流温法热分配系统流量比例变化的研究

分户热计量是目前供暖改革的趋势。流温系数热分配法是一种新型的热计量方法,详细论述了该方法的理论依据,建立了系统流量比例变化的关系,结果显示在用户数量、立管数量以及散热器数量满足一定的关系时,用户调节室内温度对系统流量的影响很小,仍可视为定流量系统。

流温法热分配系统研制及应用

论述一种新型的热计量方法——流温系数热分配法的工作原理、基本结构、创新点及实现方式。试点工程测试结果表明,适用于多种供暖系统的新建建筑热计量和既有建筑供热计量改造。

流温法热分配系统研制及应用

目前,我国北方分户热计量节能改造迫在眉睫。流温系数热分配法是一种新型的热计量方法,详细论述了该方法的工作原理、基本结构、创新点及实现方式。试点工程测试结果表明,这种将热量表计量关键要素——流量、温度引入热分配技术中而形成的计量方法构成的系统具有安装简便、运行稳定、计量合理、查询方便、性价比高等特点,适用于多种供暖系统的新建建筑热计量和既有建筑供热计量改造。

既有建筑供热计量节能改造的成功案例及流温法热分配系统简介

榆中县是甘肃省和兰州市确定的供热体制改革试点县,2008年10月,榆中县供热办采用北京众力德邦智能机电科技有限公司自主研发的"DRN流温法热分配系统"("流量温度法"已经在2009年3月15日发布的《供热计量技术规程》(JGJ173-2009)中被列入国家行业标准),对榆中县三电锅炉房供热区域实施了既有建筑供热节能计量改造,经一个采暖季的实际使用,完全达到了国家对供热体制改革和供热计量的相关要求,取得了明显的节能效果和良好的使用效果,本文从案例实施的方案选择入手,对案例项目的大量现场数据进行了统计与分析,以期对我国北方地区即将展开的大规模的既有建筑供热计量与节能改造工作提供有益的借鉴与建议。

国内首创——“流温法热分配系统”——通过科技成果评估

2008年4月10日经建设部科技发展促进中心组织，于北京新大都饭店国际会议中心一层C厅，举办了关于“流温法热分配系统”科技成果评估会。由中国建筑科学研究院的郎四维担任评估委员会主任，清华大学建筑学院建筑技术科学系狄洪发担任评估委员会副主任，参会委员有徐伟（中国建筑科学研究院），王树铎（中国科学物理研究所），

流温法热计量系统及温控技术在寒冷地区工程中的应用

新修订的《严寒和寒冷地区居住建筑节能设计标准》JGJ26-2010和新疆维吾尔自治区工程建设标准《严寒和寒冷地区居住建筑节能设计标准实施细则》J11921-2010进一步谈到了分室温控和分户计量推广应用。流温法热计量系统及温控技术经引入吸收,现已应用于本工程中。文章简要介绍流温法热计量系统及温控技术的方法和特点,并对采用该方法的冠农花园城邦小区工程中应用做简要介绍。

流温法热分配系统在供热工程中的应用

介绍了一种新型的热分配系统-流温法,它是将温度和流量引入到热分配计量技术中,有效的实现了使热用户按需取热,真正的实现对用户用热进行公平、科学的热计量,彻底改变过去福利供热的旧观念,推动供热事业的发展。

INVESTIGATION ON DRYING CHARACTERISTIC OF MEDICAL PILL USING MICROWAVE-CONVECTIVE DRYING

The combined microwave-convective drying is a novel drying method and has many advantages, such as swift drying, equable drying and sterilization. This paper studies the drying characteristic of medical pill in microwave-convective drying process. The influential parameters of pill drying characteristics including pill size, quality, air velocity, temperature and the input power of microwave, are experimentally investigated. Results show that the drying process is influenced by the intrinsic heat of microwave power, and the environment and the resistance of mass transfer. It has the advantage of the microwave-convective drying in saving energy, reducing labor intensity and sterilizing. The method with the high efficiency is suitable for pharmacy industry.

