7 research outputs found
NumeriÄko istraživanje efekata poroznih svojstava i debljine sloja na performance protonske izmjenjivaÄke membrane gorive Äelije
In this study, fluid flow and concentration distribution on the cathode side of a
Proton Exchange Membrane Fuel Cell were numerically analyzed. The problem
domain consists of a cathode gas flow channel, cathode gas diffusion layer and
cathode catalyst layer. The governing equations, continuity, momentum and
concentration equations were discritized by the control volume method and
solved using a computer program based on SIMPLE algorithm. Simulations were
made for different values of gas diffusion layer porosity, catalyst layer porosity
and the ratio of the cathode gas diffusion layer thickness to the gas flow channel
height. Using the results of these simulations, the effects of these parameters on
flow, oxygen concentration and current density distribution were analyzed. It is
observed that increasing the porosities of the gas diffusion layer and catalyst
layer increases the current and power densities. The increase in the porosity
of the gas diffusion layer also increases the oxygen concentration in both gas
diffusion and catalyst layers but decreases the oxygen concentration in gas flow
channel. Simulations also showed that increasing porosity of the catalyst layer
increases the oxygen concentration in a catalyst layer but decreases the oxygen
concentration in a gas flow channel and gas diffusion layer. It is also seen that the
effect of the gas diffusion layer porosity is more dominant on cell performance
compared to the catalyst layer porosity. The analysis of the effect of the ratio of
the cathode gas diffusion layer thickness to the gas flow channel height on the
cell performance showed that the increasing ratio of the cathode gas diffusion
layer thickness to the gas flow channel height decreases the current and power
densities. An analysis of the data obtained from simulations also shows that
increasing the ratio of the cathode gas diffusion layer thickness to the gas flow
channel height increases the oxygen concentration in the gas flow channel but
decreases the oxygen concentration in both gas diffusion and catalyst layers.U ovom radu je numeriÄki analizirano strujanje fluida i raspodjela koncentracije
protonske izmjenjivaÄke membrane na katodnoj strani gorive Äelije. Problemska
domena se sastoji od kanala katode kroz koji struji plin, difuznog sloja plina
na strani katode kao i katodnog katalitiÄkog sloja. Generalne jednadžbe,
jednadžbe kontinuiteta, jednadžbe koliÄine gibanja i jednadžbe koncentracije
su diskretizirane metodom kontrolnog volumena i rijeÅ”ene koristeÄi raÄunarski
program koji je baziran na algoritmu SIMPLE. Simulacije su napravljene za
razliÄite vrijednosti poroznosti difuzijskog sloja na strani plina, poroznosti
katalitiÄkog sloja i omjera debljine difuzijskog sloja na strani plina i visine kanala
kroz koji struji plin. KoristeÄi rezultate ovih simulacija, analizirani su efekti ovih
parametara na strujanje, koncentraciju kisika i raspodjelu gustoÄe struje. UoÄeno
je da se s poveÄavanjem poroznosti difuzijskog sloja na strani plina i katalitiÄkog
sloja, poveÄava se jakost struje i snage. PoveÄavanjem poroznosti difuzijskog
sloja na strani plina, poveÄava se i koncentracija kisika i u difuzijskom sloju na
strani plina i u katalitiÄkom sloju, ali se smanjuje koncentracija kisika u kanalu
kroz koji struji plin. Simulacije su takoÄer pokazale da poveÄavanjem poroznosti
u katalitiÄkom sloju poveÄavaju u njemu koncentraciju kisika, ali smanjuje
se koncentracija kisika u kanalu strujanja plina kao i u difuzijskom sloju na
strani plina. TakoÄer je uoÄeno da je efekt poroznosti u difuzijskom sloju na
straniplina bitno utjecajniji na performanse gorive Äelije od poronosti kataltiÄkog
sloja. Analiza efekta omjera debljine difuzijskog sloja na strani plina na katodi
i visine kanala kroz koji struji plin na performance gorive Äelije je pokazala da
se poveÄavanjem debljine difuzijskog sloja plina na katodi u odnosu na visinu
kanala, smanjuje jakost struje i gustoÄu snage. Analiza podataka dobivena
simulacijom takoÄer pokazuje da se poveÄavanjem omjera debljine difuzijskog
sloja plina na strani katode prema visini kanala, poveÄava koncentraciju kisika
u kanalu strujanja plina ali smanjuje koncentraciju kisiku i u dufuzijskom sloju
plina i katalitiÄkom sloju
NumeriÄko istraživanje efekata poroznih svojstava i debljine sloja na performance protonske izmjenjivaÄke membrane gorive Äelije
In this study, fluid flow and concentration distribution on the cathode side of a
Proton Exchange Membrane Fuel Cell were numerically analyzed. The problem
domain consists of a cathode gas flow channel, cathode gas diffusion layer and
cathode catalyst layer. The governing equations, continuity, momentum and
concentration equations were discritized by the control volume method and
solved using a computer program based on SIMPLE algorithm. Simulations were
made for different values of gas diffusion layer porosity, catalyst layer porosity
and the ratio of the cathode gas diffusion layer thickness to the gas flow channel
height. Using the results of these simulations, the effects of these parameters on
flow, oxygen concentration and current density distribution were analyzed. It is
