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Giedre Streckiene currently works at the Department of Building Energetics, Vilnius Gediminas Technical University. Giedre does research in Thermal Engineering.
Ventilation systems have an energy saving potential by making the most of the good advantage of natural ventilation. However, its major limitation is the unpredictability of the driving forces leading to a mismatch between building demand and system performance. This paper presents an analysis of the operation of an innovative building ventilation system (a HiVent system). The developed system provides a ventilation method with the increased functionality of a roof turbine ventilator that can ensure air exchange inside the building, when the wind does not rotate the RTV sufficiently or completely due to a reduced speed. The system is equipped with an isobaric air tank storage and air tank turbofan. The main advantage of this system is that it uses only renewable wind energy. The case analysis has showed that the system functionality (the duration of time when the set exhaust airflow rate is ensured) can be increased by 12–25%. Analytical formalization and experimental testing of the system components has shown how their characteristics should be combined with each other; what improvements have potential to increase the efficiency of the system. This disclosure of the coherence of their interaction contributes to new knowledge about the use of renewable energy sources and ventilation technologies.
Dovydas Rimdžius; Juozas Bielskus; Giedrė Streckienė; Violeta Motuzienė; Vytautas Martinaitis. Operation analysis of the developed building ventilation system using turbofans and mechanical wind energy storage. Building and Environment 2021, 196, 107703 .
AMA StyleDovydas Rimdžius, Juozas Bielskus, Giedrė Streckienė, Violeta Motuzienė, Vytautas Martinaitis. Operation analysis of the developed building ventilation system using turbofans and mechanical wind energy storage. Building and Environment. 2021; 196 ():107703.
Chicago/Turabian StyleDovydas Rimdžius; Juozas Bielskus; Giedrė Streckienė; Violeta Motuzienė; Vytautas Martinaitis. 2021. "Operation analysis of the developed building ventilation system using turbofans and mechanical wind energy storage." Building and Environment 196, no. : 107703.
Latent heat thermal energy storage systems allow storing large amounts of energy in relatively small volumes. Phase change materials (PCMs) are used as a latent heat storage medium. However, low thermal conductivity of most PCMs results in long melting (charging) and solidification (discharging) processes. This study focuses on the PCM melting process in a fin-and-tube type copper heat exchanger. The aim of this study is to define analytically natural convection heat transfer coefficient and compare the results with experimental data. The study shows how the local heat transfer coefficient changes in different areas of the heat exchanger and how it is affected by the choice of characteristic length and boundary conditions. It has been determined that applying the calculation method of the natural convection occurring in the channel leads to results that are closer to the experiment. Using this method, the average values of the heat transfer coefficient (have ) during the entire charging process was obtained 68 W/m2K, compared to the experimental result have = 61 W/m2K. This is beneficial in the predesign stage of PCM-based thermal energy storage units.
Saulius Pakalka; Kęstutis Valančius; Giedrė Streckienė. Experimental and Theoretical Investigation of the Natural Convection Heat Transfer Coefficient in Phase Change Material (PCM) Based Fin-and-Tube Heat Exchanger. Energies 2021, 14, 716 .
AMA StyleSaulius Pakalka, Kęstutis Valančius, Giedrė Streckienė. Experimental and Theoretical Investigation of the Natural Convection Heat Transfer Coefficient in Phase Change Material (PCM) Based Fin-and-Tube Heat Exchanger. Energies. 2021; 14 (3):716.
Chicago/Turabian StyleSaulius Pakalka; Kęstutis Valančius; Giedrė Streckienė. 2021. "Experimental and Theoretical Investigation of the Natural Convection Heat Transfer Coefficient in Phase Change Material (PCM) Based Fin-and-Tube Heat Exchanger." Energies 14, no. 3: 716.
With the growing demand for energy efficient HVAC systems and integration of renewable energy sources, existing energy transformers are being improved and new solutions are being sought. Various energy storage technologies are applied to solve unpredictable renewable energy flows. This paper investigates an innovative ventilation system with roof turbine ventilator and variable volume isobaric air tank, which is used to store an excessive wind energy. The study focuses mainly on isobaric air storage tank operation. The experimental results of the tank charging and discharging processes under different operation conditions are presented. These conditions include different weights placed on the top of the storage and air flow rates in the wind tunnel. The operation of the tank during one windy day in chosen location is studied. The obtained data showed the initial results of the operation of the developed ventilation system and possible modifications in order to improve its functionality.
