Research on Force and Thermal Phenomena of Short Circuited Melted Mark in Electrical Fire
This paper mainly does a research on force and thermal phenomena of short circuited melted mark in electrical fire. The primary short circuited melted mark and secondary short circuited melted mark were prepared by the experiment, and were characterized by metallographic microscope, powder X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy, the role of forces and heat in short circuited melted mark in electrical fire were demonstrated and investigated. It is found that they show a similar shape that the melted ball close to one side for anode melted marks, and their particles show the specific and uniform direction and the most particle size of anode melted marks are larger than the particle size of cathode melted marks, both below the copper wire grain size 64.2nm, similarly, it can be clearly seen that the ratio of O: Cu in deposit layer of all melted marks are below 0.5. Finally, these above special phenomena gave short circuited melted mark the primary statement from the theoretical point of view.
Study on discrimination between primary and secondary molten marks using carbonized residue
Abstract In most places where a fire started, electric molten marks that may be the cause of the fire are found. Various methods have been studied for identifying these electric molten marks to be either the cause of a fire (a primary molten mark (PMM)) or one caused by the flames of the fire (a secondary molten mark (SMM)). Little was studied, however, on their identification using the carbonized residue remaining in the molten marks. In this study, therefore, it was examined whether it was possible to discriminate between the PMMs and SMMs by analyzing the crystal structure of the carbon in the carbonized residue, which came from PVC insulation, remaining in the primary and the SMMs. As a result, it has been found that PMMs contain both graphitized carbon and amorphous carbon, whereas SMMs only contain amorphous carbon.
Effects of Equipment Dimensions on Liquid Mixing Time of Bubble Column with Draft Tube
The liquid mixing time of a bubble column with a draft tube is experimentally studied. The diameter and height of the column, the diameter and length of the draft tube, and the mode of sparging gas were changed and the liquid mixing time was measured.The lengths of bottom and top clearances have significant effects on the liquid mixing time. The liquid mixing time increases with increasing column aspect ratio of height to diameter. The liquid mixing time of the bubble column with a draft tube is longer than that of a standard bubble column when the column aspect ratio is relatively high. The liquid mixing time has a minimum when the diameter ratio of draft tube to column is 0.5 to 0.6. These effects of equipment dimensions are expressed by an equation. In the experiment using different solutions, the liquid mixing time becomes shorter with increasing liquid surface tension, or with increasing liquid viscosity.