Violeta Misevičiūtė - Academia.edu (original) (raw)
Papers by Violeta Misevičiūtė
Journal of building engineering, Oct 1, 2023
Ventilation systems are known as intensive energy used building engineering system. Heat exchange... more Ventilation systems are known as intensive energy used building engineering system. Heat exchangers are the main equipments used for energy transformation in building engineering systems as well as in ventilation sys-tems. The conventional heat exchangers design methods do not belie the ways for efficiency energy use in building engineering system's heat exchangers. The method of Pinch technology mostly used for industrial process integration that could be applied to analyze possi-bilities of process integration is first time adopted to evaluate processes integration of building engineering systems. The paper deals with analyze of integration possibilities of ventilation system. The approach covers several possible cases of integration. Analysis is based on heat exchangers used for heat recov-ery and heat transfer in ventilation systems modification cases during the heating season. As results for ventilation system integration possibilities there are represented heat exchangers ...
An oversized heating system downgrades energy efficiency of the system and causes higher energy c... more An oversized heating system downgrades energy efficiency of the system and causes higher energy consumption. This paper presents a research where heating loads of passive building were calculated using different methods and compared to each other. The heating loads of the same passive building were calculated using three different methods: according to the Lithuanian heating design regulations, Passive house planning package and dynamic simulation program EnergyPlus. Assuming that EnergyPlus simulation is more accurate than steady – state methods underlying the two other methods, the results of the analysis show that the Lithuanian heating design regulations leads to the oversizing of the heating system for passive buildings.
Energy and Buildings, 2010
This paper presents the application of degree-days utilized for the exergy analysis of buildings.... more This paper presents the application of degree-days utilized for the exergy analysis of buildings. The climate is observed as a basis for the exergy analysis of the energy usage of buildings. The definitions and functions of the outdoor temperature distribution density and its cumulative distribution frequency are introduced in the analysis. There are several relative exergy indicators for local climate
Mokslas - Lietuvos ateitis
The main users of district heating (DH) systems are multi-apartment buildings – 53% of these buil... more The main users of district heating (DH) systems are multi-apartment buildings – 53% of these buildings in Lithuania are supplied with heat from DH systems. Heating systems in buildings are the largest final consumer of energy, accounting for almost half of total energy consumption in many European countries. One of the measures planned for the Lithuanian energy policy in the heat sector of renewable energy sources (RES) until 2030 is the installation of heat pumps (HP) in the DH networks. The purpose of the study is to evaluate the technological possibilities of integrating HP into existing buildings to evaluate the low temperature heat supply. To evaluate the potential temperature lowering of the building heating system, a graph of the lowest possible building heating system temperatures is set, according to which the heat pump for the heating substation is selected, which would raise the temperature of the heat carrier supplied from DH networks to the required temperature for the ...
Disertacijoje nagrinėjamos procesų integracijos metodo taikymo galimybės sprendžiant efektyvaus e... more Disertacijoje nagrinėjamos procesų integracijos metodo taikymo galimybės sprendžiant efektyvaus energijos vartojimo pastatų inžinerinėse sistemose problemas. Tarp pastato inžinerinių sistemų darbe išskiriamos ženkliau energiją naudojančios, mikroklimatą pastatuose formuojančios sistemos. Klasikiniai tyrimo metodai, skirti šilumos mainams šilumokaičiuose, kurie atlieka šilumos perdavimo funkciją, nagrinėti pateikia gana ribotus sprendinius, kaip efektyviai naudoti energiją juose. Pagrindinis disertacijos tikslas – įvertinti procesų integravimo metodo taikymo galimybes viešųjų pastatų inžinerinių sistemų termodinaminiam efektyvumui nustatyti ir gerinti. Disertacijoje taip pat siekiama derinti procesų integracijos galimybes inžinerinėse sistemose siekiant minimizuoti eksergijos srautus jose. Darbe sprendžiami keli pagrindiniai uždaviniai: probleminių, energinio efektyvumo požiūriu, pastato inžinerinių sistemų, įrenginių ir procesų jose nustatymas, vėdinimo sistemų projektinių sprendimų...
Mokslas - Lietuvos ateitis, 2017
In the buildings with large glazed areas the biggest problem is the space overheating during the ... more In the buildings with large glazed areas the biggest problem is the space overheating during the warm season. This causes increased energy demand for cooling. The survey was carried out during the warm and cold seasons in two office buildings with large glazed areas. The methodology was prepared for evaluating indoor climate parameters using objective and subjective evaluation. The measurements have shown that there are problems with lighting in workplaces of both buildings during both the warm and cold seasons. The biggest problem is too dry air during the cold period, an acceptable temperature is also not always in the building No. 2. The survey has shown that some employees are dissatisfied with the indoor climate in the workplace, the bigger dissatisfaction is in building No. 2. Assessing according to the O. Fanger methodology was obtained that the number of PPD is in the normal range during the cold period, whereas close to the limit when the building can not be operated in the...