Giedrė Streckienė; Juozas Bielskus; Dovydas Rimdžius; Vytautas Martinaitis; Violeta Motuzienė. Experimental Analysis of an Air Storage Tank in Wind Driven Ventilation System. E3S Web of Conferences 2021, 231, 02003 .
AMA StyleGiedrė Streckienė, Juozas Bielskus, Dovydas Rimdžius, Vytautas Martinaitis, Violeta Motuzienė. Experimental Analysis of an Air Storage Tank in Wind Driven Ventilation System. E3S Web of Conferences. 2021; 231 ():02003.
Chicago/Turabian StyleGiedrė Streckienė; Juozas Bielskus; Dovydas Rimdžius; Vytautas Martinaitis; Violeta Motuzienė. 2021. "Experimental Analysis of an Air Storage Tank in Wind Driven Ventilation System." E3S Web of Conferences 231, no. : 02003.
Flow-mixing is common in technological processes, and both ejectors and turbofans can produce an interaction between flows with different energy potentials. Ejectors have been extensively used, and their analytical models have been widely presented. To the best of the authors’ knowledge, there is a lack of studies exploring the efficiencies of turbofans. The goal of this paper is to compare thermodynamic processes in these devices. Their efficiencies are compared in terms of compression and entrainment ratios. A comprehensive one-dimensional subsonic thermodynamic models of the ejector and turbofan are presented. The quantitative indices are obtained for the same initial conditions expressed as the ratio of differences in enthalpies for ideal compression and ideal expansion. When initial conditions are equal to the numeric value of the combination of the isentropic efficiency of the evaluated components (numerical case 0.16), both devices have the same efficiencies; at lower initial conditions (numerical case 0.10), a turbofan’s entrainment ratio is 1.5 times and compression efficiency 1.25 times higher; at higher values of initial conditions (numerical case 0.28), the ejector is more efficient. Such distinctive characteristics of turbofans and the nature of their variation may correspond to the specific application areas of technological equipment that require certain flow-mixing parameters.
Vytautas Martinaitis; Dovydas Rimdžius; Juozas Bielskus; Giedrė Streckienė; Violeta Motuzienė. Preliminary Comparison of the Performance of Thermodynamic Models of the Subsonic Ejector and Turbofan. Strojniški vestnik – Journal of Mechanical Engineering 2020, 66, 325 -336.
AMA StyleVytautas Martinaitis, Dovydas Rimdžius, Juozas Bielskus, Giedrė Streckienė, Violeta Motuzienė. Preliminary Comparison of the Performance of Thermodynamic Models of the Subsonic Ejector and Turbofan. Strojniški vestnik – Journal of Mechanical Engineering. 2020; 66 (5):325-336.
Chicago/Turabian StyleVytautas Martinaitis; Dovydas Rimdžius; Juozas Bielskus; Giedrė Streckienė; Violeta Motuzienė. 2020. "Preliminary Comparison of the Performance of Thermodynamic Models of the Subsonic Ejector and Turbofan." Strojniški vestnik – Journal of Mechanical Engineering 66, no. 5: 325-336.
Vis plačiau naudojant šilumos siurblius pastatų šildymui šaltuoju metų sezonu, išryškėja jų garintuvo šilumokaičio užšalimo problema. Šiame straipsnyje aptariamos pagrindinės užšalimo sukeliamos problemos, jų įtaka sistemos veikimui bei įrenginio efektyvumui – COP. Taip pat pateikiamos pagrindinės šerkšno ir ledo susidarymo mažinimo bei valdymo priemonės. Pastarosios išskiriamos į dvi grupes: aktyviąsias ir pasyviąsias. Aktyviosios priemonės daugiau susijusios su šilumos siurblio šilumokaičių paviršiaus apdirbimu, bet jų įtaka, palyginus su aktyviosiomis priemonėmis, yra mažesnė. Tarp aktyviųjų priemonių, kurių įtaka didesnė, bene, populiariausios yra reversinis šilumos siurblio ciklas ir karštų garų apėjimo linija (ang. hot gas bypass). Kitos apžvelgiamos priemonės reikalauja papildomos įrangos, dėl kurių išauga sistemos kaštai bei sudėtingumas. Vis dėlto, geriausią rezultatą galima pasiekti derinant aktyviąsias ir pasyviąsias priemones.
