Thermal-Economic Modeling of a Micro-CHP Unit Based on a Stirling Engine

2013 ◽  
Author(s):  
Ana C. Ferreira ◽  
Senhorinha Teixeira ◽  
Christophe Ferreira ◽  
José Teixeira ◽  
Manuel L. Nunes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Power Plants ◽  
High Efficiency ◽  
Numerical Study ◽  
Mathematical Formulation ◽  
Economic Modeling ◽  
Stirling Engine ◽  
Thermodynamic Efficiency ◽  
Plant Component ◽  
Partial Load

The last decade has witnessed a growing interest in the use of Stirling engine cogeneration systems for residential applications, due to their prospect for high efficiency, good performance at partial load, fuel flexibility, including the possible use of renewables, low emissions, vibration and noise levels. Stirling engines have sealed operating chambers, low wear and, as a consequence, low operating costs. In the European building sector, micro-cogeneration power plants are being designed to fulfill the heating requirements of the building and, additionally, generate electricity for internal consumption or for feeding into the local grid. Thermal-economic evaluation represents an effective tool to optimize a power plant with this type of technology. The mathematical formulation includes a set of equations able to describe and simulate the physical system, as well as a set of equations that define the cost of each plant component. This paper presents a numerical study faithfully simulating the real conditions of a micro-CHP unit based on an alpha type Stirling Engine. The simulations were performed through a MatLab® code that assesses the thermodynamic efficiency, including heat transfer limitations and pumping losses throughout the system. Results showed that heat-transfer limitations strongly affect cycle efficiency, particularly in the regenerator case. The pumping losses are less important when hydrogen or helium are used.

scholarly journals Heat Transfer and Fluid Dynamics Measurements in the Expansion Space of a Stirling Cycle Engine

2006 ◽  
Author(s):  
Nan Jiang ◽  
Terrence W. Simon
Keyword(s):  
Heat Transfer ◽  
High Efficiency ◽  
Stirling Engine ◽  
Transfer Coefficients ◽  
Head Region ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Engine Design ◽  
Region Flow ◽  
Design Calculations

The heater (or acceptor) of a Stirling engine, where most of the thermal energy is accepted into the engine by heat transfer, is the hottest part of the engine. Almost as hot is the adjacent expansion space of the engine. In the expansion space, the flow is oscillatory, impinging on a two-dimensional concavely-curved surface. Knowing the heat transfer on the inside surface of the engine head is critical to the engine design for efficiency and reliability. However, the flow in this region is not well understood and support is required to develop the CFD codes needed to design modern Stirling engines of high efficiency and power output. The present project is to experimentally investigate the flow and heat transfer in the heater head region. Flow fields and heat transfer coefficients are measured to characterize the oscillatory flow as well as to supply experimental validation for the CFD Stirling engine design codes. Presented also is a discussion of how these results might be used for heater head and acceptor region design calculations.

Through Flow Calculations for Convective Cooling Turbines

2014 ◽  
Author(s):  
Li Haibo ◽  
Chunwei Gu
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Calculation Method ◽  
Conjugate Heat Transfer ◽  
High Efficiency ◽  
Thermodynamic Efficiency ◽  
Inlet Temperature ◽  
Flow Calculation ◽  
Through Flow ◽  
The Impact

Conjugate heat transfer is a key feature of modern gas turbine, as cooling technology is widely applied to improve the turbine inlet temperature for high efficiency. Impact of conjugate heat transfer on heat loads and thermodynamic efficiency is a key issue in gas turbine design. This paper presented a through flow calculation method to predict the impact of heat transfer on the design process of a convective cooled turbine. A cooling model was applied in the through flow calculations to predict the coolant requirements, as well as a one-dimensional mixing model to evaluate some key parameters such as pressure losses, deviation angles and velocity triangles because of the injection cooling air. Numerical simulations were performed for verification of the method and investigation on conjugate heat transfer within the blades. By comparing these two calculations, it is shown that the through flow calculation method is a useful tool for the blade design of convective cooled turbines because of its simplicity and flexibility.

scholarly journals Research of functionality of using a storage tank for regulating heating load of a gas piston mini-CHPP

