Special Issue "Modelling of Thermal and Energy Systems"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "Thermal Management".

Deadline for manuscript submissions: 31 July 2021.

Special Issue Editor

Prof. Dr. Francisco Vera García
E-Mail Website
Guest Editor
Univ Politecn Cartagena, Escuela Tecn Super Ingn Ind, Dept Ingn Term & Fluidos, Cartagena, Spain
Interests: internal combustion engines; two-phase flow; heat exchangers design; evaporation & condensation processes; efficiency use of energy; thermal & PV solar energy; water desalinization

Special Issue Information

Dear Colleagues,

At present, in the Industry 4.0 era, it is possible to respond to the behavior of several real systems with a very good adjustment. Modelling tools are present in the majority of engineering disciplines, including energy, manufacturing, reliability, business, etc. However, it is interesting to define Modelling properly, to separate from and not confuse Modelling with simulation.

A correct model solves the physical equations representing the real phenomena that are going to take place in a real system. The fidelity of the model will be strongly determined by the correct physical laws included in the model, the simplifying assumptions, and subjected validation process for the model. A model is able to obtain parameters from different integrated parts of a complex system. In addition, a model is a powerful tool to optimize and to predict a real system.

Meanwhile, a simulation is the statistical response of a system; therefore, the reliability of a simulation is based on the amount of disposable data for the simulated system. In fact, Big Data techniques simulate a known system, but they are not able to get a response from new systems.

Utilizing Modelling tools, we are able to accurately predict the energy flows, power requirements, energy consumption, temperature, humidity, pressure, etc. for several components and their interconnections to develop complex Modelling systems. It is possible to evaluate the impact of a specific measure on a component (i.e., a partial optimization, changes of an environmental/internal parameter, etc.) and to obtain the impact of the whole system. Furthermore, the combination of Modelling and experimentation is the best strategy for the analysis, acquisition of knowledge, optimization, and control of a thermal or energy system.

This Special Issue focuses on the analysis, design, validation, response, and implementation of Modelling of Thermal and Energy Systems. The topics of interest for the Special Issue include (but are not limited to):

  • Modelling of thermal systems;
  • Modelling of complex energy systems;
  • Thermal correlations Modelling;
  • Two-phase flow Modelling;
  • Heat exchangers Modelling and design.;
  • Modelling of internal combustion engines;
  • Reliability and failure detection Modelling;
  • Air conditioning and refrigerant systems;
  • Computational fluid dynamics (CFD) for thermal and energy systems;
  • Modelling of thermal processes (evaporation and condensation);
  • Modelling of energy flows.;
  • Optimization and efficiency use of energy systems;
  • Renewable energy models, thermal and PV solar energy, wind, biomass, biofuels, etc.;
  • Modelling of the desalinization process;
  • Thermal energy storage Modelling;
  • Modelling of building energy consumption, isolation of buildings, etc.

Prof. Dr. Francisco Vera García
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

 

Keywords

  • Thermal systems
  • Energy systems
  • Thermal correlations
  • Heat exchangers
  • Internal combustion engines
  • Reliability
  • Failure detection
  • Air conditioning systems
  • Refrigerant systems
  • Computational fluid dynamics (CFD)
  • Evaporation
  • Condensation
  • Energy flows
  • Optimization of energy systems
  • Renewable energies
  • Desalinization process
  • Thermal energy storage
  • Building energy consumption

Published Papers (20 papers)

