温度环境试验及其标准综述(一)温度对装备的影响及温度试验的重要性

阐述了温度试验在军工产品研制生产中的重要地位和用途,温度环境对装备的主要影响和典型故障模式;介绍了GJB 150/150A、HB 6167/6167A、GB/T 2423等我国主要军用、民用环境试验系列标准中包括的各种典型温度试验程序及其用途和模拟的环境;说明了各种典型试验程序规定或要求的温度试验各种特点和剪裁方法,并汇总列于一个表格中,以便于查阅,列出了温度试验标准中对温度试验箱和测试仪器仪表的要求,最后讨论了受试产品温度稳定、温度试验箱的选用,确保受试产品经受正确的温度条件、受试产品温度响应测量和温度试验中断处理等技术。本文分为四大部分:第一部分阐述温度对装备的影响、故障机理和温度试验的重要性;第二部分阐述了GJB150/150A、HB 6167/6167A和GB/T 2423等主要环境试验标准中的典型温度试验程序;第三部分详细说明了各种温度试验的试验温度和试验持续时间及其区别和剪裁方法;第四部分介绍了各种标准对温度试验设备的要求,温度试验设定点,确保试验温度准确施加和试验中断处理等温度试验技术。本文为其中第一部分。     

温度环境试验及其标准综述(四)温度试验技术

<正>1温度试验设备和辅助仪器1.1对温度试验箱的要求温度试验设备包括高温箱、低温箱、高低温箱、温度冲击箱和快速温度变化箱。虽然都是用来产生温度条件,不同的温度试验项目对温度试验设备的要求有所不同。对试验箱的结构和参数要求也略有区别(见表1)但不管什么试验箱,它们都应能产生并保持试验方法标准中所规定的试验条件,并在规定的容差范围,以确保试验结果的重现性。1.2对辅助设备和仪器的要求     

温度环境试验及其标准综述（二）典型温度试验程序

温度试验一般包括高、低温贮存试验,高、低温工作和短时工作试验,温度冲击试验和温度变化试验。GJB 150/150A、HB 6167/6167A、GB/T 2423等系列环境试验标准中的主要温度试验程序如表1所示。上述三个系列标准对应的国外标准是810C/810F,RTCA DO160B/160F和IEC 68号出版物。表1中还说明了各种试验程序的目的和模拟的环境。     

提高温度冲击试验设备控制精度的方法

分析了温度冲击试验箱放试品的有效空间的试验温度与控制仪表上的控制温度值不符，而产生过试验和欠试验的原因，并提供了实用的改进方法。     

车载电子电器设备的温度变化试验

ISO16750《道路车辆电气及电子设备的环境条件和试验》系列国家标准转化已进入报批阶段。系列标准的第4部分《气候负荷》引用IEC 60068-2-14规定的试验N：温度变化（GB/T2423.22）中的试验Na：规定转换时间的温度快速变化和试验Nb：按规定温度变化速率的温度变化试验。2009年1月,IEC对60068-2-14进行了技术性改版。将IEC 60068-2-33《温度变化导则》（GB/T2424.13）的内容并入;对试验及温度变化容差的描述和要求、编辑和插图都做了修改和修订。等同采标的GB/T2423.22的改版修订工作已在进行,估计2010年稍晚就可以发布。这里就当前国际标准和将发布等同国标的试验方法对车载电子电器设备的温度变化试验进行描述,同时对试验要素和及其应用要素作一些介绍。ISO16750《道路车辆电气及电子设备的环境条件和试验》系列国家标准转化已进入报批阶段。系列标准的第4部分《气候负荷》引用IEC 60068-2-14规定的试验N：温度变化（GB/T2423.22）中的试验Na：规定转换时间的温度快速变化和试验Nb：按规定温度变化速率的温度变化试验。2009年1月,IEC对60068-2-14进行了技术性改版。将IEC 60068-2-33《温度变化导则》（GB/T2424.13）的内容并入;对试验及温度变化容差的描述和要求、编辑和插图都做了修改和修订。等同采标的GB/T2423.22的改版修订工作已在进行,估计2010年稍晚就可以发布。这里就当前国际标准和将发布等同国标的试验方法对车载电子电器设备的温度变化试验进行描述,同时对试验要素和及其应用要素作一些介绍。     

恒温箱温度偏差分析

人工模拟环境试验中气候环境试验的条件是否真实,主要取决于试验用恒温箱技术性能指标,其中温度偏差是恒温箱最重要的技术指标.分析和研究温度偏差的大小、性质和产生原因,采取必要的调整修正措施,可消除或减少偏差,以提高试验质量.     

温度冲击试验标准的介绍和分析

本文从试验目的和应用对象对试验设备要求和试验条件等方面对GJB 150、GB 2423、810F三个系列标准的温度冲击试验进行了介绍和分析,指出了其共同点和不同点,重点说明温度冲击与温度变化试验概念上的区别,简单介绍了810F中的基于高温循环的温度冲击试验程序的应用和该程序中高温循环部分的实施方法.     

