SwePub - search: L773:1359 4311

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1.	Bengtsson, Cecilia, 1974, et al. (author) Co-ordination of pinch technology and the MIND method : applied to a Swedish board mill 2002 In: Applied Thermal Engineering. - 1359-4311 .- 1873-5606. ; 22:2, s. 133-144 Journal article (peer-reviewed)abstract By combining the pinch technology and the MIND method, it is possible to identify beneficial and energy-efficient measures in a complex industrial energy system. By tackling a problem on the two different aggregation levels, the result is thoroughly evaluated and durable measures are achieved. The strength of the combination of methods is elucidated in a case study where a Scandinavian pulp and paper mill is analysed. The studied problem concerns pre-evaporation of effluents in a board mill using excess heat. Different alternatives are evaluated, taking into account economic, technical and practicable constraints. The results show that it is cost-effective to pre-evaporate the effluent using excess heat in the studied mill.
2.	Bengtsson, Cecilia, 1974, et al. (author) Utilization of excess heat in the pulp and paper industry - a case study of technical and economic opportunities 2002 In: Applied Thermal Engineering. - 1359-4311. ; 22:9, s. 1069-1081 Journal article (peer-reviewed)abstract Newly developed methods and tools based on pinch technology are used in a case study to investigate the potential and economy of using excess heat for pre-evaporation of chemo thermo mechanical pulp effluent and heat pumping in an integrated pulp and paper mill. The new tools give information about the system that traditional pinch tools such as the grand composite curve or the composite curves would not reveal. For example, the highest temperature levels possible where excess heat can be released are identified together with the amount of excess heat at each temperature level. The new curves are also able to provide information about where heaters and coolers are placed in an existing system. The matrix method has been used successfully in order to find an economically feasible heat exchanger network retrofit for the release of the excess heat found with the curves.The results of the case study show that a pre-evaporation plant can be integrated with the overall process with just a few modifications in the existing process. There are also opportunities for heat pumping in the system. Both projects have a pay-back period shorter than required for implementation.
3.	Feng, Xiao, et al. (author) Critical COP for an economically feasible industrial heat-pump application 1997 In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 17:1/January 1997, s. 93-101 Journal article (peer-reviewed)abstract In this paper, the expression for critical COP is derived for an economically feasible industrial heat-pump application. It is a function of the price ratio between input energy and heating, the price ratio between equipment and energy, and the payback period. Using this critical COP, a preliminary assessment can be made of whether an industrial heat-pump application is worth discussing further. The influences of various economic factors on the critical COP for different types of heat pumps are also discussed.
4.	Harvey, Simon, 1965, et al. (author) Predicting black liquor gasification combined cycle powerhouse performance accounting for off-design gas turbine operation 2004 In: Applied Thermal Engineering. - 1359-4311. ; 24:1, s. 111-126 Journal article (peer-reviewed)abstract Estimating potential electric power generation in the pulping industry by implementing black liquor gasification combined cycle (BLGCC) technology is an important issue, given the anticipated future demand for "green" electricity. Full-scale BLGCC technology has not yet been commercially demonstrated. Therefore, performance studies of this technology require the use of computer simulation tools, with the pertaining challenge of simulating gas turbine operation on gasified black liquor fuel. Exact future plant size is usually unknown; therefore many studies adopt a simplified model assuming an engine sized to match the available fuel stream, with generic characteristics representative of a given class of engine. The performance of a fixed size engine operating at off-design conditions on low calorific value fuel is in most cases lower. This work attempts to quantify the resulting difference between performance estimates based on these two assumptions. The calculations are performed for a BLGCC powerhouse integrated with the Swedish KAM reference pulp mill, for which the biofuel (bark and black liquor) available on-site is more than sufficient to satisfy the mill steam demand. The surplus can therefore be used for additional power generation, which however implies the use of low efficiency condensing steam turbine units. Alternatively, surplus biofuel can be exported for use elsewhere. This study investigates both of these options.
