Inward freezing of water in cylinders

The problem of one-dimensional inward solidification of a saturated liquid in a circular cylinder has been investigated both experimentally and theoretically with the boundary surface maintained at a constant temperature. A mathematical model has been developed using the integral heat balance method used by Bell. Experimental measurements of the location of the interface boundary and the temperature distribution in the solid region as a function of time have been compared with the new model and with those of other investigators.     

建筑采暖设计软件HPM的应用

HPM是PKPM系列建筑、结构、水暖电集成化CAD系统中采暖设计软件。该软件具有自动化程序高,制图、计算一体化的特点,实际工作中,软件本身有些局了性。通过对HPM的使用,提出了HPM软件在采暖设计工作中存在的问题,以及相应的解决方法,为设计工作的顺利进行提供了帮助。     

Mechanical properties of Tylose gel and chocolate in the freezing range

The mechanical properties of solid foods have not been extensively studied. This is due to the fact that most foods behave as viscous fluids or viscoelastic “solids”. In the case of freezing of foods or by considering solid foods (i.e. chocolate), food can be considered as a solid system. This paper presents results obtained with Tylose^® (a model food made of a methyl cellulose gel – 74% water content) and chocolate. The Young's modulus, the Poisson ratio, the bulk modulus and the coefficient of thermal expansions have been determined using specific procedures. These results can be of interest to model the thermomechanical behavior of foods undergoing freezing.     

基于分类回归树算法的在线静态电压稳定裕度评估

随着电力负荷的不断增加,电压稳定问题日益凸显;为防止电压失稳,电网运行人员迫切需要了解电网当前的运行状态。提出运用分类回归树算法构建决策树模型,对静态电压稳定裕度进行在线评估。首先根据PV曲线分析和电压稳定裕度计算获得决策树训练样本集;然后通过模态分析和相关系数分析降低属性集的维度,确定训练决策树的输入属性;最后利用离线数据,运用决策树分类回归树算法训练出在线电压稳定裕度的评估规则。以某省实际电网为例对所提方法进行验证,其决策规则具有较高的准确性,能够实时地评估电网运行状态。     

Quick and empirical correlations for refrigerant pressure drop in mobile air conditioning system evaporators

In heat exchanger design and simulation, a precise refrigerant pressure drop prediction is difficult because of limited correlation's accuracy. In the present paper, several quick and accurate empirical correlations for refrigerant pressure drop of the typical evaporators (laminated plate evaporator and minichannel parallel flow (MCPF) evaporator) used in mobile air conditioning (MAC) system were proposed. A factor which was related with the refrigerant mass flow rate, thermodynamic properties and refrigerant status was introduced. The types of evaporator and refrigerant were considered in the correlations which were available under typical MAC evaporator application conditions. The analysis results showed the refrigerant pressure drops were implied in a linear relationship with the proposed factor. The predicted data agreed with the experimental data very well. For laminated palate evaporators, the average deviations were 1.8% and 0.7% for R134a and R1234yf, respectively. For MCPF evaporator, the average deviations were 4.5% and 0.6% for R134a and R1234yf, respectively.     

Subcooled liquid density measurements and PvT measurements in the vapor phase for 3,3,3-trifluoroprop-1-ene (R1243zf)

The fluorinated propene isomer R1243zf (3,3,3-trifluoroprop-1-ene, CF₃CFCH₂, CAS number 677-21-4) is a potential alternative refrigerant with short atmospheric lifetime, low-GWP, and low acute toxicity; however, because of its flammability it is being considered primarily as a component in blends. In this paper, 302 subcooled liquid density data and 101 vapor phase PvT data are presented. The subcooled liquid density data are measured for eight isotherms, evenly separated approximately from 283 K to 353 K, for pressures from close to saturation to 35 MPa and the vapor phase PvT data are measured for six isochores for temperatures approximately from 278 K to 368 K and for pressures approximately from 260 kPa to 912 kPa. In addition, a saturated liquid density correlation, a Tait correlation for the subcooled liquid density data, and a Martin–Hou Equation of State for the vapor phase PvT data are presented.     

Measurement of Neutron-Production Double-Differential Cross Sections for Intermediate Energy Pion Incident Reaction

Neutron-production double-differential cross sections for 870-MeV π⁺ and π ^- and 2.1-GeV π⁺ mesons incident on iron and lead targets were measured with NE213 liquid scintillators by time-of-flight technique. NE213 liquid scintillators 12.7cm in diameter and 12.7cm thick were placed in directions of 15°, 30°, 60°, 90°, 120° and 150°. The typical flight path length was 1.5 m. Neutron detection efficiencies were derived from the calculation results of SCINFUL and CECIL codes. The experimental results were compared with the cascade-evaporation calculation code NUCLEUS. The calculation results are higher typically by a factor of two than the experimental data at neutron energies below about 30MeV. NUCLEUS overestimates π^+-incident neutron-production cross sections in forward angles at neutron energies of 100 to 500 MeV.     

Dimensionless correlations of frost properties on a cold plate

This study proposes dimensionless correlations for predicting the properties of frost formed on a cold plate. Frosting experiments are carried out to obtain the correlations with various environmental parameters including the air temperature, air velocity, absolute humidity, and cooling plate temperature. The thickness, density, surface temperature, effective thermal conductivity, average heat and mass transfer coefficients of the frost layer are correlated as functions of the Reynolds number, Fourier number, absolute humidity, and dimensionless temperature by using a dimensional analysis. The correlations proposed in this study agree well with the experimental data within a maximum error of 10%, and can be used to predict the average frost properties in the following ranges: the air temperature of 5–15 °C, air velocity of 1.0–2.5 m s⁻¹, absolute humidity of 0.00322–0.00847 kg kg_a⁻¹, and cooling plate temperature of −35–−15 °C.     

某酱油厂灭菌罐保温及其施工技术

采用两种不同的保温材料对同一异型设备进行保温施工,表明根据设备运行的工况条件选择保温材料,确定合理的施工方案,对实际工程具有重要意义。     

为酒立法,造福中华

由于我国在酒类产、销领域管理上的薄弱，已严重危及到酒类行业的整体形象和健康发展，其关键就在于没有法制化的管理。所以，应尽快为酒类立法，建立国家酒类产销管理的行政审批制度和完善的酒类行业准入管理体系，尽快实现依法制酒，依法卖酒。(陶然)