87 research outputs found
Experimental and analytical performance investigation of air to air two phase closed thermosyphon based heat exchangers
In recent years, the use of wickless heat pipes (thermosyphons) in heat exchangers has been on the rise, particularly in gas to gas heat recovery applications due to their reliability and the level of contingency they offer compared to conventional heat exchangers. Recent technological advances in the manufacturing processes and production of gravity assisted heat pipes (thermosyphons) have resulted in significant improvements in both quality and cost of industrial heat pipe heat exchangers. This in turn has broadened the potential for their usage in industrial waste heat recovery applications. In this paper, a tool to predict the performance of an air to air thermosyphon based heat exchanger using the ε-NTU method is explored. This tool allows the predetermination of variables such as the overall heat transfer coefficient, effectiveness, pressure drop and heat exchanger duty according to the flow characteristics and the thermosyphons configuration within the heat exchanger. The new tool's predictions were validated experimentally and a good correlation between the theoretical predictions and the experimental data, was observed. © 2014 Elsevier Ltd. All rights reserved
Neutron/proton ratio of nucleon emissions as a probe of neutron skin
The dependence between neutron-to-proton yield ratio () and neutron
skin thickness () in neutron-rich projectile induced reactions is
investigated within the framework of the Isospin-Dependent Quantum Molecular
Dynamics (IQMD) model. The density distribution of the Droplet model is
embedded in the initialization of the neutron and proton densities in the
present IQMD model. By adjusting the diffuseness parameter of neutron density
in the Droplet model for the projectile, the relationship between the neutron
skin thickness and the corresponding in the collisions is obtained.
The results show strong linear correlation between and
for neutron-rich Ca and Ni isotopes. It is suggested that may be used
as an experimental observable to extract for neutron-rich nuclei,
which is very significant to the study of the nuclear structure of exotic
nuclei and the equation of state (EOS) of asymmetric nuclear matter.Comment: 7 pages, 5 figures; accepted by Phys. Lett.
Azimuthal asymmetry of direct photons in intermediate energy heavy-ion collisions
Hard photon emitted from energetic heavy ion collisions is of very
interesting since it does not experience the late-stage nuclear interaction,
therefore it is useful to explore the early-stage information of matter phase.
In this work, we have presented a first calculation of azimuthal asymmetry,
characterized by directed transverse flow parameter and elliptic asymmetry
coefficient , for proton-neutron bremsstrahlung hard photons in
intermediate energy heavy-ion collisions. The positive and negative
of direct photons are illustrated and they seem to be anti-correlated to the
corresponding free proton's flow.Comment: 7 pages, 4 figures; accepted by Physics Letters
Coincidence probability as a measure of the average phase-space density at freeze-out
It is pointed out that the average semi-inclusive particle phase-space
density at freeze-out can be determined from the coincidence probability of the
events observed in multiparticle production. The method of measurement is
described and its accuracy examined.Comment: LateX, 9 pages, no figure
Scaling of Anisotropic Flow and Momentum-Space Densities for Light Particles in Intermediate Energy Heavy Ion Collisions
Anisotropic flows ( and ) of light nuclear clusters are studied by
Isospin-Dependent Quantum Molecular Dynamics model for the system of Kr
+ Sn at intermediate energy and large impact parameters.