Mokslas - Lietuvos ateitis, 2017
The paper provides the results of experimental and theoretical test of a wavy fin and tube heat e... more The paper provides the results of experimental and theoretical test of a wavy fin and tube heat exchanger used to cool air in a ventilation system when the wavy fin of the heat exchanger is dry and wet. The experimental tests, performed in the range of 1000<Re<4500 of the Reynolds number applying LMTD-LMED methodology, determined the dependency of the heat transfer coefficient on the supplied air flow rate with the varying geometry of the heat exchanger (the number of tube rows, the distance between fins, the thickness of the fin and the diameter of the tube). The experimental tests were performed on 9 heat exchangers in heating and 6 heat exchangers in cooling mode. After processing the results of the experimental tests, empirical equation defining the characteristics of the heat transfer coefficient of all heat exchangers were derived. The maximum heat transfer coefficient deviation is 11.6 percent. The correction factor of the wet fin (Lewis number) depending on the number ...
19-toji Lietuvos jaunųjų mokslininkų konferencijos ciklo „Mokslas – Lietuvos ateitis”. Pastatų inžinerinės sistemos, 2016
Mažaenergiuose pastatuose šilumos šaltiniu pasirenkant šilumos siurblio sistemą remiamasi standar... more Mažaenergiuose pastatuose šilumos šaltiniu pasirenkant šilumos siurblio sistemą remiamasi standartuose nurodytais siste-mos komponentų rodiklių intervalais, tačiau nėra aiški atskirų verčių iš nurodytų intervalų daroma įtaka sistemos veikimo e-fektyvumui. Darbe nagrinėjama gruntinio šilumos siurblio sistema mažaenergiame pastate. Sudaryta skaičiuojamoji schema TRNSYS programoje. Apskaičiuotas sistemos sezoninio energinio efektyvumo rodiklis, įvertinta gruntinio šilumokaičio gręžinių kiekio (ilgio) ir akumuliacinės talpos tūrio įtaka veikimo efektyvumui, remiantis standartuose nurodytomis vertėmis. Mažiausias SPF pasiekiamas gruodžio mėnesį, didžiausias – spalį. Didėjant gręžinių ilgiui arba akumuliacinės talpos tūriui SPF didėja. Keičiant gręžinių kiekį, skirtingais mėnesiais SPF sumažėjo iki 15 % ir padidėjo iki 17 %, keičiant akumuliaci-nės talpos tūrį, SPF sumažėjo iki 2 % ir padidėjo iki 0,3 %, lyginant su pradiniu variantu. Sumažinus gręžinių kiekį dviem gręžiniais pastebimas ž...
<jats:p>Straipsnyje analizuojama vėdinimo sistemos komponento ‒ neįstiklinto pratakaus saul... more <jats:p>Straipsnyje analizuojama vėdinimo sistemos komponento ‒ neįstiklinto pratakaus saulės kolektoriaus visai vėdinimo sistemai daroma įtaka. Eksperimentinis stendas sumontuotas VGTU Aplinkos inžinerijos fakultete, saulės siena integruota ant pietinio fakulteto fasado. Pratakus saulės kolektorius dažniausiai naudojamas pirminiam šviežio oro pašildymui. Darbe tiriama, kaip kinta vėdinimo sistemos energijos sąnaudos naudojant ir nenaudojant saulės sieną. Nagrinėjamas pratakusis saulės kolektorius bei jo daroma įtaka plokštelinio šilumogrąžio efektyvumui. Taip pat siekiama nustatyti saulės sienos efektyvumą bei tiekiamojo oro temperatūrinį prieaugį. Gauti rezultatai pateikiami grafiškai, analizuojama jų priklausomybė nuo kintančių aplinkos parametrų.</jats:p>
The paper provides the results of experimental tests of a wavy fin and tube heat exchanger used t... more The paper provides the results of experimental tests of a wavy fin and tube heat exchanger used to heat (cool) air in a ventilation system when the finned plate of the heat exchanger is dry and wet. The experimental tests, performed in the range of 1000<Re<4500 of the Reynolds number, determined the dependency of the heat transfer coefficient on the amount of supplied air with the varying geometry of the heat exchanger (the number of tube rows, the distance between fins, the thickness of the fin and the diameter of the tube). The experimental tests were performed on 9 heat exchangers in heating mode (dry fin) and 6 heat exchangers in cooling mode (wet fin). The ratio of heat transfer coefficient values when the fin is dry and wet varies from 0.79 to 1.12. After processing the results of the experimental tests, equations defining the dependency of the heat transfer coefficient on the amount of air and varying geometric parameters of the heat exchanger were derived, based on whi...
