Statistical Modeling of the Serviceability of Sewage Pumps

Sewage pumping stations represent an element of the sewer system, which is directly responsible for affecting serviceability; i.e., failing pumps may result in combined sewer overflows or flooding. However, failures of sewage pumps are not yet incorporated in sewer assessments due to lack of data. This paper presents the analysis of pump failure data provided by two sewer management authorities in The Netherlands. Pump failures have been studied accounting for the nature of the failures, the operation and maintenance procedures of the management authority, the aging of the pumps, and the changes in the environment of pumps. The analysis shows that sewage pumps fail relatively often due to the composition of sewage and the discontinuous operation of the pumps. The interarrival time and the duration of failures are highly variable and independent of the specific function of the pump. Resulting pump failure characteristics are applied in a Monte Carlo simulation to calculate the impact of failures on combined sewer overflow volumes. The results indicate that the serviceability of sewer systems is significantly affected by failing pumps. Therefore, including pump availability in sewer system assessments should be considered.     

板式热交换器及其在供热系统中的应用

介绍了板式热交换器的结构、原理、设计选用方法并与列管式、螺旋板式换热器对比，详细论述了其优缺点及在供热系统中的使用效果、工程实例和试运情况。     

氧化铝生产中传热系数的研究

大多数氧化铝生产工序的能耗与换热设备传热效率的高低有密切关系。分析了氧化铝生产过程中的传热和传质特征。结合生产实测数据,对氧化铝生产中典型换热设备的传热系数进行研究,为设计、生产提供了理论基础。     

真空电阻炉的复合热屏蔽

本文试图建立一种分析法代替传统采用的试凑法,对真空电阻炉的复合热屏蔽进行设计、计算。文中推导了传热学公式,并在此基础上,阐明了复合屏的特性,提出了设计原理与方法。     

170t钢包热循环过程瞬态传热计算分析

针对安钢二炼轧直接浇注钢种(Q235系列)钢包热循环过程钢水温降问题,建立了基于传热微分方程的Turbo-C程序数学模型.通过该模型的对比计算分析,找出了影响钢水温降的几个关键环节,提出了相应改进措施.数据验证结果表明,该模型能够较好符合现场实际,具有一定的参考价值.     

Simultaneous Inverse Identification of Transient Thermal Properties and Heat Sources Using Sparse Sensor Information

A study is presented herein on the simultaneous inverse identification of transient internal heat generation, transient thermal diffusivity, and constant convection coefficients. The formulations of the direct and inverse problems are presented in the context of finite-element analysis and nonlinear optimization, respectively. A real-coded genetic algorithm was used to solve the inverse problem because of the global convergence properties of this optimization technique. It was found through numerical studies that heat generation and thermal conductivity as functions of time can be simultaneously and consistently estimated from sparse sensor information, as long as convection coefficients are known. However, treating convection coefficients as unknown may significantly affect the accuracy of the estimated thermal diffusivity function and to a lesser extent, the accuracy of the heat generation function. The numerical experiments showed, however, that the Biot number can be accurately estimated when the convection coefficients are not well known. These results can have wide and important implications in problems related to monitoring and quality control of structures.     

Heat transfer performance of porous titanium

Porous titanium fibre materials with different structural parameters were prepared by vacuum sintering method. The thickness,porosity and wire diameter of prepared materials were investigated to understand the effects of structural parameters on pool heat transmission performance of titanium fibre porous material. As a result,better heat transfer performance is obtained when overheating is less than 10 °C. In addition,when the wire diameter is smaller,the heat transfer is better. However,when superheating is above 10 °C,heat transfer performance can be improved by increasing the wire diameter. Moreover,thickness influences the superficial area of the prepared material and affects the thermal resistance when bubbles move inside the material; superficial area and thermal resistance are the two key factors that jointly impact the heat transfer in relation to the thickness of the materials. Experimental results also show that the materials of 3 mm in thickness exhibit the best performance for heat transmission. Furthermore,changes in porosity affect the nucleation site density and the resistance to bubble detachment; however,the nucleation site density and the resistance to bubble detachment conflict with each other. In summary,the titanium fibre porous material with a 50% porosity exhibits suitable heat transfer performance.     

Design of School Building HVAC Retrofit with Hybrid Geothermal Heat-Pump System

This paper describes a proposed energy-efficient retrofit of a heating, ventilating, and air-conditioning system for a school building in southeastern Wyoming. The existing system consists of six conventional constant air volume heating and ventilating units with heat provided by a gas-fired hot water boiler. The proposed replacement is a novel system application that consists of a geothermal heat pump (GHP) system with a supplemental solar thermal collector array. Ventilation air heat recovery and variable-speed pumping are also included. Innovative design of both the ground loop and the interior building loop are accomplished using a whole system approach. System simulation analyses show a simple payback period of less than 10 years. An extra benefit of the GHP system not accounted for in the economic analysis is added cooling capability.     

