86,676 research outputs found
Space air-conditioning of mechanically-ventilated rooms : computation of flow and heat transfer
No full textComputational studies of two- and three-dimensional, turbulent
recirculating flows within mechanically-ventilated enclosures are
reported. Two principal cases are examined: (i) two-dimensional
offset jets: and (ii) three-dimensional flow induced in rooms by
supply jets emanating from low or high side-wall registers. The
calculations were undertaken using iterative finite-domain proceedures
which solve the conservation equations for mass, momentum and
enthalpy, together with additional transport equations for the
turbulent kinetic energy and its dissipation rate . The effect of
buoyancy waS. explicitly accounted for when modelling these equations,
in order that they could be employed to simulate buoyant flow in
ventilated rooms. Computations of the mean velocity, temperature and
convective heat transfer distribution are reported, and compared with
experimental data where available.
A modified version of the two-dimensional elliptic code of Pun
and Spalding (1977) was employed to simulate the offset jet case.
These involve the discharge of a turbulent jet parallel to a flat
surface and eventually attaching to it. The investigations covered a
wide range of offset ratio (3.5-32.4). and the computed flow
properties are compared with measurements from several sources. These
comparisons show good agreement downstream of the reattachment point,
while some discrepancies are evident upstream from this location. The
differences therefore occur mainly in the recirculating flow region,
and are believed to arise from shortcoming in the starting profiles,
the turbulance model and the treatment of the near-wall flow.
A three-dimensional elliptic finite-domain code was developed to
simulate the complex, jet-induced flow within rectangular enclosures.
The code was verified using both laminar and turbulent flow test cases
on simpler geometries. Comparisons with the measurements and
predictions reported by previous researchers were employed for this
purpose. Subsequentlyr the ventilated room simulations were
undertaken using three different ventilation arrangements with thermal
conditions corresponding to isothermall non-buoyant (constant
property) and buoyancy"affected flows. The computations were again
compared with experimental and numerical predictions of previous
researchers. This comparison displayed generally good agreement with
these sources.
A study of the flow and convective heat exchange within a
warm-air heated rom, for which buoyancy effects are significant# is
also reported in a bound paper (Alamdari, Hammonda nd Mohammad, 1986)
for three different heat loads. Its aim to assess the balance between
accuracy and economy provided by the present higher-level method
compared with the intermediate-level convection model of Alamdari and
Hammond (1982) when used to supply building thermal simulation
programs with accurate convection heat transfer data. The computed
results of both models were compared, and indicate that the
intermediate-level is a valuable alternative source that can satisfy
the needs of building thermal modellers. It provides resonable
accuracy at a very modest cost in computing terms
EU network carriers, low cost carriers and consumer behaviour: A Delphi study of future trends
No full textThis paper uses a Delphi panel of 26 air transport experts to forecast the
structure of air transport in the EU in 2015 in respect of network carriers, low
cost airlines and passenger behaviour. Secondary research was used to construct
a number of scenarios about the future structure and strategy of EU network and
low cost airlines and also traveller behaviour. Consensus of opinions was sought
amongst the panel in a two-round process. The consensus opinion of the Delphi
experts was that; network carrier consolidation will reduce EU players to less
than five, there will be only two or three large low cost carriers, Business
Class products will disappear on short hauls. and leisure travellers will take
an increasing number of multiple short-duration holidays
Regional development in airlines and travel agents relationship.
No full textOn average, 17% of airline operating cost are attributed to distribution costs which are associated with commissions to travel agents, ticketing, credit card fees, CRS fees and promotion. In recent years, airlines in North America and in Europe have been questioning the role of travel agents in the distribution chain and renegotiating commission fee structures. As a result, some large agents have introduced a management fee philosophy where the clients, especially corporations, pay a fee to the travel agent in return for predetermined services. Such services include providing up-to-the minute reports on travel patterns of employees, effectiveness of travel policies, advice on complicated itineraries, etc. Such changes in airline and travel agent relationships initially started in the US and were followed by the European carriers. However, Asian carriers have been slow in following their US and European counterparts. This raises a number of questions: What are the barriers, if any for Asian carriers, to follow their counter parts in Europe and US? Would airlines in the three regions be able to bypass travel agents and sell directly to their customers? Would the customers prefer to go direct to airlines? Would there be a variation in the airlines, and agents, relationship in each region? This paper addresses these questions by analysing the distribution strategies of major carriers in the US, Europe and Asia. It also discusses the changing relationship between airlines and travel agents, and the trend towards direct selling by airlines in each region
Experimental heat/mass transfer studies of turbulent wall-bounded jets associated with mechanicallly ventilated enclosures
No full textThe development and use of a'n experimental test rig
is reported which is capable of modelling two- and
three-dimensional wall-bounded air jets. This test rig
was primarily produced in order to facilitate the
experimental verification of computer codes for
calculating convective heat transfer within mechanically-
ventilated enclosures. Special attention was therefore
given in the design of the rig to heat transfer
measurements within such enclosures.