5.	Wang, Lieke, et al. (author) Optimal design of plate heat exchangers with and without pressure drop specifications 2003 In: Applied Thermal Engineering. - 1359-4311. ; 23:3, s. 295-311 Journal article (peer-reviewed)abstract The traditional design method for plate heat exchangers(PHEs), either epsilon-number of transfer units (epsilon-NTU) or logarithmic mean temperature difference method, involves many trials in order to meet the pressure drop constraints. This can be avoided through the developed design method, which takes the full utilization of the allowable pressure drops as a design objective. The proposed method is valid for the design situations with and without pressure drop specifications. In the case of the design with pressure drop specification, only one stream can fully utilize the allowable pressure drop. In the case of no pressure drop specification, allowable pressure drops can be determined through economical optimization. Compared to the previous design method, the proposed method does not require many trial iterations. Instead, all heat exchanger parameters, including plate size, number of passes, path, fluid velocity, etc., are determined in a straightforward way. Moreover, the suggested method can guarantee that the optimized values of allowable pressure drops can be fully utilized simultaneously by the two streams. In addition, the optimal corrugation angle is discussed for the most common chevron-type PHEs. (C) 2002 Elsevier Science Ltd. All rights reserved.
6.	Wang, Lieke, et al. (author) Response to Dr. Polley's comments on the paper 'Optimal design of plate heat exchangers with and without pressure drop specification' by L. Wang and B. Sunden 2003 In: Applied Thermal Engineering. - 1359-4311. ; 23:16, s. 2149-2150 Journal article (other academic/artistic)
7.	Gebremedhin, Alemayehu, 1962- (author) The role of a paper mill in a merged district heating system 2003 In: Applied Thermal Engineering. - 1359-4311 .- 1873-5606. ; 23:6, s. 769-778 Journal article (peer-reviewed)abstract Recent studies have shown that there is great potential benefit in utilities collaborating around heat supply. Analyses based on an extended system boundary clarify the advantage of mutual co-operation in the district heating markets. The purpose of this study is to show how far a local paper mill affects the degree of co-operation between two utilities. Current and future electricity prices and existing and potential plants are considered in the different scenarios in the study. The results in all the scenarios clearly show that the paper mill plays an active role in an integrated heat supply system. The scenario where co-operation, new plants and future electricity prices are considered, gives the lowest total system cost. A new back pressure turbine with a higher electricity-to-heat output ratio in combination with high trade prices promotes increased electricity and heat generation in the co-generation plant. The proportion of combined heat and power in district heating would increase if co-operation between the players were encouraged. ⌐ 2003 Elsevier Science Ltd. All rights reserved.
8.	Gustafsson, Stig-Inge (author) Economic benefits from load management in a carpentry factory 1996 In: Applied Thermal Engineering. - : Elsevier. - 1359-4311 .- 1873-5606. ; 16:10, s. 829-834 Journal article (peer-reviewed)abstract As a result of a National Referendum and a subsequent parliament decision Sweden will phase out its nuclear power stations before the year 2010. This source of electricity accounts for about half the total electricity usage and therefore other sources must be constructed, or the country must use less electricity. One way to accomplish this, according to economic theory, is to increase the price of electricity, and we will probably be subject to such actions, at least if there is a risk of a shortage of electricity. Hitherto, most interest for saving energy has been emphasised on space and domestic hot water heating in buildings. The major part of electricity, however, is used in industry, and is therefore worth studying in more detail. One small carpentry plant which manufactures wooden staircases and fibreboard panels for ceilings has been studied. Using monitored data for 1 year of their electricity usage and costs, the amount of money which could be saved by the owner of the factory, if different load management measures had been applied, has been calculated. Thus it was possible to find the maximum cost for equipment that can turn off some processes, such as timber dryers, for short periods.
