Advanced Materials Research Vols. 538-541

Abstract: The appropriate temperature is a critical factor for an enclosure with a stability guarantee. Therefore, in the prerequisite of vibration and Electro Magnetic Compatibility (EMC) being satisfied, how to make effective thermal design is what the research staff are generally concerned about. Firstly, a comprehensive description of the overall structure for a sealed enclosure is provided. Then the cooling plate is designed by using the method of theoretical calculation. At the same time, the temperature of the enclosure is analyzed by using Flow Simulation; the distribution of temperature field for the enclosure is obtained. Both classical heat transfer theory and a computational approach are used to verify the enclosure cooling performance. It turns out that applying the method of combining the theoretical calculation and simulation analysis cannot only improve the reliability of thermal analysis, but can also provide some valuable references to the research staff.

Abstract: Thermal conductivity is an important property when high heat dissipation is a requirement during the use of the cast component. This study was carried out to study the effect of heat treatment on thermal conductivity of three common aluminum die casting alloys. Measurement of thermal conductivity was done by the Hot Disk method. A substantial increase in thermal conductivity was measured as a result of heat treatment. Microstructural changes due to heat treatment was examined by optical and scanning electron microscopy.

Abstract: Several studies and design of cooling systems for hot stamping tools have already been made. The phase transformations which occur during the process are known, and numerical simulations are now very close to the reality [1]. However these studies are often related to a specific part and can hardly be extrapolated to other parts. This paper presents several results based on a thermo-mechanical analysis which can be used to make a first design of a cooling system for hot stamping tool. A theoretical study describes the heat transfer from the tools to the cooling pipes related to different flow parameters. Numerical simulation with the software COMSOL Multiphysics has been carried out to obtain results about cooling rate and maximum stress into the tool against geometry parameters. The heat transfer model used for simulation has been validated through experiment. To finish a data analysis describes the relationship between the different parameters, more specifically their impact on the cooling. With this study we can now determine which pipes’ location and size and flow properties are likely to provide the most efficient cooling system, and which parameter we must modify to optimize it.

Abstract: A radiator is one of the most important components in vehicular cooling system whose excellent fluid flow and heat transfer characteristics guarantees the engine operations. The calculation workload for performance simulation of a whole radiator is too huge due to its size. Experimental study is the conventional method to study radiator performance. This paper put forward a numerical simulation method and radiator heat transfer units were taken as study objects. Orthogonal experiment method was adopted to arrange multi-factor and multi-level calculation schemes. 23 samples with different fin parameters were simulated to investigate their thermal-hydraulic performances. Compared with experimental testing, this method greatly reduced sample manufacturing cost and testing cost, and offered data support for the effect factor study of radiator heat transfer units.

Abstract: With the thermal expansion-metallograph method and hardness measurement,the critical point at of LF2 steel was determined at Gleeble1500 thermal mechaical simulator.By measuring different expanding curves of CCT in different cooling rate,CCT curve diagram was obtained.The affect of cooling rate on steel microstructure and hardness was studied.The results shown that there are four phase zone in the CCT diagram which meaning four different transformation may take place at LF2 steel cooling process,including ferrite ,pearlite,bainite,as well as martensite phase transformation.The Ms point is 320°C.All those provide the references for welding practice and help to establish new process.

Abstract: A 2D mathematical Model for heat transfer during solidification in the secondary cooling was established on researching the process of beam blank continuous casting. Meanwhile, the boundary conditions of heat transfer was subdivided into four parts, which is the radiation, spray cooling, heat conduction through roller and water accumulated evaporation in secondary cooling zoon, and improved the results accuracy. Moreover, heat transfer simulation software was designed and developed by a 2D mathematical Model based on FLUENT. The secondary development language UDF (User Define Function) and Scheme (a dialect of LISP) of FLUENT were used during the development. The software provided a platform for researching on the solidification and optimization of a secondary cooling system for a caster machine of beam blank.

Abstract: The thermal decomposition of coal-bearing strata kaolinite-potassium acetate(CK/KAc) intercalation complex has been studied using X-ray diffraction (XRD), thermogravimetry and differential thermogravimetric (TG-DTG) and infrared emission spectroscopy (IES). The XRD results show that the KAc has been successfully intercalated into coal-bearing strata kaolinite with an obvious basal distance increase of the first basal peak. The TG results show that the thermal decomposition of the intercalation complex occurs in four main steps (a) the loss of adsorbed water (b) the loss of coordination water (c) the loss of potassium acetate and (d) water through dehydroxylation. The IES of CK/KAc give the evidence on the changes of structure. These make all explanation have the sufficient evidence.

Abstract: T2 phase(Mo₅SiB₂) is a key component of the two Mo-Si-B tri-phase alloys under hot research. However, there is little research on T2 phase, especially its mechanic characteristics, due to the difficulty of fabrication of pure T2. In this present work, the thermodynamics of an advanced technology to fabricate pure T2 phase i.e. IRHP (In-situ Reactively Hot-Pressing) using elemental powders was analyzed. Formation free enthalpies at different temperatures for the compounds in Mo-Si-B system were calculated. Adiabatic temperatures and molten fractions of T2 phase at different initial temperatures for the reaction of synthesizing T2 phase were evaluated. The results show that it is feasible to in-situ synthesize T2 phase from elemental powders. T2 phase can not be synthesized using SHS(Self-propagating High-temperature Synthesis) mode of combustion. On the contrary, the explosion mode of combustion (IRHP) is receivable. Adiabatic temperature and molten fraction of T2 phase are relevant to initial temperature.

Abstract: Evaporation of refrigerant-oil mixture was studied in a smooth and micro-fin tube without / with four different inserts (twined coil, wire coil, twisted tape, and helical-coil). The refrigerant was R-600a and the oil was the EMKARATE RL 32H with a viscosity 150 SUS. The test was conducted at a saturation temperature of 15 , vapor qualities from 0.1 to 0.49, inlet oil concentration from 0 to 5 mass% oil, mass flux of 200 – 500 and heat flux of 10.24 . The enhancement factor (EFs) is larger for the lower oil concentration (at l %), while the ratios for the higher oi1 concentration (at 5%) are generally smaller than l and decreased rapidly as the oil concentration increased. In addition, new correlations to estimate the evaporation heat transfer coefficients for the R-600a mixed with the lubricating oil in micro-fin tube containing different inserts have been developed.

Abstract: A basis based on temperature field is developed to control the cooling rate of plates during roller quenching in high-pressure zone. In order to determine the optimal cooling rate of plate during roller quenching, temperature field of SPV490 plate during quenching was calculated. Then a formula for calculating cooling rate of the center for plate at a certain cooling intensity during roller quenching in high-pressure zone was put forward and the control basis for cooling rate of plate during roller quenching in high-pressure zone was suggested. The cooling rates and corresponding heat transfer coefficients of SPV490 plates with different thickness during roller quenching in high-pressure zone were determined with the given basis.