Investigations on Performance of Stirling Engine Regenerator Matrix

2011 ◽  
Author(s):  
D. J. Shendage ◽  
S. B. Kedare ◽  
S. L. Bapat
Keyword(s):  
Pressure Drop ◽  
Penetration Depth ◽  
High Efficiency ◽  
Stirling Engine ◽  
Operating Conditions ◽  
Dead Volume ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Wire Radius ◽  
Thermal Penetration Depth

Stirling engine technology has attracted attention due to recent environmental and energy problems. The regenerator is the main component in high efficiency Stirling engines. A suitable regenerator must be designed for each Stirling machine to provide high performance. The aim of the present work is to find a feasible number of screens in regenerator by taking into account the pressure drop, dead volume, the thermal penetration depth and geometry of regenerator. The second order cyclic analysis with realistic assumptions is carried out for a single cylinder, beta Stirling engine with rhombic drive for predecided operating conditions, such as pressure of 30 bar, hot side temperature of 750 K, speed of 1440 rpm and hydrogen as the working fluid. It is intended to design and develop the Stirling engine with capacity ≥ 1.5 kWe and the efficiency of drive mechanism and alternator is assumed as 85% each. Miyabe’s and Martini’s approaches are used to simulate regenerator performance considering non-sinusoidal motion of displacer and piston. The results reveal that the flow loss increases remarkably to attain higher value of regenerator effectiveness. However, increase in the speed results into an increase in the mass flow rate of the working fluid. It is observed that regenerator effectiveness decreases only marginally over the range of speeds considered. It is also ensured for selected regenerator screen that the thermal penetration depth (239 μm) should be greater than wire radius of mesh (20.5 μm). For present set of operating and geometrical parameters, length of regenerator is fixed as 22 mm which gives regenerator effectiveness as 0.965. Further, the practice to fill more screens than the designed number of screens in the regenerator, while assembling is not advantageous. It increases pressure drop which results in reduced power output. These are some of the important conclusions.

Single-Phase Heat Transfer and Pressure Drop of Water Cooled Inside Horizontal Smooth Tubes in the Transitional Flow Regime

2010 ◽  
Author(s):  
Josua P. Meyer ◽  
Leon Liebenberg ◽  
Jonathan A. Olivier
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Transition Region ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Transitional Flow ◽  
Working Fluid ◽  
Tube Heat Exchanger ◽  
Smooth Tubes

Heat exchangers are usually designed in such a way that they do not operate in the transition region. This is usually due to a lack of information in this region. However, due to design constraints, energy efficiency requirements or change of operating conditions, heat exchangers are often forced to operate in this region. It is also well known that entrance disturbances influence where transition occurs. The purpose of this paper is to present experimental heat transfer and pressure drop data in the transition region for fully developed and developing flows inside smooth tubes using water as the working fluid. The use of different inlet disturbances were used to investigate its effect on transition. A tube-in-tube heat exchanger was used to perform the experiments, which ranged in Reynolds numbers from 1 000 to 20 000, with Prandtl numbers being between 4 and 6 while Grashof numbers were in the order of 105. Results showed that the type of inlet disturbance could delay transition to a Reynolds number as high as 7 000, while other inlets expedited it, confirming results of others. For heat transfer, though, it was found that transition was independent of the inlet disturbance and all commenced at the same Reynolds number, 2 000–3 000, which was attributed to secondary flow effects.

scholarly journals Experimental Investigation of Embedded Micropin-Fins for Single-Phase Heat Transfer and Pressure Drop

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Chirag R. Kharangate ◽  
Ki Wook Jung ◽  
Sangwoo Jung ◽  
Daeyoung Kong ◽  
Joseph Schaadt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Friction Factor ◽  
Integrated Circuit ◽  
Single Phase ◽  
Absolute Error ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pin Fin

