The Experts below are selected from a list of 3936 Experts worldwide ranked by ideXlab platform
Markus Preisinge - One of the best experts on this subject based on the ideXlab platform.
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experimental characterization and comparison of an axial and a cantilever micro turbine for small scale organic rankine cycle
Applied Thermal Engineering, 2018Co-Authors: Andreas P Weis, Tobias Popp, Jonas Mulle, Josef Haue, Diete Uggema, Markus PreisingeAbstract:Abstract Electricity generation from waste heat by means of Organic Rankine Cycle is a promising method to increase the Efficiency of industrial processes. However, due to special boundary conditions, such systems have to be robust, efficient in full load as well as in part load and scalable down to the power range of less than 15 kW. This study presents experimental results on the behaviour of two small-scale turbines, an axial impulse turbine and a radial cantilever turbine with a maximum power of about 12 kW. The turbine characteristics (Isentropic Efficiency and swallowing capacity) are given with respect to pressure ratio (ranging from 12 to 24) and rotational speed (ranging from 18,000 to 30,000 rotations per minute). For the axial turbine, a maximum Isentropic Efficiency of 73.4% has been reached in the ORC test bed. The maximum Isentropic Efficiency of the cantilever turbine is even higher and reaches 76.8%. The values are compared to volumetric expanders and it is shown that micro-turbines can compete even in the power range addressed in this study. As the turbine characteristics are given for full load and part load conditions, they can be implemented in simulation tools to allow for a more realistic calculation of ORCs with fluctuating heat sources.
Eckhard A. Groll - One of the best experts on this subject based on the ideXlab platform.
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Improved design method of a rotating spool compressor using a comprehensive model and comparison to experimental results
IOP Conference Series: Materials Science and Engineering, 2017Co-Authors: Craig R. Bradshaw, Greg Kemp, Joe Orosz, Eckhard A. GrollAbstract:An improvement to the design process of the rotating spool compressor is presented. This improvement utilizes a comprehensive model to explore two working uids (R410A and R134a), various displaced volumes, at a variety of geometric parameters. The geometric parameters explored consists of eccentricity ratio and length-to-diameter ratio. The eccentricity ratio is varied between 0.81 and 0.92 and the length-to-diameter ratio is varied between 0.4 and 3. The key tradeoffs are evaluated and the results show that there is an optimum eccentricity and length-to-diameter ratio, which will maximize the model predicted performance, that is unique to a particular uid and displaced volume. For R410A, the modeling tool predicts that the overall Isentropic Efficiency will optimize at a length-to-diameter ratio that is lower than for R134a. Additionally, the tool predicts that as the displaced volume increases the overall Isentropic Efficiency will increase and the ideal length-to-diameter ratio will shift. The result from this study are utilized to develop a basic design for a 141 kW (40 tonsR) capacity prototype spool compressor for light-commercial air-conditioning applications. Results from a prototype compressor constructed based on these efforts is presented. The volumetric Efficiency predictions are found to be very accurate with the overall Isentropic Efficiency predictions shown to be slightly over-predicted.
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Influence of Volumetric Displacement and Aspect Ratio on the Performance Metrics of the Rotating Spool Compressor
2014Co-Authors: Craig R. Bradshaw, Greg Kemp, Joseph S. Orosz, Eckhard A. GrollAbstract:A theoretical study of the influence of geometric design and scaling is presented for the rotating spool compressor. This study uses the previously developed comprehensive compressor model for the rotating spool compressor developed by Bradshaw and Groll (2013). The compressor aspect ratio (axial length to bore diameter) is varied between roughly 0.2 and 3.5 at eccentricity ratios (rotor diameter to bore diameter) of 0.825, 0.85, 0.893, and 0.92. It is found that for a given eccentricity ratio, there exists an optimum aspect ratio that maximizes the volumetric Efficiency. Additionally, the eccentricity ratio shows a high level of sensitivity to the overall performance of the compressor. As the eccentricity ratio decreases, the overall Isentropic Efficiency of the compressor increases until an eccentricity ratio of 0.85. Below an eccentricity ratio of 0.85 the overall Isentropic Efficiency does not increase despite an increase in volumetric Efficiency. The scaling study modifies the displaced volume using a set of scaling rules to determine the size of the compressor features as the compressor displacement changes. The study finds that as the volumetric displacement increases, the volumetric Efficiency asymptotically increases. It is also found that there is an optimum in overall Isentropic Efficiency as the volumetric displacement increases which suggests a trade-off between sealing and port restrictions. Using the results of these two studies a 6 th and 7 th generation prototype spool compressor is proposed which has the potential to increase the overall Isentropic Efficiency by 5% and 6%, respectively.
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Experimental testing of an oil-flooded hermetic scroll compressor
International Journal of Refrigeration, 2013Co-Authors: I H Bell, James E. Braun, Eckhard A. Groll, W. Travis HortonAbstract:In this work, a residential air conditioning compressor designed for vapor injection has been modified in order to inject large quantities of oil into the working chamber in order to approach an isothermal compression process. The compressor was tested with oil injection mass flow fractions of up to 45%. At an evaporating temperature of -10 C and condensing temperature of 30 C, the overall Isentropic Efficiency was up to 70% at the highest oil injection rate. Overall, over the testing envelope investigated, there are no significantly negative effects experienced for the compressor and the compressor Isentropic Efficiency and refrigerant mass flow rate improve monotonically as the oil injection rate is increased.
Andreas P Weis - One of the best experts on this subject based on the ideXlab platform.