Analizuojamos asmens sveikatos priežiūros įstaigose esamos su mikroklimato parametrais ir oro kok... more Analizuojamos asmens sveikatos priežiūros įstaigose esamos su mikroklimato parametrais ir oro kokybe susijusios problemos, nagrinėjama informacija apie poliklinikos pacientų ir personalo šiluminio komforto pojūtį. Straipsnyje aprašomi mikroklimato parametrų ir oro kokybės rodiklių tyrimo rezultatai, matavimus atlikus asmens sveikatos priežiūros paslaugas teikiančioje įstaigoje. Šiluminio komforto ir oro kokybės užtikrinimo lygis analizuotas šiltuoju ir šaltuoju metų laikotarpiu, trijose skirtingos paskirties, modernizuotose ir nemodernizuotose patalpose. Minėtose patalpose atlikti matavimai, kurių metu fiksuotos oro temperatūros, santykinės drėgmės ir CO2 koncentracijos ore vertės. Atliekant tyrimą taikyta EN ISO 7730 tarptautiniame standarte pateikta metodika ir vertinant šiluminio komforto lygį buvo vykdyta poliklinikos pacientų ir personalo anketinė apklausa. Matavimo rezultatai parodė, kad šiltuoju metų laikotarpiu oro kokybės rodikliai tirtose patalpose atitiko higienos normose...
Mokslas - Lietuvos ateitis, 2018
The purpose of the study was to determine which ventilation system centralized or decentralized i... more The purpose of the study was to determine which ventilation system centralized or decentralized in viewpoint of economic, energy and comfort is more advantageous in an individual residential house. The relevance of the work is related to the increasing energy efficiency requirements for newly built buildings and the resulting problems of the sick building syndrome due to insufficient ventilation of the rooms. The installation and operation costs of systems were identified. The Life Cycle Analysis (LCA) method was applied to estimate the amount of pollutants and primary energy consumed throughout the lifetime of ventilation systems. Measurements of indoor climate parameters were made; the results compared with the hygiene norms valid in Lithuania. The results of the analysis showed that the decentralized ventilation system is the most advantageous for economic and environmental impacts, but centralized ventilation system ensuring a better indoor climate. Santrauka Tyrimo tikslas buvo...
Applied Thermal Engineering, 2018
Intensive use of energy is related to the inefficient use of processes in building engineering sy... more Intensive use of energy is related to the inefficient use of processes in building engineering systems. In well-insulated nonresidential buildings ventilation systems are among the most energy intensive HVAC systems. The main components of an energy (and exergy) efficient ventilation system are heat exchangers. The paper presents the analysis of process integration possibilities in a ventilation system. Only air heating for ventilation purposes is analysed. The method of Pinch technology, mostly used for industrial process integration, is adopted for a ventilation system of a building for the first time. In the paper, several different cases of integration are analysed by using actual BMS data of a shopping centre. The results confirmed that process integration influences the thermodynamic efficiency of the system and that integrated systems consume less energy and exergy in comparison with the non-integrated ones. The case study shows that the seasonal energy demand of the system before integration is 26% higher compared to integrated system and the exergy demand is 45% higher.
International Journal of Environmental Science and Development, 2015
In the current study, research on the performance characteristics of an adsorption cooling system... more In the current study, research on the performance characteristics of an adsorption cooling system supplied by solar energy is presented. The main task for the analyzed system was to ensure cooling load for the non-residential building in cold climate country. A 8.0 kW adsorption thermal cooling system was studied. The system got heat produced by evacuated tube solar collectors. The parametric simulation study was carried using a TRNSYS (Transient Systems Simulation) program to determine the influence of various parameters on the system performance. The dependencies of collector slope and the total absorber area on solar fraction, discarded energy, coefficient of performance, seasonal performance factor were studied. The highest solar fraction, coefficient of performance and seasonal performance factor values were obtained if the collector slope was approximately 30 degrees and the absorber area was 16 m 2 for the analyzed cases. The total primary energy consumption of the system was examined for various cases of primary energy factor for auxiliary heat and consumed electricity. On the basis of the results, it was proposed the expression of total primary energy consumption. The obtained results could be used for the recommendation preparations for decision makers to select a small scale solar cooling adsorption system.