Tomas Kropas; Giedrė Streckienė. ORINIO ŠILUMOS SIURBLIO ŠILUMOKAIČIO UŽŠALIMO MAŽINIMO IR VALDYMO BŪDAI. 23-osios Lietuvos jaunųjų mokslininkų konferencijos „Mokslas – Lietuvos ateitis“ 2020 metų teminės konferencijos „Pastatų energetika“ (2020 m. gegužės 15 d.) straipsnių rinkinys. 2020, 1 .
AMA StyleTomas Kropas, Giedrė Streckienė. ORINIO ŠILUMOS SIURBLIO ŠILUMOKAIČIO UŽŠALIMO MAŽINIMO IR VALDYMO BŪDAI. 23-osios Lietuvos jaunųjų mokslininkų konferencijos „Mokslas – Lietuvos ateitis“ 2020 metų teminės konferencijos „Pastatų energetika“ (2020 m. gegužės 15 d.) straipsnių rinkinys.. 2020; ():1.
Chicago/Turabian StyleTomas Kropas; Giedrė Streckienė. 2020. "ORINIO ŠILUMOS SIURBLIO ŠILUMOKAIČIO UŽŠALIMO MAŽINIMO IR VALDYMO BŪDAI." 23-osios Lietuvos jaunųjų mokslininkų konferencijos „Mokslas – Lietuvos ateitis“ 2020 metų teminės konferencijos „Pastatų energetika“ (2020 m. gegužės 15 d.) straipsnių rinkinys. , no. : 1.
Designing a heat exchanger/accumulator which can store a high quantity of heat in a brief period of time is one of the most important technological challenges. In this study, heat exchangers are designed for industrial processes with high heat recovery and storage rates where steam is used and the release of this steam to the atmosphere is cyclical and lasts for a short period of time. In order to recover and store the highest possible amount of energy from the steam, an efficient heat recovery and storage system is required. Phase change materials (PCMs) which allow storing large amount of energy in relatively small volumes could be used in thermal energy storage (TES) systems. However, low thermal conductivity of most PCMs causes long melting and solidification processes, especially when high energy recovery and storage rates are required, which leads to the development of complex geometries of heat exchanger (HX) and a significant increase in production costs. The aim of this study is to experimentally compare and assess the operation of two PCM-based copper heat exchangers (PCM-HX) with different geometrical parameters. This study focuses on the configuration of a PCM-HX which would ensure faster heat exchange and lower production costs. Two different configurations of fin-and-tube HX (denoted by PCM-HX1 and PCM-HX2) were analysed. Experimental investigation shows that both PCM-HXs achieve similar results but taking into consideration the complexity of production, it is concluded that the PCM-HX2 ensures better performance (PCM-HX2: melting time 8 min, solidification – 0.25 min; PCM-HX1: melting time 10 min, solidification – 1.25 min).
Saulius Pakalka; Kęstutis Valančius; Giedrė Streckienė. Experimental comparison of the operation of PCM-based copper heat exchangers with different configurations. Applied Thermal Engineering 2020, 172, 115138 .
AMA StyleSaulius Pakalka, Kęstutis Valančius, Giedrė Streckienė. Experimental comparison of the operation of PCM-based copper heat exchangers with different configurations. Applied Thermal Engineering. 2020; 172 ():115138.
Chicago/Turabian StyleSaulius Pakalka; Kęstutis Valančius; Giedrė Streckienė. 2020. "Experimental comparison of the operation of PCM-based copper heat exchangers with different configurations." Applied Thermal Engineering 172, no. : 115138.
With the growth of energy-efficient building sector, ventilation systems are becoming increasingly important not only of fresh air supply but also in terms of energy consumption. The aim of this paper is to describe and analyse the operation of an air handling unit (AHU) with a heat pump using energy and exergy analyses under the variable environmental temperature (from –30 °C to 10 °C). The application of selected methods is illustrated in a case study of an AHU using environmental temperatures of Vilnius city during heating season (from the beginning of October to the end of April). An analytical method for determining distribution of the environmental (outdoor air) temperature is used. Energy and exergy analyses showed periods when the highest amounts of energy and exergy were consumed and the greatest exergy losses occurred. This allowed to reveal the component of the system with the highest exergy losses – the heat pump evaporator. Therefore, further research is needed for its design and application. At the end of the article, the seasonal indicators of the AHU with heat pump operation were calculated: coefficient of performance and exergy efficiency. The presented research procedure could be applied to the analysis of other energy systems and processes in them.