Vestnik IGEU ◽  
2021 ◽  
pp. 21-30
Author(s):  
N.V. Kolesnichenko ◽  
S.M. Safiants ◽  
A.B. Biryukov ◽  
O.V. Litvinov
Keyword(s):  
Heat Transfer ◽  
Storage Tank ◽  
High Efficiency ◽  
Numerical Study ◽  
District Heating ◽  
Heating System ◽  
Hot Water ◽  
Water Supply Systems ◽  
Heating Load ◽  
Supply Systems

The use of a storage tank to regulate the loads of the mini-CHP plant improves the technical and economic indicators of its operation. However, the results of studies of the use of a storage tank in heating systems, in contrast to hot water supply systems, are poorly represented. The purpose of the study is to determine the conditions and indicators under which the use of a storage tank to regulate the heating load of a mini-CHPP is economically viable. The study of the heat grid is based on solving the standard heat balance and heat transfer equations. Modeling of heat transfer in the heat recovery circuit of a cogeneration unit is carried out by approximating the passport specification of the equipment in the range of operating loads from 50 to 100 %. Modeling the standing time of the outside air temperatures is carried out in accordance with the method of B. Shifrinson and V.Ya. Khasilev. The conditions of the numerical study are quite typical for the heating network of Donetsk. For the first time, to satisfy the conditions of a numerical study, the dependence of the available and used thermal capacity of the storage tank on the outside air temperature has been established for different values of the design volume of the tank. The quantitative characteristics of the influence of the design volume of the storage tank on electricity generation during peak, half-peak and minimum power system loads are investigated. The reliability of the results obtained is determined by the correct use of proven methods for calculating the operation parameters of water heating system and heat devices. The study shows that the use of a storage tank to regulate the heating load of a mini-CHPP is technically and economically feasible. With the design volume of the storage tank in the range of 65–126 m3 per 1 MW of the connected heating load, the simple payback period of the mini-CHPP varies insignificantly and can be considered acceptable. The presence of a storage tank allows realizing the maneuverable capabilities of cogeneration units, while maintaining a high share of energy generation in combined mode. The district heating coefficient, equal to one, allows achieving high efficiency of fuel utilization for generation of both electrical and thermal energy. The research results can be used in municipal heat supply systems when introducing gas piston cogeneration units.

Development of a Thermal-Hydraulic Analysis Code for Helical Coiled Once Through Steam Generator

2018 ◽  
Author(s):  
Jun Huang ◽  
Junli Gou ◽  
Haifu Ma ◽  
Jie Fan ◽  
Jianqiang Shan
Keyword(s):  
Heat Transfer ◽  
Steam Generator ◽  
Nuclear Power ◽  
Power Plants ◽  
High Efficiency ◽  
Fluid Model ◽  
Computer Code ◽  
Medium Size ◽  
Hydraulic Characteristics ◽  
Pressurized Water

Due to their advantages, such as compactness and high efficiency in heat transfer, helically coiled heat exchangers have been widely used by different type of nuclear power plants, especially by small and medium size reactors (SMRs). In order to analyze the thermal-hydraulic characteristics of a helical coiled once through steam generator (OTSG) for a small integral pressurized water reactor, a computer code is developed in this paper. The code is based on two-fluid model. The constitutive correlations are recommended based on the assessments with the compiled databases from the reviewed literatures. NUSOL SG is validated and verified against heat transfer in helical coiled tubes, and the calculation results agree well with the experiment data. The present study could provide references for the investigators to perform further investigations on the thermal hydraulic characteristics of helical coiled OTSGs.

Development of a Heat Transfer Correlation for Supercritical CO2 Based on Multiple Data Sets

2012 ◽  
Author(s):  
Tiberiu Preda ◽  
Eugene Saltanov ◽  
Igor Pioro ◽  
Kamiel S. Gabriel
Keyword(s):  
Heat Transfer ◽  
Critical Point ◽  
Supercritical Water ◽  
Wall Temperature ◽  
Supercritical Co2 ◽  
Power Plants ◽  
Operating Conditions ◽  
Thermodynamic Efficiency ◽  
New Correlation ◽  
Multiple Data Sets