Synthesis of Large-scale Multistream Heat Exchanger Networks Based on Stream Pseudo Temperature

Effective temperature level of stream, namely stream pseudo temperature, is determined by its actual temperature and heat transfer temperature difference contribution value. Heat transfer temperature difference con-tribution value of a stream depends on its heat transfer film coefficient, cost per unit heat transfer area, actual tem-perature, and so on. In the determination of the suitable heat transfer temperature difference contribution values of the stream, the total annual cost of multistream heat exchanger network (MSHEN) is regarded as an objective func-tion, and genetic/simulated annealing algorithm (GA/SA) is adopted for optimizing the heat transfer temperature difference contribution values of the stream. The stream pseudo temperatures are subsequently obtained. On the ba-sis of stream pseudo temperature, optimized MSHEN can be attained by the temperature-enthalpy (T-H) diagram method. This approach is characterized with fewer decision variables and higher feasibility of solutions. The calcu-lation efficiency of GA/SA can be remarkably enhanced by this approach and more probability is shown in search-ing the global optimum solution. Hence this approach is presented for solving industrial-sized MSHEN which is difficult to deal by traditional algorithm. Moreover, in the optimization of stream heat transfer temperature differ-ence contribution values, the effects of the stream temperature, the heat transfer film coefficient, and the construc-tion material of heat exchangers are considered, therefore this approach can be used to optimize and design heat exchanger network (HEN) with unequal heat transfer film coefficients and different of construction materials. The performance of the proposed approach has been demonstrated with three examples and the obtained solutions are compared with those available in literatures. The results show that the large-scale MSHEN synthesis problems can be solved to obtain good solutions with the modest computational effort.

Numerical simulation of friction stir butt-welding of 6061 aluminum alloy

A two-dimensional computational fluid dynamics model was established to simulate the friction stir butt-welding of 6061 aluminum alloy. The dynamic mesh method was applied in this model to make the tool move forward and rotate in a manner similar to a real tool, and the calculated volumetric source of energy was loaded to establish a similar thermal environment to that used in the experiment. Besides, a small piece of zinc stock was embedded into the workpiece as a trace element. Temperature fields and vector plots were determined using a finite volume method, which was indirectly verified by traditional metallography. The simulation result indicated that the temperature distribution was asymmetric but had a similar tendency on the two sides of the welding line. The maximum temperature on the advancing side was approximately 10 K higher than that on the retreating side. Furthermore, the precise process of material flow behavior in combination with streamtraces was demonstrated by contour maps of the phases. Under the shearing force and forward extrusion pressure, material located in front of the tool tended to move along the tangent direction of the rotating tool. Notably, three whirlpools formed under a special pressure environment around the tool, resulting in a uniform composition distribution.

New approach to develop a 3D non-isothermal computational framework for injection molding process based on level set method

The simulation of three-dimensional （3D） non-isothermal, non-Newtonian fluid filling process is an extremely difficult task and remains a challenging problem, which includes polymer melt flow with free surface coupled with transient heat transfer. This paper presents a full 3D non-isothermal two-phase flow model to predict the complex flow in melt filling process, where the Cross-WLF model is applied to characterize the rheological behav- ior of polymer melt. The governing equations are solved using finite volume method with SIMPLEC algorithm on collocated grids and the melt front is accurately captured by a high resolution level set method. A domain exten- sion technique is adopted to deal with the complex cavities, which greatly reduces the computational burden. To verify the validity of the developed 3D approach, the melts filling processes in two thin rectangular cavities （one of them with a cylindrical insert） are simulated. The predicted melt front interfaces are in good agreement with the experiment and commercial software prediction. For a case with a rather complex cavity, the dynamic filling process in a hemispherical shell is successfully simulated. All of the numerical results show that the developed numerical procedure can provide a reasonable orediction for injection molding process.

Optimal nonlinear excitation of decadal variability of the North Atlantic thermohaline circulation

Nonlinear development of salinity perturbations in the Atlantic thermohaline circulation(THC) is investigated with a three-dimensional ocean circulation model,using the conditional nonlinear optimal perturbation method.The results show two types of optimal initial perturbations of sea surface salinity,one associated with freshwater and the other with salinity.Both types of perturbations excite decadal variability of the THC.Under the same amplitude of initial perturbation,the decadal variation induced by the freshwater perturbation is much stronger than that by the salinity perturbation,suggesting that the THC is more sensitive to freshwater than salinity perturbation.As the amplitude of initial perturbation increases,the decadal variations become stronger for both perturbations.For salinity perturbations,recovery time of the THC to return to steady state gradually saturates with increasing amplitude,whereas this recovery time increases remarkably for freshwater perturbations.A nonlinear(advective) feedback between density and velocity anomalies is proposed to explain these characteristics of decadal variability excitation.The results are consistent with previous ones from simple box models,and highlight the importance of nonlinear feedback in decadal THC variability.

