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排序方式: 共有996条查询结果,搜索用时 15 毫秒
81.
针对石板坡长江大桥复线桥结构和施工特点生产的专用水泥通过对水泥矿物组成及水化热的控制,对降低混凝土温升,提高混凝土体积稳定性和耐久性起到了直接、有效的作用。采用专用水泥配制的高性能混凝土具有良好的综合技术性能。 相似文献
82.
确定焊接反变形的数值模拟及规律分析 总被引:2,自引:0,他引:2
焊接接头附近局部的加热及冷却使被焊结构产生残余应力及角变形.目前在船厂精度控制中,通常采用构件焊接后对某些部位进行火工校正的方法来控制残余角变形.文章提供了另外一种有效控制结构残余角变形的方法:对结构焊前施加弹性的反向变形.利用热弹塑性有限元法来模拟结构的焊接过程,并对不同板厚、不同热源的结构分别进行数值模拟,最终确定焊接结构的弹性反变形规律:焊接前施加弹性反变形的结构在焊接后角变形趋于零. 相似文献
83.
C. -H. Chien J. -Y. Jang Y. -H. Chen S. -C. Wu 《International Journal of Automotive Technology》2008,9(4):437-445
People use cars so frequently that they always consider the air-conditioning, and thermal comfort of the driver and passenger
when buying a new car. Therefore accurate simulation of the thermal performance of automobile air conditioners to improve
human comfort has become increasingly important. In order to improve the thermal comfort of passengers, 3-D flow motion and
thermal behavior within vehicles must be analyzed. In this paper, a numerical simulation was used to investigate thermal behavior
in a vehicle. Because air temperature at an air vent is related to the cooling capacity of the air conditioner, the cooling
capacity was calculated using ɛ-NTU (effective number of transfer unit) theoretical equations. Using the air temperature relationship between inlet and outlet
vents as boundary conditions, a 3-D unsteady κ-ɛ turbulent model was used to give a transient analysis simulation of the temperature field and flow conditions in a vehicle’s
passenger cabin. Cooling cycle analysis and conjugate heat transfer analysis at the inside surface of the cabin’s ceiling,
floor and sides were also considered. The predicted temperature distributions in the vehicles passenger cabin were in good
agreement with those obtained experimentally. 相似文献
84.
K. M. Saqr M. K. Mansour M. N. Musa 《International Journal of Automotive Technology》2008,9(2):155-160
The potential for thermoelectric power generation (via waste heat recovery onboard automobiles) to displace alternators and/or
provide additional charging to a vehicle battery pack has increased with recent advances in thermoelectric material processing.
In gasoline fueled vehicles (GFVs), about 40% of fuel energy is wasted in exhaust heat, while a smaller amount of energy (30%)
is ejected through the engine coolant. Therefore, exhaust-based thermoelectric generators (ETEG) have been a focus for GFV
applications since the late 1980s. The conversion efficiency of modern thermoelectric materials has increased more than three-fold
in the last two decades; however, disputes as to the thermal design of ETEG systems has kept their overall efficiency at limited
and insufficient values. There are many challenges in the thermal design of ETEG systems, such as increasing the efficiency
of the heat exchangers (hot box and cold plate), maintaining a sufficient temperature difference across the thermoelectric
modules during different operating conditions, and reducing thermal losses through the system as a whole. This paper focuses
on a review of the main aspects of thermal design of ETEG systems through various investigations performed over the past twenty
years. This paper is organized as follows: first, the construction of a typical ETEG is described. The heat balance and efficiency
of ETEG are then discussed. Then, the third section of this paper emphasizes the main objectives and challenges for designing
efficient ETEG systems. Finally, a review of ETEG research activities over the last twenty years is presented to focus on
methods used by the research community to address such challenges. 相似文献
85.
承台大体积混凝土水化热分析与施工控制 总被引:5,自引:0,他引:5
结合援孟加拉国中孟友谊六桥主桥承台设计与施工,利用Midas/Civil有限元计算分析软件对承台大体积混凝土水化热进行仿真分析,掌握水化热变化规律及其应力影响,据此指导现场施工控制。结果表明:仿真分析很好地反映了水化热变化规律及其应力影响,混凝土质量优良,没有出现温度裂缝,可供类似大体积混凝土设计与施工借鉴。 相似文献
86.
针对施工单位在选择使用沥青混合料搅拌设备导热油炉中存在的问题,提出合理选择使用导热油炉。 相似文献
87.
利用设计的有机朗肯循环系统回收某重型车用柴油机的排气能量,通过台架试验,获得了变工况下柴油机排气余热能分布特性。分析了有机工质蒸发压力、过热度以及柴油机工况变化对有机朗肯循环系统性能的影响,以系统净输出功率和热效率为优化目标,确定了适用于有机朗肯循环系统的最佳蒸发压力。研究结果表明,当有机工质蒸发压力为1.8 MPa时,有机朗肯循环系统的净输出功率最大可以达到12.69kW,热效率可以达到11.19%;将有机工质加热至过热状态并不能明显提高有机朗肯循环系统的净输出功率。 相似文献
88.
89.
90.
阐述了转轮式全热交换器的显热和潜热效率,分析了空调系统中显热和潜热的能耗构成。通过对转轮式全热交换器和显热交换器热回收率的比较,得出使用全热交换器的节能效果更加明显的结论。结合国内舰船空调通风系统的现状和发展趋势,提出了转轮式全热交换器在舰船空调通风系统中应用的可能性。 相似文献