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Research

Article
Influence of Errors in Known Constants and Boundary Conditions on Solutions of Inverse Heat Conduction Problem
Energies 2021, 14(11), 3313; https://doi.org/10.3390/en14113313 - 04 Jun 2021
Viewed by 220
Abstract
This work examines the effects of the known boundary conditions on the accuracy of the solution in one-dimensional inverse heat conduction problems. The failures in many applications of these problems are attributed to inaccuracy of the specified constants and boundary conditions. Since the [...] Read more.
This work examines the effects of the known boundary conditions on the accuracy of the solution in one-dimensional inverse heat conduction problems. The failures in many applications of these problems are attributed to inaccuracy of the specified constants and boundary conditions. Since the boundary conditions and material properties in most thermal problems are imposed with uncertainty, the effects of their inaccuracy should be understood prior to the inverse analyses. The deviation from the exact solution has been examined for each case according to the errors in material properties, boundary location, and known boundary conditions. The results show that the effects of such errors are dramatic. Based on these results, the applicability and limitations of the inverse heat conduction analyses have been evaluated and discussed. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Organic Rankine Cycle Optimization Performance Analysis Based on Super-Heater Pressure: Comparison of Working Fluids
Energies 2021, 14(9), 2548; https://doi.org/10.3390/en14092548 - 29 Apr 2021
Viewed by 310
Abstract
The organic Rankine cycle (ORC) is widely accepted to produce electricity from low-grade thermal heat sources. In fact, it is a developed technology for waste-heat to electricity conversions. In this paper, an ORC made up of super-heater, turbine, regenerator, condenser, pump, economizer and [...] Read more.
The organic Rankine cycle (ORC) is widely accepted to produce electricity from low-grade thermal heat sources. In fact, it is a developed technology for waste-heat to electricity conversions. In this paper, an ORC made up of super-heater, turbine, regenerator, condenser, pump, economizer and evaporator is considered. An optimization model to obtain the maximum performance of such ORC, depending on the super-heater pressure, is proposed and assessed, in order to find possible new working fluids that are less pollutant with similar behavior to those traditionally used. The different super-heater pressures under analysis lie in between the condenser pressure and 80% of the critical pressure of each working fluid, taking 100 values uniformly distributed. The system and optimization algorithm have been simulated in Matlab with the CoolProp library. Results show that the twelve working fluids can be categorized into four main groups, depending on the saturation pressure at ambient conditions (condenser pressure), observing that the fluids belonging to Group 1, which corresponds with the lower condensing pressure (around 100 kPa), provide the highest thermal efficiency, with values around η=2325%. Moreover, it is also seen that R123 can be a good candidate to substitute R141B and R11; R114 can replace R236EA and R245FA; and both R1234ZE and R1234YF have similar behavior to R134A. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
A MCDM Methodology to Determine the Most Critical Variables in the Pressure Drop and Heat Transfer in Minichannels
Energies 2021, 14(8), 2069; https://doi.org/10.3390/en14082069 - 08 Apr 2021
Viewed by 377
Abstract
This paper proposes a methodology aiming at determining the most influent working variables and geometrical parameters over the pressure drop and heat transfer during the condensation process of several refrigerant gases using heat exchangers with pipes mini channels technology. A multi-criteria decision making [...] Read more.
This paper proposes a methodology aiming at determining the most influent working variables and geometrical parameters over the pressure drop and heat transfer during the condensation process of several refrigerant gases using heat exchangers with pipes mini channels technology. A multi-criteria decision making (MCDM) methodology was used; this MCDM includes a mathematical method called SIMUS (Sequential Interactive Modelling for Urban Systems) that was applied to the results of 2543 tests obtained by using a designed refrigeration rig in which five different refrigerants (R32, R134a, R290, R410A and R1234yf) and two different tube geometries were tested. This methodology allows us to reduce the computational cost compared to the use of neural networks or other model development systems. This research shows six variables out of 39 that better define simultaneously the minimum pressure drop, as well as the maximum heat transfer, saturation pressure fluid entering the condenser being the most important one. Another aim of this research was to highlight a new methodology based on operation research for their application to improve the heat transfer energy efficiency and reduce the CO2 footprint derived of the use of heat exchangers with minichannels. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Passive Heating and Cooling of Photovoltaic Greenhouses Including Thermochromic Materials