18-toji Lietuvos jaunųjų mokslininkų konferencijos ciklo „Mokslas – Lietuvos ateitis”. Pastatų inžinerinės sistemos, 2015
Straipsnyje nagrinėjamas oro tiekimo–šalinimo įrenginys, esantis Vilniaus Gedimino technikos univ... more Straipsnyje nagrinėjamas oro tiekimo–šalinimo įrenginys, esantis Vilniaus Gedimino technikos universiteto Pastato energetinių ir mikroklimato sistemų laboratorijoje. Nagrinėjamos įrenginio elementų charakteristikos, energijos pernaša įrenginyje ir naudojant TRNSYS modeliavimo priemonę sukuriamas jo matematinis modelis, kuriame vaizduojami visi elementai. Pasiūlytas valdymo mechanizmas, leidžiantis modeliuoti vėdinimo įrenginio veikimą charakteringais laikotarpiais, taip pat, taikant ekserginės analizės principus, sukurtas matematinis algoritmas, atliekantis viso įrenginio ekserginio naudingumo koeficiento skaičiavimą. Modeliavimas atliktas visų metų laikotarpiu, nustatytas vidutinis metinis ekserginis vėdinimo įrenginio naudingumo koeficientas – 75,36 %.
Mokslas - Lietuvos ateitis, 2014
The paper analyses the impact of the supplied airflow rate of the solar wall used for heating air... more The paper analyses the impact of the supplied airflow rate of the solar wall used for heating air in an air handling unit on the effectiveness of the solar wall. The article reviews experimental and theoretical papers and presents the expressions determining the efficiency indicators of the solar wall. Experimental research into the solar wall at a constant airflow rate was carried out on 5–6 April 2014. Temperatures, overall efficiencies and an increase in temperature were established on the vertical solar wall counting the area of 100 m2 and fixed on the south façade of Vilnius Gediminas Technical University. An increase in the average temperature, in the course of the conducted experiment, reached 7.5 °C. Under constant airflow rate, temperature efficiency increases along with solar irradiation. The average estimated temperature efficiency reaches 72 percent. The overall effectiveness of the solar wall decreases when solar irradiation increases. Straipsnyje nagrinėjama saulės sie...
The 9th International Conference "Environmental Engineering 2014", 2014
The European Directive on Energy Performance of Buildings (EPBD) obliges to accept measures for i... more The European Directive on Energy Performance of Buildings (EPBD) obliges to accept measures for improving the energy efficiency in buildings. As buildings become more airtight ventilation takes an important role in building. Ventilation efficiency as a rule is achieved using heat recovery. The efficiency of the air heat recovery is varies depending on the applied type of heat exchanger and changes during the year. A dozen of heat recovery units, renewable energy sources and technologies can be applied to ventilation system to increase an efficiency of it. It should be an opportunity to add ventilation system with renewable energy sources. Such energy recovery and renewable energy technologies as air heat recovery unit, air-to-water heat pump, and unglazed solar collector (UTSC) for ventilation system of the building are analyzed. TRNSYS simulation tool is applied. Simulation results of three technologies (heat recovery unit, air heat pump and unglazed solar collector) using ventilation system performance during the year is presented. Main indicators of UTSC are presented. Simulation results and obtained experimental data of individual cases of such system are compared.
Scientific Journal of Riga Technical University. Environmental and Climate Technologies, 2011
The installation of a heat storage tank is a very costeffective way to improve the performance an... more The installation of a heat storage tank is a very costeffective way to improve the performance and flexibility of a CHP plant. Such a heat storage tank usually accumulates heat by thermal stratification. This phenomenon is caused by the thermal buoyancy because of the difference in temperature between cold and hot water. The heat storage tank may have three operating modes, i. e. charge, discharge and storage in a CHP plant. When CHP units, which charge the heat storage tank, operate at full load, usually only two operation modes occur in the tank, i.e. charge and discharge. The paper presents numerical simulation of heat storage tank operation modes in a CHP plant using PHOENICSa multipurpose computation fluid dynamics (CFD) software. Twodimensional and three-dimensional transient models were created and solved numerically. Three domain grids were tested. Several charging and discharging processes with different flow rates were simulated. The influence of flow rate on the degree of thermal stratification during charging and discharging processes is analyzed. The computation possibilities and limitations of the numerical experiments are pointed out. Special attention is given to the validation of the numerical solutions. The validation of simulated results is made by comparison with the real data from the heat storage installed in the Hvide Sande CHP plant.
Mokslas - Lietuvos ateitis, 2011
The paper analyzes the influence of integrating the processes taking place in the ventilation equ... more The paper analyzes the influence of integrating the processes taking place in the ventilation equipment of a public building on the thermal transmittance of heat exchangers. Pinch analysis helped with determining changes in the thermal transmittance of heat exchangers per year. The article examines the dependency of the thermal transmittance of heat exchangers on the disposed quantity of streams. The total thermal transmittance of heat exchangers is higher if several streams of lower parameters are used. Without additional economical calculations, the thermal transmittance of heat exchangers can assess their size, price and be used for the purposes of comparing the obtained results showing that designing such systems is useful for evaluating the possibilities of integrating the processes taking place in ventilation equipment. Santrauka Analizuojama viešosios paskirties pastato vėdinimo įrenginyje vykstančių procesų integracijos įtaka šilumokaičių šiluminiam pralaidumui. Taikant Pinc...