Three-dimensional (3D) stacked integrated circuit (IC) chips offer significant performance improvement, but offer important challenges for thermal management including, for the case of microfluidic cooling, constraints on channel dimensions, and pressure drop. Here, we investigate heat transfer and pressure drop characteristics of a microfluidic cooling device with staggered pin-fin array arrangement with dimensions as follows: diameter D = 46.5 μm; spacing, S ∼ 100 μm; and height, H ∼ 110 μm. Deionized single-phase water with mass flow rates of m˙ = 15.1–64.1 g/min was used as the working fluid, corresponding to values of Re (based on pin fin diameter) from 23 to 135, where heat fluxes up to 141 W/cm2 are removed. The measurements yield local Nusselt numbers that vary little along the heated channel length and values for both the Nu and the friction factor do not agree well with most data for pin fin geometries in the literature. Two new correlations for the average Nusselt number (∼Re1.04) and Fanning friction factor (∼Re−0.52) are proposed that capture the heat transfer and pressure drop behavior for the geometric and operating conditions tested in this study with mean absolute error (MAE) of 4.9% and 1.7%, respectively. The work shows that a more comprehensive investigation is required on thermofluidic characterization of pin fin arrays with channel heights Hf < 150 μm and fin spacing S = 50–500 μm, respectively, with the Reynolds number, Re < 300.

scholarly journals Problems of sodium using in pulsating heat pipe made from fused silica

2018 ◽  
Vol 207 ◽  
pp. 04004
Author(s):  
Radovan Nosek ◽  
Tatiana Liptáková ◽  
Libor Trško ◽  
Zuzana Kolková ◽  
Milan Malcho ◽  
...  
Keyword(s):  
High Temperature ◽  
Heat Pipe ◽  
Alkali Metals ◽  
High Efficiency ◽  
Fused Silica ◽  
Operating Conditions ◽  
Liquid Sodium ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
High Temperature Reaction

You Heat pipe is a high efficiency heat transfer element, depends on the evaporation, condensation and circulation of inside working fluid. The working fluid of a high temperature pulsating heat pipe is generally alkali metals, and sodium heat pipe can operate in range of 500-1100°C. In order to investigate terminal velocity of working fluid, the glass pulsating heat pipe was produced for experimental purposes. The experiment was carried out, in order to simulate real operating conditions in range of 500-1100°C. Sudden boiling of liquid sodium (b.p. = 883°C at 1 atm) inside the all quartz-made heat pipe results in high-temperature reaction of sodium vapour with the inner wall surface. The reaction became more aggressive with increasing vapour temperature and resulted in heat pipe explosion. The evaluation of damage character is analysed in this paper.

Parametric Analysis of the Thermal Components of an Alpha-Stirling Engine for Cogeneration Applications

2017 ◽  
Author(s):  
Ana C. Ferreira ◽  
Senhorinha F. C. F. Teixeira ◽  
José C. Teixeira ◽  
Luís A. Barreiros Martins
Keyword(s):  
Heat Exchanger ◽  
Parametric Analysis ◽  
Thermodynamic Cycle ◽  
Power Production ◽  
Stirling Engine ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Energy Needs ◽  
Temperature Heat ◽  
In Series

Stirling engines efficiency, the increased maintenance interval periods, the variety of energy sources and the relatively low gas emissions makes Stirling technology an interesting choice as prime mover for cogeneration applications. These are some of the reasons that justify the attention received from researchers in the last years, focused in its modelling, optimization and its application in the suppression of buildings energy needs. In this study, an alpha-Stirling engine was numerically modelled. At this configuration, the working fluid flows between expansion and compression spaces by alternate crossing of, a high temperature heat exchanger (heater), a regenerator and a low temperature heat exchanger (cooler). Thus, the engine is considered as a set of five components connected in series. MatLab® environment was used to implement a software-code to model the thermodynamic cycle of the Stirling engine. The modular code allows investigating the influence of different geometrical and thermal parameters of all the engine components that affects its power production and the efficiency, the effectiveness of heat exchangers and the design itself of the power plant. This parametric analysis helps finding some restriction values for geometrical parameters that cannot be solved through the optimization procedures. For instance, at some point, there is a geometrical limit for which the increase in heat transfer is overlapped by the void volume or pumping losses increase. The parametric analysis led to an enhanced configuration of the numerical model, which resulted in the increase of engine thermal efficiency (about 13.4%), with a power production close to 5 kW.

