Thermal-EHD contacts lubricated with oil/refrigerant solutions: a new cavitation modeling approach based on refrigerant solubility

A first cavitation modeling with thermal effects for oil/refrigerant solutions lubricated ElastoHydroDynamic (EHD) point contacts is reported in this work. The solubility of the oil/refrigerant system is introduced into the Generalized Reynolds equation coupled with the elasticity equation and the energy conservation equation. The numerical results show a very good agreement with the published experimental results concerning film thickness prediction. Moreover, the present model describes the cavitation region on a physical basis. A discussion with other cavitation models from the literature is proposed. It puts into light the necessity of taking into account the solubility of the refrigerant into oil for such problems. Compared to pure oil, oil/refrigerant solutions can potentially reduce the amount of liquid oil for the next contact due to its higher cavitation intensity.

Electronic thermodynamics part 1: Thermo-electromechanical system modeling, instrumentation, and simulation

This research proposes to obtain a mathematical model that describes the dynamic operation of a brushed DC motor, to obtain a state function considering the electrical, mechanical, and thermal effects of the DC motor. The dynamic evolution of the proposed function is evaluated by simulation using Matlab software, and by applying different values of the step type inputs for the brushed motor excitation employing pulse width modulation (PWM) to obtain a wide range of operations. Experimental results show that the developed state function, provides a reliable approximation to estimate the voltage, armature current, mechanical torque, and temperature of the brushed DC motor, showing an error percentage of 0.2%.

Examining the potential of damage in threat zones around LPG storage sphere in Hassi R’Mel city, Algeria

Purpose This study aims to determine the maximum extent of damage in the threat zones, the result of a catastrophic failure in one liquefied petroleum gas storage sphere, located in storage and transfer center in Hassi R’Mel city, Algeria. Design/methodology/approach To reach the desired results, we relied on ALOHA® v. 5.4.7 software (Areal Locations of Hazardous Atmospheres) for accidents simulation, and on Google Earth as an output tool to show results on the city map. Findings The results prove that the city of Hassi R’Mel is almost completely threatened by thermal effects resulting from a boiling liquid expanding vapor explosion phenomenon, which can reach a distance of 3.9 km. Originality/value Determining the extent to which the damages resulting from an industrial accident may reach is of great importance in preventing industrial hazards, as well as in decision-making in the field of urbanization.

Identifying signatures of thermal and non-thermal reaction pathways in plasmon induced H2 + D2 exchange reaction

In this work we demonstrate a strategy for identifying experimental signatures of thermal and non-thermal effects in plasmon mediated heterogeneous catalytic chemistry, a topic widely debated and discussed in the literature. Our method is based on monitoring the progress of plasmon-induced (or thermally-driven) reaction, carried out in a closed system, all the way to equilibrium. Initial part of evolution of the reaction provides information about kinetics, whereas at later times the equilibrium concentrations provide information about effective temperature at the reaction sites. Combining these two pieces of information we estimate the activation energies. Using this strategy on H 2 (g) + D 2 (g) <-->2 HD(g) isotope exchange reaction, catalyzed by Au nanoparticles under thermally-driven and light-induced conditions, we estimate the activation energies to be 0.75 ± 0.02 eV and 0.21 ± 0.02 eV, respectively. These vastly different activation energies observed are interpreted as a signature of different reaction pathways followed by the system under thermally-driven and light-induced conditions.