Dynamic Modelling of Small Scale and High Temperature ORC System Using Simulink and CoolProp

2020 ◽  
Author(s):  
Radheesh Dhanasegaran ◽  
Antti Uusitalo ◽  
Teemu Turunen-Saaresti
Keyword(s):  
High Temperature ◽  
Dynamic Model ◽  
High Speed ◽  
Waste Heat ◽  
Fluid Pressure ◽  
Dynamic Modelling ◽  
Working Fluid ◽  
Small Scale ◽  
Condensation Process ◽  
Feed Pump

Abstract In the present work, a dynamic model has been developed for the small-scale high-temperature ORC experimental test rig at the LUT University that utilizes waste heat from a heavy-duty diesel engine exhaust. The experimental facility consists of a high-speed Turbogenerator, heat exchanger components such as recuperator, condenser, and evaporator with a pre-feed pump to boost the working fluid pressure after the condensation process constituting a cycle. The turbogenerator consists of a supersonic radial-inflow turbine, a barske type main-feed pump, and a permanent magnet type generator components connected on a single shaft. Octamethyltrisiloxane (MDM) is the chosen organic working fluid in this cycle. Matlab-Simulink environment along with the open-source thermodynamic and transport database Cool-Prop has been chosen for calculating the thermodynamic properties of the dynamic model. A functional parameter approach has been followed for modeling each block component by predefined input and output parameters, aimed at modeling the performance characteristics with a limited number of inputs for both design and off-design operations of the cycle. The dynamic model is validated with the experimental data in addition to the investigation of exhaust gas mass flow regulation that establishes a control strategy for the dynamic model.

Experimental Investigation of a Small-Scale Orc Turbo-Generator Supported On Gas-Lubricated Bearings

2021 ◽  
Author(s):  
Kévin Rosset ◽  
Olivier Pajot ◽  
Jurg Schiffmann
Keyword(s):  
High Speed ◽  
Waste Heat ◽  
Electrical Power ◽  
Organic Rankine Cycle ◽  
Mechanical Efficiency ◽  
Load Level ◽  
Working Fluid ◽  
Small Scale ◽  
Electrical Machine ◽  
Turbo Generator

Abstract Waste heat recovery is expected to contribute to reducing CO2 emissions from trucks. Organic Rankine cycle (ORC) systems show the highest potential for this application, but still lack efficient small-scale expansion devices, in practice. A novel turbo-generator supported on gas-lubricated bearings is presented in this paper. The device combines a single-stage radial-inflow turbine and a permanent-magnet machine in a single rotating part supported on aerodynamic bearings, lubricated with the working fluid (R245fa). The oil-free expander was tested within a dedicated ORC test setup. It was driven up to its nominal speed of 100 kRPM, generated up to 2.3 kW of electrical power, and reached a peak overall efficiency of 67%. Although the prototype was not actively cooled, the mechanical losses of the rotor shaft and the iron loss of the electrical machine reached their nominal levels. Only the copper loss was at a part-load level. The electro-mechanical efficiency of the turbo-generator reached 91% and is expected to increase while testing the device at higher load. This proof of concept confirms the high-speed and low-loss potential of gas-lubricated bearings for small-scale dynamic expanders.

Application of Microchannel Condensers for Small Scale Kalina Waste Heat Recovery Systems

2015 ◽  
Author(s):  
Brian M. Fronk ◽  
Kyle R. Zada
Keyword(s):  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Heat Exchangers ◽  
Waste Heat ◽  
Fluid Pressure ◽  
Working Fluid ◽  
Small Scale ◽  
Water Mixture ◽  
Ammonia Water