多通道外场温度自动巡测仪

为了获得歼击机飞行中电子舱内的温度及温度变化速率，以提出机载电子设备环境试验和可靠性试验用应力，特研制了多通道外场温度自动巡测仪，本文介绍该仪器的硬件及软件结构特点、设计的基本思想，并给出了主要技术指标，然后阐述了该仪器各部分的工作原理，接口方式以及在歼击机上的应用结果等。     

温度—高度试验的剪裁研究

本文探讨了GJB150.6中规定的各试验步骤的考核目标,分析了美国军用规范和某新研产品研制规范对温度—高度试验的剪裁情况,提出了对于该项试验标准的剪裁意见。     

温度环境试验及其标准综述（三）温度试验的试验条件和剪裁方法

如前所述,温度试验程序多种多样,不同的环境试验标准中规定的试验程序和试验条件也不尽相同,本文将最典型的军用和民用环境试验标准中规定的温度试验程序分类汇总在表1中,并列出各试验程序对应的试验条件和作了相应的说明。     

CHEMICAL MEASUREMENT OF MEAN TEMPERATURE

Mean temperature is employed universally as an index to the energy status of the environment, and to indicate probable reaction rates of physical and biological processes in nature. A versatile chemical method of temperature integration, based on the temperature dependence of sucrose hydrolysis, has been tested in central Pennsylvania. The chemical technique (after Pallmann) permits economical mass sampling of air, water, and soil temperatures in situations where conventional methods are too expensive or otherwise unsatisfactory. Short-wave radiation effects are negligible since the sensing elements are transparent. Repeatability is excellent: in field tests duplicate sensors yield the same mean temperature ± 0.02°C. Non-linearity of sensor response has been resolved, and the data can be related directly to measurements obtained in standard climatological networks. The technique can be used to good advantage in a variety of hydrological investigations, including evaporation, consumptive-use, and them pollution studies.     

温度试验中产品温度稳定的研究

阐述了温度试验中产品达到温度稳定的重要性,以及温度稳定的概念和确定方法。指出了直接测量法是最直观、最有效的方法,并对如何实施直接测量法提出了见解。另外还对影响产品温度稳定的外部因素进行了一些研究。     

Impingement of threadfin shad: Effects of temperature and hydrography

A model is presented that allows testing of hypotheses concerning the effects of temperature and change in temperature on impingement. The model is evaluated using data from the Tennessee Valley Authority's Kingston Steam Plant, Watts Bar Reservoir, Tennessee, USA for two fish species impinged in large numbers in the United States: threadfin and gizzard shad,Dorosoma petenense andD. cepedianum. Hydrographic characteristics near the intake screens were mapped to help explain the possible role of hydrography in distributing fish across the screens. Understanding the role of temperature and hydrography in impingement of fish provides a basis for new intake designs that may reduce impingement and helps in the development of methods to reduce impingement at existing facilities. The temperature modeling approach and conclusions about hydrographic effects might be applied to other systems in which cold-stressed schooling fish are impinged.Research sponsored by the Office of Health and Environmental Research, US Department of Energy, under contract W-7405-eng-26 with Union Carbide Corporation.Publication No. 1872, Environmental Sciences Division, ORNL.     

Observed Winter Warming of the Chesapeake Bay Estuary (1949–2002): Implications for Ecosystem Management

A large number of studies have documented 20th century climate variability and change at the global, hemispheric, and regional levels. However, understanding the implications of climate change for environmental management necessitates information at the level of the ecosystem. Historical monitoring data from the Chesapeake Bay estuary were used to identify temporal patterns of estuarine temperature anomalies in the surface (1 m) and subsurface (15 m) between 1949 and 2002. Data indicated a trend in surface and subsurface warming of +0.16°C and +0.21°C per decade, respectively, driven by warming during winter and spring. These trends suggest warming of the estuary since the mid-20th century of approximately 0.8–1.1°C. Estuarine temperatures correlated well with other independent data records for sea surface and surface air temperatures in the region and to a lesser extent, the northern hemisphere. Gross long-term temperature variability in the estuary was consistent with North Atlantic climate variability associated with the prolonged positive North Atlantic Oscillation/Arctic Oscillation and increased anthropogenic radiative forcing, although localized environmental drivers likely are important as well. A simple spatial analysis revealed strong seasonal latitudinal and longitudinal gradients in estuarine temperature as well as a north–south gradient in long-term temperature trends. Continued warming of the estuary will have important implications for ecosystem structure and function as well as attempts to manage existing challenges such as eutrophication and benthic hypoxia. However, such management efforts must be cognizant of the effects of various climate and nonclimate drivers of environmental variability and change operating over different spatial and temporal scales.Published online     

Thermal gradient in the vicinity of Kwale/Okpai gas plant,Delta state,Nigeria: Preliminary observations

Environmental Pollution now persist in Nigeria especially the oil-rich regions of Delta State. One of these problems is due to gas flaring. Thermal gradient resulting from the gas flared at Kwale/Okpai gas plant is hereby reported. Surface temperature variations with distance from the flare point were investigated for the four cardinal directions. The results show a surface temperature elevation of about 3.7° C above the mean normal daily temperature within a radius of 270 M. Hence the thermal equilibrium has been altered. This increase in temperature has undesirable effect on man and his environment especially on the socio-economic lives and activities of the inhabitants. It is therefore necessary that Government Agencies empowered to monitor environment such as Federal Environmental Protection Agency (FEPA) should embark on adequate remediation activities in order to stop the environmental degradation before enormous and permanent damage is caused. Furthermore, the companies involved in the gas flaring should be made to be concerned with the danger they may be causing the inhabitants in particular and the populace in general.     