A Group Contribution Method for the Correlation of Static Dielectric Constant of Ionic Liquids

Static dielectric constant is a key parameter to estimate the electro-viscous effect which plays important roles in the flow and convective heat transfer of fluids with ions in microfluidic devices such as micro reactors and heat exchangers.A group contribution method based on 27 groups is developed for the correlation of static dielectric constant of ionic liquids in this paper.The ionic liquids considered include imidazolium,pyridinium,pyrrolidinium,alkylammonium,alkylsulfonium,morpholinium and piperidinium cations and various anions.The data collected cover the temperature ranges of 278.15-343.15 K and static dielectric constant ranges of 9.4-85.6.The results of the method show a satisfactory agreement with the literature data with an average absolute relative deviation of 7.41%,which is generally of the same order of the experimental data accuracy.The method proposed in this paper provides a simple but reliable approach for the prediction of static dielectric constant of ionic liquids at different temperatures.

Convection in the Rayleigh-Bénard Flow with all Fluid Properties Variable

In the present paper, the effect of variable fluid properties （density, viscosity, thermal conductivity and specific heat） on the convection in the classical Rayleigh-Benard problem is investigated. The investigation concerns water, air, and engine oil by taking into account the variation of fluid properties with temperature. The results are obtained by numerically solving the governing equations, using the SIMPLE algorithm and covering large temperature differences. It is found that the critical Rayleigh number increases as the temperature difference increases considering all fluid properties variable. However, when the fluid properties are kept constant, calculated at the mean temperature, and only density is considered variable, the critical Rayleigh number either decreases or remains constant.

Inverse Problem of Flame Surface Properties of Wood using a Repulsive Particle Swarm Optimization Algorithm

The convective heat transfer coefficient and surface emissivity before and after flame occurrence on a wood specimen surface and the flame heat flux were estimated using the repulsive particle swarm optimization algorithm and cone heater test results. The cone heater specified in the ISO 5660 standards was used, and six cone heater heat fluxes were tested. Preservative-treated Douglas fir 21 mm in thickness was used as the wood specimen in the tests. This study confirmed that the surface temperature of the specimen, which was calculated using the convective heat transfer coefficient, surface emissivity and flame heat flux on the wood specimen by a repulsive particle swarm optimization algorithm, was consistent with the measured temperature. Considering the measurement errors in the surface temperature of the specimen, the applicability of the optimization method considered in this study was evaluated.

Superconductivity at 7.8 K in the ternary LaRu2As2 compound

Here we report the discovery of superconductivity in the ternary LaRu2As2 compound. The polycrystalline LaRu2As2 samples were synthesized by the conventional solid state reaction method. Powder X-ray diffraction analysis indicates that LaRu2As2 crystallizes in the ThCr2Si2-type crystal structure with the space group 14/ mmm （No. 139）, and the refined lattice parameters are a = 4.182（6）A and c = 10.590（3）A. The temperature dependent resistivity measurement shows a clear superconducting transition with the onset Tc （critical tempera- ture） at 7.8 K, and zero resistivity happens at 6.8 K. The upper critical field at zero temperature μ0Hc2（0） was estimated to be 1.6 T from the resistivity measurement. DC magnetic susceptibility measurement shows a bulk superconducting Meissner transition at 7.0 K, and the isothermal magnetization measurement indicates that LaRu2As2 is a type-II superconductor.

Influence of Temperature Difference Calculation Method on the Evaluation of Rankine Cycle Performance

In the new century, energy and environmental problems are becoming more critical, and the development of natural energy is desired. Low-grade Thermal Energy Conversion(LTEC) is refocused as one of the renewable energy methods. The usefulness of LTEC is expected using hot springs and waste heat. In the case of the Rankine cycle using ammonia as the working fluid, the thermal properties of the working fluid changes in the evaporator. The traditional evaluation method of heat exchanger performance is the LMTD(Logarithmic Mean Temperature Difference) method. On the other hand, the GMTD(Generalized Mean Temperature Difference) method allows the variation of thermal properties in the heat exchanger. The aim of this study is to compare the two methods for the calculation of temperature differences and the corresponding influence on the total performance of the Rankine cycle that is operated using ammonia as a working fluid. As a result, the thermal efficiency of the Rankine cycle is greater than that of the LMTD method. Moreover, the computable range of the GMTD calculation method is less than that of the LMTD calculation method.