铀氢锆反应堆脉冲参数分析

介绍了铀氢锆反应堆计算模型和程序,分析了反应性引入速率,反应性引入量,燃料瞬发负温度系数,燃料热容和瞬发中子寿命对脉冲参数的影响。计算结果表明,脉冲峰功率与反应性引入量的平方成正比;一次脉冲释放能量与反应性引入量成正比;燃料元件热容随燃料温度变化,脉冲峰功率和释放能量随燃料热容增大而增大。     

人为粗糙度强化换热技术研究概述

人为粗糙度强化换热技术的研究既具有重要的理论意义又具有广阔的应用前景,经过长期的研究和探索,人们对它的认识不断加深,研究范围不断扩大。对人为粗糙度强化换热技术的机理进行了分析,对其研究和应用现状进行了综述。     

Modelling the influence of palmitic, palmitoleic, stearic and oleic acids on apparent heat resistance of spores of Bacillus cereus NTCC 11145 and Clostridium sporogenes Pasteur 79.3

Heat resistance of spores is affected by many factors such as temperature, pH, water activity (aw) and others. Previous studies have reported that free fatty acids can affect the germination and growth of bacterial spores. In this study, we investigated the influence of free fatty acids in heating medium or in recovery medium on the heat resistance of spores of Bacillus cereus NTCC 11145 and Clostridium sporogenes Pasteur 79.3. Four free fatty acids were studied: palmitic, palmitoleic, stearic and oleic acids. During thermal treatments, the impact of these FFA in heating media was generally low, but the presence of free fatty acids in the recovery medium highly decreases bacterial spore apparent heat resistance, particularly with unsaturated fatty acids. A mathematical model was developed to describe and quantify the influence of free fatty acids in recovery media on the D-values. The z′_FFA parameter values which quantify the impact of free fatty acids were determined. The variation of this parameter value according to the free fatty acid type was compared with MIC value variation given in the literature. The model enables the decrease in D-values in the presence of free fatty acids to be estimated. The high concentrations of free fatty acids in liver or canned duck may explain the microbial stability with low sterilization values applied.     

Synthesis of single-walled carbon nanotubes by arc-vaporization under high gravity condition

Arc-vaporization is one of the common methods to synthesize single-walled carbon nanotubes (SWNTs). However the detailed synthesis mechanism is still not clear, and the synthesis of longer and chirality-selected SWNTs has not been obtained. Here influence of the gravity G = 1 g₀, 2 g₀, and 3 g₀ is studied in order to develop the synthesis method of SWNTs. Simultaneously, calculations of heat convection are also carried out by using a fluid simulation program and the results are compared with the experimental results.     

Effect of postmolding heat treatment on in vitro properties of a polyanhydride implant containing gentamicin sulfate

A polyanhydride implant containing gentamicin sulfate was fabricated using a laboratory-scale injection-molding machine. After injection molding, the implants were subject to heat treatment at 60°C for various time periods with or without nitrogen protection. The impact of this heat treatment on the in vitro properties of the implants including copolymer molecular weights, mechanical properties, and in vitro drug-release profiles was investigated. This heat treatment caused a drastic drop in the molecular weight of the copolymer. Heating without nitrogen protection resulted in the hardening of the implant, but heating in the presence of nitrogen rendered the implant less rigid. It was also found that a faster in vitro drug release profile was shown by implants heated without nitrogen protection and a pronounced slowing down in drug release was exhibited by implants heated with nitrogen protection.     

微型计算机在换热器控制系统中的应用

本文论述了微型计算机和可编程控制器（ＰＣ）控制换热器系统温度的硬件设计和控制方法。     

池式核沸腾中滑移汽泡的薄层蒸发传热模型

通过对池式核沸腾下加热壁面上滑移汽泡引起的薄层蒸发传热的分析,在若干假定基础上,建立了滑移汽泡薄层蒸发传热模型,并在该传热模型的基础上,结合管束沸腾传热机理的实验研究结果,给出了管束沸腾传热的薄层蒸发传热增强贡献的分析表达式,验证结果表明,采用建立模型计算所得单管池沸腾传热系数与实验结果的平均相对误差为±６．１％。     

纺织厂空压机余热用于对车间空气补充加热的分析

通过对空压机发热量的分析,计算得空压机实际可被回收的余热量;以湖北某纺织厂为例,对机织车间中部分冬季缺热车间进行了热量的分析,并计算出车间所需补充加热的热量。认为可以将空压机的废热通过空压余热回收系统用来制取50℃~60℃热水作为锅炉预热水和生活用水;通过比较预热前水(20℃)、预热后水(60℃)及所供饱和蒸汽(0.3 MPa,130℃)的焓值,分析了采用锅炉预热水制取蒸汽对空气进行补充加热的节能效果。得出结论:在冬季,使用锅炉预热水制取蒸汽对车间空气进行补充加热可节省费用10万元左右。     

Heat transfer augmentation for air jet impinged on a rough surface

An experimental investigation of heat transfer from a round air jet impinging normally from below onto a heated square plate was performed. The objective of the investigation was to study the effect of roughness on both the heat transfer and the fluid flow characteristics. Smooth and rough plates were, therefore, used in the course of the experiments. The heat transfer data were collected for four jet Reynolds numbers, ranging from 6500 to 19 000. The Reynolds numbers are based on the jet-exit velocity (U_e) and the nozzle-exit diameter (D), Re_e=U_eD/ν. The nozzle-to-plate distance ranged from 0.05 to 15 nozzle-exit diameter to cover both the potential core and the far regions of the jet flow. The roughness was composed of cubes of 1 mm dimension distributed uniformly along the plate. The local and average Nusselt number values for the rough plate showed an increase ranging from 8.9% to 28% over those for the smooth plate. Roughness was found to have a strong effect on the flow characteristics; it affected the mean velocity as well as the turbulence intensity of the flow. The mean velocity profiles for the smooth case at radial distances of r/D=1 and r/D=2.5 showed steeper near-wall velocity gradients compared with the profiles of the rough case, where r is the radial distance measured from the plate center along the plate centerline. In addition, roughness caused an increase in the turbulence intensity of the flow.     

Analysis of a novel metal hydride cycle for simultaneous heating and cooling

Out of the many promising applications of metal hydrides, refrigeration, heat pumping and heat transformation are important. In order to achieve improved performance, a novel three-alloy cycle is proposed in which, for heat input at an intermediate temperature, heat outputs at high temperature and also at warm temperature are obtained in addition to refrigeration. The performance of this cycle using the alloys LaNi_4.6Sn_0.4, LaNi_4.7Al_0.3 and MmNi_4.5Al_0.5 is studied based on thermodynamics and reaction kinetics. Coefficients of performance, half-cycle times and specific alloy outputs are evaluated.