Number-of-nucleon scaling of the elliptic flow () are demonstrated for the
light fragments up to = 4, and the ratio of shows a constant
value of 1/2. In addition, the momentum-space densities of different clusters
are also surveyed as functions of transverse momentum, in-plane transverse
momentum and azimuth angle relative to the reaction plane. The results can be
essentially described by momentum-space power law. All the above phenomena
indicate that there exists a number-of-nucleon scaling for both anisotropic
flow and momentum-space densities for light clusters, which can be understood
by the coalescence mechanism in nucleonic degree of freedom for the cluster
formation.Comment: 8 pages, 3 figures; to be published in Physics Letters
Scaling of anisotropy flows in intermediate energy heavy ion collisions
Anisotropic flows (, and ) of light nuclear clusters are
studied by a nucleonic transport model in intermediate energy heavy ion
collisions. The number-of-nucleon scalings of the directed flow () and
elliptic flow () are demonstrated for light nuclear clusters. Moreover,
the ratios of of nuclear clusters show a constant value of 1/2
regardless of the transverse momentum. The above phenomena can be understood by
the coalescence mechanism in nucleonic level and are worthy to be explored in
experiments.Comment: Invited talk at "IX International Conference on Nucleus-Nucleus
Collisions", Rio de Janeiro, Aug 28- Sept 1, 2006; to appear on the
proceeding issue in Nuclear Physics
Quark deconfinement in neutron star cores and the ground state of neutral matter
Whether or not deconfined quark phase exists in neutron star cores and
represents the ground state of neutral matter at moderate densities are open
questions. We use two realistic effective quark models, the three-flavor
Nambu-Jona-Lasinio model and the modified quark-meson coupling model, to
describe the neutron star matter. After constructing possible hybrid equations
of state (EOSes) with unpaired or color superconducting quark phase, we
systematically discuss the observational constraints of neutron stars on the
EOSes. It is found that the neutron star with pure quark matter core is
unstable and the hadronic phase with hyperons is denied, while hybrid EOSes
with two-flavor color superconducting phase or unpaired quark matter phase are
both allowed by the tight and most reliable constraints from two stars Ter 5 I
and EXO 0748-676. And the hybrid EOS with unpaired quark matter phase is
allowed even compared with the tightest constraint from the most massive pulsar
star PSR J0751+1807. Therefore, we conclude that the ground state of neutral
matter at moderate densities is in deconfined quark phase likely.Comment: 13 pages, 4 figure
Strange quark collectivity of meson at RHIC
Based on A Multi-Phase Transport model, the elliptic flow of
mesons which is reconstructed from at the Relativistic Heavy Ion
Collider (RHIC) energy has been studied. The results show that reconstructed
of meson can keep the earlier information before decays
and it seems to obey the number of constituent quark scaling as other mesons
and baryons. This result indicates that the mostly reflects the
parton level collectivity developed during the early stage of the collisions
and the strange and light up/down quarks have similar collectivity properties
before the hadronization.Comment: Proceeding for the "Workshop on Quark-Gluon-Plasma Thermalization",
TU Wien, Vienna, Austria, Aug. 200
On the Lorentz structure of the symmetry energy
We investigate in detail the density dependence of the symmetry energy in a
relativistic description by decomposing the iso-vector mean field into
contributions with different Lorentz covariant properties. We find important
effects of the iso-vector, scalar channel (i.e. -meson like) on the
high density behavior of the symmetry energy. Applications to static properties
of finite nuclei and to dynamic situations of heavy ion collisions are explored
and related to each other. The nuclear structure studies show only moderate
effects originating from the virtual meson. At variance, in heavy ion
collisions one finds important contributions on the reaction dynamics arising
from the different Lorentz structure of the high density symmetry energy when a
scalar iso-vector field is introduced. Particularly interesting is the
related neutron/proton effective mass splitting for nucleon transport effects
and for resonance and particle production around the threshold. We show that
the -like channel turns out to be essential for the production of
pions, when comparing with experimental data, in particular for high momentum
selections.Comment: 30 pages, 12 figures (.eps
A phenomenological equation of state for isospin asymmetric nuclear matter
A phenomenological momentum-independent (MID) model is constructed to
describe the equation of state (EOS) for isospin asymmetric nuclear matter,
especially the density dependence of the nuclear symmetry energy
. This model can reasonably describe the general
properties of the EOS for symmetric nuclear matter and the symmetry energy
predicted by both the sophisticated isospin and momentum dependent MDI model
and the Skyrme-Hartree-Fock approach. We find that there exists a nicely linear
correlation between and as well as between and , where and represent, respectively, the
slope and curvature parameters of the symmetry energy at the normal nuclear
density while and are, respectively, the
incompressibility and the third-order derivative parameter of symmetric nuclear
matter at . These correlations together with the empirical
constraints on , and lead to an
estimation of -477 MeV MeV for the
second-order isospin asymmetry expansion coefficient for the incompressibility
of asymmetric nuclear matter at the saturation point.Comment: 9 pages, 4 figures, contribution to Special Topic on Large-Scale
Scientific Facilities (LSSF) in Science in China Series G: Physics, Mechanics
& Astronom
- …