Giedrė Streckienė; Tomas Kropas. APPLICATION OF ENERGY AND EXERGY ANALYSIS TO INVESTIGATE THE OPERATION OF AN AIR HANDLING UNIT WITH HEAT PUMP. Mokslas - Lietuvos ateitis 2020, 12, 1 -6.
AMA StyleGiedrė Streckienė, Tomas Kropas. APPLICATION OF ENERGY AND EXERGY ANALYSIS TO INVESTIGATE THE OPERATION OF AN AIR HANDLING UNIT WITH HEAT PUMP. Mokslas - Lietuvos ateitis. 2020; 12 ():1-6.
Chicago/Turabian StyleGiedrė Streckienė; Tomas Kropas. 2020. "APPLICATION OF ENERGY AND EXERGY ANALYSIS TO INVESTIGATE THE OPERATION OF AN AIR HANDLING UNIT WITH HEAT PUMP." Mokslas - Lietuvos ateitis 12, no. : 1-6.
The continuous energy transformation processes in heating, ventilation, and air conditioning systems of buildings are responsible for 36% of global final energy consumption. Tighter thermal insulation requirements for buildings have significantly reduced heat transfer losses. Unfortunately, this has little effect on energy demand for ventilation. On the basis of the First and the Second Law of Thermodynamics, the concepts of entropy and exergy are applied to the analysis of ventilation air handling unit (AHU) with a heat pump, in this paper. This study aims to develop a consistent approach for this purpose, taking into account the variations of reference temperature and temperatures of working fluids. An analytical investigation on entropy generation and exergy analysis are used, when exergy is determined by calculating coenthalpies and evaluating exergy flows and their directions. The results show that each component of the AHU has its individual character of generated entropy, destroyed exergy, and exergy efficiency variation. However, the evaporator of the heat pump and fans have unabated quantities of exergy destruction. The exergy efficiency of AHU decreases from 45–55% to 12–15% when outdoor air temperature is within the range of −30 to +10 °C, respectively. This helps to determine the conditions and components of improving the exergy efficiency of the AHU at variable real-world local climate conditions. The presented methodological approach could be used in the dynamic modelling software and contribute to a wider application of the Second Law of Thermodynamics in practice.
Giedrė Streckienė; Vytautas Martinaitis; Juozas Bielskus. From Entropy Generation to Exergy Efficiency at Varying Reference Environment Temperature: Case Study of an Air Handling Unit. Entropy 2019, 21, 361 .
AMA StyleGiedrė Streckienė, Vytautas Martinaitis, Juozas Bielskus. From Entropy Generation to Exergy Efficiency at Varying Reference Environment Temperature: Case Study of an Air Handling Unit. Entropy. 2019; 21 (4):361.
Chicago/Turabian StyleGiedrė Streckienė; Vytautas Martinaitis; Juozas Bielskus. 2019. "From Entropy Generation to Exergy Efficiency at Varying Reference Environment Temperature: Case Study of an Air Handling Unit." Entropy 21, no. 4: 361.
The continuous energy transformation processes in heating, ventilation and air conditioning systems of buildings are responsible for 36% of global final energy consumption. Tighter thermal insulation requirements for buildings have significantly reduced heat transfer losses. Unfortunately, this has little effect on energy demand for ventilation. On the basis of the First and the Second Law of Thermodynamics, the concepts of entropy and exergy are applied to the analysis of ventilation air handling unit (AHU) with a heat pump in this paper. This study aims to develop a consistent approach for this purpose, taking into account the variations of reference temperature and temperatures of working fluids. An analytical investigation on entropy generation and exergy analysis are used, when exergy is determined by calculating coenthalpies and evaluating exergy flows and their directions. The results show that each component of the AHU has its individual character of generated entropy, destroyed exergy and exergy efficiency variation. However, the evaporator of heat pump and fans have unabated quantities of exergy destruction. The exergy efficiency of AHU decreases from 45-55% to 12-15% when outdoor air temperature is within the range of –30°C…+10°C, respectively. This helps to determine conditions and components of improving the exergy efficiency of the AHU at variable real-world local climate conditions. The presented methodological approach could be used in the dynamic modelling software and contribute to a wider application of the Second Law of Thermodynamics in practice.
Giedrė Streckienė; Vytautas Martinaitis; Juozas Bielskus. From Entropy Generation to Exergy Efficiency at Varying Reference Environment Temperature: Case Study of an Air Handling Unit. 2019, 1 .
