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Two metaheuristic optimisation methods were employed to solve an inverse heat transfer problem involving a phase change material (PCM). The aim was to identify the relationship ceff(T) between the effective heat capacity and temperature during melting and solidification of the PCM. Many researchers have reported a significant asymmetricity between the melting and solidification processes of PCMs. This phenomenon is usually referred to as the phase change hysteresis. To account for the phase change hysteresis, the relationship between the effective heat capacity and temperature was sought in the form of two independent ceff(T) curves; one for the melting process and the other for the solidification process. A numerical model of an air-PCM heat exchanger was employed for the development, testing, fine-tuning, and evaluation of the calculation procedure for the inverse heat transfer problem. The particle swarm optimisation method and the differential evolution method were employed for the inverse identification of the ceff(T) curves. The developed calculation procedure proved to be robust and accurate when applied to pre-simulated data where the exact solution was known to exist. When applied to the data from the experiments with the air-PCM heat exchanger, the calculation procedure confirmed its robustness (the solution was always found), but the accuracy of the results was somewhat lower. The discrepancy of between 2.9% and 15.7% was observed between the phase change enthalpies obtained by the Differential Scanning Calorimetry (DSC) and the phase change enthalpies obtained by the solution of the inverse problem. The temperatures of the phase change peaks, identified from the inverse problem, differed by between 0.34°C and 4.93°C from the temperatures obtained from the DSC analysis.
Martin Zálešák; Pavel Charvát; Lubomír Klimeš. Identification of the effective heat capacity–temperature relationship and the phase change hysteresis in PCMs by means of an inverse heat transfer problem solved with metaheuristic methods. Applied Thermal Engineering 2021, 197, 117392 .
AMA StyleMartin Zálešák, Pavel Charvát, Lubomír Klimeš. Identification of the effective heat capacity–temperature relationship and the phase change hysteresis in PCMs by means of an inverse heat transfer problem solved with metaheuristic methods. Applied Thermal Engineering. 2021; 197 ():117392.
Chicago/Turabian StyleMartin Zálešák; Pavel Charvát; Lubomír Klimeš. 2021. "Identification of the effective heat capacity–temperature relationship and the phase change hysteresis in PCMs by means of an inverse heat transfer problem solved with metaheuristic methods." Applied Thermal Engineering 197, no. : 117392.
The paper presents the comparison of optimization-regulation algorithms applied to the secondary cooling zone in continuous steel casting where the semi-product withdraws most of its thermal energy. In steel production, requirements towards obtaining defect-free semi-products are increasing day-by-day and the products, which would satisfy requirements of the consumers a few decades ago, are now far below the minimum required quality. To fulfill the quality demands towards minimum occurrence of defects in secondary cooling as possible, some regulation in the casting process is needed. The main concept of this paper is to analyze and compare the most known metaheuristic optimization approaches applied to the continuous steel casting process. Heat transfer and solidification phenomena are solved by using a fast 2.5D slice numerical model. The objective function is set to minimize the surface temperature differences in secondary cooling zones between calculated and targeted surface temperatures by suitable water flow rates through cooling nozzles. Obtained optimization results are discussed and the most suitable algorithm for this type of optimization problem is identified. Temperature deviations and cooling water flow rates in the secondary cooling zone, together with convergence rate and operation times needed to reach the stop criterium for each optimization approach, are analyzed and compared to target casting conditions based on a required temperature distribution of the strand. The paper also contains a brief description of applied heuristic algorithms. Some of the algorithms exhibited faster convergence rate than others, but the optimal solution was reached in every optimization run by only one algorithm.
Michal Brezina; Tomas Mauder; Lubomir Klimes; Josef Stetina. Comparison of Optimization-Regulation Algorithms for Secondary Cooling in Continuous Steel Casting. Metals 2021, 11, 237 .
AMA StyleMichal Brezina, Tomas Mauder, Lubomir Klimes, Josef Stetina. Comparison of Optimization-Regulation Algorithms for Secondary Cooling in Continuous Steel Casting. Metals. 2021; 11 (2):237.
