光导管冬季采光性能的实验研究

为了优化其采光性能,并为照明工程提供设计依据,对某一光导管进行了在冬季3种典型天气情况下的测量.通过本试验工作,得到了冬季各种典型天气情况下光导管的光通量、室内照度分布值,证明了光导管对散射光的采集作用.     

Sorption heat pipe—a new thermal control device for space and ground application

Sorption heat pipe (SHP) combines the enhanced heat and mass transfer in conventional heat pipes with sorption phenomena in the sorbent bed. SHP consists of a sorbent system (adsorber/desorber and evaporator) at one end and a condenser + evaporator at the other end. It can be used as a cooler/heater and be cooled and heated as a heat pipe. SHP is suggested for space and ground application, because it is insensitive to some “g” acceleration. This device can be composed of a loop heat pipe (LHP), or capillary pumped loop (CPL) and a solid sorption cooler. The most essential feature is that LHP and SHP have the same evaporator, but are working alternatively out of phase. SHP can be applied as a cryogenic cooler, or as a fluid storage canister. When it is used for cryogenic thermal control of a spacecraft on the orbit (cold plate for infrared observation of the earth, or space), or efficient electronic components cooling device (lased diode), it is considered as a cooler. When it is applied as a cryogenic storage system, it insures the low pressure of cryogenic fluid inside the sorbent material at room temperature.     

调光蓄热式CPC装置的性能研究

为了对进入室内的光线和热量进行自动控制,文章设计出了一种调光蓄热式CPC装置,该装置主要由复合抛物面聚光器(CPC)、热管、水箱组成。模拟和实验结果表明:正午时段,当太阳光线垂直或接近垂直入射时,光线透过率较小,清晨和傍晚时段,当太阳光线倾斜入射时,光线透过率较大;调光蓄热式CPC装置能够自动控制进入室内的光线,当太阳光线的入射角小于20°时(对应的时段为11:00-13:00),该装置基本上能够对太阳直射光线进行全部遮挡,当太阳光线的入射角大于40°时,直射光线基本上能够全部透过该装置;调光蓄热式CPC装置光照度透过率的实验值与模拟值随时间的变化趋势大体一致,但数值上存在一定的偏差,这主要是由于在模拟过程中没有考虑散射辐射;调光蓄热式CPC装置的光照度透过率为17%~47%,辐照度透过率为20%~42%,这表明该装置在实际应用中具有较好的调节效果;在北京室外平均温度为-8℃的条件下,调光蓄热式CPC装置可以将储热水箱的温度维持在14℃左右,这表明该装置可以将过剩的太阳能收集并存储起来。     

Analytical solution for daylight transmission via hollow light pipes with a transparent glazing

The theoretical approach originally applied for modelling of the light transmission through hollow tubular light guide with lambertian diffuser (HOLIGILM) is now generalized and adapted also to light guides furnished by transparent glazing on its base. Introducing analytical solutions for both transparent component and lambertian diffuser enables rapid numerical simulations for systems composed of several types of light guides. It straightforward permits the practical designing of novel illuminating systems taking into account the local geometrical relations like orientation, size and shape of the room as well as the prevailing exterior daylight conditions. The developed numerical tool ROOF_v3 is now extremely fast and provides highly accurate results because of exact mathematical formulae. It is shown that sunbeams interacting with short light tubes undergo only one or two internal reflections and have a preferred direction of propagation in the room. In consequence, highly illuminated areas can be recognized on the working plane. Due to the transparent glazing at light tube base the sunbeams illuminate the interior working plane or floor with circular bands. The width of this band correlates with the diameter of the light guide. Contrary to lambertian light sources, under cloudless conditions the total energy flux reaching the working plane depends on the azimuthal orientation and elevation of momentary sunbeams.     

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。     

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.     