Energies 2021, 14(2), 438; https://doi.org/10.3390/en14020438 - 15 Jan 2021
Cited by 1 | Viewed by 501
Abstract
The integration of photovoltaic technologies into greenhouse envelopes appears to be an innovative and environmentally-friendly way to supply their various energy demands. However, the effect on the inner growing conditions, especially on the temperature, must be assessed in order to effectively implement this [...] Read more.
The integration of photovoltaic technologies into greenhouse envelopes appears to be an innovative and environmentally-friendly way to supply their various energy demands. However, the effect on the inner growing conditions, especially on the temperature, must be assessed in order to effectively implement this solution. In this study, experimental temperature data were obtained over two years for four structures built with different photovoltaic technologies (mono-crystalline silicon, amorphous silicon, cadmium telluride, and an organic polymeric technology) and fitted to a thermal model in order to provide a comprehensive analysis of their potential utilization as a cover material in greenhouses. Additionally, the thermal effect of color in structures composed of several common construction materials (brick, wood, plasterboard and glass) was quantified and modelled, supplementing the thermal analysis of passive solutions for this application. In all cases, inner and ambient temperature differences of up to +20 °C, created by a passive heating effect during the day, and −5 °C, created by a passive cooling effect during the night, have been observed, suggesting the use of the photovoltaic modules with different degrees of structure coverage, complemented with the color tuning of the modules themselves as passive methods to control the temperature and light spectrum of greenhouses. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Numerical Calculation and Uncertain Optimization of Energy Conversion in Interior Ballistics Stage
Energies 2020, 13(21), 5824; https://doi.org/10.3390/en13215824 - 07 Nov 2020
Viewed by 484
Abstract
Gun firing is a process that converts propellant chemical energy to projectile kinetic energy and other kinds of energies. In order to explore the energy conversion process, firstly, the interior ballistics mathematical model and the barrel-projectile finite element model are built and solved. [...] Read more.
Gun firing is a process that converts propellant chemical energy to projectile kinetic energy and other kinds of energies. In order to explore the energy conversion process, firstly, the interior ballistics mathematical model and the barrel-projectile finite element model are built and solved. Then, the related variable values and energy values are obtained and discussed. Finally, for improving energy efficiency, the interval uncertainty optimization problem is modeled, and then solved using the two-layer nested optimization strategy and back-propagation (BP) neural network surrogate model. Calculation results show that, after optimization, the heat efficiency raises from 31.13% to 33.05% and the max rifling stress decreases from 893.68 to 859.76 Mpa, which would improve the firing performance and prolong the lifetime of the gun barrel. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Hydrothermal Investigation of a Microchannel Heat Sink Using Secondary Flows in Trapezoidal and Parallel Orientations
Energies 2020, 13(21), 5616; https://doi.org/10.3390/en13215616 - 27 Oct 2020
Cited by 1 | Viewed by 418
Abstract
Thermal performance enhancement in microchannel heat sinks has recently become a challenge due to advancements in modern microelectronics, which demand compatibility with heat sinks able to dissipate ever-increasing amounts of heat. Recent advancements in manufacturing techniques, such as additive manufacturing, have made the [...] Read more.
Thermal performance enhancement in microchannel heat sinks has recently become a challenge due to advancements in modern microelectronics, which demand compatibility with heat sinks able to dissipate ever-increasing amounts of heat. Recent advancements in manufacturing techniques, such as additive manufacturing, have made the modification of the microchannel heat sink geometry possible well beyond the conventional rectangular model to improve the cooling capacity of these devices. One such modification in microchannel geometry includes the introduction of secondary flow channels in the walls between adjacent mainstream microchannels. The present study computationally models secondary flow channels in regular trapezoidal and parallel orientations for fluid circulation through the microchannel walls in a heat sink design. The heat sink is made of silicon wafer, and water is used as the circulating fluid in this study. Continuity, momentum, and energy equations are solved for the fluid flow through the regular trapezoidal secondary flow and parallel secondary flow designs in the heat sink with I-type, C-type, and Z-type inlet–outlet configurations. Plots of velocity contours show that I-type geometry creates optimal flow disruption in the heat sink. Therefore, for this design, the pressure drop and base plate temperatures are plotted for a volumetric flow rate range, and corresponding contour plots are obtained. The results are compared with corresponding trends for the conventional rectangular microchannel design, and associated trends are explained. The study suggests that the flow phenomena such as flow impingement onto the microchannel walls and formation of vortices inside the secondary flow passages coupled with an increase in heat transfer area due to secondary flow passages may significantly improve the heat sink performance. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Mechanical Integrity Assessment of Two-Side Etched Type Printed Circuit Heat Exchanger with Additional Elliptical Channel