Currently, increase in thermodynamic efficiency of water-cooled Nuclear Power Plants (NPPs) can only be achieved by raising the coolant’s operating conditions above the supercritical point. The critical point of water is 22.06 MPa and 373.95°C, making supercritical water research very power-intensive and expensive. CO2 behaves in a similar manner once in the supercritical state, but at significantly lower pressure and temperature, since critical point of CO2 is 7.37 MPa and 30.98°C. The applications of supercritical CO2 research range from using it as a modelling fluid, to supercritical turbine applications in Liquid Metal Fast Breeder Reactors (LMFBRs), and use in a supercritical Brayton cycle. Therefore, it is of prime importance to model its behaviour as accurately as possible. For this purpose, experimental data of Koppel (1960), He (2005), Kim (2005) and Bae (2007) for CO2 were analyzed, and a new correlation was developed. The dataset consists of 1409 wall temperature points with pressures ranging from 7.58 to 9.58 MPa, mass fluxes from 419 to 1200 kg/m2s, and heat fluxes from 20 to 130 kW/m2. All runs take place in bare tubes of inner diameters from 0.948 to 9.00 mm in both vertical and horizontal configurations. The proposed correlation takes a wall-temperature approach to predicting the Nusselt number. This paper compares the new correlation with other work which has been done at the University of Ontario Institute of Technology by Mokry et al. (2009), as well as with correlations by Swenson et al. (1965) and Dittus-Boelter (1930). It was found that the new correlation has an overall RMS error of 13% for Heat Transfer Coefficient (HTC) values and 5% for calculated wall temperature values. The correlation can be used as a conservative approach to predict wall temperature values in Supercritical Water Reactor (SCWR) preliminary calculations, to predict heat transfer in secondary-loop turbine/ heat exchanger applications, as with the LMFBR, and to help validate scaling parameters used for water and other coolants.

scholarly journals Numerical Study of the Effect of Magnetic Field on Nanofluid Heat Transfer in Metal Foam Environment

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Hamid Shafiee ◽  
Elaheh NikzadehAbbasi ◽  
Majid Soltani
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Porous Medium ◽  
Porous Media ◽  
Fluid Flow ◽  
Volume Fraction ◽  
Numerical Study ◽  
Computational Simulation ◽  
Thermodynamic Efficiency ◽  
Two Phase

The magnetic field can act as a suitable control parameter for heat transfer and fluid flow. It can also be used to maximize thermodynamic efficiency in a variety of fields. Nanofluids and porous media are common methods to increase heat transfer. In addition to improving heat transfer, porous media can increase pressure drop. This research is a computational simulation of the impacts of a magnetic field induced into a cylinder in a porous medium for a volume fraction of 0.2 water/Al2O3 nanofluid with a diameter of 10 μm inside the cylinder. For a wide variety of controlling parameters, simulations have been made. The fluid flow in the porous medium is explained using the Darcy-Brinkman-Forchheimer equation, and the nanofluid flow is represented utilizing a two-phase mixed approach as a two-phase flow. In addition, simulations were run in a slow flow state using the finite volume method. The mean Nusselt number and performance evaluation criteria (PEC) were studied for different Darcy and Hartmann numbers. The results show that the amount of heat transfer coefficient increases with increasing the number of Hartmann and Darcy. In addition, the composition of the nanofluid in the base fluid enhanced the PEC in all instances. Furthermore, the PEC has gained its highest value at the conditions relating to the permeable porous medium.

scholarly journals CONJUGATE MIXED CONVECTION IN AIR-COOLED HEAT SINKS USING A NON-BOUSSINESQ APPROACH

2003 ◽  
Vol 2 (1) ◽  
Author(s):  
C. R. DeAndrade ◽  
A. V. Pantaleão ◽  
E. L. Zaparoli
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Numerical Study ◽  
Mathematical Formulation ◽  
Boussinesq Approximation ◽  
Density Variation ◽  
Heat Sinks ◽  
Thermal Conductivity Ratio ◽  
Analysis Tool ◽  
Duct Flow

This work reports a numerical study of the mixed convection in finned duct flow that occurs in heat sinks devices. The laminar flow is considered fully developed and the convection-conduction coupling is treated by a conjugated approach. The mathematical formulation of this problem is constituted by the mass, momentum and energy equations. The partial differential equations system is solved by the Galerkin finite element method, adopting a pressure Poisson equation to establish the pressure-velocity coupling and to obtain a mass conserving flow. The results using the classical Boussinesq approximation (density varies linearly with the temperature in the buoyancy-term) are compared with the non-Boussinesq approach (density variation in all terms of the governing equations) showing that both the heat transfer and friction factor are affected by the new considerations. The duct aspect ratio and the solid to fluid thermal conductivity ratio influences on the heat transfer rate are also analyzed. This analysis tool was also shown appropriate for the optimization of electronic components air-cooled heat sinks.