Chicago/Turabian StyleMichal Brezina; Tomas Mauder; Lubomir Klimes; Josef Stetina. 2021. "Comparison of Optimization-Regulation Algorithms for Secondary Cooling in Continuous Steel Casting." Metals 11, no. 2: 237.
The steel industry represents a chain of technological processes, which consume a vast amount of energy and water, and produce a large quantity of emissions. A number of restrictions and regulations have therefore been recently imposed on the steel industry and involved processes aiming at the improvement of the use of resources, reduction of footprint in the natural environment as well as at the enhancement of overall efficiency of the steel production. In contrast to other research papers, the paper focuses on water use in a particular steelmaking process - continuous steel casting, which is used to cast more than 95% of the worldwide steel production. Approaches allowing the minimisation of water consumption are first identified and analysed. Spray cooling using once-through water and its substitution with dry cooling coupled with internally-cooled rollers by means of closed-loop water is computationally investigated. A 3D heat transfer and solidification model for continuous steel casting, which was validated with data from an actual steel plant, was used for this purpose. The results indicate that partial substitution of water spray cooling with dry cooling can provide a 48% lower once-through water use, which represents approximately a 1.5 m3/min reduction in water consumption. The annual potential for water savings at a steel plant operating three casters at 24/7 is about 2.4 Mm3.
Lubomír Klimeš; Michal Březina; Tomáš Mauder; Pavel Charvát; Jiří Jaromír Klemeš; Josef Štětina. Dry cooling as a way toward minimisation of water consumption in the steel industry: A case study for continuous steel casting. Journal of Cleaner Production 2020, 275, 123109 .
AMA StyleLubomír Klimeš, Michal Březina, Tomáš Mauder, Pavel Charvát, Jiří Jaromír Klemeš, Josef Štětina. Dry cooling as a way toward minimisation of water consumption in the steel industry: A case study for continuous steel casting. Journal of Cleaner Production. 2020; 275 ():123109.
Chicago/Turabian StyleLubomír Klimeš; Michal Březina; Tomáš Mauder; Pavel Charvát; Jiří Jaromír Klemeš; Josef Štětina. 2020. "Dry cooling as a way toward minimisation of water consumption in the steel industry: A case study for continuous steel casting." Journal of Cleaner Production 275, no. : 123109.
The energy industry is currently the second largest anthropogenic source of mercury pollution worldwide, and in many countries, it is by far the largest anthropogenic source of mercury emissions. Mercury emissions can be traced to almost the entire energy industry value chain. Combustion of coal is the primary source of mercury emissions in energy production. Biomass, which is considered a renewable fuel, is also a source of atmospheric mercury emissions. A general trend from landfill waste disposal to waste incineration can be observed in many countries, but waste-to-energy incineration is also a source of mercury emissions. The increased mercury levels have been recorded in fish living in the reservoirs for hydroelectricity. The adverse effects of mercury exposure on human health have been indicated in a number of studies, and there seems to be no ‘zero effect’ exposure level. As a result, the mitigation of mercury emissions is gaining more and more attention. The overview creates the base for further research for quantification of the effect of mercury emissions on the environment and on human health, which can be expressed and quantified by Mercury Footprints.
Pavel Charvát; Lubomír Klimeš; Jiří Pospíšil; Jiří Jaromír Klemeš; Petar Sabev Varbanov. An overview of mercury emissions in the energy industry - A step to mercury footprint assessment. Journal of Cleaner Production 2020, 267, 122087 .
AMA StylePavel Charvát, Lubomír Klimeš, Jiří Pospíšil, Jiří Jaromír Klemeš, Petar Sabev Varbanov. An overview of mercury emissions in the energy industry - A step to mercury footprint assessment. Journal of Cleaner Production. 2020; 267 ():122087.
Chicago/Turabian StylePavel Charvát; Lubomír Klimeš; Jiří Pospíšil; Jiří Jaromír Klemeš; Petar Sabev Varbanov. 2020. "An overview of mercury emissions in the energy industry - A step to mercury footprint assessment." Journal of Cleaner Production 267, no. : 122087.
