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By comparison to classical solutions, where certain heat elimination processes require substantial energetic input, the cooling solutions offered by heat exchangers with heat pipes offer a great advantage in the sense that they can transfer important heat fluxes by aid of a working fluid hermetically enclosed in a constant volume chamber.
The present work aims to model some of the state parameters that define phase changes taking place during heat transfer within flat micro heat pipes (FMHPs) that use acetone as a working fluid. Modeling results for the equivalent thermal conductivity in the vaporization region of the FMHP are presented. It was found that FMHP design must take into account the phase changes of the liquid by report to the heat flux and the overall length, as these parameters have an important influence on the FMHP efficiency.
The present work aimed to investigate such devices after certain degrees of usage in order to verify the evolution of surface micro-characteristics and their influence upon operating parameters. In order to achieve the abovementioned purpose, an optical evaluation of the surface was conducted using laser profilometry. Surface measurements were conducted on several injectors, after various degrees of usage, by aid of a laser profilometer equipped with a confocal sensor that has a vertical working range of 13mm and a resolution of 1μm1. After the surface micro-topography was measured, 3D and 2D representations, as well as individual profiles of the active surfaces, were analyzed and the significant parameters were determined. Surface wear and presence of combustion residues was analyzed in terms of its influence upon operating conditions.
In judicial ballistics, in the case of rifled firearms it is relatively simple for experts to identify the used weapon from traces left on the projectile, as the rifling of the barrel leaves imprints on the bullet, which remain approximately identical even after the respective weapon is fired 100 times with the same barrel. However, in the case of smoothbore firearms, their identification becomes much more complicated. As the firing cap suffers alterations from being hit by the firing pin, determination of the force generated during impact creates the premises for determining the type of firearm used to shoot the respective cartridge. The present paper proposes a simple impact model that can be used to evaluate the force generated by the firing pin during its impact with the firing cap. The present research clearly showed that each rifle, by the combination of the three investigated parameters (impact force maximum value, its variation diagram, and impact time) leave a unique trace. Application of such a method in ballistics can create the perspectives for formulating clear conclusions that eliminate possible judicial errors in this field.
The present paper aims to investigate, the efficiency of a braking system based on compression release, called a Jake Brake. In such a system, the exhaust valve is actuated at a certain predetermined angle of the crankshaft.
The presented research was conducted on an experimental rig based on a four-stroke mono-cylinder diesel engine model Lombardini 6 LD400. Pressure and temperature evolutions were monitored before and during the use of the Jake Brake system. As the generated phonic pollution is the main disadvantage of such systems, noise generated in the vicinity of the engine was monitored as well. The monitored parameters were then plotted in diagrams that allowed evaluating the performances of the system.
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