Thermally driven ammonia/water Kalina cycles have shown some promise for improving the efficiency of electricity production from low temperature reservoirs (T < 200°C). However, there has been limited application of these systems to exploiting widely available, disperse, waste heat streams for smaller scale power production (∼ 1 kWe). Factors limiting increased deployment of these systems include large, costly heat exchangers, and concerns over safety of the working fluid. The use of mini and microchannel (D < 1 mm) heat exchangers has the potential to decrease system size and cost, while also reducing the working fluid inventory, enabling penetration of Kalina cycles into these new markets. To demonstrate this potential, a detailed heat exchanger model for a liquid-coupled microchannel ammonia/water condenser is developed. The heat exchanger is sized to provide the required heat transfer area for a 1 kWe Kalina system with a source and sink temperature of 150° and 20°C, respectively. An additional constraint on heat exchanger size is that the fluid pressure loss is maintained below some threshold value. A parametric analysis is conducted to assess the effect of different correlations/models for predicting the underlying heat and mass transfer and pressure drop of the ammonia/water mixture on the calculated heat exchanger area. The results show that accurately minimizing the size of the overall system is dependent upon validated zeotropic heat and mass transfer models at low mass fluxes and in small channels.

Dynamic Modelling of Small Scale and High Temperature ORC System Using Simulink and CoolProp

2021 ◽  
Author(s):  
Radheesh Dhanasegaran ◽  
Antti Uusitalo ◽  
Teemu Turunen-Saaresti
Keyword(s):  
High Temperature ◽  
Dynamic Modelling ◽  
Small Scale

scholarly journals Thin Gas Film Isothermal Condensation in Aerodynamic Bearings

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Eliott Guenat ◽  
Jürg Schiffmann
Keyword(s):  
High Speed ◽  
Waste Heat ◽  
Load Capacity ◽  
Saturation Pressure ◽  
Operating Conditions ◽  
Fluid Film ◽  
Small Scale ◽  
Vapor Compression ◽  
Density Profiles ◽  
Film Pressure

Abstract High-speed small-scale turbomachinery for waste heat recovery and vapor compression cycles is typically supported on gas-lubricated bearings operating close to the saturation conditions of the lubricant. Under particular conditions, the gas film might locally reach the saturation pressure with potentially hazardous effects on the performance of the gas bearing. The present work introduces a model based on the Reynolds equation and the development of cavitation modeling in liquid-lubricated bearings for condensing gas bearings. The effect of condensation on load capacity and pressure and density profiles is investigated for two one-dimensional bearing geometries (parabolic and Rayleigh step) and varying operating conditions. The results suggest that the load capacity is generally negatively affected if condensation occurs. An experimental setup consisting of a Rayleigh-step gas journal bearing with pressure taps to measure the local fluid film pressure is presented and operated in R245fa in near-saturated conditions. The comparison between the evolution of the fluid film pressure under perfect gas and near saturation conditions clearly suggests the occurrence of condensation in the fluid film. These results are corroborated by the very good agreement with the model prediction.

Experimental study of small scale and high expansion ratio ORC for recovering high temperature waste heat

Energy ◽  
2020 ◽  
Vol 208 ◽  
pp. 118321 ◽  
Author(s):  
Antti Uusitalo ◽  
Teemu Turunen-Saaresti ◽  
Juha Honkatukia ◽  
Radheesh Dhanasegaran
Keyword(s):  
Experimental Study ◽  
High Temperature ◽  
Waste Heat ◽  
Expansion Ratio ◽  
Small Scale

A Copper Microchannel Heat Exchanger for MEMS-Based Waste Heat Thermal Scavenging

2014 ◽  
Author(s):  
E. Borquist ◽  
A. Baniya ◽  
S. Thapa ◽  
D. Wood ◽  
L. Weiss
Keyword(s):  
Heat Exchanger ◽  
Thermal Energy ◽  
Waste Heat ◽  
Heated Surface ◽  
Copper Substrate ◽  
Working Fluid ◽  
Bottom Plate ◽  
Small Scale ◽  
Thermal Source ◽  
Micro Channels