The present review provides an overview and critical analysis of recently published simulation approaches and experimental studies addressing the phase change hysteresis (PCH) and supercooling (SC) of phase change materials (PCMs). In terms of the enthalpy-temperature h(T) relationships for the solid-liquid phase changes, the PCH is a temperature delay of the h(T) curves between the melting and solidification process, while SC means that solidification does not start at the nominal solidification temperature and a lower temperature is needed for the nucleation to start. However, the PCH and SC are often neglected in the studies dealing with thermal energy storage in PCMs. Several studies indicate that experimental techniques and conditions can significantly influence the behaviour of PCMs, including the PCH and SC. Another issue is the difference in the behaviour of small samples, such as those used in the differential scanning calorimetry (DSC), and the behaviour of bulk PCM. As the DSC results are often used as inputs in simulations of systems with the bulk PCM, this issue is of high importance. Further, the entire amount of PCM does not always fully melt and solidify, and thus partial phase transitions are common in many real-life applications. Several modelling approaches have been proposed to address the PCH and SC of PCM. While simulations of complete phase change cycles are rather straightforward even with the PCH and SC involved, incomplete phase change cycles with partial phase transitions are much more challenging, and this issue has not yet been satisfactorily solved. The simulation techniques identified in the literature search were analysed, assessed, and compared to each other. The results indicate that there are only a few modelling approaches for partial phase transitions, and only some of them are reasonably validated with experimental data.
Lubomir Klimes; Pavel Charvat; Mahmood Mastani Joybari; Martin Zálešák; Fariborz Haghighat; Karthik Panchabikesan; Mohamed El Mankibi; Yanping Yuan. Computer modelling and experimental investigation of phase change hysteresis of PCMs: The state-of-the-art review. Applied Energy 2020, 263, 114572 .
AMA StyleLubomir Klimes, Pavel Charvat, Mahmood Mastani Joybari, Martin Zálešák, Fariborz Haghighat, Karthik Panchabikesan, Mohamed El Mankibi, Yanping Yuan. Computer modelling and experimental investigation of phase change hysteresis of PCMs: The state-of-the-art review. Applied Energy. 2020; 263 ():114572.
Chicago/Turabian StyleLubomir Klimes; Pavel Charvat; Mahmood Mastani Joybari; Martin Zálešák; Fariborz Haghighat; Karthik Panchabikesan; Mohamed El Mankibi; Yanping Yuan. 2020. "Computer modelling and experimental investigation of phase change hysteresis of PCMs: The state-of-the-art review." Applied Energy 263, no. : 114572.
Mass transfer plays a critical role in the efficiency of photocatalytic oxidation (PCO) technology for air purification applications. There has been limited work on the exploration of mass transfer in the PCO reactor with the non-ideal flow. In this work, the performance of a continuous heterogeneous ultraviolet photocatalytic oxidation (UV-PCO) reactor was investigated and addressed under mass transfer limitation and axial dispersion. First, CFD modeling was used to determine the flow distribution in the reactor at various airflow rates. The residence time distribution (RTD) analysis with a tracer gas (CO2) was carried out for the experimental validation of the simulation model and good agreement between experimental and simulation data was achieved. Further, a quick and straightforward methodology employing an axial dispersion plug flow model was used to study the RTD. The proposed model could predict the residence time distribution of CO2 with high accuracy. Results of the RTD for CO2 in the presence and absence of a PCO filter (silica fiber felts (SFF) modified with TiO2) were almost identical due to the high porosity of the filter. The model was then used for the evaluation of the axial dispersion of methyl ethyl ketone (MEK) at different flow rates. Owing to a low value of the Peclet number (Pe < 100), the flow in the reactor deviated from an ideal plug flow and dispersion could not be ignored. The photocatalysis reaction of MEK by the SFF filter under the mass-transfer-controlled regime was further addressed. A steady-state mass balance equation was implemented for the assessment of the performance of the UV-PCO reactor in the presence of axial dispersion and mass transfer limitation. The mass transfer coefficient was calculated with the use of the developed model and a correlation for the Sherwood number was proposed to relate the mass transfer coefficient to the flow rate and fiber structure. The proposed correlation was assessed and compared with the other empirical formulas available in the literature.
