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Estudo numérico e experimental do armazenamento de energia por calor latente em um leito fixo / Numerical and experimental study of energy storage for latent heat in a fixed bedMoraes, Raykleison Igor dos Reis 20 August 2018 (has links)
Orientador: Kamal Abdel Radi Ismail / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T09:32:00Z (GMT). No. of bitstreams: 1
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Previous issue date: 2012 / Resumo: O presente trabalho consiste na investigação numérica e experimental do carregamento de um leito fixo com material de mudança de fase no interior das cápsulas esféricas. O modelo matemático é baseado na equação da energia e a solução obtida com a técnica numérica em diferenças finitas com o esquema da malha móvel. O acoplamento do fluido de trabalho com as cápsulas foi feita utilizando o balanço de energia com o material de mudança de fase, obtendo a temperatura em função do tempo e da posição no leito. O modelo desenvolvido mostra os efeitos da temperatura de entrada, vazão mássica, diâmetro da cápsula esférica, material das cápsulas, tempo de carregamento e altura do armazenado. A Validação e otimização dos resultados foi feita com base nos resultados experimentais apresentados. As equações empíricas apresentadas podem ser ferramentas úteis como forma alternativa nos projetos de armazenadores com erro médio de ± 11% e a incerteza nos dados experimentais para a temperatura é de ± 0,5oC. Todos os resultados são analisados e discutidos / Abstract: The present work is to investigate numerical and experimental and the charging of fixed bed PCM within the spherical capsules. The mathematical model is based on the energy equation and the solution obtained with the numerical technique of finite difference scheme with mesh mobile. The coupling of the working fluid with the capsules was conducted using the energy balance of the phase change material, obtaining the temperature versus time and bed position. The model shows the effects of the inlet temperature, mass flow rate, diameter of the spherical capsule, the capsule material, charging time and the stored height. Validation and optimization of the results was based on experimental results. The empirical equations presented can be useful tools as an alternative projects in storages with average error of 11% and the uncertainty of the experimental data for temperature is 0.5oC. All results are analyzed and discussed / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica
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Estudo numerico da solidificação em geometria anular / Numerical study of solidification in annular geometryJesus, Antonio Batista de 27 April 1998 (has links)
Orientador: Kamal Abdel Radi Ismail / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-24T15:15:51Z (GMT). No. of bitstreams: 1
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Previous issue date: 1998 / Resumo: O processo de solidificação de um material de mudança de fase em região anular ao redor de um cilindro resfriado pela passagem de um fluido em seu interior é estudado numericamente com vistas à aplicação em sistemas de armazenamento de calor latente. A solução do problema de mudança de fase é feita utilizando a técnica de imobilização de fronteira, onde aplica-se uma transformação de coordenadas, de maneira que no novo sistema a fronteira móvel e irregular seja fixa e paralela às demais. A condução de calor no material de mudança de fase é acoplada à condução na parede do cilindro e à convecção no interior deste. O método de volumes finitos é utilizado para a discretização das equações do modelo matemático que são em seguida resolvidas computacionalmente. São analisados aspectos relativos à implementação da técnica de imobilização, como o surgimento de termos pseudo-convectivos e pesudo-anisotrópicos por conseqüência da mudança de variáveis. Também são estudados aspectos relacionados com o acoplamento da condução de calor no cilindro e no material de mudança de fase e a convecção no fluido refrigerante. São apresentadas comparações com outros trabalhos da literatura e um conjunto de resultados para o caso de água como material de mudança de fase / Abstract: Solidification of a phase-change material in an annulus around a cylinder, which carries inside it a coolant fluid, is studied numerically for application in latent heat thermal energy storage. The boundaryimmobilization technique is used for solving the phase-change problem. A coordinate transformation is performed so that in the new system the moving and irregular boundary becomes fixed and parallel to the others. Heat conduction in the phase-change material is coupled with conduction in the inner tube wall and convection in the coolant. The fmite-volume methodology is used for discretization of the equations from the mathematical model which are then solved by a computer programo Some aspects related with the application of the boundaryimmobilization technique are analyzed such as the appearance of pseudo-convective and pseudo-anisotropic terms as a consequence of the change of variables. Aspects related to the coupling of conduction ill the cylinder wall and phase-change material with convection in the coolant fluid are also studied. Comparisons with other solutions available in the literature are presented as well results for the specific case of water being the phasechange material / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica
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Energy storage in phase change materials in cylindrical containersMenon, Anilkumar S. January 1981 (has links)
No description available.