Comparison Between MCFC/Gas Turbine and MCFC/Steam Turbine Combined Power Plants

2003 ◽  
Author(s):  
Roberto Bove ◽  
Piero Lunghi
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
High Efficiency ◽  
Electric Energy ◽  
Thermodynamic Efficiency ◽  
Molten Carbonate ◽  
Advantages And Disadvantages

Worldwide, the main power source to produce electric energy is represented by fossil fuels, principally used at the present time in large combustion power plants. The main environmental impacts of fossil fuel-fired power plants are the use of non-renewable resources and pollutants emissions. An improvement in electric efficiency would yield a reduction in emissions and resources depletion. In fact, if efficiency is raised, in order to produce an amount unit of electric energy, less fuel is required and consequently less pollutants are released. Moreover, higher efficiency leads to economic savings in operating costs. A generally accepted way of improving efficiency is to combine power plants’ cycles. If one of the combined plants is represented by a fuel cell, both thermodynamic efficiency and emissions level are improved. Fuel cells, in fact, are ultra-clean high efficiency energy conversion devices because no combustion occurs in energy production, but only electrochemical reactions and consequently no NOx and CO are produced inside the cell. Moreover, the final product of the reaction is water that can be released into the atmosphere without particular problems. Second generation fuel cells (Solid Oxide FC and Molten Carbonate FC) are particularly suitable for combining cycles, due to their high operating temperature. In previous works, the authors had analyzed the possibility of combining Molten Carbonate Fuel Cell (MCFC) plant with a Gas Turbine and then a MCFC with a Steam Turbine Plant. Results obtained show that both these configurations allow to obtain high conversion efficiencies and reduced emissions. In the present work, a comparison between MCFC-Gas Turbine and MCFC-Steam Turbine is conducted in order to evaluate the main advantages and disadvantages in adopting one solution instead of the other one.

Off-Design Performance of Multipressure Heat Recovery Boilers

1995 ◽  
Author(s):  
Nicola Bettagli ◽  
Bruno Facchini
Keyword(s):  
Heat Recovery ◽  
Power Plants ◽  
High Efficiency ◽  
Combined Cycle ◽  
Thermodynamic Efficiency ◽  
Heat Recovery Steam Generator ◽  
Gas Temperature ◽  
Recovery Boilers ◽  
Very High ◽  
Plant Behaviour

Combined cycle power plants are systems with very high thermodynamic efficiency. Off-design plant behaviour prediction is very important to allow for high efficiency regulation of systems. The aim of this paper is to study heat recovery steam generator (HRSG) performance, varying inlet gas temperature and mass flow rate. One, two and three pressure level heat recovery boilers are considered. A HRSG simulation program based on heat transfer and thermodynamic fundamental laws is carried out.

scholarly journals Use of Stirling Engine for Waste Heat Recovery

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4133
Author(s):  
Peter Durcansky ◽  
Radovan Nosek ◽  
Jozef Jandacka
Keyword(s):  
Solar Energy ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Power Plants ◽  
High Efficiency ◽  
Waste Heat ◽  
Stirling Engine ◽  
Modeling Techniques ◽  
Theoretical Predictions ◽  
Solar Power Plants

Even though this discovery dates back to 1816, the greatest advancement in technology and understanding of Stirling-cycle devices has occurred in the last 50 years. Although their mass production is currently limited to special-purpose machines, its prospective use is in combination with renewable sources and indicates a potential for commercial purposes. The lack of commercial success, despite obvious advantages, is probably due to a lack of appropriate modeling techniques and theoretical predictions of what these devices can achieve. Nowadays the Stirling engine has found its use mainly in solar power plants, where it represents the only piston engine converting solar energy into mechanical and then electricity with relatively high efficiency. The Stirling engine also appears to be suitable for recovering waste heat, especially in heavy industry. The numerical model was adapted for the existing Cleanergy Stirling engine, to evaluate the possibilities of this one engine for waste heat recovery. This paper also deals with application options and individual parameters that affect the efficiency of this Stirling engine for waste heat recovery. The analysis showed that this kind of engine is capable of recovering and utilizing heat above 300 °C, which determines its possible use with solar energy.

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