Mojtaba Malayeri; Chang-Seo Lee; Fariborz Haghighat; Lubomir Klimes. Modeling of gas-phase heterogeneous photocatalytic oxidation reactor in the presence of mass transfer limitation and axial dispersion. Chemical Engineering Journal 2020, 386, 124013 .
AMA StyleMojtaba Malayeri, Chang-Seo Lee, Fariborz Haghighat, Lubomir Klimes. Modeling of gas-phase heterogeneous photocatalytic oxidation reactor in the presence of mass transfer limitation and axial dispersion. Chemical Engineering Journal. 2020; 386 ():124013.
Chicago/Turabian StyleMojtaba Malayeri; Chang-Seo Lee; Fariborz Haghighat; Lubomir Klimes. 2020. "Modeling of gas-phase heterogeneous photocatalytic oxidation reactor in the presence of mass transfer limitation and axial dispersion." Chemical Engineering Journal 386, no. : 124013.
Lubomír Klimeš; Jiří Pospíšil; Josef Štětina; Petr Kracík. Semi-empirical balance-based computational model of air-cooled condensers with the A-frame layout. Energy 2019, 182, 1013 -1027.
AMA StyleLubomír Klimeš, Jiří Pospíšil, Josef Štětina, Petr Kracík. Semi-empirical balance-based computational model of air-cooled condensers with the A-frame layout. Energy. 2019; 182 ():1013-1027.
Chicago/Turabian StyleLubomír Klimeš; Jiří Pospíšil; Josef Štětina; Petr Kracík. 2019. "Semi-empirical balance-based computational model of air-cooled condensers with the A-frame layout." Energy 182, no. : 1013-1027.
Earlier applications of phase change material (PCM)-to-air heat exchangers (PAHXs) reported the insufficient cooling charging energy needed for complete solidification of the PCM in free cooling systems. Also, the prediction of PAHX performance under low airflow regimes is a system limitation for free cooling applications. Besides, the implementation of the long wave thermal radiation cooling concept has not gained much attention in the free cooling design of PAHX units. This paper reports the development of PAHX system for building envelope applications that promotes the thermal radiation loss to the sky during night-time to maximize the cooling potential. A 2D numerical model has been developed considering the PCM thermal behavior, short and long wave radiation, and convection phenomena. New thermal boundaries of long-wave radiation have been proposed between system elements and the sky temperature. In addition, the model considered various forms of convective heat transfer phenomena. The apparent heat capacity method was used to simulate the thermal storage process. Experimentally obtained data and inter-model comparison were used to validate the proposed model. Two full-scale prototypes of the developed PAHX system were designed and tested under real conditions using two different types of PCMs. A parametric analysis was conducted to investigate the system thermal behavior under various air velocity profiles in the air channel and various inlet air temperature conditions. The results indicate that the building envelope integrated PAHX can use the sky radiation as a cooling source.
Mohamed Dardir; Mohamed El Mankibi; Fariborz Haghighat; Lubomir Klimes. Development of PCM-to-air heat exchanger for integration in building envelope–modeling and validation. Solar Energy 2019, 190, 367 -385.
AMA StyleMohamed Dardir, Mohamed El Mankibi, Fariborz Haghighat, Lubomir Klimes. Development of PCM-to-air heat exchanger for integration in building envelope–modeling and validation. Solar Energy. 2019; 190 ():367-385.
Chicago/Turabian StyleMohamed Dardir; Mohamed El Mankibi; Fariborz Haghighat; Lubomir Klimes. 2019. "Development of PCM-to-air heat exchanger for integration in building envelope–modeling and validation." Solar Energy 190, no. : 367-385.
Steelmakers focus on producing high quality steel to minimize defects, as this strategy maximizes their productivity and profit. The paper describes how to create a macro model of solidification of continuously cast steel. The described model is fully 3D, non-stationary and is implemented in a form suitable for GPU (Graphics Processing Unit). The formation of blank cracks follows the continuous casting of steel from the beginning and is a problem for the production of some steel grades. The various criteria that can predict the occurrence of defects in continuous steel casting can serve to optimize the casting process, control the blank cooling, and then predict the quality of the resulting blank.