Journal of building engineering, Oct 1, 2023
Ventilation systems are known as intensive energy used building engineering system. Heat exchange... more Ventilation systems are known as intensive energy used building engineering system. Heat exchangers are the main equipments used for energy transformation in building engineering systems as well as in ventilation sys-tems. The conventional heat exchangers design methods do not belie the ways for efficiency energy use in building engineering system's heat exchangers. The method of Pinch technology mostly used for industrial process integration that could be applied to analyze possi-bilities of process integration is first time adopted to evaluate processes integration of building engineering systems. The paper deals with analyze of integration possibilities of ventilation system. The approach covers several possible cases of integration. Analysis is based on heat exchangers used for heat recov-ery and heat transfer in ventilation systems modification cases during the heating season. As results for ventilation system integration possibilities there are represented heat exchangers ...
An oversized heating system downgrades energy efficiency of the system and causes higher energy c... more An oversized heating system downgrades energy efficiency of the system and causes higher energy consumption. This paper presents a research where heating loads of passive building were calculated using different methods and compared to each other. The heating loads of the same passive building were calculated using three different methods: according to the Lithuanian heating design regulations, Passive house planning package and dynamic simulation program EnergyPlus. Assuming that EnergyPlus simulation is more accurate than steady – state methods underlying the two other methods, the results of the analysis show that the Lithuanian heating design regulations leads to the oversizing of the heating system for passive buildings.
Energy and Buildings, 2010
This paper presents the application of degree-days utilized for the exergy analysis of buildings.... more This paper presents the application of degree-days utilized for the exergy analysis of buildings. The climate is observed as a basis for the exergy analysis of the energy usage of buildings. The definitions and functions of the outdoor temperature distribution density and its cumulative distribution frequency are introduced in the analysis. There are several relative exergy indicators for local climate
Mokslas - Lietuvos ateitis
The main users of district heating (DH) systems are multi-apartment buildings – 53% of these buil... more The main users of district heating (DH) systems are multi-apartment buildings – 53% of these buildings in Lithuania are supplied with heat from DH systems. Heating systems in buildings are the largest final consumer of energy, accounting for almost half of total energy consumption in many European countries. One of the measures planned for the Lithuanian energy policy in the heat sector of renewable energy sources (RES) until 2030 is the installation of heat pumps (HP) in the DH networks. The purpose of the study is to evaluate the technological possibilities of integrating HP into existing buildings to evaluate the low temperature heat supply. To evaluate the potential temperature lowering of the building heating system, a graph of the lowest possible building heating system temperatures is set, according to which the heat pump for the heating substation is selected, which would raise the temperature of the heat carrier supplied from DH networks to the required temperature for the ...
Disertacijoje nagrinėjamos procesų integracijos metodo taikymo galimybės sprendžiant efektyvaus e... more Disertacijoje nagrinėjamos procesų integracijos metodo taikymo galimybės sprendžiant efektyvaus energijos vartojimo pastatų inžinerinėse sistemose problemas. Tarp pastato inžinerinių sistemų darbe išskiriamos ženkliau energiją naudojančios, mikroklimatą pastatuose formuojančios sistemos. Klasikiniai tyrimo metodai, skirti šilumos mainams šilumokaičiuose, kurie atlieka šilumos perdavimo funkciją, nagrinėti pateikia gana ribotus sprendinius, kaip efektyviai naudoti energiją juose. Pagrindinis disertacijos tikslas – įvertinti procesų integravimo metodo taikymo galimybes viešųjų pastatų inžinerinių sistemų termodinaminiam efektyvumui nustatyti ir gerinti. Disertacijoje taip pat siekiama derinti procesų integracijos galimybes inžinerinėse sistemose siekiant minimizuoti eksergijos srautus jose. Darbe sprendžiami keli pagrindiniai uždaviniai: probleminių, energinio efektyvumo požiūriu, pastato inžinerinių sistemų, įrenginių ir procesų jose nustatymas, vėdinimo sistemų projektinių sprendimų...
Mokslas - Lietuvos ateitis, 2017
In the buildings with large glazed areas the biggest problem is the space overheating during the ... more In the buildings with large glazed areas the biggest problem is the space overheating during the warm season. This causes increased energy demand for cooling. The survey was carried out during the warm and cold seasons in two office buildings with large glazed areas. The methodology was prepared for evaluating indoor climate parameters using objective and subjective evaluation. The measurements have shown that there are problems with lighting in workplaces of both buildings during both the warm and cold seasons. The biggest problem is too dry air during the cold period, an acceptable temperature is also not always in the building No. 2. The survey has shown that some employees are dissatisfied with the indoor climate in the workplace, the bigger dissatisfaction is in building No. 2. Assessing according to the O. Fanger methodology was obtained that the number of PPD is in the normal range during the cold period, whereas close to the limit when the building can not be operated in the...
