Search results for "Heat Transfer"

Termoidraulica del sodio - elementi teorici e sperimentali

1982

1985

From the break-down in the viscosity and from the increase of the intensity of the scattered light, associated with the entrance into the two-phase region, the pressure dependence of the demixing temperature of solutions of PVC 37 000, PVC 75 000 and PVC 100 000 in phenetole and PVC 75 000 in o-xylene was measured up to 1 000 bar. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) The application of pressure increases the demixing temperatures of PVC in both solvents by about 1 K/100 bar. For a qualitative forecast of the pressure effects, the solubility parameter theory in combination with the corresponding states principle, and an empirical correlatio…

An experimental study for the characterization of fluid dynamics and heat transport within the spacer-filled channels of membrane distillation modules

2018

Abstract The thermo-fluid dynamic behavior of spacer-filled channels for membrane distillation was investigated experimentally. Several different geometry were investigated thanks to customized reference spacers manufactured using a 3D printer. In particular, two sets of experiments were conducted: in the first set, cylindrical filaments were orthogonally arranged and the flow attack angle was made to vary from 0o to 90o; in the second set, the flow attack angle was kept symmetrical and the filament angle was made to vary from 30° to 150°. Each spacer was tested for Reynolds numbers between 200 and 900 in the hot channel, while maintaining a constant temperature difference of 13 °C between …

Noise-enhanced stability of periodically driven metastable states

2000

We study the effect of noise-enhanced stability of periodically driven metastable states in a system described by piecewise linear potential. We find that the growing of the average escape time with the intensity of the noise is depending on the initial condition of the system. We analytically obtain the condition for the noise enhanced stability effect and verify it by numerical simulations.

Second‐order analysis of marked inhomogeneous spatiotemporal point processes: Applications to earthquake data

2018

To analyse interactions in marked spatio-temporal point processes (MSTPPs), we introduce marked second-order reduced moment measures and K-functions for inhomogeneous second-order intensity reweigh ...

Rare events and scaling properties in field-induced anomalous dynamics

2012

We show that, in a broad class of continuous time random walks (CTRW), a small external field can turn diffusion from standard into anomalous. We illustrate our findings in a CTRW with trapping, a prototype of subdiffusion in disordered and glassy materials, and in the L\'evy walk process, which describes superdiffusion within inhomogeneous media. For both models, in the presence of an external field, rare events induce a singular behavior in the originally Gaussian displacements distribution, giving rise to power-law tails. Remarkably, in the subdiffusive CTRW, the combined effect of highly fluctuating waiting times and of a drift yields a non-Gaussian distribution characterized by long sp…

Relaxation of Electron Spin during High-Field Transport in GaAs Bulk

2011

A semiclassical Monte Carlo approach is adopted to study the multivalley spin depolarization of drifting electrons in a doped n-type GaAs bulk semiconductor, in a wide range of lattice temperature ($40<T_L<300$ K) and doping density ($10^{13}<n<10^{16}$cm$^{-3}$). The decay of the initial non-equilibrium spin polarization of the conduction electrons is investigated as a function of the amplitude of the driving static electric field, ranging between 0.1 and 6 kV/cm, by considering the spin dynamics of electrons in both the $\Gamma$ and the upper valleys of the semiconductor. Doping density considerably affects spin relaxation at low temperature and weak intensity of the driving electric fiel…

Boolean Models: Maximum Likelihood Estimation from Circular Clumps

1990

This paper deals with the problem of making inferences on the maximum radius and the intensity of the Poisson point process associated to a Boolean Model of circular primary grains with uniformly distributed random radii. The only sample information used is observed radii of circular clumps (DUPAC, 1980). The behaviour of maximum likelihood estimation has been evaluated by means of Monte Carlo methods.

Thermodynamic approach to vortex production and diffusion in inhomogeneous superfluid turbulence

2014

In this paper, we use a non-equilibrium thermodynamic framework to generalize a previous nonlocal model of counterflow superfluid turbulence to incorporate some new coupled terms which may be relevant in the evolution of inhomogeneous vortex tangles. The theory chooses as fundamental fields the energy density, the heat flux, and the averaged vortex line length per unit volume. The constitutive quantities are assumed to depend on the fundamental fields and on their first spatial derivatives, allowing us to describe thermal dissipation, vortex diffusion and a new contribution to vortex formation. The restrictions on the constitutive relations are deduced from the entropy principle, using the …

On the thermomechanical behavior of the European target assembly design of IFMIF-EVEDA lithium test loop under start-up transient scenarios

2013

Uncoupled thermomechanical transient analyses have been carried out to investigate the behavior of IFMIF-EVEDA lithium test loop bayonet backplate target assembly under two selected start-up transient operational scenarios. The first transient scenario considered foresees that the target assembly, starting from the initial uniform temperature of 50 C, is heated up uniquely by convective heat transfer with lithium, flowing from inlet to outlet nozzle at its reference nominal temperature and pressure, until its nominal steady state thermal field distribution is reached. The second transient scenario foresees, more realistically, that the target assembly, starting from the uniform temperature …