Energies 2020, 13(18), 4711; https://doi.org/10.3390/en13184711 - 10 Sep 2020
Viewed by 614
Abstract
Printed circuit heat exchangers (PCHEs) are often subject to high pressure and temperature difference between the hot and cold channels which may cause a mechanical integrity problem. A conventional plate heat exchanger where the channel geometries are semi-circular and etched at one side [...] Read more.
Printed circuit heat exchangers (PCHEs) are often subject to high pressure and temperature difference between the hot and cold channels which may cause a mechanical integrity problem. A conventional plate heat exchanger where the channel geometries are semi-circular and etched at one side of the stacked plate is a common design in the market. However, the sharp edge tip channel may cause high stress intensity. Double-faced type PCHE appears with the promising ability to reduce the stress intensity and stress concentration factor. Finite element analysis simulation has been conducted to observe the mechanical integrity of double-etched printed circuit heat exchanger design. The application of an additional ellipse upper channel helps the stress intensity decrease in the proposed PCHE channel. Five different cases were simulated in this study. The simulation shows that the stress intensity was reduced up to 24% with the increase in additional elliptical channel radius. Besides that, the horizontal offset channels configuration was also investigated in this study. Simulation results show that the maximum stress intensity of 2.5 mm offset configuration is 9% lower compared to the maximum stress intensity of 0 mm offset. This work proposed an additional elliptical upper channel with a 2.5 mm offset configuration as an optimum design. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Nonlinear Optimization of Turbine Conjugate Heat Transfer with Iterative Machine Learning and Training Sample Replacement
Energies 2020, 13(17), 4587; https://doi.org/10.3390/en13174587 - 03 Sep 2020
Viewed by 984
Abstract
A simple yet effective optimization technique is developed to solve nonlinear conjugate heat transfer. The proposed Nonlinear Optimization with Replacement Strategy (NORS) is a mutation of several existing optimization processes. With the improvements of 3D metal printing of turbine components, it is feasible [...] Read more.
A simple yet effective optimization technique is developed to solve nonlinear conjugate heat transfer. The proposed Nonlinear Optimization with Replacement Strategy (NORS) is a mutation of several existing optimization processes. With the improvements of 3D metal printing of turbine components, it is feasible to have film holes with unconventional diameters, as these holes are created while printing the component. This paper seeks to optimize each film hole diameter at the leading edge of a turbine vane to satisfy several optimum thermal design objectives with given design constraints. The design technique developed uses linear regression-based machine learning model and further optimizes with strategic improvement of the training dataset. Optimization needs cost and benefit criteria are used to base its decision of success, and cost is minimized with maximum benefit within given constraints. This study minimizes the coolant flow (cost) while satisfying the constraints on average metal temperature and metal temperature variations (benefits) that limit the useful life of turbine components. The proposed NORS methodology provides a scientific basis for selecting design parameters in a nonlinear design space. This model is also a potential academic tool to be used in thesis works without demanding extensive computing resources. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Development of a Variable Valve Actuation Control to Improve Diesel Oxidation Catalyst Efficiency and Emissions in a Light Duty Diesel Engine
Energies 2020, 13(17), 4561; https://doi.org/10.3390/en13174561 - 03 Sep 2020
Cited by 4 | Viewed by 787
Abstract
Growing interest has arisen to adopt Variable Valve Timing (VVT) technology for automotive engines due to the need to fulfill the pollutant emission regulations. Several VVT strategies, such as the exhaust re-opening and the late exhaust closing, can be used to achieve an [...] Read more.