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experimental characterization and comparison of an axial and a cantilever micro turbine for small scale organic rankine cycle
Applied Thermal Engineering, 2018Co-Authors: Andreas P Weis, Tobias Popp, Jonas Mulle, Josef Haue, Diete Uggema, Markus PreisingeAbstract:Abstract Electricity generation from waste heat by means of Organic Rankine Cycle is a promising method to increase the Efficiency of industrial processes. However, due to special boundary conditions, such systems have to be robust, efficient in full load as well as in part load and scalable down to the power range of less than 15 kW. This study presents experimental results on the behaviour of two small-scale turbines, an axial impulse turbine and a radial cantilever turbine with a maximum power of about 12 kW. The turbine characteristics (Isentropic Efficiency and swallowing capacity) are given with respect to pressure ratio (ranging from 12 to 24) and rotational speed (ranging from 18,000 to 30,000 rotations per minute). For the axial turbine, a maximum Isentropic Efficiency of 73.4% has been reached in the ORC test bed. The maximum Isentropic Efficiency of the cantilever turbine is even higher and reaches 76.8%. The values are compared to volumetric expanders and it is shown that micro-turbines can compete even in the power range addressed in this study. As the turbine characteristics are given for full load and part load conditions, they can be implemented in simulation tools to allow for a more realistic calculation of ORCs with fluctuating heat sources.
Lisheng Pan - One of the best experts on this subject based on the ideXlab platform.
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improved analysis of organic rankine cycle based on radial flow turbine
Applied Thermal Engineering, 2013Co-Authors: Lisheng Pan, Huaixin WangAbstract:With attention to the drawback of specifying Isentropic Efficiency of expander (or turbine) in Organic Rankine Cycle (ORC) analysis, in order to enhance reliability of analysis results, this article replaces the constant Isentropic Efficiency by internal Efficiency of optimal radial flow turbine for each condition. With both analysis methods, namely internal Efficiency analysis method and conventional analysis method, 14 subcritical ORC working fluids are studied with hot water of 90℃, pinch point temperature of 5℃ and condensing temperature of 30℃. Results with both analysis methods are compared. The results show that turbine internal Efficiency is determined by expansion ratio in rotor and decreases with the rise of expansion ratio in rotor. There are differences between cycle net power output with internal Efficiency analysis method and that with conventional analysis method. The differences can change the results in optimizing fluid. It is significant to apply computational optimal Efficiency instead of constant Isentropic Efficiency in ORC analysis.
Muhammad Imran - One of the best experts on this subject based on the ideXlab platform.
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Experimental and numerical analysis of a reciprocating piston expander with variable valve timing for small-scale organic Rankine cycle power systems
Applied Energy, 2019Co-Authors: Jorrit Wronski, Muhammad Imran, Morten Juel Skovrup, Fredrik HaglindAbstract:Abstract This paper presents a reciprocating expander concept for organic Rankine cycle applications using a novel rotating variable timing admission valve system, enabling the adjustment of the expansion ratio in real time while the expander is running. An organic Rankine cycle experimental test rig with n-pentane as the working fluid and a single-cylinder reciprocating piston expander was developed. Experiments were conducted for evaporation temperatures ranging from 125 °C to 150 °C and condensation temperatures ranging from 20 °C to 40 °C. The performance of the reciprocating piston expander was investigated in terms of the torque of the expander, pressure inside the cylinder, Isentropic Efficiency of the expander, and net power produced by the expander. Based on the experimental data, a dynamic model of the system was formulated in the object-oriented language, Modelica. The model was validated using the experimental results and then used to predict the performance of the expander. Special attention was paid to the robust modelling of the valve actuation to avoid computational inefficiencies caused by singularities of state variables or their derivatives. The results indicate that the expander produces up to 2.5 kW of electricity from a low-temperature heat source while operating at pressure ratios ranging from 10 to 16.5 with an Isentropic Efficiency of approximately 70%. The relative differences between the model and the measurements of the Isentropic Efficiency and power output of the expander per revolution were ±10% and ±30%, respectively.
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design and experimental investigation of a 1 kw organic rankine cycle system using r245fa as working fluid for low grade waste heat recovery from steam
Energy Conversion and Management, 2015Co-Authors: Usman Muhammad, Muhammad Imran, Byung Sik ParkAbstract:Abstract This work presents an experimental investigation of a small scale (1 kW range) organic Rankine cycle system for net electrical power output ability, using low-grade waste heat from steam. The system was designed for waste steam in the range of 1–3 bar. After the organic Rankine cycle system was designed and thermodynamic simulation was performed, equipment selection and construction of test rig was carried out. R245fa was used as working fluid, a scroll type expansion directly coupled with electrical generator produced a maximum electrical power output of 1.016 kW with 0.838 kW of net electrical power output. The thermal Efficiency of the system was 5.64%, net Efficiency was 4.66% and expander Isentropic Efficiency was 58.3% at maximum power output operation point. Maximum thermal Efficiency was 5.75% and maximum expander Isentropic Efficiency obtained was 77.74% during the experiment. Effect of superheating of working fluid at expander inlet was also investigated which show that an increase in the degree of superheating by 1 °C reduces thermal Efficiency of system by 0.021% for current system. The results indicated that the measured electric power output and enthalpy determined power output (after accounting for Isentropic Efficiency) differed by 40%. Similarly, the screw pump converted 42.25% of electric power to the enthalpy determined pumping power delivered to the working fluid. Both expander and screw pump were losing power in electric and mechanical losses (generator/motor) presenting a need of further development of these components for better Efficiency. Heat loss in piping is also a factor for improving Efficiency along with the ability of heat exchangers and control system to maintain the least possible degree of superheat of working fluid at expander inlet.