AMA StyleGiedrė Streckienė, Vytautas Martinaitis, Juozas Bielskus. From Entropy Generation to Exergy Efficiency at Varying Reference Environment Temperature: Case Study of an Air Handling Unit. . 2019; ():1.
Chicago/Turabian StyleGiedrė Streckienė; Vytautas Martinaitis; Juozas Bielskus. 2019. "From Entropy Generation to Exergy Efficiency at Varying Reference Environment Temperature: Case Study of an Air Handling Unit." , no. : 1.
Renewable energy sources (RES) and their transformation technologies become more attractive in building sector as energy demand and emissions to the environment increase. Along with renewable energy transformation technologies, the importance of energy storage also arises as these RES are characterized by volatility and energy mismatch over time. For this reason, engineering systems which use RES are becoming increasingly dynamic. This study examines ongoing processes in a vertical cylindrical storage tank designed to cover domestic hot water demand in a building. Simultaneous dynamic mode of operation when the energy is being charged and at the same time discharged from the storage tank is analysed. Experiments are performed and stratification number describing thermal stratification is calculated. The obtained data are used for the development and validation of the numerical model. Using Ansys Fluent software, the influence of different discharge rate on operation mode of the storage tank is investigated. Graphical and numerical interpretation of results is performed.
Tomas Kropask; Giedrė Streckienė; Anton Frik. AKUMULIACINĖS TALPYKLOS DINAMINIO VEIKIMO EKSPERIMENTINIS IR SKAITINIS TYRIMAS / EXPERIMENTAL AND NUMERICAL RESEARCH OF DYNAMIC OPERATION OF HEAT STORAGE TANK. Mokslas - Lietuvos ateitis 2019, 11, 1 -5.
AMA StyleTomas Kropask, Giedrė Streckienė, Anton Frik. AKUMULIACINĖS TALPYKLOS DINAMINIO VEIKIMO EKSPERIMENTINIS IR SKAITINIS TYRIMAS / EXPERIMENTAL AND NUMERICAL RESEARCH OF DYNAMIC OPERATION OF HEAT STORAGE TANK. Mokslas - Lietuvos ateitis. 2019; 11 ():1-5.
Chicago/Turabian StyleTomas Kropask; Giedrė Streckienė; Anton Frik. 2019. "AKUMULIACINĖS TALPYKLOS DINAMINIO VEIKIMO EKSPERIMENTINIS IR SKAITINIS TYRIMAS / EXPERIMENTAL AND NUMERICAL RESEARCH OF DYNAMIC OPERATION OF HEAT STORAGE TANK." Mokslas - Lietuvos ateitis 11, no. : 1-5.
Ventilation and air conditioning systems are emerging as the major energy consumers in low energy buildings. The objective of this paper is to present new methodology for assessment of Air Handling Units (AHUs) taking into account the variations of reference temperature. The methodology using the concept of coenthalpy, developed for heat exchangers and published by the authors previously has been used. Four AHUs that comprise energy transfer devices, such as: Water-to-Air Heater (WAH), Heat Recovery Exchanger (HRE) and Heat Pump (HP) have been investigated. Thermodynamic parameters including Coefficient of Performance (COP), universal and functional exergy efficiencies have been used to compare AHUs and to calculate the exergy destruction in AHU components at variable environment temperature -30°C...+10°C. The results of this study show that using HRE the COP and exergy efficiencies are significantly better compared with AHU without HRE. Using the HRE of higher effectiveness, the thermodynamic indicators can be improved considerably. The study shows that AHUs equipped with HP with advanced control method and HRE are more advantageous compared with other investigated AHUs. The presented methodology could have practical application for evaluating of energy and exergy efficiency of AHUs at different reference temperatures when designing HVAC systems and implementing optimum control methods.
Vytautas Martinaitis; Giedre Streckiene; Audrius Bagdanavicius; Juozas Bielskus. A comparative thermodynamic analysis of air handling units at variable reference temperature. Applied Thermal Engineering 2018, 143, 385 -395.
AMA StyleVytautas Martinaitis, Giedre Streckiene, Audrius Bagdanavicius, Juozas Bielskus. A comparative thermodynamic analysis of air handling units at variable reference temperature. Applied Thermal Engineering. 2018; 143 ():385-395.
Chicago/Turabian StyleVytautas Martinaitis; Giedre Streckiene; Audrius Bagdanavicius; Juozas Bielskus. 2018. "A comparative thermodynamic analysis of air handling units at variable reference temperature." Applied Thermal Engineering 143, no. : 385-395.