9.	Gustafsson, Stig-Inge (author) Municipal thermal and electricity loads : A case study in Linköping 1998 In: Applied Thermal Engineering. - : Elsevier. - 1359-4311 .- 1873-5606. ; 18:5, s. 257-263 Journal article (peer-reviewed)abstract Linear programming models used for optimisation of various energy systems have received increased interest during the last ten years. One reason for this is the use of personal computers. Models with thousands of variables and constraints can now be rapidly optimised. If integers are introduced, which are necessary when increments or steps in cost functions are part of the model, the computing power is of even higher interest. However, many scientific authors do not discuss in detail how the model is designed and what basic data lie behind this design. This paper presents an attempt to study municipal thermal and electricity loads, and further how to divide data for one year into useful segments for linear and mixed integer programming purposes
10.	Gustafsson, Stig-Inge (author) Optimization and simulation of building energy systems 2000 In: Applied Thermal Engineering. - 1359-4311 .- 1873-5606. ; 20:18, s. 1731-1741 Journal article (peer-reviewed)abstract The Mixed Integer Linear Programming (MILP) technique is a useful tool for the optimization of energy systems. However, the introduction of integers in linear models results in a severe drawback because the ranging process is no longer available. Therefore, it is not possible to study what happens to the solution if input data are changed. In this paper, we compare a MILP model of a building with a simulation model of an identical case. Both models describe a building with a number of possible retrofits. Using the MILP technique, the optimal retrofit strategy is calculated, after which certain input data are changed. The optimization results in the lowest possible Life-Cycle Cost (LCC) of the building, and the paper describes how much the LCC will change if the property owner chooses other solutions. An increase in a particular data value may cause the LCC to increase or decrease. It may also be unchanged. Only a few data reduce the LCC when their values are increased.
11.	Heidari, Tari Mehrdad, et al. (author) Modelling of thermal energy storage in industrial energy systems the method development of MIND 2002 In: Applied Thermal Engineering. - 1359-4311 .- 1873-5606. ; 22:11, s. 1195-1205 Journal article (peer-reviewed)abstract Industrial energy efficiency is of vital importance as regards environment and industrial profitability. Optimisation of industrial energy systems may show a way towards improved use of resources in energy supply as well as in production processes. The deregulation of the electricity market in some countries increases flexibility in electricity contracts. Taking advantage of the price structure in these contracts is one of the ways to minimise the energy costs and decrease the influence on the environment. Thermal energy stores are very suitable facilities for achieving these goals, having the capability of moving energy use from one period of time to another and thereby influencing not only energy cost but also costs related to power demand if electric energy use is involved. In this paper, the influence on energy costs, energy and material flows resulting from the use of energy storage is discussed. Energy storage has been modelled by using MIND (Method for analysis of INDustrial energy systems) in the form that has recently been developed by the author. A case study from the pulp and paper industry has been used to verify this. © 2002 Elsevier Science Ltd. All rights reserved.
12.	Ji, Xiaoyan, et al. (author) Survey of experimental data and assessment of calculation methods of properties for the air–water mixture 2003 In: Applied Thermal Engineering. - 1359-4311 .- 1873-5606. ; 23:17, s. 2213-2228 Journal article (peer-reviewed)abstract Thermodynamic properties of the air-water mixture at elevated temperatures and pressures are of importance in the design and simulation of the advanced gas turbine systems with water addition. In this paper, comprehensive available experimental data and calculation methods for the air-water mixture were reviewed. It is found that the available experimental data are limited, and the determined temperature is within 75 °C. New experimental data are needed to supply in order to verify the model further. Three kinds of models (ideal model, ideal mixing model and real model) were used to calculate saturated vapor composition and enthalpy for the air-water mixture, and the calculated results of these models were compared with experimental data and each other. The comparison shows that for the calculation of saturated vapor composition, the reliable range of the ideal model and ideal mixing model is up to 10 bar. The real model is reliable over a wide temperature and pressure range, and the model proposed by Hyland and Wexler is the best one of today. However, the reliability of the Hyland and Wexler model approved by experimental data is only up to 75 °C and 50 bar, and it is necessary to propose a new predictive model based on the available experimental data to be used up to elevated temperatures and pressures. In the calculation of enthalpy, compared to the ideal model, the calculated results of the ideal mixing model are closer to those of real model.
13.	Westerlund, Lars, et al. (author) Heat and mass transfer simulations of the absorption process in a packed bed absorber 1998 In: Applied Thermal Engineering. - 1359-4311 .- 1873-5606. ; 18:12, s. 1295-1308 Journal article (peer-reviewed)abstract Numerical modelling of the absorption process in a cross-current absorber has been performed with FLOW3D, a commercially available software. The simulations are verified by comparisons with experimental results. The modelling of mass and heat transfer is discussed. Comparisons regarding the overall capacity as well as transfer rates show good agreement between experiments and simulations. It is possible to model the mass and heat transfer for a cross-current absorber if the equilibrium line for the absorption solution is known.
