| In this paper, temperature field of water solution was calculated by non-linear finite element method. The relations of temperature and time were obtained, and micro-movement of liquid cooling medium was studied by molecular dynamics. Finally, the result was proved through the experiment of the steel hardening.Based on the principle of heat transfer to establish non-linear finite element model, it identified the analysis of cell, mesh generation, boundary conditions and so on. The basic course of numerical simulation was given. The results showed the center in cooling rate of specimens was much slower than the edge's in the beginning. By the experiments, the cooling curves of samples at different temperature and position reduced closely in the end, so the temperature was more difference between the center and surface of samples in the quenching-process. At last, we found the temperature of cooling medium was above 618℃near the interface of contact, which was higher than the temperature of other area in the cooling medium.The process of temperature field was investigated by molecular dynamics simulation, too. When the system temperature at 80℃-600℃, the water molecules in cubic container were at a vapor-liquid-state co-existence and its form resembled at the room temperature. When the temperature above all the 600℃, the water molecules evenly distributed in everywhere of the space, and the liquid water was completely vaporized at the same time. When the molecules of water vapor state contacted with low-temperature liquid water, it came into the liquid molecules and this process liked liquid metal cooling crystallization. First, the critical grain emerged in the progress, then a number of small clusters were formed by the critical grain. Finally, small clusters slowly grew up with time at the low temperature and clusters gradually grew up together. According to the results of finite element and molecular dynamics simulation,10wt%NaCl solution and PAG fluid were applied. The results showed the transition-status of 10wt%NaCl solution and PAG fluid were not same, because that they would have part steam-state molecule in the 353K, and 10wt%NaCl solution would not be completely vaporized in the 636℃. Only a part of molecules were existing the side space in the vapor-liquid-state co-existence. However, PAG fluid had been vaporized in the 723K.10wt.%NaCl solution produced a small bubble than pure water, that its "film stage" was shorter than water's in cooling process, which was not same besides the PAG solution. By experiment analyze, solution cooling medium was instant vaporization at the first stage of contaction. The heat of sample surface would move into the environment through cooling medium.Quenching experiment was designed to verify the results. Some phenomenons observed which were coated by vapor blanket in the cooling beginning stage of specimen surface in the experiment. It transformed into boiling phase for the vapor blanket crack in the advance of cooling process. The sample surface had some distributed small water moleculars. The surface temperature was so low that water was not evaporated. The results of calculations had been confirmed successfully. At the same time, water solution's temperature of the sample surface was rised rapidly. Finaly, when the sample accessed to high-temperature, it transformed into vapor. The temperature of medium from a distance the surface of sample was changed little and the state of substance was changed unsignificantly. |
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