In order to use efficiently residual, waste or renewable energy, the application of phase change materials (PCM) grows in building energy systems. At the same time, this poses new technological challenges in choosing specific materials, system design solutions, because it requires a specific knowledge of the heat transfer process during the phase change. The aim of the work is to investigate the heat transfer in a PCM based thermal energy storage unit using the COMSOL Multiphysics software. In the analysis, the properties of the material were evaluated during the phase change. This allowed to determine that the thermal conductivity of the material is of great importance for the intensification of heat transfer. In addition, the analysis of several points in the analyzed object revealed that the phase change does not occur in the surface layer of the PCM during the period under consideration. In order to avoid that, additional solutions such as integrating heat-conductive materials into the PCM or increasing the surface area of the heat transfer could be used. Santrauka Siekiant efektyviai išnaudoti perteklinę, atliekinę ar atsinaujinančių energijos išteklių gaminamą energiją, vis dažniau taikomas fazinio virsmo medžiagų (FVM) panaudojimas pastato energetinėse sistemose. Kartu tai kelia naujus technologinius iššūkius pasirenkant konkrečias medžiagas, sistemų projektinius sprendinius, nes reikia gerai išmanyti šilumos mainų procesą vykstant fazės virsmui. Šiame darbe siekiama ištirti šilumos mainus šilumos kaupiklyje su fazinio virsmo medžiagomis naudojantis COMSOL Multiphysics programa. Analizės metu įvertintos medžiagos savybės vykstant fazės virsmui. Tai leido nustatyti, kad medžiagos šilumos laidumo koeficientas turi didelę reikšmę šilumos mainų intensyvinimui. Be to, atskirų taškų analizė tyrimo objekte atskleidė, kad per nagrinėjamąjį laikotarpį FVM paviršiniame sluoksnyje fazės virsmas neįvyksta. Siekiant to išvengti, galimi papildomi sprendimai, tokie kaip šilumai laidžių medžiagų integravimas į FVM arba šilumos mainų paviršiaus ploto didinimas.
Saulius Pakalka; Kęstutis Valančius; Giedrė Streckienė; Vaidvilė Ulbikaitė. FAZINIO VIRSMO MEDŽIAGOS CHARAKTERISTIKŲ ŠILUMOS KAUPIKLYJE SKAITINIS MODELIAVIMAS / SIMULATION OF THE PHASE CHANGE MATERIALS’ CHARACTERISTICS IN A THERMAL ENERGY STORAGE. Mokslas - Lietuvos ateitis 2018, 10, 1 -7.
AMA StyleSaulius Pakalka, Kęstutis Valančius, Giedrė Streckienė, Vaidvilė Ulbikaitė. FAZINIO VIRSMO MEDŽIAGOS CHARAKTERISTIKŲ ŠILUMOS KAUPIKLYJE SKAITINIS MODELIAVIMAS / SIMULATION OF THE PHASE CHANGE MATERIALS’ CHARACTERISTICS IN A THERMAL ENERGY STORAGE. Mokslas - Lietuvos ateitis. 2018; 10 ():1-7.
Chicago/Turabian StyleSaulius Pakalka; Kęstutis Valančius; Giedrė Streckienė; Vaidvilė Ulbikaitė. 2018. "FAZINIO VIRSMO MEDŽIAGOS CHARAKTERISTIKŲ ŠILUMOS KAUPIKLYJE SKAITINIS MODELIAVIMAS / SIMULATION OF THE PHASE CHANGE MATERIALS’ CHARACTERISTICS IN A THERMAL ENERGY STORAGE." Mokslas - Lietuvos ateitis 10, no. : 1-7.
The ventilation heat recovery exchanger (HRE) for low energy buildings is becoming one of the important heat transformers in the HVAC systems. The purpose of this paper is to develop the possibilities of exergy analysis for the HRE, when the reference temperature (RT) is variable. The method was prepared through consideration of the exergy flow direction changes, when variable RT was placed below, above and across the operating temperature of working fluids. By using the coenthalpy diagrams, there were obtained three functional exergy efficiencies which had greater sensitivity than universal exergy efficiency. The prepared solution allows the reliable using of the ubiquitous thermodynamic (exergy) analysis for energy chain in the HVAC systems. This methodology may be developed for other heat exchangers with different mass flows, operated at near-environmental temperatures. The results could have a practical application for designing the HVAC systems and implementing their exergy optimum operation controls.