Josef Stetina; Michal Brezina; Lubomir Klimes; Tomas Mauder. The real-time macro-solidification macro model for crack prediction. 38TH MEETING OF DEPARTMENTS OF FLUID MECHANICS AND THERMODYNAMICS 2019, 2118, 030043 .
AMA StyleJosef Stetina, Michal Brezina, Lubomir Klimes, Tomas Mauder. The real-time macro-solidification macro model for crack prediction. 38TH MEETING OF DEPARTMENTS OF FLUID MECHANICS AND THERMODYNAMICS. 2019; 2118 (1):030043.
Chicago/Turabian StyleJosef Stetina; Michal Brezina; Lubomir Klimes; Tomas Mauder. 2019. "The real-time macro-solidification macro model for crack prediction." 38TH MEETING OF DEPARTMENTS OF FLUID MECHANICS AND THERMODYNAMICS 2118, no. 1: 030043.
The influence of latent heat thermal energy storage integrated with the solar absorber plate was investigated through lab experiments and computer simulations. Two experimental solar air collectors were built. One collector had the solar absorber plate made of sheet metal while that of the other collector consisted of nine aluminium panels containing a paraffin-based PCM. The square-wave variation of the solar radiation intensity was considered, and a good agreement was observed between the computer simulations and experimental data. The peak-to-peak amplitudes of the outlet air temperature were reduced from 11 K (the collector with the metal sheet absorber) to 5 K (the collector with the absorber plate containing the PCM). The main contribution of the study consists in the experimental approach and in the validated model of the solar air collector for TRNSYS simulation tool. The experiments were conducted in an environmental chamber fitted with a solar simulator under both the quasi steady-state and the transient boundary conditions. In comparison to other studies with experiments conducted outdoors, the controlled environment of the climatic chamber allowed for the reduction of the uncertainty on the side of the boundary conditions, e.g. the influence of wind speed, wind direction, and cloudiness.
Pavel Charvát; Lubomír Klimeš; Ondřej Pech; Jiří Hejčík. Solar air collector with the solar absorber plate containing a PCM – Environmental chamber experiments and computer simulations. Renewable Energy 2019, 143, 731 -740.
AMA StylePavel Charvát, Lubomír Klimeš, Ondřej Pech, Jiří Hejčík. Solar air collector with the solar absorber plate containing a PCM – Environmental chamber experiments and computer simulations. Renewable Energy. 2019; 143 ():731-740.
Chicago/Turabian StylePavel Charvát; Lubomír Klimeš; Ondřej Pech; Jiří Hejčík. 2019. "Solar air collector with the solar absorber plate containing a PCM – Environmental chamber experiments and computer simulations." Renewable Energy 143, no. : 731-740.
The energy saving potential (ESP) of passive cooling of buildings with the use of an air-PCMheat exchanger (cold storage unit) was investigated through numerical simulations. One of the goals of the study was to identify the phase change temperature of a PCM that would provide the highest energy saving potential under the specific climate and operating conditions. The considered air-PCM heat exchanger contained 100 aluminum panels filled with a PCM. The PCM had a thermal storage capacity of 200 kJ/kg in the phase change temperature range of 4 ∘ C. The air-PCM heat exchanger was used to cool down the outdoor air supplied to a building during the day, and the heat accumulated in the PCM was rejected to the outdoors at night. The simulations were conducted for 16 locations in Europe with the investigated time period from 1 May–30 September. The outdoor temperature set point of 20 ∘ C was used for the utilization of stored cold. In the case of the location with the highest ESP, the scenarios with the temperature set point and without the set point (which provides maximum theoretical ESP) were compared under various air flow rates. The average utilization rate of the heat of fusion did not exceed 50% in any of the investigated scenarios.
Pavel Charvát; Lubomír Klimeš; Martin Zálešák. Utilization of an Air-PCM Heat Exchanger in Passive Cooling of Buildings: A Simulation Study on the Energy Saving Potential in Different European Climates. Energies 2019, 12, 1133 .
