光导管采光性能实验研究与分析

该文从实验出发,通过测量夏季3种典型天气状况下光导管的采光性能,得到光通量变化和照度分布的曲线,并同冬季的试验结果进行比较,结果表明夏季晴天时室内光通量值是冬季晴天时的4倍,多云天和阴天时都为冬季的2～3倍.通过比较分析证明,季节变化对光导管的光传输量的影响很大,太阳高度角于室内照度分布的影响也很大.     

辽宁大连地区标准阴天条件下光导管效率与照度分布的模拟分析

利用光导管室内照度计算软件HOLIGILM,在辽宁省大连地区对国内主流规格光导管的效率和照度分布进行研究。设定3个典型的时间段和不同长径比,仿真计算出光导管效率及照度分布图。结果表明:标准阴天条件下的光导管效率是长径比的减函数,照度均匀分布且随着半径增加而逐级减小,且不随太阳位置及时间变化而产生明显的变化。     

空气源相变蓄能复叠式热泵供暖系统的研究

以空气源相变蓄能复叠式热泵供暖系统为基础,选取晴天、阴雨雪天气2个典型天气工况分别对热泵、储能等各部分模块进行试验数据采集,通过理论计算与实验分析表明,系统在冬季晴天时系统COP要明显高于阴雨雪天气工况,系统在极端天气工况下,随着室外环境温度逐步增大,热泵耗功缓缓下降,而随着环境温度降低,热泵耗功呈上升趋势。研究结果表明,较高的蒸发温度及较低的冷凝温度使热泵循环COP值处于较高水平,因此在不同工况下时,系统仍可高效稳定运行。     

多地区气象环境因子与散射比关系的建模分析

统计收集了2001—2015年北京和武汉逐时太阳辐射资料,对两地分别选取典型气象年并据此探讨对比两地散射比受天文气象环境因子的影响程度,在交叉细分天气类型的情况下,分别建立并对比各地区适合的数学模型.结果表明:1)北京地区散射比与清晰度指数相关性更强,线性化程度更好;2)不同地区散射比受太阳高度角影响程度有差异,差异较...     

拉萨地区被动太阳能传统民居测试研究

针对拉萨地区某一经过被动太阳能改造典型藏族单层民居,分别在冬、夏季测试了室外气温、太阳辐射强度和不同房间的室内温度.分析测试结果后发现:在拉萨的典型天气条件下(冬季室外平均气温约为0℃,日照时间内太阳总辐射平均强度约为0.45kW/m2),采用大面积南向单玻外窗的被动太阳房室内最低温度与其他房间接近.平均温度和最高温度分别比其他房间提高约3℃和7℃;而被动太阳房在夏季并未出现明显的过热现象.针对该地区被传统民居室内温度整体偏低、被动太阳房室内温度波动大的现状,提出了加强建筑保温和蓄热性能的改造建议.     

夏玉米潜热通量的变化规律研究

针对生态系统的辐射收支、热量平衡和蒸发蒸腾分配对系统的水分转化和有效利用研究,利用波文比自动气象站观测了夏玉米在不同生育时期、不同天气情况下潜热通量的日变化、逐日变化以及逐月变化过程.结果表明,潜热通量日变化曲线是典型单峰型,潜热通量和太阳净辐射的逐日变化曲线、逐月变化曲线吻合,阴天潜热通量的峰值滞后于晴天和多云.     

南昌地区太阳辐射资源分析

利用太阳监测系统监测的数据分析南昌地区季节、月、日太阳辐射的变化和规律。结果表明:南昌地区夏、秋、冬季节太阳直射总辐射强度每小时均值最大为1 026 W/m2;该地区冬季受阴雨天气影响导致冬季的日照时间极短;从都为晴朗天气的太阳辐射情况比较来看,冬季的直射总辐射强度与夏季其实差异不大,但因冬季的全天日照时间低于夏季的原因,直射总辐射量冬季时仍然会低于夏季时。分析南昌太阳直射总辐射强度频数分布可知,超过100 W/m2的太阳直射辐射强度占到太阳直射总辐射强度的59.31%,而且分布比较稳定。     

秦岭山区民居冬季室内热环境测试

为考察秦岭山地民居冬季室内热舒适状况,选取当地典型二层生土和砖砌民居作为研究对象,对其冬季室内温度、相对湿度、室内照度和壁面温度进行现场测试并记录室外温湿度与太阳辐射强度.通过对测试数据分析,给出了不同外围护材料下民居室内热环境的定量评价,在此基础上提出改进其室内热环境的建议.     