Growing interest has arisen to adopt Variable Valve Timing (VVT) technology for automotive engines due to the need to fulfill the pollutant emission regulations. Several VVT strategies, such as the exhaust re-opening and the late exhaust closing, can be used to achieve an increment in the after-treatment upstream temperature by increasing the residual gas amount. In this study, a one-dimensional gas dynamics engine model has been used to simulate several VVT strategies and develop a control system to actuate over the valves timing in order to increase diesel oxidation catalyst efficiency and reduce the exhaust pollutant emissions. A transient operating conditions comparison, taking the Worldwide Harmonized Light-Duty Vehicles Test Cycle (WLTC) as a reference, has been done by analyzing fuel economy, HC and CO pollutant emissions levels. The results conclude that the combination of an early exhaust and a late intake valve events leads to a 20% reduction in CO emissions with a fuel penalty of 6% over the low speed stage of the WLTC, during the warm-up of the oxidation catalyst. The same set-up is able to reduce HC emissions down to 16% and NOx emission by 13%. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Convective Drying of Ceramic Bricks by CFD: Transport Phenomena and Process Parameters Analysis
Energies 2020, 13(8), 2073; https://doi.org/10.3390/en13082073 - 21 Apr 2020
Cited by 4 | Viewed by 895
Abstract
In the manufacturing process of ceramic brick, the step of drying needs the control of process variables to uniformly dry the porous material, producing a good end-product. The majority of numerical simulations involving drying of ceramic materials is performed considering only the solid [...] Read more.
In the manufacturing process of ceramic brick, the step of drying needs the control of process variables to uniformly dry the porous material, producing a good end-product. The majority of numerical simulations involving drying of ceramic materials is performed considering only the solid domain, resulting in a very simplified and limited study. This way, the objective of this work is the analysis of the drying process with hot air of an industrial hollow clay brick inside the oven at different temperatures by using computational fluid dynamic (CFD). The results of the temperature and water mass distribution inside the brick and of air in the oven at different times of the drying process are shown, analyzed and checked with experimental data, and it was obtained in a concordance with the data. An equation to calculate the brick water mass diffusivity depending on the drying air temperature was proposed. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
System Characteristics Analysis for Energy Management of Power-Split Hydraulic Hybrids
Energies 2020, 13(7), 1837; https://doi.org/10.3390/en13071837 - 10 Apr 2020
Cited by 3 | Viewed by 942
Abstract
Hydraulic hybrid powertrains provide an opportunity for specific applications, such as heavy-duty vehicles based on high-power density, which has not been included in other types of hybrid powertrains. Among the various architectures of hybrid vehicles, power-split hybrids have a greater possibility of producing [...] Read more.
Hydraulic hybrid powertrains provide an opportunity for specific applications, such as heavy-duty vehicles based on high-power density, which has not been included in other types of hybrid powertrains. Among the various architectures of hybrid vehicles, power-split hybrids have a greater possibility of producing better fuel efficiency than other hybrid architectures. This study analyzed the possible energy-saving characteristics of power-split hydraulic hybrid vehicles (HHVs); this has not been comprehensively described in previous studies. A typical configuration of power-split HHVs was modeled with the FTP-72 driving cycle using a novel simulation method that considered the dynamic and thermal behaviors together. The characteristics were analyzed in comparison to a power-split hydrostatic transmission (HST), which is designed with the same conditions except for hydraulic energy storage. The power-split HHV not only has a better fuel efficiency, but it also shows system energy-saving characteristics. The power-split HHV has more chances for engine idling, which is directly related to fuel consumption savings due to engine stop. Additionally, more engine idling time enables the system to operate in a more efficient area on the engine map by load leveling. The results for the system temperature show that the power-split HHV offers the possibility to deliver better thermal management because it prevents the waste of braking power, which is especially crucial for hydraulic systems in comparison to other power systems such as electric or mechanical power systems. The ease of thermal management results in less energy consumption for cooling down the system temperature by minimizing the cooling system, as well as in a better thermal stability for the hydraulic system. The power-split HHV characteristics analyzed in this study can be used to design and organize the system control logic while developing power-split HHVs. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Study of the Miller Cycle on a Turbocharged DI Gasoline Engine Regarding Fuel Economy Improvement at Part Load
Energies 2020, 13(6), 1500; https://doi.org/10.3390/en13061500 - 22 Mar 2020
Cited by 2 | Viewed by 718
Abstract
This contribution is focused on the fuel economy improvement of the Miller cycle under part-load characteristics on a supercharged DI (Direct Injection) gasoline engine. Firstly, based on the engine bench test, the effects with the Miller cycle application under 3000 rpm were studied. [...] Read more.