The growing necessity for increased efficiency and sustainability in energy systems such as MEMS devices has driven research in waste heat scavenging. This approach uses thermal energy, which is typically rejected to the surrounding environment, transferred to a secondary device to produce useful power output. This paper investigates a MEMS-based micro-channel heat exchanger (MHE) designed to operate as part of a micro-scale thermal energy scavenging system. Fabrication and operation of the MHE is presented. MHE operation relies on capillary action which drives working fluid from surrounding reservoirs via micro-channels above a heated surface. Energy absorption by the MHE is increased through the use of a working fluid which undergoes phase change as a result of thermal input. In a real-world implementation, the efficiency at which the MHE operates contributes to the thermal efficiency of connected small-scale devices, such as those powered by thermoelectrics which require continual heat transfer. This full system can then more efficiently power MEMS-based sensors or other devices in diverse applications. In this work, the MHE and micro-channels are fabricated entirely of copper with 300μm width channels. Copper electro-deposition onto a copper substrate provides enhanced thermal conductivity when compared to other materials such as silicon or aluminum. The deposition process also increases the surface area of the channels due to porosity. Fabrication with copper produces a robust device, which is not limited to environments where fragility is a concern. The MHE operation has been designed for widespread use in varied environments. The exchanger working fluid is also non-specific, allowing for fluid flexibility for a range of temperatures, depending on the thermal source potential. In these tests, the exchanger shows approximately 8.7 kW/m2 of thermal absorption and 7.6 kW/m2 of thermal transfer for a dry MHE while the wetted MHE had an energy throughput of 8.3 kW/m2. The temperature gradient maintained across the MHE bottom plate and lid is approximately 30 °C for both the dry and wetted MHE tests though overall temperatures were lower for the wetted MHE.

Comparative Assessment of Thermal Protective Characteristics of Metal and Ceramic Shields of Flow Paths of High-Temperature Gas Dynamic Facilities

2020 ◽  
pp. 52-75
Author(s):  
V.A. Tovstonog
Keyword(s):  
High Temperature ◽  
High Speed ◽  
Thermal Protection ◽  
Modern Technology ◽  
Flow Path ◽  
Comparative Assessment ◽  
Working Fluid ◽  
Gas Dynamic ◽  
Heat Shields ◽  
Ramjet Engines

In modern technology, gas dynamic facilities with a flow path of a high-temperature working fluid are widely used. Their effectiveness largely depends on the maximum achievable temperature, which is to a great extent determined by the heat resistance of structural materials and thermal protection systems of the most heat-stressed structural units. Most often, mass transfer thermal protection methods using the coolant of fuel components are used in such plants. However, in some gas dynamic facilities, such as high-speed ramjet engines, the use of such methods is only sufficient to maintain an acceptable temperature level for the elements of the flow path itself. As for the thermal protection of the enclosing structural elements which are adjacent to the path, it can be provided with either uncooled screens or heat-insulating linings. The study gives a comparative assessment of the temperature regime and characteristics of alternative types of heat shields

scholarly journals Dynamic Modelling, Experimental Identification and Computer Simulations of Non-Stationary Vibration in High-Speed Elevators

2021 ◽  
Vol 67 (6) ◽  
Author(s):  
Radomir Đokić ◽  
Jovan Vladić ◽  
Milan Kljajin ◽  
Vesna Jovanović ◽  
Goran Marković ◽  
...  
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Dynamic Behaviour ◽  
Dynamic Modelling ◽  
Control Program ◽  
Specific Method ◽  
Unique Method ◽  
Stationary Vibration ◽  
Vertical Vibrations ◽  
Stiffness And Damping

Modelling the dynamic behaviour of elevators with high lifting velocities (contemporary elevators in building construction and mine elevators) is a complex task and an important step in the design process and creating conditions for safe and reliable exploitation of these machines. Due to high heights and lifting velocities, the standard procedures for dynamic exploitation are not adequate. The study presents the method of forming a dynamic model to analyse nonstationary vibrations of a rope with time-varying length with nonholonomic boundary conditions in the position where the rope is connected with the cabin (cage) and in the upcoming point of its winding onto the pulley (drum). A unique method was applied to identify the basic parameters of the dynamic model (stiffness and damping) based on experimental measures for a concrete elevator. Due to the verification of this procedure, the experiment was conducted on a mine elevator in RTB Bor, Serbia. Using the obtained computer-experimental results, the simulations of the dynamic behaviour of an empty and loaded cage were shown. In addition, the study shows the specific method as the basis for forming a control program that would enable the decrease in vertical vibrations during an elevator starting and braking mode.