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Salz/Zeolith-Komposite für die Sorptionswärmespeicherung / Salt/Zeolite Composites for Sorption Heat StorageNonnen, Thomas 01 August 2016 (has links) (PDF)
Zeolithgranulate sind etablierte Materialien für die Speicherung von Wärme mittels Wassersorption. Eine Erhöhung der Wärmespeicherdichte des Granulats ist durch Kombination mit hygroskopischen Salzen wie Calciumchlorid, Magnesiumchlorid oder Magnesiumsulfat möglich. In der vorliegenden Dissertation wird gezeigt, dass die Wär-mespeichereigenschaften derartiger Komposite von der Deliqueszenzluftfeuchte des Salzes, von der Salzbeladung und von der Luftfeuchte bei der Wassersorption abhängen. Liegt die Luftfeuchte unterhalb der Deliqueszenzluftfeuchte des Salzes, so nehmen Was-serbeladungshub, Wärmespeicherdichte und thermische Leistung mit steigender Salz-beladung um bis zu 71 % ab. Dies wird darauf zurückgeführt, dass Salzionen in die Mik-roporen des Zeoliths inkludiert werden und das für die Wassersorption zur Verfügung stehende Volumen verringern. Unterhalb der Deliqueszenzluftfeuchte ist das einge-brachte Salz daher thermochemisch inaktiv. Oberhalb der Deliqueszenzluftfeuchte und oberhalb einer salz- und luftfeuchteabhängigen Mindestsalzbeladung kommt es zur Ausbildung einer Salzlösung im Sekundärporensystem des Granulats. Die Absorption von Wasserdampf in der Salzlösung führt gegenüber dem salzfreien Granulat zu einer Steigerung von Wasserbeladungshub und Wärmespeicherdichte um bis zu 53 %. Dies geht jedoch einher mit einer Verringerung der thermischen Leistung um bis zu 50 %. Die Hydratation von kristallinem Salz im Granulat spielt gegenüber Salzinklusion und Ausbildung der Salzlösung nur eine untergeordnete Rolle. Die aus den experimentellen Befunden abgeleiteten Erkenntnisse konnten in ein semiempirisches mathematisches Modell überführt werden, welches den Wasserbeladungshub der Komposite quantitativ beschreibt. / Zeolite beads are established materials for the storage of heat by water sorption. An increase of the heat storage density of the beads is possible via the combination with hygroscopic salts. In this thesis it is shown, that the heat storage properties of compo-sites of this kind depend in a complex manner on the deliquescence humidity of the salt, on the salt loading, and on the humidity during water sorption. When the humidity is below the deliquescence humidity of the salt, water loading lift, heat storage density, and thermal power are reduced by up to 71 % with increasing salt content. This is at-tributed to the inclusion of salt into the micropores of the zeolite and the reduction of the volume available for the sorption of water. Thus, below the deliquescence humidity, the salt is thermochemically inactive. Above the deliquescence humidity and above a salt- and humidity-dependend minimum salt loading, a salt solution is formed in the secondary pore system of the beads. The absorption of water vapor in the salt solution gives rise to an increase of the water loading lift and of the heat storage density by up to 53 %, compared to the salt-free zeolite beads. However, this is accompanied by a reduc-tion of the thermal power output by up to 50 %. The hydration of crystalline salt in the beads is only of minor importance for the composites. The findings from the experi-mental work were transferred into a semi-empirical mathematical model, which de-scribes the water loading lift of the composites.