氧化铝溶出工艺中各种套管传热系数的比较

以氧化铝生产溶出过程中的套管换热器为研究对象,采用工程分析方法对其换热过程进行了分析,得出了单套管、三套管、四套管三种不同套管的传热系数,并对其进行了比较。结果表明,相同的矿浆流量下三套管的换热效果较好。     

13Cr-L80的热处理工艺研究

为了达到13Cr-L80油井管生产技术要求，必须根据其具体使用条件进行热处理。通过对其机械性能的检验，主要是针对其强度和冲击功指标制定了热处理制度。     

高温低氧燃烧锅炉传热特性研究

介绍一种新型工业锅炉 -高温低氧燃烧锅炉 ,研究其传热特性。实验研究表明 :炉内燃烧火焰边界趋于消失 ,体积明显增大 ,火焰颜色变浅 ,无局部高温区 ,辐射传热得到强化。提高空气预热温度可加大炉气和水冷壁间传热。为开发推广新型工业锅炉奠定基础     

钢的连铸过程结晶器与铸坯之间的传热分析

针对连铸过程中的结晶器传热模型，分析总结了结晶器与坯壳之间的热阻构成，并研究了结晶器壁和坯壳界面热流的影响因素，为传热模型的求解和结晶器锥度的优化设计提供了理论依据。     

Percolation Induced Heat Transfer in Deep Unsaturated Zones

Subsurface temperature data from a borehole located in a desert wash were measured and used to delineate the conductive and advective heat transfer regimes, and to estimate the percolation quantity associated with the 1997–1998 El Ni?o precipitation. In an arid environment, conductive heat transfer dominates the variation of shallow subsurface temperature most of the time, except during sporadic precipitation periods. The subsurface time-varying temperature due to conductive heat transfer is highly correlated with the surface atmospheric temperature variation, whereas temperature variation due to advective heat transfer is strongly correlated with precipitation events. The advective heat transfer associated with precipitation and infiltration is the focus of this paper. Disruptions of the subsurface conductive temperature regime, associated with the 1997–1998 El Ni?o precipitation, were detected and used to quantify the percolation quantity. Modeling synthesis using a one-dimensional coupled heat and unsaturated flow model indicated that a percolation per unit area of 0.7 to 1.3 m height of water in two weeks during February 1998 was responsible for the observed temperature deviations down to a depth of 35.2 m. The reported study demonstrated quantitatively, for the first time, that the near surface temperature variation due to advective heat transfer can be significant at a depth greater than 10 m in unsaturated soils and can be used to infer the percolation amount in thick unsaturated soils.     

铜精炼阳极转炉氧化期烟气的传热特性

根据能量平衡原理,建立烟气对铜液的传热模型,并对不同空气过剩系数下的烟气平均温度和传热强度进行计算。结果表明:随着空气过剩系数的增大,烟气平均温度和传热强度均有明显下降。为增强烟气对铜液的传热能力,必须适当地减小空气过剩系数。此外,针对燃烧室排烟温度较高的问题,提出采用余热装置回收烟气余热的合理建议。     

板坯连铸中间包流场及传热特征模拟研究

对某钢厂现有板坯连铸中间包进行流场模拟研究,研究结果表明,原结构的中间包内钢水停留时间短,死区体积大。通过优化设计使流场得以改善,并用数学模拟的方法进行了流场及传热特征计算,验证了水模试验得到的优化方案的合理性。     

3D Numerical Simulation of Turbulent Buoyant Flow and Heat Transport in a Curved Open Channel

A three-dimensional buoyancy-extended version of k–ε turbulence model was developed for simulating the turbulent flow and heat transport in a curved open channel. The density-induced buoyant force was included in the model, and the influence of temperature stratification on flow field was considered. The flow and temperature fields were simulated simultaneously. The model was validated by comparison with laboratory measurements, and the simulated fields were generally in good agreement with experimental data. A comparison of velocity fields in thermal and isothermal flow in curved open channel is presented and the effects of channel curvature and buoyant force on the velocity fields are also discussed.     

二次精炼渣钢反应及成渣热对钢液温度的影响

通过现场实验,分阶段定量分析了出钢至出ＶＤ过程,渣钢反应热及成渣热对钢液温度的影响。结果表明,这两种热对钢液降温的影响极小,完全可以忽略。     

Potential of Renewable Energies in Turkey

Turkey has a large economy and, thus, it expects a very large growth in energy demand. Today, Turkey’s economy is mainly dependent on oil, natural gas, and electricity. On the other hand, Turkey’s energy production meets nearly 35% of its total primary energy consumption. Turkey is an energy importing country. Turkey presently has considerable renewable energy sources. The most important renewable sources are hydropower, wind, solar, geothermal, and biomass. Turkey has about 1% of the total world hydroelectric potential and its significant potential for geothermal power production is ranked seventh in the world. This paper presents the energy situation and potential of the renewable energy sources in Turkey.     

Heat Flow through Soils and Effects on Thermal Storage Cycle in High-Mass Structures

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.