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William A. Marra 《Canadian Metallurgical Quarterly》2006,19(1):55-58
The solar radiation absorbed in massive building components is stored and later emitted as long-wave thermal radiation into the interior space. Heat storage capacity is directly related to the mass of the building envelope surrounding this space and particularly that of high-mass, homogeneous earthen or cementitious material. A thermal storage cycle is created by the time-lag effect if sufficient mass is available. A similar strategy applied to the lunar and/or Martian regolith would provide a surface structure with micrometeorite and radiation protection, thermal insulation, and natural supplemental heat energy that would significantly reduce the energy requirements met by mechanical equipment. HEAT2 is an energy simulation program that solves heat transfer problems using the partial differential heat conduction equation in two dimensions with the method of explicit finite differences. HEAT2 simulation data suggests that, although thermal mass is most suitable for climates where desired indoor temperatures fall within a large daily external temperature gradient, the heat storage cycle is least effective at the annual extremes occurring in midwinter and in midsummer. A more moderate climate will allow the heat storage cycle to modulate between positive and negative heat flows which are then shifted to align with peak load conditions, reducing energy demand. Also, diurnal and seasonal temperature gradients can initiate a sequence of phase transitions in the soil’s moisture content affecting the overall conductivity. This study will present a more accurate explanation of the heat transfer processes occurring in soils of varying compositions when thermal properties are altered by transient climatic conditions. 相似文献
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Effects of Heat Treatments on the Properties and Microstructures of Extruded Mg-Nd-Zr Alloy 总被引:1,自引:0,他引:1
EffectsofHeatTreatmentsonthePropertiesandMicrostructuresofExtrudedMg-Nd-ZrAlloyLuoZhi-ping(罗治平);ZhangShao-Qing(张少卿);LuLi-Qi(鲁... 相似文献
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等离子喷涂热障涂层技术广泛应用于航空发动机热端部件的高温防护。应用大气等离子喷涂法成功制备了纳米氧化铈氧化钇稳定的氧化锆(CYSZ)涂层,并与常规氧化钇稳定氧化锆(YSZ)涂层在1300℃下热处理10小时,研究高温对两种涂层性能的影响,与常规的YSZ涂层相比,CeO2的掺杂使涂层具有更高的稳定性。经过高温处理,CYSZ涂层的相结构没有发生明显变化。显微形貌结果表明,CYSZ涂层没有产生裂纹缺陷,涂层中纳米区域晶粒度随着温度的升高略有增大,这表明了纳米结构的CYSZ涂层具有更优异的高温稳定性。热循环氧化实验结果证明,CYSZ涂层具有更长的热循环寿命以及优异的高温抗氧化性能。 相似文献
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采用大气等离子喷涂技术制备了纳米氧化锆热障涂层。利用FESEM、XRD和拉曼光谱开展了纳米氧化锆热障涂层的微观组织和物相组成的高温演变研究。微观组织分析结果表明,纳米氧化锆热障涂层始终保持着独特的“纳米-微米”双态结构,而其中纳米晶粒大小随着服役温度和服役时间的增加而增大,但仍保持纳米结构;物相分析结果表明,纳米氧化锆热障涂层主要由非平衡四方相组成,并不随服役环境的变化而变化;而拉曼峰形状及位置的变化则进一步揭示了高温服役环境会造成涂层组织缺陷减少和声子散射降低,从而导致热导率的上升。 相似文献
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铸造镍基合金热处理工艺对组织与性能的影响 总被引:5,自引:0,他引:5
本文采用了金相显微镜、X-射线衍射、电子探针和透射电子显微镜相结合的方法,研究了热处理工艺对铸造镍基合金组织的形态、成分、结构及机械性能与切削加工性能的影响。研究结果表明,该合金在950~1150℃范围内,有P相、μ相、M6C及少量σ相析出,经1250℃×1h固溶处理后,具有最佳的综合机械性能和满意的切削加工性能。 相似文献
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Jean C?té Marie-Hélène Fillion Jean-Marie Konrad 《Canadian Metallurgical Quarterly》2011,137(9):834-842
This paper presents an experimental study of the effect of porosity and particle size on the hydraulic conductivity and thermal conductivity of sand-sized crushed granite particles with diameters ranging from 0.08–10?mm. The results show that the hydraulic conductivity varies with particle size and porosity, but thermal conductivity varies primarily with porosity. Estimating methods found in the literature are used in an attempt to predict the measured hydraulic and thermal conductivities of the crushed granite materials. The results show that the hydraulic conductivity model of Chapuis generally yields accurate estimated values for d102n3/(1-n)2 larger than 0.01??mm2. Below this critical point, the estimating method progressively yields larger values of hydraulic conductivity. A new set of empirical parameters are proposed to extend the use of this method to crushed granite materials at low d102n3/(1-n)2 values. It is also shown that predicted thermal conductivity values obtained with the C?té and Konrad model agree well with the experimental data. Issues regarding the extension of the models to coarser materials are discussed. 相似文献
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In the steel industry it is of great importance to be able to control the surface temperature and heating or cooling rates during heat treatment processes. In this paper, a steel slab is heated up to 1300°C in an industrial reheating furnace and the temperature data are recorded during the reheating process. The transient local surface temperature, heat flux and effective heat transfer coefficient of the steel slab ares calculated using a model for inverse heat conduction. The calculated surface temperatures are compared with the temperatures achieved by using a model of the heating process with the help of the software STEELTEMP® 2D. The results obtained show very good agreement and suggest that the inverse method can be applied to similar high temperature applications with very good accuracy. 相似文献
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In northern Alaska, the ground is largely underlain by permafrost. Many engineering problems in this region can be attributed to the variations of ground thermal regime. Engineering projects such as construction of gas pipelines must be based on a good understanding of ground thermal regime and its interaction with seasonal climate changes. Numerical modeling is used to simulate a multimedia system with transient heat transfer in this research. The system includes a snow cover on the top, a shallow lake in the middle, and soils beneath the lake. The finite-element method is used for the spatial domain solution, and the finite-difference method is used for the temporal domain solution. The model is applied to three sites in northern Alaska for a nine-month period during the winter of 1995–1996. The result reveals the impacts of thaw lake on the ground thermal regime, the formation of the talik, as well as the formation of ice in the lake. The model is verified against field observations. The difference between the simulated and observed ice thickness is less than 3%. 相似文献
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本文比较了添加Cr合金元素的Fe_3Al金属间化合物在不同热处理工艺条件下的室温力学性能。通过轧制后的二次700℃/lh油冷处理,合金的室温塑性有较大的改善。 相似文献
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热处理工艺对弹簧钢组织和性能的影响 总被引:5,自引:1,他引:4
综述了微合金化、调质热处理、感应热处理、形变热处理对弹簧钢组织和性能的影响。感应热处理加热速度快,钢组织细化,无脱碳,高的强韧性、疲劳寿命和抗弹减性,近年来已广泛应用。 相似文献
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本文主要研究了2.25C r-1M o钢正火处理后显微组织和回火过程中碳化物相对钢的强韧性的影响,奥氏体化处理后进行冷却(加速冷却和空冷),得到的显微组织为粒状贝氏体和先共析铁素体。对于2.25C r-1M o厚钢板,显微组织和碳化物相的变化是造成2.25C r-1M o钢强韧性能变化的主要原因。 相似文献