AMA StylePavel Charvát, Lubomír Klimeš, Martin Zálešák. Utilization of an Air-PCM Heat Exchanger in Passive Cooling of Buildings: A Simulation Study on the Energy Saving Potential in Different European Climates. Energies. 2019; 12 (6):1133.
Chicago/Turabian StylePavel Charvát; Lubomír Klimeš; Martin Zálešák. 2019. "Utilization of an Air-PCM Heat Exchanger in Passive Cooling of Buildings: A Simulation Study on the Energy Saving Potential in Different European Climates." Energies 12, no. 6: 1133.
Thermally activated building structures with latent heat thermal energy storage (LHTES) are relatively new elements of building thermal energy systems. The system considered in the present study involved lightweight wall panels with a plaster containing a microencapsulated phase change material (PCM). The polyethylene tubes of small diameter for heat transfer fluid were embedded in the plaster. The wall panel system could be used for both heating and cooling. The PCM provided short-term thermal energy storage in case of intermittent supply of heat and cold (e.g. in case of a PV powered heat pump). A 1D computer model of the wall system was developed and implemented as a TRNSYS type. Consequently, an optimization model based on the 1D model of the system was developed. The optimization model employed a metaheuristic particle swarm optimization method. The aim of the optimization was to determine the position of the tubes for HTF, relative to the surface of the panel, that would provide fast thermal response and, at the same time, high amount of stored heat. The optimization was performed for heating operation.
Lubomír Klimeš; Pavel Charvát; Milan Ostrý. An optimization study into thermally activated wall system with latent heat thermal energy storage. IOP Conference Series: Earth and Environmental Science 2019, 238, 012016 .
AMA StyleLubomír Klimeš, Pavel Charvát, Milan Ostrý. An optimization study into thermally activated wall system with latent heat thermal energy storage. IOP Conference Series: Earth and Environmental Science. 2019; 238 (1):012016.
Chicago/Turabian StyleLubomír Klimeš; Pavel Charvát; Milan Ostrý. 2019. "An optimization study into thermally activated wall system with latent heat thermal energy storage." IOP Conference Series: Earth and Environmental Science 238, no. 1: 012016.
The paper deals with the comparison of the one-dimensional (1D) and three-dimensional (3D) models of a thermally activated wall panel with a microencapsulated phase change material. The 3D model was created in the off-the-shelf simulation tool COMSOL Multiphysics. The 1D model was an in-house developed TRNSYS type. The main advantage of the 1D model is the short computation time but it comes at the expense of lower accuracy and less detailed results. In most building performance simulations, however, detailed knowledge of the temperature distribution over the surface of a wall is not important. For this reason, the results of both models were compared in terms of the mean surface temperature of the wall panels, the outlet water temperature, and the overall heating and cooling capacity of the panels. The two models provided very similar results for the practical range of water flow rates. The mass flow rate of water had a relatively small influence on the mean surface temperature and the heating and cooling capacity of the panels. For the one-tube mass flow rates of water between 0.25 and 2 g/s, the mean surface temperature was in the range of 28–29.5C in the heating scenario and 21–21.5C in the cooling scenario, with the heating and cooling capacity ranges of 65 W/m2 to 75 W/m2 and 35 W/m2 to 40 W/m2, respectively.
L. Klimeš; P. Charvát; M. Ostrý. Thermally activated wall panels with microencapsulated PCM: comparison of 1D and 3D models. Journal of Building Performance Simulation 2018, 12, 404 -419.
AMA StyleL. Klimeš, P. Charvát, M. Ostrý. Thermally activated wall panels with microencapsulated PCM: comparison of 1D and 3D models. Journal of Building Performance Simulation. 2018; 12 (4):404-419.
Chicago/Turabian StyleL. Klimeš; P. Charvát; M. Ostrý. 2018. "Thermally activated wall panels with microencapsulated PCM: comparison of 1D and 3D models." Journal of Building Performance Simulation 12, no. 4: 404-419.
