EXPERIMENTAL PERFORMANCE OF BUILT-IN-STORAGE SOLAR WATER HEATING SYSTEMS IN LABORATORY AND FIELD CONDITIONS

Hourly thermal performance (both in laboratory and field conditions) of three designs of built-in-storage solar water heating systems of 100 litres capacity each has been reported. A different storage tank design is used in each of the three cases. Design I consists of three tanks connected in series; in Design II, a parallelepipedic tank is divided into five zones with baffles; Design III is a simple parallelepipedic tank. The first two designs help in inducing thermal stratification in the tank. It is seen from the results that the performance of Design II is the best of the three. © 1997 by John Wiley & Sons, Ltd.     

STUDY OF CHARGING OF STRATIFIED STORAGE TANKS WITH FINITE WALL THICKNESS

This paper presents a numerical and experimental study of finite wall thickness on stratification during charging of soar thermal storage tanks. A numerical two-dimensional spectral-element model has been used. Predictions of the model are compared with experimental data, and with a one-dimensional plug flow model. The fluid inlet effect on the stratification is minimized in the experiments by the use of a proper diffuser design with a settling mesh. Both heat conduction in the tank wall and the developing flow in the tank have a significant effect on stratification during charging at low flow rates. The one-dimensional plug flow model is shown to be inferior to the two-dimensional model in representing the experimental data. Yet, a simple one-dimensional flow model corrected for both centreline velocity and mixing effects has given comparable results to the more expensive two-dimensional model. © 1997 by John Wiley & Sons, Ltd., Int. J. Energy Res., vol 21, 411–427 (1997).     

蒸气爆炸研究现状及问题分析

本文通过对蒸气爆炸研究现状的分析,提出了几个蒸气爆炸研究中亟需解决的问题并阐述了它们的研究意义。这些问题包括分层、泄压速度和泄压率以及压力储罐裂缝发展对蒸气爆炸过程的影响。这几个问题的解决有助于对蒸气爆炸机理的了解。     

塔里木盆地玉北地区断裂构造差异变形及其控制因素

为揭示断裂构造差异变形特征及其成因机制,在二维和三维地震资料精细断裂解释的基础上,对塔里木盆地玉北地区断裂构造分层、分期和分区发育强度差异性进行了研究。结果表明:纵向上,断裂可以分为以逆冲构造为主的盐下基底构造、以盖层滑脱为主的盐上下古生界、以断层相关褶皱为主的上古生界和新生界4个构造层,自盐上下古生界至新生界构造变形总体逐渐减弱;平面上,玉北地区东部断裂活动更为强烈,以叠瓦冲断构造为主,次级断裂更为发育,密集分布,而玉北地区中西部冲断作用较弱,以逆冲滑脱、高角度逆冲构造为主,次级断裂不太发育,相对分散分布;断裂演化时间上,加里东中期玉北地区东部断裂活动强,中西部断裂活动较弱,加里东晚期—海西早期、海西晚期东部断裂相对稳定,中西部断裂活动相对较强,反映断裂活动自东向西的迁移特征;断裂构造发育位置、走向和分布受先存基底构造、构造应力场背景和膏盐岩滑脱层等共同控制;加里东中期断裂主要密集发育于先存基底构造薄弱带,受SE向挤压应力控制,断裂沿中、下寒武统由NW向朝SE向被动逆冲,形成多排NE向差异分布的逆冲断裂带。     

一种Al-Zn-Mg合金板材焊缝裂纹的原因分析及预防措施

Al-Zn-Mg合金板材在使用加工中焊接时焊缝处出现裂纹,分析了裂纹产生的原因,确认裂纹缺陷是因铸锭内部组织中存在粗大金属化合物聚集,该粗大化合物在板材轧制变形过程中产生分层所致.并从合金的元素含量、熔铸温度、搅拌方式、在线过滤等方面提出了避免该类缺陷的措施.     

Thermal response of a series- and parallel-connected solar energy storage to multi-day charge sequences

The thermal response of a multi-tank thermal storage was studied under variable charge conditions. Tests were conducted on an experimental apparatus that simulated the thermal charging of the storage system by a solar collector over predetermined (prescribed) daylong periods. The storage was assembled from three standard 270 L hot-water storage tanks each charged through coupled, side-arm, natural convection heat exchangers which were connected in either a series- or parallel-flow configuration. Both energy storage rates and tank temperature profiles were experimentally measured during charge periods representative of two consecutive clear days or combinations of a clear and overcast day. During this time, no draw-offs were conducted. Of particular interest was the effect of rising and falling charge-loop temperatures and collector-loop flow rate on storage tank stratification levels. Results of this study show that the series-connected thermal storage reached high levels of temperature stratification in the storage tanks during periods of rising charge temperatures and also limited destratification during periods of falling charge temperature. This feature is a consequence of the series-connected configuration that allowed sequential stratification to occur in the component tanks and energy to be distributed according to temperature level. This effect was not observed in the parallel charge configuration. A further aspect of the study investigated the effect of increasing charge-loop flow rate on the temperature distribution within the series-connected storage and showed that, at high flow rates, the temperature distributions were found to be similar to those obtained during parallel charging. A disadvantage of both the high-flow series-connected and parallel-connected multi-tank storage is that falling charge-loop temperatures, which normally occur in the afternoon, tend to mix and destratify the storage tanks.     

温度分层对小型熔盐单罐释热过程影响

为了探究温度分层对小型熔盐单罐释热过程的影响,对释热前单罐内熔盐有、无温度分层两种工况下的释热过程进行了实验研究。通过对隔板内外侧熔盐温度、换热器出口处水温、释热过程累积释热效率等参数进行分析发现：释热过程中维持熔盐稳定的温度分层是提高单罐释热效率的关键因素,而浸没式换热器取热时产生的扰动会破坏熔盐温度分层,影响释热效率,需要对其进行优化。研究结果为内置浸没式换热器的小型熔盐单罐系统的优化提供了有效依据。     

不同结构储热水箱分层特性的实验研究

在太阳能集热系统中,储热水箱内的温度分层效果受不同水箱结构的影响巨大。为研究这一特性,搭建了一套储热水箱分层特性测试实验台,对直接进口式、三层孔板式和盒状结构水箱进行了测试实验。水箱内初始水温为70℃,在相同的进水温度和不同的流量条件下,根据实验数据绘制了不同结构水箱内的各层温度变化曲线。结果显示,进水流量越大,水箱内混合效应越大,各层温度趋于一致的时间越短。在热力学定律的基础上,计算并分析了3种结构水箱的取出效率、（火用）和Str数等分层特性指标。结果表明,3种结构中,盒状结构水箱内的温度分层效果最好,对热量的利用率最高,盒装结构有效地抑制了冷热水混合效应,其次为三层孔板式水箱,而直接进口式水箱的温度分层效果最差。