Experimental Investigation on a 3 kW Air Tesla Expander With High Speed Generator

2020 ◽  
Author(s):  
Avinash Renuke ◽  
Federico Reggio ◽  
Paolo Silvestri ◽  
Alberto Traverso ◽  
Matteo Pascenti
Keyword(s):  
High Speed ◽  
Experimental Tests ◽  
Working Fluid ◽  
Small Scale ◽  
Efficient Design ◽  
Electric Generator ◽  
Vibrational Response ◽  
Machine Maintenance ◽  
Performance Results

Abstract Tesla bladeless turbomachines are recently being investigated due to many advantages such as its simple design and ease of manufacturing. If an efficient design is achieved, this will be a promising machine in the area of small-scale power generation and energy harvesting. This paper focuses on the experimental performance investigation of 3 kW (rated power) Tesla bladeless expander. The Tesla expander and electric generator are housed in a single casing making it first of its kind being tested with such configuration. The expander is fed with air and operated at high rotational speeds up to 40000 rpm. The test is carried out with different number of nozzles to understand its effect on the performance. Results show that the peak efficiency for two nozzles is better than one nozzle and four nozzle configurations for the same inlet pressure conditions. Experimental tests revealed that this turbine is most efficient Tesla turbine till now with air as a working fluid. Furthermore, one of the most important losses in Tesla turbomachines, nozzle loss, is experimentally characterized. Specific vibrational tests were carried out to obtain complete machine dynamical characterization. The vibrational response characterization of the turbine enabled us to recognize a disk mode family solicited by the air flow and to perform a proper machine maintenance and balancing aiming to reduce the energy of its operational vibration.

Micro Gas Turbine Integrated With a Supercritical CO2 Brayton Cycle Turbine: Layout Comparison and Thermodynamic Analysis

2020 ◽  
Author(s):  
Fabrizio Reale ◽  
Raniero Sannino ◽  
Raffaele Tuccillo
Keyword(s):  
Gas Turbine ◽  
Supercritical Co2 ◽  
Waste Heat ◽  
Thermal Power ◽  
Energy Systems ◽  
Working Fluid ◽  
Small Scale ◽  
Brayton Cycle ◽  
Part Load ◽  
Micro Gas Turbine

Abstract In an energetic scenario where both distributed energy systems and smart energy grids gain increasing relevance, the research focus is also on the detection of new solutions to increase overall performance of small-scale energy systems. Waste heat recovery (WHR) can represent a good solution to achieve this goal, due to the possibility of converting residual thermal power in thermal engine exhausts into electrical power. The authors, in a recent study, described the opportunities related to the integration of a micro gas turbine (MGT) with a supercritical CO2 Brayton Cycle (sCO2 GT) turbine. The adoption of Supercritical Carbon Dioxide (sCO2) as working fluid in closed Brayton cycles is an old idea, already studied in the 1960s. Only in recent years this topic returned to be of interest for electric power generation (i.e. solar, nuclear, geothermal energy or coupled with traditional thermoelectric power plants as WHR). In this technical paper the authors analyzed the performance variations of different systems layout based on the integration of a topping MGT with a sCO2 GT as bottoming cycle; the performance maps for both topping and bottoming turbomachinery have been included in the thermodynamic model with the aim of investigating the part load working conditions. The MGT considered is a Turbec T100P and its behavior at part load conditions is also described. The potential and critical aspects related to the integration of the sCO2 GT as bottoming cycle are studied also through a comparison between different layouts, in order to establish the optimal compromise between overall efficiencies and complexity of the energy system. The off-design analysis of the integrated system is addressed to evaluate its response to variable electrical and thermal demands.

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