Mokslas - Lietuvos ateitis, 2017
The paper provides the results of experimental and theoretical test of a wavy fin and tube heat e... more The paper provides the results of experimental and theoretical test of a wavy fin and tube heat exchanger used to cool air in a ventilation system when the wavy fin of the heat exchanger is dry and wet. The experimental tests, performed in the range of 1000<Re<4500 of the Reynolds number applying LMTD-LMED methodology, determined the dependency of the heat transfer coefficient on the supplied air flow rate with the varying geometry of the heat exchanger (the number of tube rows, the distance between fins, the thickness of the fin and the diameter of the tube). The experimental tests were performed on 9 heat exchangers in heating and 6 heat exchangers in cooling mode. After processing the results of the experimental tests, empirical equation defining the characteristics of the heat transfer coefficient of all heat exchangers were derived. The maximum heat transfer coefficient deviation is 11.6 percent. The correction factor of the wet fin (Lewis number) depending on the number ...
19-toji Lietuvos jaunųjų mokslininkų konferencijos ciklo „Mokslas – Lietuvos ateitis”. Pastatų inžinerinės sistemos, 2016
Mažaenergiuose pastatuose šilumos šaltiniu pasirenkant šilumos siurblio sistemą remiamasi standar... more Mažaenergiuose pastatuose šilumos šaltiniu pasirenkant šilumos siurblio sistemą remiamasi standartuose nurodytais siste-mos komponentų rodiklių intervalais, tačiau nėra aiški atskirų verčių iš nurodytų intervalų daroma įtaka sistemos veikimo e-fektyvumui. Darbe nagrinėjama gruntinio šilumos siurblio sistema mažaenergiame pastate. Sudaryta skaičiuojamoji schema TRNSYS programoje. Apskaičiuotas sistemos sezoninio energinio efektyvumo rodiklis, įvertinta gruntinio šilumokaičio gręžinių kiekio (ilgio) ir akumuliacinės talpos tūrio įtaka veikimo efektyvumui, remiantis standartuose nurodytomis vertėmis. Mažiausias SPF pasiekiamas gruodžio mėnesį, didžiausias – spalį. Didėjant gręžinių ilgiui arba akumuliacinės talpos tūriui SPF didėja. Keičiant gręžinių kiekį, skirtingais mėnesiais SPF sumažėjo iki 15 % ir padidėjo iki 17 %, keičiant akumuliaci-nės talpos tūrį, SPF sumažėjo iki 2 % ir padidėjo iki 0,3 %, lyginant su pradiniu variantu. Sumažinus gręžinių kiekį dviem gręžiniais pastebimas ž...
<jats:p>Straipsnyje analizuojama vėdinimo sistemos komponento ‒ neįstiklinto pratakaus saul... more <jats:p>Straipsnyje analizuojama vėdinimo sistemos komponento ‒ neįstiklinto pratakaus saulės kolektoriaus visai vėdinimo sistemai daroma įtaka. Eksperimentinis stendas sumontuotas VGTU Aplinkos inžinerijos fakultete, saulės siena integruota ant pietinio fakulteto fasado. Pratakus saulės kolektorius dažniausiai naudojamas pirminiam šviežio oro pašildymui. Darbe tiriama, kaip kinta vėdinimo sistemos energijos sąnaudos naudojant ir nenaudojant saulės sieną. Nagrinėjamas pratakusis saulės kolektorius bei jo daroma įtaka plokštelinio šilumogrąžio efektyvumui. Taip pat siekiama nustatyti saulės sienos efektyvumą bei tiekiamojo oro temperatūrinį prieaugį. Gauti rezultatai pateikiami grafiškai, analizuojama jų priklausomybė nuo kintančių aplinkos parametrų.</jats:p>
The paper provides the results of experimental tests of a wavy fin and tube heat exchanger used t... more The paper provides the results of experimental tests of a wavy fin and tube heat exchanger used to heat (cool) air in a ventilation system when the finned plate of the heat exchanger is dry and wet. The experimental tests, performed in the range of 1000<Re<4500 of the Reynolds number, determined the dependency of the heat transfer coefficient on the amount of supplied air with the varying geometry of the heat exchanger (the number of tube rows, the distance between fins, the thickness of the fin and the diameter of the tube). The experimental tests were performed on 9 heat exchangers in heating mode (dry fin) and 6 heat exchangers in cooling mode (wet fin). The ratio of heat transfer coefficient values when the fin is dry and wet varies from 0.79 to 1.12. After processing the results of the experimental tests, equations defining the dependency of the heat transfer coefficient on the amount of air and varying geometric parameters of the heat exchanger were derived, based on whi...