This contribution is focused on the fuel economy improvement of the Miller cycle under part-load characteristics on a supercharged DI (Direct Injection) gasoline engine. Firstly, based on the engine bench test, the effects with the Miller cycle application under 3000 rpm were studied. The results show that the Miller cycle has different extents of improvement on pumping loss, combustion and friction loss. For low, medium and high loads, the brake thermal efficiency of the baseline engine is increased by 2.8%, 2.5% and 2.6%, respectively. Besides, the baseline variable valve timing (VVT) is optimized by the test. Subsequently, the 1D CFD (Computational Fluid Dynamics) model of the Miller cycle engine after the test optimization at the working condition of 3000 rpm and BMEP (Brake Mean Effective Pressure) = 10 bar was established, and the influence of the combined change of intake and exhaust valve timing on Miller cycle was studied by simulation. The results show that as the effect of the Miller cycle deepens, the engine’s knocking tendency decreases, so the ignition timing can be further advanced, and the economy of the engine can be improved. Compared with the brake thermal efficiency of the baseline engine, the final result after simulation optimization is increased from 34.6% to 35.6%, which is an improvement of 2.9%. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Studying the Role of System Aggregation in Energy Targeting: A Case Study of a Swedish Oil Refinery
Energies 2020, 13(4), 958; https://doi.org/10.3390/en13040958 - 20 Feb 2020
Cited by 2 | Viewed by 806
Abstract
The definition of appropriate energy targets for large industrial processes is a difficult task since operability, safety and plant layout aspects represent important limitations to direct process integration. The role of heat exchange limitations in the definition of appropriate energy targets for large [...] Read more.
The definition of appropriate energy targets for large industrial processes is a difficult task since operability, safety and plant layout aspects represent important limitations to direct process integration. The role of heat exchange limitations in the definition of appropriate energy targets for large process sites was studied in this work. A computational framework was used which allows to estimate the optimal distribution of process stream heat loads in different subsystems and to select and size a site wide utility system. A complex Swedish refinery site is used as a case study. Various system aggregations, representing different patterns of heat exchange limitations between process units and utility configurations were explored to identify trade-offs and bottlenecks for energy saving opportunities. The results show that in spite of the aforementioned limitations direct heat integration still plays a significant role for the refinery energy efficiency. For example, the targeted hot utility demand is reduced by 50–65% by allowing process-to-process heat exchange within process units even when a steam utility system is available for indirect heat recovery. Furthermore, it was found that direct process heat integration is motivated primarily at process unit level, since the heat savings that can be achieved by allowing direct heat recovery between adjacent process units (25–42%) are in the same range as those that can be obtained by combining unit process-to-process integration with site-wide indirect heat recovery via the steam system (27–42%). Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Planned Heating Control Strategy and Thermodynamic Modeling of a Natural Gas Thermal Desorption System for Contaminated Soil
Energies 2020, 13(3), 642; https://doi.org/10.3390/en13030642 - 03 Feb 2020
Cited by 1 | Viewed by 652
Abstract
This paper presents a planned heating control strategy applied for a natural gas thermal desorption system for polluted soil to achieve the dynamic adjustment of the heating time and energy consumption. A lumped-parameter model for the proposed system is established to examine effects [...] Read more.
This paper presents a planned heating control strategy applied for a natural gas thermal desorption system for polluted soil to achieve the dynamic adjustment of the heating time and energy consumption. A lumped-parameter model for the proposed system is established to examine effects of the natural gas mass flow rate and the excess air coefficient on the heating performance of the target soil. The control strategy is explored to accomplish the heating process as expected with constant temperature change rate or constant volumetric water content change rate at different phases by adapting the natural gas flow. The results demonstrate that the heating plan can be realized within the scheduled 36 days and the total natural gas consumption can be reduced by 24% (1487 kg) compared to that of the open-loop reference condition, which may be widely applied for other thermal remediation systems of the polluted soil. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Thermo-Economic Analysis of a Hybrid Ejector Refrigerating System Based on a Low Grade Heat Source
Energies 2020, 13(3), 562; https://doi.org/10.3390/en13030562 - 23 Jan 2020
Cited by 4 | Viewed by 854
Abstract
The rising of the global energy demand requires the use of alternative energy conversion systems employing renewable sources. In the refrigeration and air conditioning fields, heat driven ejector systems represent a promising way to produce the cooling effect by using available low-grade temperature [...] Read more.