14.	Abas, Naeem, et al. (author) Dynamic simulation of solar water heating system using supercritical CO2 as mediating fluid under sub-zero temperature conditions 2019 In: Applied Thermal Engineering. - Oxford, UK : Pergamon Press. - 1359-4311 .- 1873-5606. ; 161 Journal article (peer-reviewed)abstract CO2 is becoming increasingly important as a mediating fluid, and simulation studies are indispensable for corresponding developments. In this study, a simulation-based performance investigation of a solar water heating system using CO2 as a mediating fluid under sub-zero temperature condition is performed using the TRNSYS (R) software. The maximum performance is achieved at a solar savings fraction of 0.83 during July. The as lowest solar savingss fraction of 0.41 is obtained during December. The annual heat production of the proposed system under Fargo climate is estimated to be about 2545 kWh. An evacuated glass tube solar collector is designed, fabricated and tested for various climate conditions. Moreover, a detailed comparison of the system's performance at sub/supercritical and supercritical pressures shows that the annual heat transfer efficiency of the modeled system is 10% higher at supercritical pressure than at sub/supercritical pressures. This result can be attributd to the strong convection flow of CO2 caused by density inhomogeneities, especially in the near critical region. This condition resuls in high heat transfer rates.
15.	Abdi, Amir, et al. (author) Experimental comparative analysis of close-contact and constrained melting of n-eicosane in a finned rectangular cavity 2023 In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 219 Journal article (peer-reviewed)abstract The present study demonstrates and visualizes the two modes of constrained melting and close-contact melting in a rectangular cavity enhanced with fins. Three configurations of fin with different lengths and numbers are tested in different horizontal, inclined, and vertical orientations. N-eicosane is used as the phase change material, and the experiments are performed with water as the heat transfer fluid at the inlet conditions of 50 degrees C, 55 degrees C, and 60 degrees C. In general, the close-contact melting time is shorter by 42-50%, compared to the convection dominated constrained melting in the unenhanced cavity without fins. By using fins to enhance the process, the melting time is reduced by 49% and 35% in the constrained and the close-contact modes, respectively, compared to the unfinned cavity in each mode. The thermal performance is observed to be superior in the horizontal and the inclined orientations. In these orientations, the buoyancy-driven structures are not blocked by fins in the con-strained mode. In the close-contact mode, the solid specimens attain more consistent contact with the base of the cavity and with the extended heat transfer area at the inclined and horizontal conditions. In the vertical orientation, the asymmetrical melting by the fins results in a rotational movement of the solid PCM and close -contact perturbations. The variations in the number of fins are found to have minor effects on the overall close-contact-induced melting. On the other hand, increasing the length of the fins is a more promising measure, providing consistent and prolonged contact.
16.	Abdi, Amir, et al. (author) Experimental investigation of solidification and melting in a vertically finned cavity 2021 In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 198 Journal article (peer-reviewed)abstract Extending the heat transfer area is a simple technique to improve the thermal performance of phase change materials with low thermal conductivity. However, as the governing mechanisms differ in solidification and melting, fins can affect the processes in different ways. This demands assessment of fin enhancement in a combined analysis on both solidification and melting, often neglected in literature. This paper presents visual-izations of solidification and melting of n-eicosane in a rectangular cavity and experimentally investigates the enhancing effect of vertical fins with varying number and length. Experiments were conducted at water inlet temperature ranges of 15-25 degrees C and 50-60 degrees C for the solidification and melting processes, respectively. The results show that the vertical fins can be more influential in solidification rather than in melting with similar losses in the storage capacity. In the solidification process, as natural convection is absent, the mean power is enhanced by a maximum of 395% with a 10% loss in the storage capacity, as compared to the benchmark. In the melting case, the mean power is increased by a maximum of 90% with a 9% loss in the storage capacity. Although increasing the surface area with vertical fins contributes to development of convective structures, it makes a modest enhancement. In overall, increasing the fin volume fraction, in exchange for the loss in the storage capacity, enhances the solidification significantly while it has relatively low enhancement effect in melting. At the end, the performed experiments could be helpful for validation of future simulation tools with complex features, particularly solidification models lacking in literature.