observed that increasing the porosities of the gas diffusion layer and catalyst
layer increases the current and power densities. The increase in the porosity
of the gas diffusion layer also increases the oxygen concentration in both gas
diffusion and catalyst layers but decreases the oxygen concentration in gas flow
channel. Simulations also showed that increasing porosity of the catalyst layer
increases the oxygen concentration in a catalyst layer but decreases the oxygen
concentration in a gas flow channel and gas diffusion layer. It is also seen that the
effect of the gas diffusion layer porosity is more dominant on cell performance
compared to the catalyst layer porosity. The analysis of the effect of the ratio of
the cathode gas diffusion layer thickness to the gas flow channel height on the
cell performance showed that the increasing ratio of the cathode gas diffusion
layer thickness to the gas flow channel height decreases the current and power
densities. An analysis of the data obtained from simulations also shows that
increasing the ratio of the cathode gas diffusion layer thickness to the gas flow
channel height increases the oxygen concentration in the gas flow channel but
decreases the oxygen concentration in both gas diffusion and catalyst layers.U ovom radu je numeriÄki analizirano strujanje fluida i raspodjela koncentracije
protonske izmjenjivaÄke membrane na katodnoj strani gorive Äelije. Problemska
domena se sastoji od kanala katode kroz koji struji plin, difuznog sloja plina
na strani katode kao i katodnog katalitiÄkog sloja. Generalne jednadžbe,
jednadžbe kontinuiteta, jednadžbe koliÄine gibanja i jednadžbe koncentracije
su diskretizirane metodom kontrolnog volumena i rijeÅ”ene koristeÄi raÄunarski
program koji je baziran na algoritmu SIMPLE. Simulacije su napravljene za
razliÄite vrijednosti poroznosti difuzijskog sloja na strani plina, poroznosti
katalitiÄkog sloja i omjera debljine difuzijskog sloja na strani plina i visine kanala
kroz koji struji plin. KoristeÄi rezultate ovih simulacija, analizirani su efekti ovih
parametara na strujanje, koncentraciju kisika i raspodjelu gustoÄe struje. UoÄeno
je da se s poveÄavanjem poroznosti difuzijskog sloja na strani plina i katalitiÄkog
sloja, poveÄava se jakost struje i snage. PoveÄavanjem poroznosti difuzijskog
sloja na strani plina, poveÄava se i koncentracija kisika i u difuzijskom sloju na
strani plina i u katalitiÄkom sloju, ali se smanjuje koncentracija kisika u kanalu
kroz koji struji plin. Simulacije su takoÄer pokazale da poveÄavanjem poroznosti
u katalitiÄkom sloju poveÄavaju u njemu koncentraciju kisika, ali smanjuje
se koncentracija kisika u kanalu strujanja plina kao i u difuzijskom sloju na
strani plina. TakoÄer je uoÄeno da je efekt poroznosti u difuzijskom sloju na
straniplina bitno utjecajniji na performanse gorive Äelije od poronosti kataltiÄkog
sloja. Analiza efekta omjera debljine difuzijskog sloja na strani plina na katodi
i visine kanala kroz koji struji plin na performance gorive Äelije je pokazala da
se poveÄavanjem debljine difuzijskog sloja plina na katodi u odnosu na visinu
kanala, smanjuje jakost struje i gustoÄu snage. Analiza podataka dobivena
simulacijom takoÄer pokazuje da se poveÄavanjem omjera debljine difuzijskog
sloja plina na strani katode prema visini kanala, poveÄava koncentraciju kisika
u kanalu strujanja plina ali smanjuje koncentraciju kisiku i u dufuzijskom sloju
plina i katalitiÄkom sloju
Assessment of 3D velocity vector fields and turbulent kinetic energy in a realistic aortic phantom using multi-point variable-density velocity encoding
ISSN:1097-6647ISSN:1532-429
Experimental and Numerical Study of Ascending Aorta Hemodynamics Through 3D Particle Tracking Velocimetry and Computational Fluid Dynamics
Advances in Biological Liquid Crystals
Biological Liquid Crystal, a rich set of soft materials with rod-like structures widely existed in nature, possess typical lyotropic liquid crystalline phase properties both in vitro (e.g. cellulose, peptides and protein assemblies), and in vivo (e.g. cellular lipid membrane, packed DNA in bacteria and aligned fibroblasts). Given the ability to undergo phase transition in response to various stimuli, numerous practices have been exercised to spatially arrange biological liquid crystals. In this mini-review, the fundamental understanding of interactions between rod-shaped biological building blocks and their orientational ordering across multiple length scales is addressed. Discussions are made with regard to the dependence of physical properties of non-motile objects on the first-order phase transition and the coexistence of multi-phases in passive liquid crystalline systems. This review also focuses on how the applied physical stimuli drives the reorganization of constituent passive particles for a new steady-state alignment. A number of recent progresses in the dynamics behaviours of active liquid crystals are presented, and particular attention has been given to those self-propelled animate elements, like the formation of motile topological defects, active turbulence, correlation of orientational ordering and cellular functions. Finally, future implications and potential applications of the biological liquid crystalline materials are discussed