The world trade volume of Liquefied Natural Gas (LNG) is increasing year by year. Unlike gaseous natural gas (NG), which is transported through a fixed network of pipelines, LNG offers more flexibility to both the exporters and the importers as it can be transported between any pair of exporting and receiving LNG terminals. The LNG process, consisting of liquefaction, transportation, storage, and regasification of LNG, is accompanied by certain energy demands. The paper focuses on the evaluation of the chain of energy transformations involved in the LNG process. Based on the review of existing information, the entire process is evaluated from the view of the potential use of LNG for direct storage of cold and indirect storage of power. The analysis of the existing data shows that the overall efficiency of using LNG for operative energy storage depends very much on the technologies involved and on the overall capacity of the particular technology. The combination of energy-efficient liquefaction technologies and regasification technologies with energy recovery makes it possible to employ LNG as an energy storage medium even when transported over large distances.
Jiří Pospíšil; Pavel Charvát; Olga Arsenyeva; Lubomir Klimes; Michal Špiláček; Jiří Jaromír Klemeš. Energy demand of liquefaction and regasification of natural gas and the potential of LNG for operative thermal energy storage. Renewable and Sustainable Energy Reviews 2018, 99, 1 -15.
AMA StyleJiří Pospíšil, Pavel Charvát, Olga Arsenyeva, Lubomir Klimes, Michal Špiláček, Jiří Jaromír Klemeš. Energy demand of liquefaction and regasification of natural gas and the potential of LNG for operative thermal energy storage. Renewable and Sustainable Energy Reviews. 2018; 99 ():1-15.
Chicago/Turabian StyleJiří Pospíšil; Pavel Charvát; Olga Arsenyeva; Lubomir Klimes; Michal Špiláček; Jiří Jaromír Klemeš. 2018. "Energy demand of liquefaction and regasification of natural gas and the potential of LNG for operative thermal energy storage." Renewable and Sustainable Energy Reviews 99, no. : 1-15.
Lubomír Klimeš; Tomáš Mauder; Pavel Charvát; Josef Štětina. Front tracking in modelling of latent heat thermal energy storage: Assessment of accuracy and efficiency, benchmarking and GPU-based acceleration. Energy 2018, 155, 297 -311.
AMA StyleLubomír Klimeš, Tomáš Mauder, Pavel Charvát, Josef Štětina. Front tracking in modelling of latent heat thermal energy storage: Assessment of accuracy and efficiency, benchmarking and GPU-based acceleration. Energy. 2018; 155 ():297-311.
Chicago/Turabian StyleLubomír Klimeš; Tomáš Mauder; Pavel Charvát; Josef Štětina. 2018. "Front tracking in modelling of latent heat thermal energy storage: Assessment of accuracy and efficiency, benchmarking and GPU-based acceleration." Energy 155, no. : 297-311.
Nowadays, people are increasingly interested in renewable energy sources and accumulation of energy for its efficient use. The use of non-renewable resources is progressively decreasing due to their adverse changes in climate conditions and high production of CO2 emissions. This work deals with the problem of heat accumulation by means of the phase change of a material using the Stefan problem, which serves to describe the temperature distribution in the medium and to determine the location of the interface between the solid and liquid phase. This approach is used to determine desired properties and thermal behaviour of the material under different accumulation requirements. The main objective was to create and solve an optimization model in order to determine heat transfer conditions and other parameters to ensure the extrema of thermal behaviour characterization.
Michal Brezina; Lubomir Klimes; Josef Stetina. Optimization of Material Properties of Phase Change Materials for Latent Heat Thermal Energy Storage. MENDEL 2018, 24, 47 -54.
AMA StyleMichal Brezina, Lubomir Klimes, Josef Stetina. Optimization of Material Properties of Phase Change Materials for Latent Heat Thermal Energy Storage. MENDEL. 2018; 24 (1):47-54.
Chicago/Turabian StyleMichal Brezina; Lubomir Klimes; Josef Stetina. 2018. "Optimization of Material Properties of Phase Change Materials for Latent Heat Thermal Energy Storage." MENDEL 24, no. 1: 47-54.