The rising of the global energy demand requires the use of alternative energy conversion systems employing renewable sources. In the refrigeration and air conditioning fields, heat driven ejector systems represent a promising way to produce the cooling effect by using available low-grade temperature sources. In this paper, a thermo-economic analysis of a waste heat recovery hybrid ejector cycle (WHRHEC) was carried out. A thermodynamic model was firstly developed to simulate a WHRHEC able to obtain chilled water with a cooling load of 20 kW, by varying the working fluids and the pinch point values in the heat exchangers. Specific single- and two-phase heat transfer correlations were used to estimate the heat transfer surface and therefore the investment costs. The operative ranges that provide a reasonable compromise between the set-up costs and the cycle performances were then defined and compared to the current waste heat-driven technologies, such as absorption chillers and organic Rankine cycles (ORCs) coupled with vapor compression cycles (VCCs). The last part of the paper presents an economic analysis providing the map of the design (plant size) and contingent (specific cost of energy, waste heat availability) variables that lead to the economic convenience of a WHRHEC system when integrated to a conventional VCC plant. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Improvements of a Failure Database for Marine Diesel Engines Using the RCM and Simulations
Energies 2020, 13(1), 104; https://doi.org/10.3390/en13010104 - 24 Dec 2019
Cited by 6 | Viewed by 878
Abstract
Diesel engines are widely used in marine transportation as a direct connection to the propeller and as electrical principal or auxiliary generator sets. The engine is the most critical piece of equipment on a vessel platform; therefore, the engine’s reliability is paramount in [...] Read more.
Diesel engines are widely used in marine transportation as a direct connection to the propeller and as electrical principal or auxiliary generator sets. The engine is the most critical piece of equipment on a vessel platform; therefore, the engine’s reliability is paramount in order to optimize safety, life cycle costs, and energy of the boat, and hence, vessel availability. In this paper, the improvements of a failure database used for a four-stroke high-speed marine diesel engine are discussed. This type of engine is normally used in military and civil vessels as the main engine of small patrols and yachts and as an auxiliary generator set (GENSET) for larger vessels. This database was assembled by considering “failure modes, effects, and criticality analysis (FMECA),” as well as an analysis of the symptoms obtained in an engine failure simulator. The FMECA was performed following the methodology of reliability-centered maintenance (RCM), while the engine response against failures was obtained from a failure simulator based on a thermodynamic one-dimensional model created by the authors, which was adjusted and validated with experimental data. The novelty of this work is the methodology applied, which combines expert knowledge of the asset, the RCM methodology, and the failure simulation to obtain an accurate and reliable database for the prediction of failures, which serves as a key element of a diesel engine failure diagnosis system. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
An Energetic Model for Detonation of Granulated Solid Propellants
Energies 2019, 12(23), 4459; https://doi.org/10.3390/en12234459 - 22 Nov 2019
Cited by 2 | Viewed by 724
Abstract
Unexpected detonation of granular solid energetic materials is a key safety issue in the propellants manufacturing industry. In this work, a model developed for the characterization of the early stages of the detonation process of granular solid energetic materials is presented. The model [...] Read more.
Unexpected detonation of granular solid energetic materials is a key safety issue in the propellants manufacturing industry. In this work, a model developed for the characterization of the early stages of the detonation process of granular solid energetic materials is presented. The model relies on a two-phase approach which considers the conservation equations of mass, momentum, and energy and constitutive relations for mass generation, gas-solid particle interaction, interphase heat transfer, and particle-particle stress. The work considers an extension of approximated Riemann solvers and Total Variation Diminishing (TVD) schemes to the solid phase for the numerical integration of the problem. The results obtained with this model show a good agreement with data available in the literature and confirm the potential of the numerical schemes applied to this type of model. The results also permit to assess the effectiveness of different numerical schemes to predict the early stages of this transient combustion process. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Fast Heating Model for the Aircraft Cabin Air
Energies 2019, 12(18), 3565; https://doi.org/10.3390/en12183565 - 18 Sep 2019
Cited by 1 | Viewed by 727
Abstract
Maintaining a suitable cabin air temperature distribution is essential for providing an acceptable thermal environment for passengers and crew. However, cabin air may be very cold for the first flight in winter morning. It could be difficult to heat quickly the cabin air [...] Read more.
