

heavy-duty Diesel

long haul truck

organic Rankine cycle (ORC)

internal combustion engine

transcritical Rankine cycle

expander

trilateral flash cycle

waste heat recovery

Motorn, SB3, Sven Hultins Gata 8, Chalmers
Opponent: Vincent Lemort, University of Liège, Belgium

Author

Jelmer Johannes Rijpkema

Chalmers, Mechanics and Maritime Sciences, Combustion and Propulsion Systems, Engines and Propulsion Systems

Experimental Results of an Organic Rankine Cycle with R1233zd(E) for Waste Heat Recovery from the Coolant of a Heavy-Duty Truck Engine

Exhaust Waste Heat Recovery from a Heavy-Duty Truck Engine: Experiments and Simulations

Combining Low- and High-Temperature Heat Sources in a Heavy Duty Diesel Engine for Maximum Waste Heat Recovery Using Rankine and Flash Cycles

Energy and Thermal Management, Air-Conditioning, and Waste Heat Utilization,; Vol. 2nd ETA Conference(2018)p. 154-171

Paper in proceeding

Climate change caused by greenhouse gas emissions originating from human activity is the biggest environmental challenge facing the world today, and heavy duty vehicles powered by internal combustion engines are responsible for approximately 5 % of the world's yearly greenhouse gas emissions. Since the internal combustion engine will be the main source of propulsion for such vehicles in the near future, it will be necessary to increase the efficiency of heavy duty engines in order to reduce their environmental impact. Increasing engine efficiency will reduce the amount of fuel consumed per kilometer driven and thus reduce the CO2 emissions of heavy duty vehicles. More than half of the energy in the fuel burned in a heavy duty engine is lost in the form of heat. One way to increase engine efficiency is to recover this waste heat and convert it into useful energy. This thesis therefore explores the possibility of using thermodynamic cycles for waste heat recovery. In a thermodynamic cycle, energy is used to heat (and possibly evaporate) a pressurized fluid. The energy contained in this high-temperature and high-pressure fluid is then used to generate power, effectively adding power to the engine and increasing its efficiency. Using experiments and simulations, this thesis evaluates the performance of several heat sources, thermodynamic cycles, and working fluids for waste heat recovery from heavy-duty engines. The results show that recovering heat from the exhaust gases and the engine coolant at elevated temperatures could potentially reduce the fuel consumption of heavy duty engines by almost 10 %.

Waste Heat Recovery - Low Temperature, Part II

Swedish Energy Agency (2017-013961), 2018-03-01 -- 2020-02-01.

Areas of Advance

Transport

Energy

Subject Categories

Applied Mechanics

Energy Engineering

Vehicle Engineering

Infrastructure

Chalmers Laboratory of Fluids and Thermal Sciences

ISBN

978-91-7905-486-1

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4953

Publisher

Chalmers University of Technology

Motorn, SB3, Sven Hultins Gata 8, Chalmers

Online

Opponent: Vincent Lemort, University of Liège, Belgium

More information

Latest update

5/12/2021