The analogy between heat and mass transfer and the
application of the naphthalene sublimation technique are
explained. Also use of phase change paints in heat
transfer measurements in general, and wall-jets in
particular, is discussed and experimentally demonstrated.
The boundary conditions for the application of each of the
above two methods are then specified. The mass transfer
method may be used for the case of a heated plate and a
jet at ambient temperature while the phase change paint
method is applicable to a heated jet.
Heat/mass transfer studies are carried out for two
different geometries. First beneath a plane wall-jet-
obstructed by a normal flat-plate (Alamdari, Hammond and
Montazerin (1986 bound paper)), where the data are
compared with the computations of the 'intermediate-level'
convection model of Alamdari and Hammond (1982) and the
high-level 'elliptic' finite domain flow model of Pun and
Spalding (1977). The comparison has been a clear
demonstration of the capabilities of the computer codes
and has shown that although their results over flat
surfaces are in good agreement with the test data, their
predictions for jets flowing round corners need further
research. Secondly the flow and heat transfer
characteristics of a three-dimensional jet parallel to a
flat plate has been studied. In this case the flow field
and mass transfer are modelled and an equation is finally
derived which estimates the average heat transfer over a
plate parallel to a bluff-jet for a variety of off-set
heights, Reynolds numbers and nozzle aspect ratios and can
readily be used by design engineers handling such flows
Convective heat transfer within mechanically-ventilated building spaces
No full textA hierarchy of interacting and interdependent approaches have
been developed for calculating internal surface convective heat
transfer coefficients within mechanically-ventilated rooms. A
'high-level' computer code is developed for non-bucyant and
buoyant flow based on the "elliptic' code of Pun and Spalding
(1977), in which 'upwind' finite-difference approximations to the
governing partial-differential equations for continuity, momentum
and thermal energy are formulated in terms of 'primitive'
pressure-velocity variables. Closure of these time-averaged,
elliptic equations is obtained via transport equations for both
the turbulence kinetic energy and its dissipation rate. The
high-level code solves the difference equations for a
predetermined size, staggered grid in an iterative 'line-by-line'
manner using a guess-and-correct procedure.
An 'intermediate-level' computer code (the ROOM-CHT program)
has also been developed for the above purpose, which employs
'informed" estimates of the flow and thermal field based on the
known mean flow properties of wall-jets. The corresponding heat
transfer distribution across the room surface is calculated using
wall-jet profile analysis or improved data correlations for
bucyancy-driven convection as appropriate.
Caqputations are presented for a room into which air is
injected through a low or high side wall register. The supply of
air governed by both cyclic and modulating control was examined.
The intermediate-level code is advocated as being the most
appropriate for meeting the requirements of dynamic building
thermal models. This code was verified by comparison with the
high-level code and with experimental measurements. The oomputed
heat transfer coefficients from the intermediate-level code were
found to be in good agreement with that of the high-level code.
Both indicate significantly higher values than those which would
be obtained from established design guides. These high values
suggest errors in building thermal models based on guide data,
including substantial under-estimation of preheat times
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
[Newspaper Clipping: Author Claims Evidence of Second JFK Assassin #1]
No full textNewspaper article titled "Author Claims Evidence of Second JFK Assassin." The article states that author Richard J. Whalen concluded "that there is circumstantial evidence to support the theory of a second assassin in the shooting of President John F. Kennedy.
Also By The Same Author: AKTiveAuthor, a Citation Graph Approach to Name Disambiguation
No full textThe desire for definitive data and the semantic web drive for inference over heterogeneous data sources requires co-reference resolution to be performed on those data. In particular, name disambiguation is required to allow accurate publication lists, citation counts and impact measures to be determined. This paper describes a graph-based approach to author disambiguation on large-scale citation networks. Using self-citation, co-authorship and document source analyses, AKTiveAuthor clusters papers, achieving precision of 0.997 and recall of 0.818 over a test group of eight surname clusters
John F. Kennedy telegram to Roosevelt
No full textJersey Homesteads (later the Borough of Roosevelt) was established in the 1930s as an agro-industrial cooperative community. It was established specifically for urban Jewish garment workers, many of whom had emigrated from Europe. President John F. Kennedy sent a telegram to the citizens of Roosevelt, New Jersey, apologizing for not being able to attend the memorial dedication in honor of former President Franklin Delano Roosevelt. (Jersey Homesteads became Roosevelt in 1945 in honor of the president.) President Kennedy expressed his gratitude to the people of Roosevelt for constructing the memorial, and commented that it will serve as a constant reminder of Roosevelt's good works
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
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