Techno-Economic Evaluation of the Effect of Impurities on the Performance of Supercritical CO2 Cycles

2019 ◽  
Author(s):  
Ladislav Vesely ◽  
Vaclav Dostal ◽  
Jayanta Kapat ◽  
Subith Vasu ◽  
Scott Martin
Keyword(s):  
Economic Evaluation ◽  
Heat Exchanger ◽  
High Efficiency ◽  
Operating Conditions ◽  
Rate Of Return ◽  
Working Fluid ◽  
Levelized Cost Of Electricity ◽  
Tube Heat Exchanger ◽  
Power Cycle ◽  
Effect Of Impurities

Abstract The development of new power generation technologies are necessary to meet growing energy demands and emission requirements. The supercritical carbon dioxide (S-CO2) cycle is one such technology; it has relatively high efficiency, potential to enable 100% carbon capture, and compact components. The S-CO2 cycle is adaptable to almost all of the existing power producing methods including fossil, solar, and nuclear technologies. However, it is known that the best combination of the operating conditions, equipment, working fluid and cycle layout determine the maximum achievable efficiency of a cycle. Impurities in the cycle have some effect on the S-CO2 power cycle as presented in our previous work. The effect of impurities is positive or negative and affects all components. The effect of mixture compositions on the techno-economic evaluation is important information for the global understanding of the effect of mixtures on the S-CO2 power cycle. This paper focuses on the techno-economic evaluation of a hypothetical power plant with the S-CO2 power cycle. Two cases are considered for techno-economic evaluation. The difference between these cases is in the heat source and the associated heat exchanger (PCHE and shell and tube heat exchanger). Cost estimation was performed for three indicators (the levelized cost of electricity, the internal rate of return, and the net present value), which are important for economic viability and the rate of return of the project.

CFD Simulation of an Alfa-Stirling Engine to Study the Geometrical Parameters on the Engine Performance

2019 ◽  
Author(s):  
Ana C. Ferreira ◽  
Senhorinha F. C. F. Teixeira ◽  
Ricardo F. Oliveira ◽  
José C. Teixeira
Keyword(s):  
Heat Exchanger ◽  
Power Output ◽  
Cfd Simulation ◽  
Engine Performance ◽  
Stirling Engine ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Cold Temperatures ◽  
Temperature Heat

Abstract An alpha-Stirling configuration was modelled using a Computational Fluid Dynamic (CFD), using ANSYS® software. A Stirling engine is an externally heated engine which has the advantage of working with several heat sources with high efficiencies. The working gas flows between compression and expansion spaces by alternate crossing of, a low-temperature heat exchanger (cooler), a regenerator and a high-temperature heat exchanger (heater). Two pistons positioned at a phase angle of 90 degrees were designed and the heater and cooler were placed on the top of the pistons. The motion of the boundary conditions with displacement was defined through a User Defined Function (UDF) routine, providing the motion for the expansion and compression piston, respectively. In order to define the temperature differential between the engine hot and the cold sources, the walls of the heater and cooler were defined as constant temperatures, whereas the remaining are adiabatic. The objective is to study the thermal behavior of the working fluid considering the piston motion between the hot and cold sources and investigate the effect of operating conditions on engine performance. The influence of regenerator matrix porosity, hot and cold temperatures on the engine performance was investigated through predicting the PV diagram of the engine. The CFD simulation of the thermal engine’s performance provided a Stirling engine with 760W of power output. It was verified that the Stirling engine can be optimized when the best design parameters combination are applied, mostly the regenerator porosity and cylinders volume, which variation directly affect the power output.

Computational Modeling for a Microchannel Electronics Cooler

2007 ◽  
Author(s):  
Joseph Dix ◽  
Amir Jokar ◽  
Robert Martinsen
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Single Phase ◽  
Operating Conditions ◽  
Coolant Fluid ◽  
Working Fluid ◽  
Flow Parameters ◽  
Flow And Heat Transfer ◽  
Through Flow ◽  
Phase Fluid

The objective of this study is to analyze the single-phase fluid flow and heat transfer through a microchannel electronics cooler with a hydraulic diameter of about 300 microns. For this purpose, commercial computational fluid dynamics software was used to first characterize the existing design that uses purified water as coolant fluid. The flow parameters of the cooler were then adjusted in order to optimize the design. Geometry modifications were used next to enhance heat transfer, and to reduce pressure drop and erosion from possible impurities in the working fluid. Different working fluids were also considered to investigate possible reductions in corrosion and further increases in heat transfer. Alternative combinations of boundary and operating conditions were explored during optimization. The results of this study showed the microchannel cooler had capacity in rejecting more thermal energy with less pressure drop through flow optimization and geometry modification.