光管翅片管热管式佘热锅炉在Consteel电炉的应用

介绍了Consteel电炉余热回收特点,并根据不同的温度和含尘研制了光管一翅片管一热管式余热锅炉,设计中充分考虑了结构合理、热稳定性好、检修维护方便,并给出现场测试数据与理论计算结果的对比,在Consteel电炉余热回收中使用光管一翅片管一热管式余热锅炉,既回收了烟气显热又减少环境污染,有着良好的推广前景。     

带内集管的分体式太阳能热水器及其实验研究

为了实现太阳能热水器和建筑的结合,设计了一种分体式全玻璃真空管太阳能热水器。它由集热器、室内储水箱、上升管和下降管组成,其集热器的每根真空管内有一个分水管,分水管通过集箱内的集管与下降管相连。与已有的太阳能热水器相比,其分水管把真空管内的冷、热水流道分开,减少了冷热水流相互干扰,提高了热水器效率,同时实现了分体式太阳能热水器系统的自然循环。实验表明,带内集管的分体式太阳能热水器比不带内集管的分体式太阳能热水器有更高的效率。     

高温热管工质的选择

高温热管是高温技术领域的一种高效传热设备。本文讨论高温热管工质的选择。首先介绍选择的准则，然后比较讨论了碱金属制品作为工质的某些特征，最后批出了钢－钾合金作为高温热管工质的优越性。     

Investigation into the performance of a micro gravitational heat pipe and a micro gravitational heat pipe with artery

The performance of a normal micro gravitational heat pipe was investigated using the analytical and numerical models previously developed. An innovative structure of the heat pipe, i.e. the micro gravitational heat pipe with artery, was then proposed in an attempt to overcome some of the drawbacks of the normal pipe. The thermal behaviour of the new type of heat pipe was simulated, and this was compared with that of a normal micro heat pipe. A performance estimation of both pipes was carried out based on the simulation results. Copyright © 2002 John Wiley & Sons, Ltd.     

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.     

重力热管传热波动特性研究及抑制方法探讨

重力热管在启动、稳定操作、工况条件变化时的脉冲沸腾和温度波动现象，对热管的传热效果和使用寿命有不利影响。采用简单的弹簧抑泡装置，可以抑制热管内工质产生气泡，吸收气泡中的热能，使工质温度分布趋于均匀，同时，可以强化工质和管壁间的对流换热。实验表明，采用弹簧式抑泡装置的重力热管强化传热效果十分明显。     

Experimental study of heat transfer of buried finned pipe for ground source heat pump applications

Ground heat exchangers have vital importance for ground source heat pump applications. Various configurations tried to improve heat transfer in the soil. A new kind of aluminium finned pipe buried in the soil for this aim. In order to compare effectiveness of the Al finned pipe over the traditional PPRC pipe an experimental study carried out. The experimental GSHP system was installed at Y?ld?z Technical University Davupasa Campus on 800 m² surface area with no special surface cover. Temperature data were collected using thermocouples buried in soil horizontally and vertically at various distances from the pipe center and at the inlet and the outlet of the ground heat exchanger. Experimental results were compared with results from analytical study. To compare effectiveness of the Al finned pipe and PPRC pipe a new parameter defined as transferred amount of heat per unit mass of working fluid per unit time for this aim. It is found that Al finned pipe has higher heat transfer values than the traditional PPRC pipe.     

Numerical investigation on latent heat thermal energy storage in a phase change material using a heat exchanger

The use of a heat exchanger using phase change material (PCM) is an example of latent heat thermal energy storage (LHTES). In this study, the charging of PCM (RT50) is studied in a double pipe heat exchanger. The designing of the heat exchanger needs to be optimized for operating and boundary conditions to store latent heat efficiently. The size of the equipment and the amount of PCM are also important to calculate the latent heat storage capacity of the LHTES device. In this study, the amount of PCM taken is quite high to avoid sensible heat transfer and to maximize the heat content of PCM. The charging process of PCM is numerically simulated using an enthalpy-porosity model. The study includes the effect of inlet temperature and flow rate of high-temperature-fluid (HTF) and concludes that both play an important role in determining the charging time. The continuous increase in inlet temperature of HTF can decrease the charging time of PCM in the heat exchanger. However, the continuous increase in the HTF flow rate cannot show the same effect. The charging time can only be minimized with a specified flow rate regime for a specific inlet temperature of HTF. These factors consequently affect the efficiency of the heat exchanger.     

Numerical analysis reliability control for a double‐pipe heat exchanger with virtual entropy generation method

There are two primary laws including the first and second laws of thermodynamics that should be used to assess a process. Generally, only the first law of thermodynamics is investigated in numerical solutions, so it is possible to exist some numerical results that do not satisfy the second law of thermodynamics because of numerical errors. To achieve reliable numerical outcomes, it is better to apply two indexes of HEAT BALANCE ERROR and VIRTUAL ENTROPY GENERATION, which come from the second law of thermodynamics. In other words, an approach to develop computational fluid dynamics investigations is to take second law of thermodynamics into consideration. In this study, two different models including counterflow double‐pipe heat exchanger and single‐pipe with constant wall temperature are simulated in various cases with different efficiencies and temperature ratios. It is found that 46 cases of total 523 double‐pipe models and 24 cases of total 402 simulations of single‐pipe models had unacceptable results regarding to two mentioned criteria. The results revealed that it is less likely to gain unreliable results in smaller efficiency and lower inlet temperature for double‐pipe heat exchanger and single‐pipe respectively.     

