Papers by Keyword: Organic Rankine Cycle (ORC)

Abstract: Vehicle exhaust waste heat utilization can improve automotive vehicle fuel efficiency to optimize energy use and reduce CO2 greenhouse gas emissions to protect the environment. This paper introduces several methods of using engine waste heat, mainly on the Semiconductor thermoelectric power generation technology and the Organic Rankine Cycle power generation technology, and in-depth study on their system structure, principles and key technologies respectively and get important conclusions.

Abstract: Exergy analysis is performed for transcritical Organic Rankine Cycle (ORC) with internal heat exchanger based on the second law of thermodynamics. Effects of source temperature as well as turbine inlet pressure (TIP) are investigated on the exergy destructions (or anergies) of the system as well as exergy efficiency. Results show that irreversibility of the system decreases with increasing TIP or decreasing source temperature. Exergy efficiency decreases with increasing source temperature; however has a maximum value with respect to TIP.

Abstract: The optimum working conditions of 11 working fluids under different heat source temperatures for an organic Rankine cycle (ORC) were located in our previous work. In the current work, the system irreversibility of each candidate were calculated and compared at their optimal operating conditions. Obvious variation trends of both the cycle efficiency and irreversibility were found for different types of organic fluids. It is suggested, when selecting working fluid for our ORC system, the critical temperature should be as close as possible to the heat source temperature to achieve high cycle efficiency but avoid large irreversibility. The relationships between the structure of the molecules and the critical temperature of the working fluids are investigated qualitatively and potentially meaningful for the rational selection of proper organic fluids for certain ORCs.

Abstract: To improve fuel economy, an Organic Rankine Cycle (ORC) system is proposed to recover waste heat from heavy-duty diesel engines. R123 and R245fa were selected as working fluids. Extensive numerical simulations were conducted to find thermal efficiency of the system under different evaporation pressures, mass flow rates of working fluids and temperature of engine exhaust gases. Results show that the system thermal efficiency was increased with the increase in evaporation pressure for both R123 and R245fa. Efficiency of R123 system was found to be greater than that of R245fa system. For Rankine cycle with both R123 and R245fa, mass flow rate range varied with the evaporation pressure. Limited by evaporation rates and thermal decomposition of the working fluid, the range of mass flow rates in R245fa system was narrower than the R123 system. The thermal efficiency with different temperatures of engine exhaust gases was similar under the fixed evaporation pressure.

Abstract: Supercritical Rankine cycles using organic fluids as working fluids in converting low-grade energy to high-grade power energy are investigated in the study. The main purpose is to identify suitable working fluids which may yield high system efficiencies in a supercritical Organic Rankine Cycle (ORC) system. R123, R134a, R152a, R22, and R245fa are used for the research. Results show that: at a constant superheating of expansion outlet, system efficiency improves with the increasing of evaporation pressure for all the working fluids and supercritical ORC has a higher efficiency than sub-ORC process. Furthermore, R152a performs the best compared with other refrigerants and is suitable for SORC system.

Abstract: Application of a light-weight material, such as an aluminum alloy, on a turbine impeller can enhance the efficiency of an Organic Rankine Cycle power plant that operates at temperatures below 150 °C. The density of an aluminum alloy only one-third that of steel. However, increased strength of aluminum alloys is needed for turbine impeller qualification. Investment casting was chosen to produce radial inflow turbine impeller due to their complex geometry and precision. It can replace machining process, which is time-consuming and less efficient because of material removal. This study describes the investment casting process used to produce a radial inflow impeller turbine. The study also identifies defects, microstructures and properties of radial inflow turbine impeller. The turbine impeller were produced from Al-7Si-4Mg alloy with 0.38, 3.82, and 6.0 wt. % Cu. Visual examination showed that the turbine impeller was free of macro defects and misruns. Microstructures were characterized by Optical Microscopy and SEM. The structures consisted of α-Al, Si eutectic, AlMgSi, AlMgFeSi (Chinese script) and CuAl₂. The higher hardness value of 54HRB was affected by Cu content due to the good mechanical properties of fasa CuAl₂^.

Abstract: Organic Rankine cycle (ORC) is a modified rankine cycle with working fluids, of organic material (Refrigerant). Refrigerant pentane has low boiling point, therefore ORC can be used in power plant which uses low temperature resources, such as solar thermal exhausted gases and geothermal wells. Organic Rankine Cycle (ORC) is used to convert heat energy into mechanical energy or electricity generated by a low temperature of the hot sun. The working fluid used is HCR12, HCR22, HCR134a and Pentane. Simulations performed with an organic Rankine cycle temperature and pressure with cycle tempo program. By programming the simulation cycle tempo and got the result on the maximum power a turbine to the conditions of the working fluid Pentane to the input turbine T = 700C and pressure = 2 bar can generate 2.07 kW. Turbocharger is one of the alternatives in the energy conversion of the energy of motion into electrical energy. Turbocharger rotation will be used to turn a generator and converts the energy of motion into electrical energy.

Abstract: For recycling complementary energy efficiently, WMs latent heat of vaporization is made full use of in a free piston based organic rankine cycle exhaust gas energy recovery (ORC-FP) system. In this paper, the model of ORC-FP system has been established by the software GT-suite 7.0. Three sensitive factors (WMs gas ratio, piston damping coefficient and power WMs pressure) will be discussed by simulation results. The conclusions are shown as follows: Firstly, when WM state is 450K, 1.1MPa (Power WM) and 320K, 1.1MPa (Cooling WM) at inlet, the systems single cycle efficiency is highest about 69.21%, and the lowest is about 42.32%. Certain fluctuation of single cycle (SC) efficiency exists between two adjacent cycle, and the highest difference can reach 26.89%. Secondly, the systems total cycle (TC) efficiency decreases along with the increasing of damping coefficient (piston load). At the minimum piston damping coefficient (about 7500 N-s/m), the systems highest total cycle efficiency is 46.53%, and at the maximum (about 8750 N - s/m), the lowest total cycle efficiency is 35.66%. Thirdly, when damping coefficient is 7500 N-s/m, the higher pressure of WM is, the higher the systems total cycle efficiency is. In the pressure of 1.1MPa, the system reaches the highest efficiency which is about 46.53%, and in the pressure of 0.9 MPa reaches the lowest which is about 26.74%.

Abstract: In order to determine the operating characteristics of a small-scale ORC (organic Rankine cycle) system for various low temperature heat sources, experiments were carried out. A small-scale ORC power generation system adopting R-245fa as a working fluid was designed and manufactured. Hot water was used for the heat source and the temperature was controlled by the 110 kW electric resistance heaters which provided up to 150 °C. Cooling temperature was controlled by a circulating water chiller to simulate various heat sink environments. An open-drive oil-free scroll expander directly connected to a high-speed synchronous generator was installed in the ORC unit. The efficiencies of the cycle and the expander, electric power of the developed ORC system with respect to the operating conditions were investigated by experiments. The factors which influence the performance of the oil-free scroll expander were analyzed and discussed.

Abstract: In this study, energetic based fluid selection for a solid oxide fuel cell-organic rankine combined power system is investigated. 9 dry organic fluids with varied critical temperatures are chosen and their corresponding ORC cycle performances are evaluated at different turbine inlet temperatures and exhaust gas temperature (waste heat source) from the upper cycle. It is found that actual ORC cycle efficiency for each fluid strongly depends on the waste heat recovery performance of the heat recovery vapor generator. Exhaust gas temperature determines the optimal fluid which yields the highest efficiency.