Flow boiling heat transfer of a non-azeotropic mixture inside a single microchannel

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.This study moves from the need to study flow boiling of zeotropic mixture in microchannels. In the recent years much attention has been paid to the possible use of fluorinated propene isomers for the substitution of high-GWP refrigerants. The available HFOs (hydrofluoroolefins) cannot cover all the air-conditioning, heat pump, and refrigeration systems when used as pure fluids because their thermodynamic properties are not suitable for all operating conditions and therefore some solutions may be found using blends of refrigerants, to satisfy the demand for a wide range of working conditions. In the present paper a mixture of R1234ze(E) and R32 (0.5/0.5 by mass) has been studied. The local heat transfer coefficient during flow boiling of this mixture in a single microchannel with 0.96 mm diameter is measured at a pressure of 14 bar, which corresponds to a bubble temperature of 26.3°C. The flow boiling data taken in the present test section are discussed, with particular regard to the effect of heat flux, mass velocity and vapor quality. The heat transfer coefficients are compared against some predicting models available in the literature. Furthermore, the new experimental data are compared to flow boiling data of pure R1234ze(E) and pure R32 to analyze the heat transfer penalization due to the mass transfer resistance of this zeotropic mixture

ANTIMICROBIAL PROPERTIES OF PLATELET-RICH PLASMA

Autologous platelet concentrates have been widely used in various medical fields in order to promote tissue regeneration. The significance behind their use lies in the presence of growth factors in platelets \u3b1-granules that enhance wound healing by promoting cell chemotaxis, proliferation and differentiation. In addition, anti-inflammatory and antibacterial properties of platelet concentrates have been recently pointed out. In this study, the antimicrobial effect of pure platelet-rich plasma (P-PRP) was evaluated against microorganisms isolated from oral cavity, such as Candida albicans, Enterococcus faecalis, Pseudomonas aeruginosa, Streptococcus agalactiae and Streptococcus oralis. Blood samples were obtained from healthy donors. The antibacterial activity of P-PRP, was evaluated as the minimum inhibitory concentration (MIC), determined through the microdilution two-fold serial method, and the minimum microbicidal concentration (MMC), determined by subculturing microbial samples from MIC tests to solid media. MIC results showed that P-PRP was able to inhibit the growth of E. faecalis, C. albicans, S. agalactiae and S. oralis, but not of P. aeruginosa strains. Moreover, MMB tests showed that C. albicans was less suceptible to P-PRP than other microorganisms. In conclusion, this study shows that, in adjunct to its well established regenerative properties, P-PRP possess an antimicrobial activity and so might represent a valuable product in the fight against infection

Optimization of hybrid sol-gel coating for dropwise condensation of pure steam

We developed hybrid organic-inorganic sol-gel silica coatings with good durability in harsh environment (high temperatures, high vapor velocities) and with slightly hydrophobic behavior, sufficient to promote dropwise condensation (DWC) of pure steam. DWC is a very promising mechanism in new trends of thermal management and power generation systems to enhance the heat transfer during condensation as compared to film-wise condensation (FWC). The sol-gel coatings have been prepared from methyl triethoxy silane (MTES) and tetraethyl-orthosilicate (TEOS) and deposited on an aluminum substrate. The coatings were optimized in terms of precursor ratio and annealing temperature highlighting potentials and limits of such mixtures. A comprehensive surface characterization before and after saturated steam condensation tests has been performed and related to the thermal measurements for evaluating the heat transfer augmentation as compared to FWC obtained on untreated aluminum surfaces. The results showed that the developed hybrid organic-inorganic sol-gel silica coatings are promising DWC promoters

Caracterização de sementes de Paspalum lepton Schult.

SIEPE

Estratégia de sobrevivência de panicum maximum tanzânia sob pastejo rotacionado.

Foi avaliada a dinâmica de perfilhamento do capim-tanzânia ao longo de um ano, visando caracterizar sua estratégia de sobrevivência em 5 touceiras. As maiores taxas de natalidade ocorreram em janeiro (76,6 p.100) e março (51,3 p.100) e as menores em junho (19,7 p.100) e agosto (13,2 p.100). As maiores taxas de mortalidade ocorreram em janeiro (72,5 p.100) e março (55,2 p.100) e as menores em abril (28,8 p.100) a outubro (24,4 p.100). Houve florescimento quando o fotoperíodo foi inferior a 11,5 horas (abril-agosto), onde as taxas de natalidade foram menores devido à dominância apical. Entre janeiro e abril houve intensa renovação de perfilhos. Grande proporção de perfilhos da geração que surgiu em março sobreviveu durante o período seco. Portanto, nesta geração, devem ser aplicadas técnicas de manejo visando à perenidade do pasto

Influência da assepsia na germinação de sementes de Paspalum regnellii Mez.

CONGREGA

Absorção de nitrato e de amônio em cultivares de Panicum maximum.

A forma de absorção e o padrão de partição de N em Panicum maximum cvs. Tanzânia e Aruana foram determinados utilizando-se técnicas isotópicas. O experimento foi desenvolvido em casa de vegetação na Embrapa Pecuária Sudeste, em São Carlos SP. Soluções nutritivas enriquecidas com 15NO3 ou 15NH4 foram utilizadas para estimar a absorção de amônio e nitrato. Nas folhas em expansão, bainhas e lâminas das folhas novas e hastes o conteúdo de N total foi maior no capim-tanzânia; já o conteúdo de N total das raízes foi maior no capim-aruana. A variação no conteúdo de N total entre a primeira e a segunda coleta indica que nos tratamentos 15NH4 e 15NO3 os principais drenos de nitrogênio foram os perfilhos laterais e as folhas em expansão. As raízes também representaram um importante dreno de nitrogênio, exceto para o capim-tanzânia no tratamento 15NH4. O conteúdo de 15NO3 na planta inteira foi mais elevado que o de 15NH4 nos dois capins, indicando que há absorção preferencial de nitrogênio na forma de nitrato. Concluiu-se que os perfilhos laterais, as folhas em expansão e as raízes representam os principais drenos de nitrogênio do capim-tanzânia e do capim-aruana e que nestes cultivares há absorção preferencial de nitrogênio na forma de nitrato