Novel Temperature Control Technique for a Medicinal Herb Dryer System Powered by a Photovoltaic Array

Each plant has its own optimal drying temperature, especially for the medicinal herbs, because they are sensitive to heat. If the drying temperature becomes more than the optimal value, some chemical reactions will occur and influence the quality of the dried herb, such as color, taste, and aroma. While if the drying temperature becomes lower than the optimal value, the drying process will slow down, and consequently an expected degradation in the quality of the herb may occur, due to insects and fungi infestation which increase in moist conditions. This paper presents a new temperature control technique for a medicinal herb dryer system. The technique fixes the drying temperature of the medicinal herbs at 40^°C, even in cases of rapidly changing atmospheric conditions. The control of the dryer temperature is achieved through using the proportional integral (PI) controller. The designed dryer contains two systems, which are the thermal and the electrical systems. The thermal system is designed to heat the drying air by using solar energy and bio-gas fuel. Whereas the electrical system, which contains a photovoltaic (PV) modules and a battery, is designed to supply the different electrical loads of the dryer system. The control technique is investigated through simulation work by using MATLAB-SIMULINK. The simulation results indicate the high capability of the proposed technique in controlling the drying temperature, even in cases of rapidly changing atmospheric conditions.     

Impact of land use and land cover changes on the ambient temperature in a middle scale city, Takamatsu, in Southwest Japan

There is a lack of information on urban heat island impact on the thermal environment due to low populated urban sprawl, although densely populated urban sprawl impact has been identified by several researchers. The Takamatsu area has recently developed in a low populated urban sprawl style without any increase in population. This paper examined the impact of a low populated urban sprawl on the thermal environment through an analysis of the last 30 years data set and investigated the contribution of vegetation fraction and population density to the temperature trend. As a consequence, it was shown that one of the most significant causative factors of temperature increase is an expansion of non-vegetated area even without population growth. This result implied that vegetated zones should be maintained in urban areas in order to realize sustainable urbanization.     

Use of agricultural waste for the removal of nitrate-nitrogen from aqueous medium

The effectiveness of wheat straw charcoal (WSC) and mustard straw charcoal (MSC) as adsorbents for the removal of nitrate-nitrogen from water has been investigated. Commercial activated carbon (CAC) was used as a standard for comparison. The adsorption effectiveness of MSC was highest followed by CAC and WSC irrespective of the concentration of nitrate-nitrogen in the range of 0-25mg/l. The effects of temperature in the range of 15-28 degrees C on adsorption by WSC and MSC have also been investigated. It was observed that the temperature dependence of the adsorption effectiveness of MSC was higher than that of WSC and CAC. It is concluded that the MSC can be used for the in situ treatment by adsorption of nitrate-nitrogen in underground and surface water.     

NUMERICAL MODELING OF THERMAL STRATIFICATION IN A RESERVOIR WITH LARGE DISCHARGE-TO-VOLUME RATIO1

ABSTRACT: A numerical model study of thermal stratification in a high discharge-to-volume reservoir is described. Predicted temperature profiles are compared with field data for two different years. The model accurately predicts the date of fall turnover, and predicts degree of stratification and depth of the thermocline within about 20% for both years simulated. A parametric study of stratification mechanics for a high flow reservoir indicated that diffusion was the predominant heat transport mechanism in the hypolimnion, while surface effects dominated the epilimnion. Flow effects for the particular case studied, in which all inflows and outflows occur in the epilimnion, did not significantly affect stratification behavior.     

The effect of environmental conditions on the ability of a constructed wetland to disinfect municipal wastewaters

Constructed wetlands are widely used all over the world for the treatment of municipal wastewaters, which are characterized by high concentrations of pathogens. The objectives of this study were (1) to study the effect of solar radiation and temperature on the ability of a constructed wetland to reduce the concentration of total coliforms (TC), and (2) to evaluate the relationship between the presence of Salmonella spp. in the outflow and the concentration of TC. The results of this study showed that under Mediterranean environmental conditions, the percentage reduction in coliforms was lower during winter compared to all other seasons. Maximum removal of coliforms was achieved under conditions of high solar radiation and temperature. In addition, solar radiation was found to play a greater role in coliform die-off at low temperatures than at high temperatures. Finally, it was found that the probability of Salmonella spp. appearance in the outflow of the wetland was related to the concentration of TC. The increase in coliform bacteria in the effluents also increased the chances of Salmonella appearance. The risk of Salmonella spp. appearance in the outflow is minimized when the concentration of TC is below 10²/100 mL.