Vytautas Martinaitis; Giedrė Streckienė; Darius Biekša; Giedrius Šiupšinskas; Juozas Bielskus. Functional exergy efficiency of an air heat recovery exchanger under varying environmental temperature. International Journal of Exergy 2018, 25, 93 .
AMA StyleVytautas Martinaitis, Giedrė Streckienė, Darius Biekša, Giedrius Šiupšinskas, Juozas Bielskus. Functional exergy efficiency of an air heat recovery exchanger under varying environmental temperature. International Journal of Exergy. 2018; 25 (2):93.
Chicago/Turabian StyleVytautas Martinaitis; Giedrė Streckienė; Darius Biekša; Giedrius Šiupšinskas; Juozas Bielskus. 2018. "Functional exergy efficiency of an air heat recovery exchanger under varying environmental temperature." International Journal of Exergy 25, no. 2: 93.
Juozas Bielskus; Giedrius Šiupšinskas; Vytautas Martinaitis; Darius Biekša; Giedre Streckiene. Functional exergy efficiency of an air heat recovery exchanger under varying environmental temperature. International Journal of Exergy 2018, 25, 93 .
AMA StyleJuozas Bielskus, Giedrius Šiupšinskas, Vytautas Martinaitis, Darius Biekša, Giedre Streckiene. Functional exergy efficiency of an air heat recovery exchanger under varying environmental temperature. International Journal of Exergy. 2018; 25 (2):93.
Chicago/Turabian StyleJuozas Bielskus; Giedrius Šiupšinskas; Vytautas Martinaitis; Darius Biekša; Giedre Streckiene. 2018. "Functional exergy efficiency of an air heat recovery exchanger under varying environmental temperature." International Journal of Exergy 25, no. 2: 93.
In order to reduce impact to environment, a qualitative approach of energy saving is global aspect that is included in various forms of CO2 emissions, primary energy limitations and benchmarks in EU and member countries policy. Exergy analysis allows expressing the quality of energy flows in comparison to ambient or other reference conditions. Despite of this valuable information, this concept is not widely used in engineering practice. The article suggests the calculation procedure for sessional or periodical thermodynamic (exergy) efficiency in relation to variable reference conditions. Knowledge about defined procedures unlocks the possibility to fill up the implementation gap for building system engineering practice where seasonal performance parameters are widely used to express efficiency. Prepared algorithm allows determining seasonal or periodic thermodynamic efficiency of individual elements and energy transfer chains in building energy systems. Defined calculation procedure workflow is suitable for integrated approach when coupled heat transfer and fluid flow processes are explored in short time steps with dynamic simulation software tools. Presented algorithm ensures result that fits in thermodynamically correct range 0-1 and helps to summarize separate time step results. By adding duration of specific conditions, this analysis enables to identify critical peak periods and base load conditions across operation period. The presented framework fills the gap in lack of systematic expression for seasonal thermodynamic efficiency and suggests the process for calculation procedures workflow.
Karolis Janusevicius; Juozas Bielskus; Vytautas Martinaitis; Giedrė Streckienė; Dovydas Rimdžius. Expressing the Building Energy Systems Thermodynamic Seasonal Efficiency. Proccedings of 10th International Conference "Environmental Engineering" 2017, 1 .
AMA StyleKarolis Janusevicius, Juozas Bielskus, Vytautas Martinaitis, Giedrė Streckienė, Dovydas Rimdžius. Expressing the Building Energy Systems Thermodynamic Seasonal Efficiency. Proccedings of 10th International Conference "Environmental Engineering". 2017; ():1.
Chicago/Turabian StyleKarolis Janusevicius; Juozas Bielskus; Vytautas Martinaitis; Giedrė Streckienė; Dovydas Rimdžius. 2017. "Expressing the Building Energy Systems Thermodynamic Seasonal Efficiency." Proccedings of 10th International Conference "Environmental Engineering" , no. : 1.