17.	Alanne, Kari, et al. (author) Thermo-economic analysis of a micro-cogeneration system based on a rotary steam engine (RSE) 2012 In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 44, s. 11-20 Journal article (peer-reviewed)abstract A rotary steam engine (RSE) is a simple, small, quiet and lubricant-free option for micro-cogeneration. It is capable of exploiting versatile thermal sources and steam temperatures of 150 to 180 ºC, which allow operational pressures less than 10 bar for electrical power ranges of 1 to 20 kWe. An RSE can be easily integrated in commercially available biomass-fired household boilers. In this paper, we characterize the boiler-integrated RSE micro-cogeneration system and specify a two-control-volume thermodynamic model to conduct performance analyses in residential applications. Our computational analysis suggests that an RSE integrated with a 17 kWth pellet-fuelled boiler can obtain an electrical output of 1.925 kWe, in the design temperature of 150 ºC, the electrical efficiency being 9% (LHV) and the thermal efficiency 77% (LHV). In a single-family house inFinland, the above system would operate up to 1274 h/a, meeting 31% of the house’s electrical demand. The amount of electricity delivered into the grid is 989 kWh/a. An economic analysis suggests that incremental costs not exceeding € 1,500 are justifiable at payback periods less than five years, when compared to standard boilers.
18.	Ali Motamed, Mohammad, et al. (author) Part-load thermal efficiency enhancement in gas turbine combined cycles by exhaust gas recirculation 2024 In: Applied Thermal Engineering. - 1359-4311. ; 244 Journal article (peer-reviewed)abstract Gas turbine power plants are popular for offshore power generation due to high power density and their reliability. However, growing usage of renewable energies put gas turbines in a load following backup operation. These power plants suffer part-load efficiency losses when operating at less than full capacity, resulting in higher carbon dioxide (CO2) emission from natural gas combined cycles or higher consumption of carbon-free fuels in decarbonized gas turbines. In this article, a solution is proposed for enhancement of power plant part-load thermal efficiency based on exhaust gas recirculation in the gas turbine cycle. Recirculating exhaust gas into the gas turbine have been studied by several researchers and engineers due to its benefit for carbon-free combustion and carbon capture mechanisms. The proposed operation strategy is evaluated for single-spool and two-spool gas turbines operating jointly with a steam bottoming cycle harvesting the waste heat for further power production. In the suggested strategy, eliminating the necessity to cool down the recirculated gas resulted in less equipment footprint for the power plant which makes it more favorable for offshore applications. An in-house design and simulation tool is developed for evaluating gas turbines with modern gas recirculating systems and a flexibility in operation with carbon-free fuel mixtures. The enhancement in efficiency boost, emission reduction, and fuel consumption is quantified demonstrating the improvements with the proposed solution.
19.	Altorkmany, Lobna, et al. (author) Effect of Working Parameters of the Plate Heat Exchanger on the Thermal Performance of the Anti-Bact Heat Exchanger System to Disinfect Legionella in Hot Water Systems 2018 In: Applied Thermal Engineering. - : Elsevier. - 1359-4311 .- 1873-5606. ; 141, s. 435-443 Journal article (peer-reviewed)abstract The objective of the current study is to analyze the effect of different working parameters on the thermal performance of the Anti-Bact Heat Exchanger system (ABHE). The ABHE system is inspired by nature and implemented to achieve continuous disinfection of Legionella in different human-made water systems at any desired disinfection temperature. In the ABHE system, most of the energy is recovered using an efficient plate heat exchanger (PHE). A model by Engineering Equation Solver (EES) is set-up to figure out the effect of different working parameters on the thermal performance of the ABHE system. The study shows that higher supplied water temperature can enhance the regeneration ratio (RR), but it requires a large PHE area and pumping power (PP) which consequently increase the cost of the ABHE system. However, elevate temperature in use results in a reduced PHE area and PP, which accordingly reduce the cost of the ABHE system. On the other hand, the EES-based model is used to study the effect of the length and the width of the plates used in the PHE on the RR and the required area of the PHE. Finally, taking into account the geometrical parameters, flow arrangement and the initial operating conditions of the PHE, the EES-based model is used to optimize the PHE in which its area is minimized, and the RR of the ABHE system is maximized.