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Salz/Zeolith-Komposite für die SorptionswärmespeicherungNonnen, Thomas 28 June 2016 (has links)
Zeolithgranulate sind etablierte Materialien für die Speicherung von Wärme mittels Wassersorption. Eine Erhöhung der Wärmespeicherdichte des Granulats ist durch Kombination mit hygroskopischen Salzen wie Calciumchlorid, Magnesiumchlorid oder Magnesiumsulfat möglich. In der vorliegenden Dissertation wird gezeigt, dass die Wär-mespeichereigenschaften derartiger Komposite von der Deliqueszenzluftfeuchte des Salzes, von der Salzbeladung und von der Luftfeuchte bei der Wassersorption abhängen. Liegt die Luftfeuchte unterhalb der Deliqueszenzluftfeuchte des Salzes, so nehmen Was-serbeladungshub, Wärmespeicherdichte und thermische Leistung mit steigender Salz-beladung um bis zu 71 % ab. Dies wird darauf zurückgeführt, dass Salzionen in die Mik-roporen des Zeoliths inkludiert werden und das für die Wassersorption zur Verfügung stehende Volumen verringern. Unterhalb der Deliqueszenzluftfeuchte ist das einge-brachte Salz daher thermochemisch inaktiv. Oberhalb der Deliqueszenzluftfeuchte und oberhalb einer salz- und luftfeuchteabhängigen Mindestsalzbeladung kommt es zur Ausbildung einer Salzlösung im Sekundärporensystem des Granulats. Die Absorption von Wasserdampf in der Salzlösung führt gegenüber dem salzfreien Granulat zu einer Steigerung von Wasserbeladungshub und Wärmespeicherdichte um bis zu 53 %. Dies geht jedoch einher mit einer Verringerung der thermischen Leistung um bis zu 50 %. Die Hydratation von kristallinem Salz im Granulat spielt gegenüber Salzinklusion und Ausbildung der Salzlösung nur eine untergeordnete Rolle. Die aus den experimentellen Befunden abgeleiteten Erkenntnisse konnten in ein semiempirisches mathematisches Modell überführt werden, welches den Wasserbeladungshub der Komposite quantitativ beschreibt. / Zeolite beads are established materials for the storage of heat by water sorption. An increase of the heat storage density of the beads is possible via the combination with hygroscopic salts. In this thesis it is shown, that the heat storage properties of compo-sites of this kind depend in a complex manner on the deliquescence humidity of the salt, on the salt loading, and on the humidity during water sorption. When the humidity is below the deliquescence humidity of the salt, water loading lift, heat storage density, and thermal power are reduced by up to 71 % with increasing salt content. This is at-tributed to the inclusion of salt into the micropores of the zeolite and the reduction of the volume available for the sorption of water. Thus, below the deliquescence humidity, the salt is thermochemically inactive. Above the deliquescence humidity and above a salt- and humidity-dependend minimum salt loading, a salt solution is formed in the secondary pore system of the beads. The absorption of water vapor in the salt solution gives rise to an increase of the water loading lift and of the heat storage density by up to 53 %, compared to the salt-free zeolite beads. However, this is accompanied by a reduc-tion of the thermal power output by up to 50 %. The hydration of crystalline salt in the beads is only of minor importance for the composites. The findings from the experi-mental work were transferred into a semi-empirical mathematical model, which de-scribes the water loading lift of the composites.
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Thermodynamic and heat transfer evaluation of a thermic solar panelYasuda, Arthur Kenichi. January 1976 (has links)
Thesis: B.S., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1976 / Includes bibliographical references. / by A. Ken Yasuda. / B.S. / B.S. Massachusetts Institute of Technology, Department of Mechanical Engineering
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A method for determining the installed capacity of an underfloor electrical resistance heating and energy storage systemSmith, Carol Elaine. January 1985 (has links)
Call number: LD2668 .T4 1985 S64 / Master of Science
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Performance of a solar air heater incorporating thermal storageLombaard, Francois 12 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: In the present study, research was conducted to determine the
feasibility of water energy storage through which the output of
heated air by an upward facing solar air heater could be prolonged.
Following a systematic approach, a number of experimental test
swere initially performed on an upward facing solar air heater in
order to obtain a benchmark that could be used to evaluate the
influence of water storage during the day-time performance of a
solar air heater. As expected, an increase in the air mass flow rate
not only led to an increase in the collector efficiency but also to a
decrease in the temperature gain across the collector. In addition,
a number of day- and night-time experiments were executed on a
plastic covered water tank in order to evaluate it's ability to store
and discharge thermal energy. Results clearly indicated that the
plastic covered water tank was both an ideal collector and storage
medium of solar energy. Experimental results also revealed that
the plastic covered water tank was an ideal source of thermal
energy for a solar air heater during night-time operation.
Subsequently, both day- and night-time experiments were
performed on an upward facing solar air heater in which plastic
covered water tanks were installed. Day-time experimental results
revealed that the modified solar air heater still had the same
collector efficiency tendency, as observed in the initial solar air
heater experiments, but that the water energy storage led to a
dramatic decrease in the absorber plate temperature and in the
corresponding temperature gain experienced across the collector.