Design and Evaluation of a MEMS-Based Stirling Microcooler

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Dongzhi Guo ◽  
Jinsheng Gao ◽  
Alan J. H. McGaughey ◽  
Gary K. Fedder ◽  
Matthew Moran ◽  
...  
Keyword(s):  
Volume Ratio ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Dead Volume ◽  
Working Fluid ◽  
Cooling Power ◽  
Phase Lag ◽  
Power Losses ◽  
Cold Side ◽  
Swept Volume

A new Stirling microrefrigeration system composed of arrays of silicon MEMS cooling elements has been designed and evaluated. The cooling elements are to be fabricated in a stacked array on a silicon wafer. A regenerator is placed between the compression (hot side) and expansion (cold side) diaphragms, which are driven electrostatically. Air at a pressure of 2 bar is the working fluid and is sealed in the system. Under operating conditions, the hot and cold diaphragms oscillate sinusoidally and out of phase such that heat is extracted to the expansion space and released from the compression space. Parametric study of the design shows the effects of phase lag between the hot space and cold space, swept volume ratio between the hot space and cold space, and dead volume ratio on the cooling power. Losses due to regenerator nonidealities are estimated and the effects of the operating frequency and the regenerator porosity on the cooler performance are explored. The optimal porosity for the best system coefficient of performance (COP) is identified.

scholarly journals A Simulation Study on Temperature Uniformity of Photovoltaic Thermal Using Computational Fluid Dynamics

2021 ◽  
Vol 82 (1) ◽  
pp. 21-38
Author(s):  
Mohd Afzanizam Mohd Rosli ◽  
Irfan Alias Farhan Latif ◽  
Muhammad Zaid Nawam ◽  
Mohd Noor Asril Saadun ◽  
Hasila Jarimi ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Temperature Distribution ◽  
Thermal Stresses ◽  
High Efficiency ◽  
Cfd Simulation ◽  
Operating Conditions ◽  
Working Fluid ◽  
Percentage Error ◽  
Pv Module

The temperature distribution across the photovoltaic (PV) module in most cases is not uniform, leading to regions of hotspots. The cells in these regions perform less efficiently, leading to an overall lower PV module efficiency. They can also be permanently damaged due to high thermal stresses. To enable the high-efficiency operation and a longer lifetime of the PV module, the temperatures must not fluctuate wildly across the PV module. In this study, a custom absorber is designed based on literature to provide a more even temperature distribution across the PV module. This design is two standard sets of spiral absorbers connected. This design is relatively less complicated for this reason and it allows room for adjusting the pipe spacing without much complication. The absorber design is tested via computational fluid dynamics (CFD) simulation using ANSYS Fluent 19.2, and the simulation model is validated by an experimental study with the highest percentage error of 9.44%. The custom and the serpentine absorber utilized in the experiment are simulated under the same operating conditions having water as the working fluid. The custom absorber design is found to have a more uniform temperature distribution on more areas of the PV module as compared to the absorber design utilized in the experiment, which leads to a lower average surface temperature of the PV module. This results in an increase in thermal and electrical efficiency of the PV module by 3.21% and 0.65%, respectively.

scholarly journals Analysis of a second order thermodynamic model for the performance analysis of a Stirling engine prototype

2018 ◽  
Author(s):  
Miguel Torres García ◽  
Elisa Carvajal Trujillo ◽  
José Antonio Vélez Godiño ◽  
David Sánchez Martínez
Keyword(s):  
High Efficiency ◽  
Combustion Engine ◽  
Numerical Models ◽  
Operational Reliability ◽  
Stirling Engine ◽  
Working Fluid ◽  
Simple Type ◽  
Engine Model ◽  
External Combustion ◽  
External Combustion Engine

The Stirling engine is a simple type of external-combustion engine with an external combustion engine based on cyclic compression and expansion of gas at different temperature levels. It has high efficiency; low vibration levels, simple structure and can run on any combustible fuels. It has been the object of numerous studies. This paper presents an analysis of a Stirling engine model GENOA 03 for electric power generation, of 3 KW of nominal power with pressurized air as working fluid, currently under development. To improve its performance and ensure a good operational reliability, it is necessary to carry out a modelling of the engine in all its operating range. This requires complex numerical models that simulate the behaviour of any element of the engine in a cycle. Two typologies of thermodynamic models are developed in this work: isothermal and adiabatic. The main benefits and shortcomings of each model are mentioned. The geometry and conditions of the engine have been adapted through the Matlab ® tool, in order to obtain the operative conditions of the cooler that you want to replace, as well as an approximation to the expected behaviour.

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