20.	Altorkmany, Lobna, et al. (author) Experimental and Simulation Validation of ABHE for Disinfection of Legionella in Hot Water Systems 2017 In: Applied Thermal Engineering. - : Elsevier. - 1359-4311 .- 1873-5606. ; 116, s. 253-265 Journal article (peer-reviewed)abstract The work refers to an innovative system inspired by nature that mimics the thermoregulation system that exists in animals. This method, which is called Anti Bacteria Heat Exchanger (ABHE), is proposed to achieve continuous thermal disinfection of bacteria in hot water systems with high energy efficiency. In particular, this study aims to demonstrate the opportunity to gain energy by means of recovering heat over a plate heat exchanger. Firstly, the thermodynamics of the ABHE is clarified to define the ABHE specification. Secondly, a first prototype of an ABHE is built with a specific configuration based on simplicity regarding design and construction. Thirdly, an experimental test is carried out. Finally, a computer model is built to simulate the ABHE system and the experimental data is used to validate the model. The experimental results indicate that the performance of the ABHE system is strongly dependent on the flow rate, while the supplied temperature has less effect. Experimental and simulation data show a large potential for saving energy of this thermal disinfection method by recovering heat. To exemplify, when supplying water at a flow rate of 5 kg/min and at a temperature of 50 °C, the heat recovery is about 1.5 kW while the required pumping power is 1 W. This means that the pressure drop is very small compared to the energy recovered and consequently high saving in total cost is promising.
21.	Amirpour, Sepideh, 1980, et al. (author) Highly thermal conductive graphene-based heatsink tailored for electric propulsion SiC-based inverter 2024 In: Applied Thermal Engineering. - 1359-4311. ; 243 Journal article (peer-reviewed)abstract This study introduces an innovative multidisciplinary design approach for highly conductive and lightweight pin-fin-based heatsinks leveraging the advantages of graphene technology. The primary objective is to optimize the thermal management of silicon carbide (SiC) based inverters within electric vehicles (EVs). To closely emulate the real SiC power module, comprehensive analyses, including scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), are performed on the module. A detailed fluid dynamics model utilizing a 3D-conjugate heat transfer (CHT) methodology is employed to evaluate the thermal behavior of SiC power switches in contact with the coolant. The multidisciplinary analysis is initially implemented on an aluminum-based heatsink, validated experimentally, and subsequently compared to graphene. The integration of graphene in the heatsink design demonstrates notable improvements, including a 24.4 % increase in the heat transfer coefficient (HTC) and a 19.6 % reduction in thermal resistance (sink to fluid) at a 6 l/min fluid flow rate compared to its aluminum counterpart. Consequently, the SiC chips within the graphene-based heatsink exhibit an 11.5 % lower temperature rise compared to the aluminum version. The improvements in the cooling solution for SiC inverters in EVs, achieved through the adoption of graphene instead of traditional metals, serve as a proof of concept. This signifies a step forward in prioritizing the crucial balance between performance and power density.
22.	Amos, I. G., et al. (author) Design and off-design optimisation of highly loaded industrial gas turbine stages 2004 In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 24:12-nov, s. 1735-1744 Journal article (peer-reviewed)abstract A European collaborative project to investigate the design of advanced industrial gas turbine stages (DAIGTS) has now completed 30 months of a 36-month programme of work. The objectives of the project were to investigate advanced aerodynamic analysis of industrial gas turbine stages, off-design performance characteristics, prediction of aero-mechanical behaviour.This paper gives an overview of the technical progress made and includes a description of the rigs used in the study. Key results include the development of advanced CFD models to include cooling and real engine geometric features, off-design performance mapping of transonic industrial turbine stages and the development of a unique oscillating cascade rig.