基于日需水量的作物非充分实时灌溉预报模型及应用

针对传统灌溉预报中实时降水信息与典型年降水信息差异较大导致预报决策在实际生产中失效的问题,在充分考虑预报日降水和天气类型情况下,基于实时的土壤水分监测数据和天气信息,提出了基于日需水量的作物非充分实时灌溉预报模型,给出了模型涉及的短期作物系数、土壤水分修正、计划湿润层深等参数的模拟与修正办法。以冬小麦为例,提出了不同天气类型下日需水量的计算方法,并进行了在线实时灌溉预报。结果表明,该预报模型与方法能为农业水资源发挥最大效益、有效缓解水资源短缺提供依据。     

黔东南地区各季节极端干期日数的时空分布特征

利用1961—2009年黔东南地区16个地面气象站的逐日降水资料,分别统计了四季最大连续无雨日数（日降水量〈0.1mm）的时间序列,采用正交函数分解、Mann-Kendall突变检验和线性倾向估计等方法,分析了各季节极端干期日数的空间结构和时间演变规律。结果表明,黔东南地区各季节极端干期日数的时空分布存在较大差异,极端干期日数最多出现在秋季,最少是春季;夏季黔东南北部的极端干期日数多,春、秋季南部多,冬季南、北部多,西部四季相对较少,年内非均匀性特征显著。在大尺度天气系统控制下,四季极端干期日数事件的步调基本一致,黔东南中东部发生异常的频次较高,不同季节的天气系统对黔东南各区域的影响具有明显的局地性和阶段性;近49年中各季节出现极端干期日数典型多的年份比典型少的年份多;进入21世纪以后,春、秋、冬季极端干期日数均呈显著的增多趋势,而夏季变化的特征不明显。     

Splayed mirror light pipes

An expression is given for the transmission of the rectangular-section mirror light pipe. The expression is used to model throughputs for simulated solar conditions over a calender year. It is found that the splaying of a mirror light pipe results in a significant increase in throughputs particularly in winter months.     

Evaluation of dichroic material for enhancing light pipe/natural ventilation and daylighting in an integrated system

Integration of natural ventilation and daylighting in a single installation would make both technologies more attractive. One method for the integration is the use of concentric light pipe and ventilation stack. By constructing the light pipe using dichroic materials, the infrared part of the solar radiation is allowed to be transmitted to the stack but the visible light is guided by the light pipe into a room. The heat gain to the interior can be reduced and the thermal stack effect strengthened. Work presented here involved the experimental and computational evaluation of dichroic materials for enhancing both natural stack ventilation and daylighting. The transmittance of a dichroic light pipe was found to be similar to that of a light pipe with a 95% specular reflectance. The infra-red radiation transmitted through the dichroic material into a passive stack was found to enhance the natural ventilation flow by up to 14%. The effect is greater in summer than in winter, which is highly desirable as there is often a lack of driving force for natural stack ventilation in summer.     

太阳能热泵气化LNG系统的性能研究

针对液化天然气(liquefied natural gas,LNG)空温式气化器(ambient air vaporizer,AAV)在运行中表面堆霜结冰降低换热效率的问题,提出并设计一种基于太阳能热泵的LNG气化系统(DX-SAHPNV),建立系统各主要部件的动态仿真数学模型。通过数值模拟,对DX-SAHPNV改善AAV气化能力的效果和系统全年动态运行性能进行研究,并对比分析集热/蒸发器内引入LNG前后系统性能的变化。结果表明:同常规AAV相比,应用DX-SAHPNV系统后,冬、夏典型日AAV液相区和两相区长度明显缩短,结霜量减少,出口天然气平均温度分别升高3.31和7.46 K;同不引入LNG相比,DX-SAHPNV系统引入LNG时,冬、夏典型日COP分别提高9.25%和16.49%,集热效率分别提高11.07%和14.95%,DX-SAHPNV系统全年COP均值和集热效率均值分别提高13.64%和12.84%。DX-SAHPNV系统可有效提高AAV气化效果。     

Parametric studies for heating performance of an earth to air heat exchanger coupled with a greenhouse

A thermal model has been developed to investigate the potential of using the stored thermal energy of the ground for greenhouse heating with the help of an earth to air heat exchanger (EAHE) system integrated with the greenhouse located in the premises of IIT, Delhi, India. Experiments were conducted extensively during the winter period from November 2002 to March 2003, but the model developed was validated against the clear and sunny days. Parametric studies performed for EAHE coupled with the greenhouse illustrate the effects of buried pipe length, pipe diameter, mass flow rate of air, depth of ground and soil types on greenhouse air temperatures. Temperatures of greenhouse air with the experimental parameters of EAHE were found to be on an average 7–8°C more in the winter than the same greenhouse without EAHE. Greenhouse air temperatures increase in the winter with increasing pipe length, decreasing pipe diameter, decreasing mass flow rate of flowing air inside buried pipe and increasing depth of ground up to 4 m. Predicted and measured values of greenhouse air temperature, which were verified in terms of root mean square of percent deviation and correlation coefficient, exhibited fair agreement. Copyright © 2005 John Wiley & Sons, Ltd.     