In contrast, the night-time operation results clearly indicated that
the water energy storage was not only able to prolong the output of
heated air by the solar air heater, but was further able to increase
the air temperature by between 7.5 and 1.5 °e, depending on the
air mass flow rate. It was furthermore shown in the study that
available theory is able to accurately predict the performance of an
upward facing solar air heater, either with or without water energy
storage, as long as the equations are employed within their range
of validity / AFRIKAANSE OPSOMMING:In die hierdie studie is daar ondersoek ingestel na die
lewensvatbaarhied van son-energiestoring in water ten einde die
tydperk van lugverhitting deur 'n son-Iugverwarmer te verleng. 'n
Sistematiese prasedure is gevolg waardeur daar aanvanklik 'n
aantal eksperimente op 'n son-Iugverwarmer uitgevoer is am
sodoende die eienskappe van so 'n lugverhiUingstelsel, sander
energie storing, te vekry. Die resultate het getoon dat 'n toename
in die massavloei tempo van die lug lei tot 'n toename in die
kollektor effektiwiteit van die stelsel, maar terselfdetyd lei tot 'n
afname in die temperatuur styging in die kollektor. Met die
eienskappe van die lugverwarmingstelsel bekend, is daar voorts 'n
aantal dag- en nag-eksperimente uitgevoer op 'n plastiek bedekte
watertenk am die storing en vryselling van termiese energie deur
die watertenk te kwantifiseer. Die resultate het daarap gedui dat
die plastiek bedekte watertenk nie net beide 'n goeie kollektor en
stoor medium vir son-energie is nie, maar oak dat dit 'n ideale bran
van termiese energie vir 'n lugverwarmingstelsel tydens die nag is.
Met inagname van die vorige resultate, is daar dan 'n aantal
plastiek bedekte watertenks in die apparaat geinstalleer, en 'n
aantal dag- en nag-eksperimente is uitgevoer. Die dageksperimente
het getoon dat die die nuwe lugverwarmer met water
energie storing dieselfde eienskappe toon ten opsigte van die
kollektor effektiwiteit as die oorspronkilke son-Iugverwarmer. Tog,
as gevolg van die laer absoberende plaat temperature was die
temperatuur toename in die kollektor heelwat laer. In kontras
hiermee dui die nagresultate aan dat die plastiek bedekte
watertenks nie net die vermoe het am die tydperk van
lugverwarming te verleng nie, maar oak dat die lug tempertuur,
afhangende van die massavloei tempo van die lug, met tussen 1.5
en 7.5 °C verhoog kan word. Die studie het laastens oak getoon
dat dit moontlik is am met behulp van beskikbare teorie die
temperatuur toename in die kollektor van 'n son-Iugverwarmer met
of sander water energie storing, akkuraat te voorspel, mits die
vergelykings binne hul geldige gebiede gebruik word.
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Lattice potential energies and theoretical applicationsRoobottom, Helen Kay January 2000 (has links)
No description available.
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High temperature packed bed thermal storage for solar gas turbinesKlein, Peter January 2016 (has links)
A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy, 2016 / Solar powered gas micro-turbines present opportunities for off-grid power generation. Due
to the intermittent nature of the solar energy supply, existing Solar Gas Turbine (SGT) plants
employ hybridisation with fossil fuels to generate dispatchable power. In this work sensible
heat and latent heat storage solutions are investigated as a means of increasing the solar share
of a SGT cycle, thus reducing the consumption of diesel fuel.
The sensible heat storage concept was based on a pressurised packed bed of spherical ceramic
particles, using air as the heat transfer fluid. An axisymmetric, two-phase heat transfer model
of the system was developed, based on the continuous solid phase approach. The model
was successfully validated against experimental data from a packed bed of alumino-silicate
particles over the temperature ranges of gas turbine cycles (350-900 °C and 600-900 °C). The
validated numerical model was utilised to conduct a parametric design study of a six hour
(1.55 MWhth) storage system for a gas micro-turbine. The results show that a high storage
efficiency and high utilisation factor can be achieved when combining sensible heat storage
in alumina with fossil fuel hybridisation, with somewhat lower values without hybridisation.
An analysis of different inventory geometries showed that a packed bed of spherical particles
is best suited to pressurised sensible heat storage.
The latent heat storage concept was based on a pressurised packed bed of Encapsulated
Phase Change Material (EPCM) particles. Sodium sulphate was identified as a suitable phase
change material for the gas turbine cycle. The sensible heat storage model was extended
to account for intra-particle temperature gradients and phase change within the particles.
The intra-particle phase change model was validated against published experimental data
for a single EPCM sphere heated and cooled by convection. The full EPCM storage model
was further successfully validated against experimental data from a packed bed of macro-
encapsulated sodium sulphate particles with alumina shells, up to a temperature of 950 °C.
A comparison of the two storage concepts for a 7 m3 bed shows that a packed bed of en-
capsulated sodium sulphate particles would have a 36% lower energy storage capacity than
a bed of solid alumina particles. This is due to the limited melt fraction in the EPCM bed
when a temperature limit is placed on the base. Increasing the packed bed volume to 10.5 m3
would provide a comparable thermal performance to the 7 m3 solid alumina bed, at a 12%
lower storage mass. A hybrid three-layer packed bed is proposed to increase the volumetric
energy storage density. Modelling shows that this concept could provide a small increase
of 5.3% in the amount of energy discharged above 850 °C, compared to the solid alumina
particles only.
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