Conduction and convection heat transfer characteristics of water-based au nanofluids in a square cavity with differentially heated side walls subjected to constant temperatures

The present work deals with the natural convection in a square cavity filled with the water-based Au nanofluid. The cavity is heated on the vertical and cooled from the adjacent wall, while the other two horizontal walls are adiabatic. The governing differential equations have been solved by the standard finite volume method and the hydrodynamic and thermal fields were coupled together using the Boussinesq approximation. The main objective of this study is to investigate the influence of the nanoparticles’ volume fraction on the heat transfer characteristics of Au nanofluids at the given base fluid’s (i.e. water) Rayleigh number. Accurate results are presented over a wide range of the base fluid Rayleigh number and the volume fraction of Au nanoparticles. It is shown that adding nanoparticles in a base fluid delays the onset of convection. Contrary to what is argued by many authors, we show by numerical simulations that the use of nanofluids can reduce the heat transfer rate instead of increasing it

Izhlapevanje vodnih kapljic v prvi stopnji naprave za ultrazvočno razpršilno pirolizo

he present work deals with numerical modelling of aerosol evaporation in the flow of carrier gas (N2) in the 1st stage of ultrasonic spray pyrolysis device. For that we have used so called Euler-Lagrange approach, where the gas phase is treated as a continuous phase by solving the Navier-Stokes equations, while the dispersed phase is treated as a number of discrete particles, which exchange energy, momentum and mass with the continuous phase. Results are presented for the temperature field of carrier gas and water vapor, as well as for the droplets’ diameter, temperature and evaporation time.Numerično smo modelirali proces izhlapevanja aerosola (generiranega iz vode) v toku nosilnega plina (N2) v prvi stopnji naprave za ultrazvočno razpršilno pirolizo. Uporabili smo t.i. Euler-Lagrangeov pristop, ki obravnava plinsko fazo kot zvezno telo z reševanjem (v primeru turbulentnega toka časovno povprečenih) Navier-Stokesovih enačb, razpršeno fazo pa kot veliko število diskretnih delcev (mehurčkov, kapljic ali trdnih delcev), ki si z zvezno fazo izmenjujejo energijo, gibalno količino in/ali maso. Prikazani so rezultati za temperaturno polje nosilnega plina in aerosola, kakor tudi za premer, temperaturo ter čas izhlapevanja vodnih kapljic. Le ti kažejo, da je izhlapevanje najintenzivnejše v začetnem delu grelnega območja in da relativna vlažnost nosilnega plina nima pomembnega vpliva na sam proces izhlapevanja

Numerična analiza hitrega strjevanja NiTi zlitine: vpliv robnih pogojev

The objective of the present work is to analyze influence of temperature boundary conditions on the solidification process of NiTi alloy. Alloy is taken as an incompressible fluid where the heat is transferred by conduction and convection, including the thermal phase change phenomenon. The last one is modelled by the improvement procedure, so-called enthalpy-porosity formulation, where the liquid-solid mushy zone is treated as a porous zone with porosity equal to the liquid fraction. The numerical model is based on the finite volume method in body fitted coordinates with a SIMPLER scheme to couple the pressure and velocity fields. Simulation presents solidification for two cooling cases on the cylindrical part, where in the first case the adiabatic boundary condition is considered and in the second case the convective cooling over the wall is present. The results are presented for the velocity and temperature field as well as for the NiTi mass fraction during the solidification process. Results shows that velocity and temperature field is strongly affected by the different cooling condition on the cylindrical wall and therefore the solidification process of the alloy. Analysis shows that cooling on the cylindrical part is one of the major parameters for alloy solidification and therefore should not be neglected.Delo obravnava vpliv temperaturnih robnih pogojev na strjevanje NiTi zlitine s pomočjo numerične simulacije. Zlitina je obravnavana kot nestisljiva tekočina, kjer se toplota prenaša s prevajanjem in prestopom, vključno s pojavom fazne spremembe. Numerično modeliranje fazne spremembe je izvedeno z izboljšanim pristopom, imenovanim formulacija entalpija-poroznost. Pri tem pristopu je območje vmesnega faznega stanja tekoče-trdno obravnavano kot porozno območje s poroznostjo, ki je enaka deležu tekoče faze. Numerični model temelji na metodi končnih volumnov, pri čemer sta tlačno in hitrostno polje povezana s SIMPLER algoritmom. Numerična simulacija podaja strjevanje NiTi zlitine v geometriji epruvete, ki je v prvem primeru po cilindričnem delu oboda idealno izolirana (adiabatni pogoj) in v drugem primeru se preko te površine hladi zaradi okoliškega zraka. V rezultatih so predstavljeni hitrostno in temperaturno polje, kakor tudi deleži posameznih faz NiTi zlitine med procesom strjevanja. Iz rezultatov je razviden precejšen vpliv različnega robnega pogoja na hitrostno in temperaturno polje, kar posledično vpliva tudi na strjevanje zlitine. Analiza je pokazala, da je ohlajanje preko stene epruvete eden izmed vplivnejših parametrov strjevanja zlitine in ga zato ne smemo zanemariti

Methodologies for Assessing the Acceptability of Oral Formulations among children and older adults: A Systematic Review