采集太阳光的照明系统

提出一种采光面积大、结构简单、制作容易、维修方便的平面反光镜阵列汇聚采光，导光管传光，平面镜耦合，磨砂塑料盘散光的新型太阳光照明系统。考察了该系统的平面反光镜聚光特性，导光管的耦合方法及导光管透光率随光线入射角、导光管长度和导光管直径的关系。利用该系统，研究了透射光光强随导光管长度的变化规律、0．72m长导光管在不同集光比下的导光性能以及一天中聚光与不聚光条件下导光管透光率比较。结果表明，采用本系统汇聚阳光使进入导光管光线的入射角可以调整，入射角角度都比较小，从而使光线在导光管中的反射次数减少，光损失少，一天中光照亮度均匀。     

Experimental analysis on a 1:2 scale model of the double light pipe, an innovative technological device for daylight transmission

In this paper the authors present the double light pipe, an innovative technological device, designed as an evolution of a traditional light pipe, which distributes daylight to underground areas of a building, illuminating, at the same time, the passage areas thanks to a larger collector and a second transparent pipe attached to the first one. Unlike the traditional light pipe, thanks to this double illuminating function it can be located in the middle of a room, despite its encumbrance.In this paper the technological design of the double light pipe is presented and the results of an experimental analysis on a reduced scale (1:2) model are shown. Internal illuminance data over horizontal and vertical work-planes were measured in various sky conditions with or without direct solar radiation. Being this innovative device obtained by a light pipe integrated with a second pipe, it performs like a traditional light pipe for the final room and, at the same time, illuminates the intermediate room giving it uniform and high quality light, particularly indicated for wide plant areas, such as show-rooms or museums.     

Periodic analysis of a ventilated trombe wall

A periodic analysis of a ventilated Trombe wall is presented. The analysis is able to take into account the storage effects and predict the daily or long term performance of the system. The thermal flux entering an air-conditioned space (maintained at 20°C) through the wall has been evaluated. Numerical calculations have been performed corresponding to the meteorological data on 19 January 1981 at New Delhi, a typical cold winter day. Subsequent parametric studies using the simulation indicated that the critical parameters were the mass flow rate of air, depth of plane of heat retrieval and the length of the network of pipe.     

Parametric study on the performance of the earth‐to‐air heat exchanger for cooling and heating applications

To reduce energy consumption, the earth‐to‐air heat exchanger (EAHE) is a suitable technique for cooling and heating buildings. This paper studies numerically the effect of some design parameters (pipe diameter, inlet condition, pipe length, and outlet condition) on the overall performance of the EAHE system. Four diameters of the EAHE pipe (2, 3, 4, and 6 in) are studied and this numerical study has been done for summer and winter seasons for Nasiriyah city in southern Iraq. First, the built numerical model was validated against the experimental model, and the results of comparison showed a good consensus. After the validation and by using computational fluid dynamics modeling, the overall performance of the EAHE system with all pipe diameters was analyzed with ranges of air velocity, DBT or inlet temperature, and a pipe length of 50 m. The simulated results showed that the EAHE system with 6 in pipe diameter has the best values of overall performance, but from the thermal performance point of view, the 2 in pipe diameter is more suitable.     

Enhanced solar energy collection using reflector-solar thermal collector combinations

The amount of direct light gathered by a combination of reflector plus flat-plate collector has been analyzed. The calculations were done allowing variable reflector and collector orientation angles, variables latitude, and arbitrary sun hour angle away from solar noon. The effects of reflection and transmission losses and of polarization of the incident light were included. Correction was also made for the finite size of the reflector. It was found that the optimum orientation has the collector plane almost perpendicular to the plane of the reflector. This optimum orientation is approximately independent of the sun's azimuthal dependence. The optimum reflector angle is found to be between 0° and 10° above the horizon for winter solar conditions. For typical winter operating conditions the enhancement in light gathering power for direct solar radiation is about a factor of 1·4–1·7. This results in an effective increase of 100% in the useful winter heat output from a practical reflector-collector combination with a reflector angle of 0°, over the useful heat output obtained with an optimally oriented simple flat-plate collector. An approximate calculation was also made of the overall enhancement in useful heat output for diffuse solar radiation; an increase by a factor of about 1·5 is predicted. Comparison with the preliminary analysis of the performance of the Coos Bay, Oregon solar house shows substantial agreement with the predictions of the present analysis.     

A study on a ventilation stack integrated with a light pipe

A theoretical and experimental study has been conducted on the performance of a vertical light pipe that also functions as an air flow stack for night ventilation. The rectangular light pipe of height 3 m and cross-section area 0.0625 m² surrounded by an air duct of total cross-section area 0.23 m² is situated above a room of height 3.8 m and floor area 9 m². Heat transfer from the hot water in the wraparound hot water jacket to the air in the duct is assisted by stainless steel fins. The ventilation of the room, due partly to the buoyancy of the air in the duct and partly to the wind effect, amounted to nearly 10 air changes per hour which is sufficient for passive cooling during cooler night periods. The light pipe has specular reflecting walls. It was found that the transmission of daylight through the light pipe in the middle of a partly cloudy day was sufficient for illuminating the room to general illumination level.