23.	Araoz, Joseph Adhemar, 1982-, et al. (author) Non-ideal Stirling engine thermodynamic model suitable for the integration into overall energy systems 2014 In: Applied Thermal Engineering. - : Elsevier. - 1359-4311 .- 1873-5606. ; 73:1, s. 203-219 Journal article (peer-reviewed)abstract The reliability of modelling and simulation of energy systems strongly depends on the prediction accuracy of each system component. This is the case of Stirling engine-based systems, where an accurate modelling of the engine performance is very important to understand the overall system behaviour. In this sense, many Stirling engine analyses with different approaches have been already developed. However, there is a lack of Stirling engine models suitable for the integration into overall system simulations. In this context, this paper aims to develop a rigorous Stirling engine model that could be easily integrated into combined heat and power schemes for the overall techno-economic analysis of these systems. The model developed considers a Stirling engine with adiabatic working spaces, isothermal heat exchangers, dead volumes, and imperfect regeneration. Additionally, it considers mechanical pumping losses due to friction, limited heat transfer and thermal losses on the heat exchangers. The predicted efficiency and power output were compared with the numerical model and the experimental work reported by the NASA Lewis Research Centre for the GPU-3 Stirling engine. This showed average absolute errors around ±4% for the brake power, and ±5% for the brake efficiency at different frequencies. However, the model also showed large errors (±15%) for these calculations at higher frequencies and low pressures. Additional results include the calculation of the cyclic expansion and compression work; the pressure drop and heat flow through the heat exchangers; the conductive, shuttle effect and regenerator thermal losses; the temperature and mass flow distribution along the system; and the power output and efficiency of the engine.
24.	Araoz Ramos, Joseph Adhemar, 1982-, et al. (author) Development and validation of a thermodynamic model for the performance analysis of a gamma Stirling engine prototype 2015 In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 83, s. 16-30 Journal article (peer-reviewed)abstract This work presents the development and validation of a numerical model that represents the performance of a gamma Stirling engine prototype. The model follows a modular approach considering ideal adiabatic working spaces; limited internal and external heat transfer through the heat exchangers; and mechanical and thermal losses during the cycle. In addition, it includes the calculation of the mechanical efficiency taking into account the crank mechanism effectiveness and the forced work during the cycle. Consequently, the model aims to predict the work that can be effectively taken from the shaft. The model was compared with experimental data obtained in an experimental rig built for the engine prototype. The results showed an acceptable degree of accuracy when comparing with the experimental data, with errors ranging from +/- 1% to +/- 8% for the temperature in the heater side, less than +/- 1% error for the cooler temperatures, and +/- 1 to +/- 8% for the brake power calculations. Therefore, the model was probed adequate for study of the prototype performance. In addition, the results of the simulation reflected the limited performance obtained during the prototype experiments, and a first analysis of the results attributed this to the forced work during the cycle. The implemented model is the basis for a subsequent parametric analysis that will complement the results presented.
25.	Arnaudo, Monica, et al. (author) Heat recovery and power-to-heat in district heating networks – Atechno-economic and environmental scenario analysis 2021 In: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 185, s. 116388- Journal article (peer-reviewed)abstract Heat recovery from local resources is shown to be a promising solution to reduce the carbon footprint of district heating. Supermarkets equipped with a CO2 refrigeration system and a geothermal storage offer a larger heating capacity, compared to traditional solutions. While district heat could benefit from this higher heat recovery availability, supermarkets could generate an income from a capacity that would be otherwise unused. For the first time, this study applies a detailed modelling approach considering both sides of such a synergy. The objective is to assess the techno-economic and environmental impact of a coordinated control strategy. Since the heat recovery from the supermarket consumes additional electricity, power-to-heat is implemented as a solution to reduce the overall CO2 emissions. This is demonstrated by scenarios simulated for a district in Stockholm. Hourly electricity CO2 intensity and prices are implemented as signals to prioritize either the district heating central supply or heat recovery. By boosting the use of electricity when cleaner, a CO2 intensity-driven control show the potential of reducing the carbon footprint of the district (−9.4%). A control based on prices, instead, is more convenient economically both for the district (−1.4% heat cost) and for the supermarket (−32% operational cost).

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