Analizuojamos asmens sveikatos priežiūros įstaigose esamos su mikroklimato parametrais ir oro kok... more Analizuojamos asmens sveikatos priežiūros įstaigose esamos su mikroklimato parametrais ir oro kokybe susijusios problemos, nagrinėjama informacija apie poliklinikos pacientų ir personalo šiluminio komforto pojūtį. Straipsnyje aprašomi mikroklimato parametrų ir oro kokybės rodiklių tyrimo rezultatai, matavimus atlikus asmens sveikatos priežiūros paslaugas teikiančioje įstaigoje. Šiluminio komforto ir oro kokybės užtikrinimo lygis analizuotas šiltuoju ir šaltuoju metų laikotarpiu, trijose skirtingos paskirties, modernizuotose ir nemodernizuotose patalpose. Minėtose patalpose atlikti matavimai, kurių metu fiksuotos oro temperatūros, santykinės drėgmės ir CO2 koncentracijos ore vertės. Atliekant tyrimą taikyta EN ISO 7730 tarptautiniame standarte pateikta metodika ir vertinant šiluminio komforto lygį buvo vykdyta poliklinikos pacientų ir personalo anketinė apklausa. Matavimo rezultatai parodė, kad šiltuoju metų laikotarpiu oro kokybės rodikliai tirtose patalpose atitiko higienos normose...
Mokslas - Lietuvos ateitis, 2018
The purpose of the study was to determine which ventilation system centralized or decentralized i... more The purpose of the study was to determine which ventilation system centralized or decentralized in viewpoint of economic, energy and comfort is more advantageous in an individual residential house. The relevance of the work is related to the increasing energy efficiency requirements for newly built buildings and the resulting problems of the sick building syndrome due to insufficient ventilation of the rooms. The installation and operation costs of systems were identified. The Life Cycle Analysis (LCA) method was applied to estimate the amount of pollutants and primary energy consumed throughout the lifetime of ventilation systems. Measurements of indoor climate parameters were made; the results compared with the hygiene norms valid in Lithuania. The results of the analysis showed that the decentralized ventilation system is the most advantageous for economic and environmental impacts, but centralized ventilation system ensuring a better indoor climate. Santrauka Tyrimo tikslas buvo...
Applied Thermal Engineering, 2018
Intensive use of energy is related to the inefficient use of processes in building engineering sy... more Intensive use of energy is related to the inefficient use of processes in building engineering systems. In well-insulated nonresidential buildings ventilation systems are among the most energy intensive HVAC systems. The main components of an energy (and exergy) efficient ventilation system are heat exchangers. The paper presents the analysis of process integration possibilities in a ventilation system. Only air heating for ventilation purposes is analysed. The method of Pinch technology, mostly used for industrial process integration, is adopted for a ventilation system of a building for the first time. In the paper, several different cases of integration are analysed by using actual BMS data of a shopping centre. The results confirmed that process integration influences the thermodynamic efficiency of the system and that integrated systems consume less energy and exergy in comparison with the non-integrated ones. The case study shows that the seasonal energy demand of the system before integration is 26% higher compared to integrated system and the exergy demand is 45% higher.
International Journal of Environmental Science and Development, 2015
In the current study, research on the performance characteristics of an adsorption cooling system... more In the current study, research on the performance characteristics of an adsorption cooling system supplied by solar energy is presented. The main task for the analyzed system was to ensure cooling load for the non-residential building in cold climate country. A 8.0 kW adsorption thermal cooling system was studied. The system got heat produced by evacuated tube solar collectors. The parametric simulation study was carried using a TRNSYS (Transient Systems Simulation) program to determine the influence of various parameters on the system performance. The dependencies of collector slope and the total absorber area on solar fraction, discarded energy, coefficient of performance, seasonal performance factor were studied. The highest solar fraction, coefficient of performance and seasonal performance factor values were obtained if the collector slope was approximately 30 degrees and the absorber area was 16 m 2 for the analyzed cases. The total primary energy consumption of the system was examined for various cases of primary energy factor for auxiliary heat and consumed electricity. On the basis of the results, it was proposed the expression of total primary energy consumption. The obtained results could be used for the recommendation preparations for decision makers to select a small scale solar cooling adsorption system.