A study into the performance of a solar chimney and a solar photovoltaic (PV)-powered fan for ventilation applications was carried out using numerical simulations. The performance of the solar chimney was compared with that of a direct current (DC) fan powered by a solar PV panel. The comparison was carried out using the same area of the irradiated surface—the area of the solar absorber plate in the case of the solar chimney and the area of the solar panel in the case of the photovoltaic-powered fan. The two studied cases were compared under various solar radiation intensities of incident solar radiation. The results indicate that the PV-powered fans significantly outperform solar chimneys in terms of converting solar energy into the kinetic energy of air motion. Moreover, ventilation with PV-powered fans offers more flexibility in the arrangement of the ventilation system and also better control of the air flow rates in the case of battery storage.
Lubomír Klimeš; Pavel Charvát; Jiří Hejčík. Comparison of the Energy Conversion Efficiency of a Solar Chimney and a Solar PV-Powered Fan for Ventilation Applications. Energies 2018, 11, 912 .
AMA StyleLubomír Klimeš, Pavel Charvát, Jiří Hejčík. Comparison of the Energy Conversion Efficiency of a Solar Chimney and a Solar PV-Powered Fan for Ventilation Applications. Energies. 2018; 11 (4):912.
Chicago/Turabian StyleLubomír Klimeš; Pavel Charvát; Jiří Hejčík. 2018. "Comparison of the Energy Conversion Efficiency of a Solar Chimney and a Solar PV-Powered Fan for Ventilation Applications." Energies 11, no. 4: 912.
Uroš Stritih; Pavel Charvat; Rok Koželj; Lubomir Klimes; Eneja Osterman; Milan Ostry; Vincenc Butala. PCM thermal energy storage in solar heating of ventilation air—Experimental and numerical investigations. Sustainable Cities and Society 2018, 37, 104 -115.
AMA StyleUroš Stritih, Pavel Charvat, Rok Koželj, Lubomir Klimes, Eneja Osterman, Milan Ostry, Vincenc Butala. PCM thermal energy storage in solar heating of ventilation air—Experimental and numerical investigations. Sustainable Cities and Society. 2018; 37 ():104-115.
Chicago/Turabian StyleUroš Stritih; Pavel Charvat; Rok Koželj; Lubomir Klimes; Eneja Osterman; Milan Ostry; Vincenc Butala. 2018. "PCM thermal energy storage in solar heating of ventilation air—Experimental and numerical investigations." Sustainable Cities and Society 37, no. : 104-115.
Lubomir Klimes; Pavel Popela; Tomas Mauder; Josef Štétina; Pavel Charvat. Two-stage stochastic programming approach to a PDE-constrained steel production problem with the moving interface. Kybernetika 2018, 1047 -1070.
AMA StyleLubomir Klimes, Pavel Popela, Tomas Mauder, Josef Štétina, Pavel Charvat. Two-stage stochastic programming approach to a PDE-constrained steel production problem with the moving interface. Kybernetika. 2018; ():1047-1070.
Chicago/Turabian StyleLubomir Klimes; Pavel Popela; Tomas Mauder; Josef Štétina; Pavel Charvat. 2018. "Two-stage stochastic programming approach to a PDE-constrained steel production problem with the moving interface." Kybernetika , no. : 1047-1070.
Vaclav Pistek; Lubomir Klimes; Tomas Mauder; Pavel Kucera. Optimal design of structure in rheological models: an automotive application to dampers with high viscosity silicone fluids. Journal of Vibroengineering 2017, 19, 4459 -4470.
AMA StyleVaclav Pistek, Lubomir Klimes, Tomas Mauder, Pavel Kucera. Optimal design of structure in rheological models: an automotive application to dampers with high viscosity silicone fluids. Journal of Vibroengineering. 2017; 19 (6):4459-4470.
Chicago/Turabian StyleVaclav Pistek; Lubomir Klimes; Tomas Mauder; Pavel Kucera. 2017. "Optimal design of structure in rheological models: an automotive application to dampers with high viscosity silicone fluids." Journal of Vibroengineering 19, no. 6: 4459-4470.