This is an open access article distributed under the terms and conditions of the Creative Commons Attribution NonCommercial-NoDerivatives 4.0 International CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Acceptability of medicinal products in children and older populations is pivotal in ensuring adherence and therapeutic outcomes. This review systematically identifies studies reporting on formulation aspects of oral medications that affect their acceptability in these patient groups. Particular emphasis is placed on the evaluation of the methodologies employed in the studies. Sixty-eight studies were included for analysis, with 51 (75%) in children and 17 (25%) in older populations. The studies evaluated a range of oral formulations; however, the methodologies used differ considerably in participants’ characteristics, study settings, tools, acceptability definitions and criteria. It is evident that there is a lack of standardisation in study design as well as the assessment methods used in assessing acceptability of medicines in children and older populations. This review presents a systematic analysis on methods employed for assessing acceptability of oral medicines in children and older adults, to provide insights and recommendations regarding the design of reliable instruments in future studies.Peer reviewe

Food effects in paediatric medicines development for products co-administered with food

A small amount of food is commonly used to aid administration of medicines to children to improve palatability and/or swallowability. However the impact of this co-administered food on the absorption and subsequent pharmacokinetic profile of the drug is unknown. Existing information on food effects is limited to standard protocols used to evaluate the impact of a high fat meal in an adult population using the adult medication. In the absence of a substantial body of data, there are no specific guidelines available during development of paediatric products relating to low volumes of potentially low calorie food. This paper brings together expertise to consider how the impact of co-administered food can be risk assessed during the development of a paediatric medicine. Two case studies were used to facilitate discussions and seek out commonalities in risk assessing paediatric products; these case studies used model drugs that differed in their solubility, a poorly soluble drug that demonstrated a positive food effect in adults and a highly soluble drug where a negative food effect was observed. For poorly soluble drugs risk assessments are centred upon understanding the impact of food on the in vivo solubility of the drug which requires knowledge of the composition of the food and the volumes present within the paediatric gastrointestinal tract. Further work is required to develop age appropriate in vitro and in silico models that are representative of paediatric populations. For soluble drugs it is more important to understand the mechanisms that may lead to a food effect, this may include interactions with transporters or the impact of the food composition on gastro-intestinal transit or even altered gastric motility. In silico models have the most promise for highly soluble drug products although it is essential that these models reflect the relevant mechanisms involved in potential food effects. The development of appropriate in vitro and in silico tools is limited by the lack of available clinical data that is critical to validate any tool. Further work is required to identify globally acceptable and available vehicles that should be the first option for co-administration with medicines to enable rapid and relevant risk assessment

Conduction and convection heat transfer characteristics of water-based Au nanofluids in a square cavity with differentially heated side walls subjected to constant temperatures

The present work deals with the natural convection in a square cavity filled with the water-based Au nanofluid. The cavity is heated on the vertical and cooled from the adjacent wall, while the other two horizontal walls are adiabatic. The governing differential equations have been solved by the standard finite volume method and the hydrodynamic and thermal fields were coupled together using the Boussinesq approximation. The main objective of this study is to investigate the influence of the nanoparticles\u27 volume fraction on the heat transfer characteristics of Au nanofluids at the given base fluid\u27s (i.e. water) Rayleigh number. Accurate results are presented over a wide range of the base fluid Rayleigh number and the volume fraction of Au nanoparticles. It is shown that adding nanoparticles in a base fluid delays the onset of convection. Contrary to what is argued by many authors, we show by numerical simulations that the use of nanofluids can reduce the heat transfer rate instead of increasing it

Numerična analiza prenosa toplote nanotekočin voda-Au v razmerah Reyleigh-Bénardove naravne konvekcije

The present work deals with the natural convection in a square cavity filled with a water-based Au nanofluid. The cavity is heated from the lower and cooled from the adjacent wall, while the other two walls are adiabatic. Theg overning differential equations have been solved with the standard finite volume method and the hydrodynamic and thermal fields have been coupled using the Boussinesq approximation. The main objective of this study is to investigate the influence of the nanoparticlesć volume fraction on the heat-transfer characteristics of Au nanofluids at a given base-fluid (i.e., water) Rayleigh number Rabf. Accurate results are presented over a wide range of the base-fluid Rayleigh numbers (102 £ Rabf £ 105) and the volume fraction of Au nanoparticles (0 % £ j £ 10 %). It is shown that adding nanoparticles to the base fluid delays the onset of convection. Contrary to what is argued by many authors, we show, with numerical simulations, that the use of nanofluids can reduce the heat transfer instead of increasing it.V prispeveku obravnavamo naravno konvekcijo v kvadratni kotanji, napolnjeni z nanotekočino voda-Au. Kotanja je bila greta s spodnje in hlajena s priležne zgornje stene, preostali dve steni sta bili adiabatni. Vodilne diferencialne enačbe smo reševali s standardno metodo končnih prostornin. Hidrodinamično in temperaturno polje sta bila sklopljena z uporabo Boussinesqove aproksimacije. Glavni cilj prispevka je raziskati vpliv prostorninskega deleža nanodelcev na značilnosti prenosa toplote Au-nanotekočine pri podani vrednosti Rayleighjevega števila nosilne tekočine (vode) Rabf. Natančni rezultati so predstavljeni za široko območje vrednosti Rayleighjevega števila nosilne tekočine (102 £ Rabf £ 105) in prostorninskega deleža Au-nanodelcev (0 % £ j £10 %). Pokazali smo, da dodajanje nanodelcev v nosilno tekočino zakasni začetek naravne konvekcije. V nasprotju s trditvami mnogih avtorjev smo z numeričnimi simulacijami pokazali, da lahko uporaba nanodelcev prenos toplote zmanjša in ne poveča