Ventilation systems play an important role for providing suitable indoor climate in buildings. Improving these systems allows promoting energy efficiency in building sector, which is responsible for a large percentage of global energy consumption. Therefore, this work focuses on assessment of ventilation air handling unit (AHU) using thermodynamics. The exergy analysis is used to evaluate the performance of an AHU. Special attention is made about seasonally varying exergy flows of a system. As efficiency of a ventilation system is closely linked to local climate, especially to the varying reference temperature. The paper presents an approach for calculating the seasonal exergy efficiency and gives the results of the AHU analysis. The case study reveals that the highest exergy consumption is when the outdoor temperature is −2.5 °C. The AHU case with heat recovery and water heater is the most efficient comparing to other cases investigated. The use of this methodology may be extended for determining of the seasonal exergy efficiency of any other HVAC equipment.
G. Streckienė; Vytautas Martinaitis; J. Bielskus. Analysis of seasonal exergy efficiency of an air handling unit. 2017 THE 2ND INTERNATIONAL CONFERENCE ON ENERGY ENGINEERING AND SMART MATERIALS: ICEESM 2017 2017, 1 .
AMA StyleG. Streckienė, Vytautas Martinaitis, J. Bielskus. Analysis of seasonal exergy efficiency of an air handling unit. 2017 THE 2ND INTERNATIONAL CONFERENCE ON ENERGY ENGINEERING AND SMART MATERIALS: ICEESM 2017. 2017; ():1.
Chicago/Turabian StyleG. Streckienė; Vytautas Martinaitis; J. Bielskus. 2017. "Analysis of seasonal exergy efficiency of an air handling unit." 2017 THE 2ND INTERNATIONAL CONFERENCE ON ENERGY ENGINEERING AND SMART MATERIALS: ICEESM 2017 , no. : 1.
Vytautas Martinaitis; Giedrė Streckienė; Darius Biekša; Juozas Bielskus. The exergy efficiency assessment of heat recovery exchanger for air handling units, using a state property – Coenthalpy. Applied Thermal Engineering 2016, 108, 388 -397.
AMA StyleVytautas Martinaitis, Giedrė Streckienė, Darius Biekša, Juozas Bielskus. The exergy efficiency assessment of heat recovery exchanger for air handling units, using a state property – Coenthalpy. Applied Thermal Engineering. 2016; 108 ():388-397.
Chicago/Turabian StyleVytautas Martinaitis; Giedrė Streckienė; Darius Biekša; Juozas Bielskus. 2016. "The exergy efficiency assessment of heat recovery exchanger for air handling units, using a state property – Coenthalpy." Applied Thermal Engineering 108, no. : 388-397.
Karolis Januševičius; Giedrė Streckienė; Juozas Bielskus; Vytautas Martinaitis. Validation of Unglazed Transpired Solar Collector Assisted Air Source Heat Pump Simulation Model. Energy Procedia 2016, 95, 167 -174.
AMA StyleKarolis Januševičius, Giedrė Streckienė, Juozas Bielskus, Vytautas Martinaitis. Validation of Unglazed Transpired Solar Collector Assisted Air Source Heat Pump Simulation Model. Energy Procedia. 2016; 95 ():167-174.
Chicago/Turabian StyleKarolis Januševičius; Giedrė Streckienė; Juozas Bielskus; Vytautas Martinaitis. 2016. "Validation of Unglazed Transpired Solar Collector Assisted Air Source Heat Pump Simulation Model." Energy Procedia 95, no. : 167-174.
The energy chain of building energy services begins with primary energy resources and ends with building services systems (BSS). The analysis for such chain and its' elements should rely on fundamentals of thermodynamics. This paper pays attention to one of them that exergy efficiency is in the range of 0-1. In this study, exergy analysis of heat recovery exchangers for air handling units is carried out. Special attention is paid to the direction of thermal exergy flow when temperatures inducing heat transfer are close to a near-environmental temperature. On the basis of the proposed methodology, the dependency of exergy efficiency on dimensionless temperature and thermal recuperator efficiency is discussed. It is important to take the dimensionless temperature interval 0-1 into account. Here the exergy efficiency values are the lowest. Design and management measures should be used to avoid operating a heat exchanger there.
Vytautas Martinaitis; Giedrė Streckienė. Concerning exergy efficiency evaluation of heat recovery exchangers for air handling units. International Journal of Exergy 2016, 20, 381 .
AMA StyleVytautas Martinaitis, Giedrė Streckienė. Concerning exergy efficiency evaluation of heat recovery exchangers for air handling units. International Journal of Exergy. 2016; 20 (3):381.
Chicago/Turabian StyleVytautas Martinaitis; Giedrė Streckienė. 2016. "Concerning exergy efficiency evaluation of heat recovery exchangers for air handling units." International Journal of Exergy 20, no. 3: 381.