Maintaining a suitable cabin air temperature distribution is essential for providing an acceptable thermal environment for passengers and crew. However, cabin air may be very cold for the first flight in winter morning. It could be difficult to heat quickly the cabin air and to maintain an acceptable temperature gradient before boarding with the existing environmental control system. This study developed numerical model for predicting the heating process that coupled airflow and heat transfer in a cabin. The model was validated by using the experimental data obtained from an MD-82 airliner. With the validated numerical model, this investigation proposed to use an electric blanket to heat cabin air quickly and to reduce the air temperature gradient. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Analysis of Thermodynamic Models for Simulation and Optimisation of Organic Rankine Cycles
Energies 2019, 12(17), 3307; https://doi.org/10.3390/en12173307 - 27 Aug 2019
Cited by 2 | Viewed by 917
Abstract
Equations of state (EOSs) form the base of every thermodynamic model used in the design of industrial processes, but little work has been done to evaluate these in the context of such models. This work evaluates 13 EOSs for their accuracy, computational time [...] Read more.
Equations of state (EOSs) form the base of every thermodynamic model used in the design of industrial processes, but little work has been done to evaluate these in the context of such models. This work evaluates 13 EOSs for their accuracy, computational time and robustness when used in an in-house optimisation program that finds the maximum power output of an organic Rankine cycle. The EOSs represent popular choices in the industry, such as the simple cubic EOSs, and more complex EOSs such as the ones based on corresponding state principles (CSP). These results were compared with results from using the Groupe Européen de Recherches Gazières (GERG) EOS, whose error is within experimental uncertainty. It appears that the corresponding state EOSs find a solution to the optimisation problem notably faster than GERG without significant loss of accuracy. A corresponding state method which used the Peng–Robinson EOS to calculate the shape factors and a highly accurate EOS for propane as the reference EOS, was shown to have a total deviation of just 0.6% as compared to GERG while also being 10 times as fast. The CSP implementation was also more robust, being able to converge successfully more often. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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Article
Diesel Mean Value Engine Modeling Based on Thermodynamic Cycle Simulation Using Artificial Neural Network
Energies 2019, 12(14), 2823; https://doi.org/10.3390/en12142823 - 22 Jul 2019
Cited by 3 | Viewed by 1099
Abstract
This study aims to construct a reduced thermodynamic cycle model with high accuracy and high model execution speed based on artificial neural network training for real-time numerical analysis. This paper proposes a method of constructing a fast average-value model by combining a 1D [...] Read more.
This study aims to construct a reduced thermodynamic cycle model with high accuracy and high model execution speed based on artificial neural network training for real-time numerical analysis. This paper proposes a method of constructing a fast average-value model by combining a 1D plant model and exhaust gas recirculation (EGR) control logic. The combustion model of the detailed model uses a direct-injection diesel multi-pulse (DI-pulse) method similar to diesel combustion characteristics. The DI-pulse combustion method divides the volume of the cylinder into three zones, predicting combustion- and emission-related variables, and each combustion step comprises different correction variables. This detailed model is estimated to be within 5% of the reference engine test results. To reduce the analysis time while maintaining the accuracy of engine performance prediction, the cylinder volumetric efficiency and the exhaust gas temperature were predicted using an artificial neural network. Owing to the lack of input variables in the training of artificial neural networks, it was not possible to predict the 0.6–0.7 range for volumetric efficiency and the 1000–1200 K range for exhaust gas temperature. This is because the mean value model changes the fuel injection method from the common rail fuel injection mode to the single injection mode in the model reduction process and changes the in-cylinder combustion according to the injection timing of the fuel amount injected. In addition, the mean value model combined with EGR logic, i.e., the single-input single-output (SISO) coupled mean value model, verifies the accuracy and responsiveness of the EGR control logic model through a step-transient process. By comparing the engine performance results of the SISO coupled mean value model with those of the mean value model, it is observed that the SISO coupled mean value model achieves the desired target EGR rate within 10 s. The EGR rate is predicted to be similar to the response of volumetric efficiency. This process intuitively predicted the main performance parameters of the engine model through artificial neural networks. Full article
(This article belongs to the Special Issue Modelling of Thermal and Energy Systems)
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