15,526 research outputs found
Theoretical models for rates of heterogeneous reactions during combustion and gasification of liquid fuels in fluidized beds
Two mathematical models to allow computations of chemical species production or consumption rates by heterogeneous reactions taking place during combustion and gasification of liquid fuels sprayed on or injected into fluidized beds of solid particles are proposed. The possibilities envisaged here are called: the CIP (Coated Inert Particles) and the CSP (Coke Shell Particle) models. The former assumes that the injected liquid fuel immediately coats the fluidized inert particles in the bed and then goes through pyrolysis, combustion and gasification reactions. The latter presumes that the liquid fuel drops go through fast pyrolysis before meeting any inert particles and the remaining coke hollow particles react with gases in the bed. Analytical solutions for various geometries of the inert particles in the bed are presented. The work does not include the governing equations which constitute the whole mathematical model of fluidized-bed reactors. Such can be found elsewhere. The present work concentrates only on the theoretical aspects. Experimental tests would allow verification if they properly represent the processes of liquid consumption during combustion and gasification processes consuming liquid fuels in fluidized beds and which model would better fit each individual situation5811412
The Complexity of Helly- EPG Graph Recognition
Golumbic, Lipshteyn, and Stern defined in 2009 the class of EPG graphs, the
intersection graph class of edge paths on a grid. An EPG graph is a graph
that admits a representation where its vertices correspond to paths in a grid
, such that two vertices of are adjacent if and only if their
corresponding paths in have a common edge. If the paths in the
representation have at most bends, we say that it is a -EPG
representation. A collection of sets satisfies the Helly property when
every sub-collection of that is pairwise intersecting has at least one
common element. In this paper, we show that given a graph and an integer
, the problem of determining whether admits a -EPG representation
whose edge-intersections of paths satisfy the Helly property, so-called
Helly--EPG representation, is in NP, for every bounded by a polynomial
function of . Moreover, we show that the problem of recognizing
Helly--EPG graphs is NP-complete, and it remains NP-complete even when
restricted to 2-apex and 3-degenerate graphs
INCORPORATION OF A TWO-FLUX MODEL FOR RADIATIVE HEAT TRANSFER IN A COMPREHENSIVE FLUIDIZED BED SIMULATOR PART I: PRELIMINARY THEORETICAL INVESTIGATIONS
Over the last two decades, a comprehensive mathematical model and its corresponding computational program, aimed to simulate steady-state operations of bubbling fluidized bed equipments, has been continuously improved and tested. Despite its success, the simulator has employed a simple approach for radiative heat transfers. In cases of high temperatures, thermal radiation becomes an important energy transfer mode and the original model could lead to deviations above acceptable levels. The purpose of the present work was to improve the model for thermal radiation heat transfer between all solid particles in the bed section by applying a two-flux method to a non-homogeneous polydispersed particulate media in radiative equilibrium. Gases in the emulsion and in the bubbles were assumed transparent to thermal radiation. This first part of the paper presents and discusses the basic structure of the former mathematical model and of the new one
New HVAC Sustainability Index - TWI (Total Water Impact)
Sales of air conditioning are growing rapidly in buildings, more than tripling between 1990
and 2016. This energy use for air conditioning comes from a combination of rising temperatures, rising
population and economic growth. Energy demand for climate control will triple by 2050, consuming
more energy than that currently consumed altogether by the United States, the European Union
and Japan. This increase in energy will directly impact water consumption, either to directly cool a
condenser of an equipment or to serve indirectly as a basis for energy sources such as hydroelectric
power that feed these heating, ventilation and air conditioning (HVAC) systems. Knowing the unique
and growing importance of water, a new index, Total Water Impact (TWI) is presented, which allows
a holistic comparison of the impact of water use on water, air and evaporative condensation climate
systems. 200 and 500 TON (tons of refrigeration) air-cooled and water-cooled systems are theoretically
compared to evaluate the general water consumption level. The TWI index is higher in the smallest
water condensing system. That is, holistically, water consumption is higher in the water condensing
system than in the air condensing system. Thus, this index provides a new insight about energy
consumption and ultimately, about sustainability.info:eu-repo/semantics/publishedVersio
Fitorreguladores de crescimento no alongamento in vitro de Pinus greggii.
Organizado por Patricia Póvoa de Mattos, Celso Garcia Auer, Rejane Stumpf Sberze, Katia Regina Pichelli e Paulo César Botosso
Assepsia de sementes para estabelecimento in vitro de espécies medicinais nativas da Caatinga.
Objetivou-se com este trabalho, realizar diferentes testes de assepsia para o estabelecimento in vitro de três espécies nativas da Caatinga de potencial medicinal
Uma proposta de classificação de analogias para o ensino nas ciências da saúde
O objetivo desse trabalho é contribuir para o processo de ensino de Ciências da Saúde por meio da apresentação de uma nova proposta de classificação de analogias contendo suas categorias, caracterizações e tipologias, elaborada a partir de duas dissertações de mestrado. Sua formulação ocorreu após análise de livros didáticos de Enfermagem e de Fisioterapia, de questionários e entrevistas com profissionais das áreas. A proposta contém oito categorias com respectivas caracterizações e apresenta uma tipologia própria, flexível de modo a ser reconstruída e se aplica a outras áreas do conhecimento. Os resultados apontam a necessidade de ampliar o sistema de classificação utilizado no ensino de ciências de modo a contemplar as analogias encontradas no presente estudo
- …