18-toji Lietuvos jaunųjų mokslininkų konferencijos ciklo „Mokslas – Lietuvos ateitis”. Pastatų inžinerinės sistemos, 2015
Straipsnyje nagrinėjamas oro tiekimo–šalinimo įrenginys, esantis Vilniaus Gedimino technikos univ... more Straipsnyje nagrinėjamas oro tiekimo–šalinimo įrenginys, esantis Vilniaus Gedimino technikos universiteto Pastato energetinių ir mikroklimato sistemų laboratorijoje. Nagrinėjamos įrenginio elementų charakteristikos, energijos pernaša įrenginyje ir naudojant TRNSYS modeliavimo priemonę sukuriamas jo matematinis modelis, kuriame vaizduojami visi elementai. Pasiūlytas valdymo mechanizmas, leidžiantis modeliuoti vėdinimo įrenginio veikimą charakteringais laikotarpiais, taip pat, taikant ekserginės analizės principus, sukurtas matematinis algoritmas, atliekantis viso įrenginio ekserginio naudingumo koeficiento skaičiavimą. Modeliavimas atliktas visų metų laikotarpiu, nustatytas vidutinis metinis ekserginis vėdinimo įrenginio naudingumo koeficientas – 75,36 %.
Mokslas - Lietuvos ateitis, 2014
The paper analyses the impact of the supplied airflow rate of the solar wall used for heating air... more The paper analyses the impact of the supplied airflow rate of the solar wall used for heating air in an air handling unit on the effectiveness of the solar wall. The article reviews experimental and theoretical papers and presents the expressions determining the efficiency indicators of the solar wall. Experimental research into the solar wall at a constant airflow rate was carried out on 5–6 April 2014. Temperatures, overall efficiencies and an increase in temperature were established on the vertical solar wall counting the area of 100 m2 and fixed on the south façade of Vilnius Gediminas Technical University. An increase in the average temperature, in the course of the conducted experiment, reached 7.5 °C. Under constant airflow rate, temperature efficiency increases along with solar irradiation. The average estimated temperature efficiency reaches 72 percent. The overall effectiveness of the solar wall decreases when solar irradiation increases. Straipsnyje nagrinėjama saulės sie...
The 9th International Conference "Environmental Engineering 2014", 2014
The European Directive on Energy Performance of Buildings (EPBD) obliges to accept measures for i... more The European Directive on Energy Performance of Buildings (EPBD) obliges to accept measures for improving the energy efficiency in buildings. As buildings become more airtight ventilation takes an important role in building. Ventilation efficiency as a rule is achieved using heat recovery. The efficiency of the air heat recovery is varies depending on the applied type of heat exchanger and changes during the year. A dozen of heat recovery units, renewable energy sources and technologies can be applied to ventilation system to increase an efficiency of it. It should be an opportunity to add ventilation system with renewable energy sources. Such energy recovery and renewable energy technologies as air heat recovery unit, air-to-water heat pump, and unglazed solar collector (UTSC) for ventilation system of the building are analyzed. TRNSYS simulation tool is applied. Simulation results of three technologies (heat recovery unit, air heat pump and unglazed solar collector) using ventilation system performance during the year is presented. Main indicators of UTSC are presented. Simulation results and obtained experimental data of individual cases of such system are compared.
Scientific Journal of Riga Technical University. Environmental and Climate Technologies, 2011
The installation of a heat storage tank is a very costeffective way to improve the performance an... more The installation of a heat storage tank is a very costeffective way to improve the performance and flexibility of a CHP plant. Such a heat storage tank usually accumulates heat by thermal stratification. This phenomenon is caused by the thermal buoyancy because of the difference in temperature between cold and hot water. The heat storage tank may have three operating modes, i. e. charge, discharge and storage in a CHP plant. When CHP units, which charge the heat storage tank, operate at full load, usually only two operation modes occur in the tank, i.e. charge and discharge. The paper presents numerical simulation of heat storage tank operation modes in a CHP plant using PHOENICSa multipurpose computation fluid dynamics (CFD) software. Twodimensional and three-dimensional transient models were created and solved numerically. Three domain grids were tested. Several charging and discharging processes with different flow rates were simulated. The influence of flow rate on the degree of thermal stratification during charging and discharging processes is analyzed. The computation possibilities and limitations of the numerical experiments are pointed out. Special attention is given to the validation of the numerical solutions. The validation of simulated results is made by comparison with the real data from the heat storage installed in the Hvide Sande CHP plant.
Mokslas - Lietuvos ateitis, 2011
The paper analyzes the influence of integrating the processes taking place in the ventilation equ... more The paper analyzes the influence of integrating the processes taking place in the ventilation equipment of a public building on the thermal transmittance of heat exchangers. Pinch analysis helped with determining changes in the thermal transmittance of heat exchangers per year. The article examines the dependency of the thermal transmittance of heat exchangers on the disposed quantity of streams. The total thermal transmittance of heat exchangers is higher if several streams of lower parameters are used. Without additional economical calculations, the thermal transmittance of heat exchangers can assess their size, price and be used for the purposes of comparing the obtained results showing that designing such systems is useful for evaluating the possibilities of integrating the processes taking place in ventilation equipment. Santrauka Analizuojama viešosios paskirties pastato vėdinimo įrenginyje vykstančių procesų integracijos įtaka šilumokaičių šiluminiam pralaidumui. Taikant Pinc...