Failure pressure analysis of hydrogen storage pipeline under low temperature and high pressure

Low temperature and high pressure line pipes are widely used in hydrogen storage, air separation plant, liquefied natural gas (LNG) transportation etc. The material properties of pipes at low temperature are different from those at room temperature. If the medium in the pipe is corrosive, it will cause the pipe wall thickness to decrease. However, the failure pressure of the corroded hydrogen storage pipeline at extremely low temperature is lacking of adequate understanding. In this paper, we provided a novel failure pressure equation of the mild steel line pipe with corrosion defects at extremely low temperature. Firstly, a mechanical model of the line pipe with corrosion defects is established. And then, an analytical solution of the mechanical model is obtained based on elastic theory. Next, a failure pressure equation of the corroded hydrogen storage pipeline at extremely low temperature is developed. In the end, the accuracy of the failure pressure equation is verified by comparing with finite element method (FEM). The results suggest that the calculated value of the failure pressure equation is consistent with that of FEM. This paper provides a theoretical basis for the safety assessment of low temperature hydrogen storage pipeline. The new equation presented in this paper can provide useful guidance for the design of low temperature and high pressure pipelines.     

Ray tracing study for non-imaging daylight collectors

This paper presents a novel method to study how well non-imaging daylight collectors pipe diffuse daylight into long horizontal funnels for illuminating deep buildings. Forward ray tracing is used to derive luminous intensity distributions curves (LIDC) of such collectors centered in an arc-shaped light source representing daylight. New photometric characteristics such as 2D flux, angular spread and horizontal offset are introduced as a function of such LIDC. They are applied for quantifying and thus comparing different collector contours.     

Development of a cost-effective solar illumination system to bring natural light into the building core

This paper describes a novel and cost-effective way of providing direct sunlight to the core areas of a multi-storey building. In this system, sunlight is collected by a structure, called the solar canopy illumination system, which attaches to the building directly above the windows on each floor. The sunlight is then redirected by the optical components within the canopy and distributed within the building through a series of special-purpose light guides. These guides pipe the sunlight into the building, and also efficiently incorporate electric light sources so that they can provide supplemental lighting as necessary. This system combines several important energy-saving features and uses components that can be low cost in volume manufacturing. As a result, the system has the potential to be truly cost-effective based on the energy savings. The widespread adoption of such a system could substantially reduce energy consumption worldwide which would make a significant contribution toward greenhouse gas mitigation.     

An optimal design analysis of a novel parabolic trough lighting and thermal system

In order to reduce the cost and improve the efficiency of daylighting, an innovative parabolic trough solar lighting and thermal (PTL/T) system is designed and analyzed in this paper. Parabolic trough solar lighting and thermal system uses parabolic trough collector (PTC) controlled by two‐axis solar tracking system as solar collector. The collected sunlight is split by a cold mirror into visible light and infrared. The visible light is reflected by cold mirror, re‐concentrated by a second‐stage Fresnel lens, and then delivered by plastic optical fiber to the buildings for daylighting. The infrared goes through cold mirror, reaches thermal system, and is used for heating generation. The basic structure of PTL/T was outlined and described. The dimension of fiber bundle and parabolic trough was chosen after an optimal analysis. The cost of illuminating unit area was expressed as a function of illumination space dimensions and critical components efficiency. A case study was conducted to get a specific optimized illumination area and PTC area for the first time. The optimized result is to use 8‐m² PTC as collector to illuminate 500‐m² office space. The total solar energy utilization efficiency is 39.4%, with the lighting efficiency of 16.3% and thermal efficiency of 23.1%. The maximum energy savings and simple payback period were calculated for 10 typical cities when applied in residential, commercial, and industrial sectors. The amounts of greenhouse gas‐emission reductions were also calculated. The payback period in Sunbelt region is as low as less than 10 years like in Los Angeles. The results show the proposed PTL/T system is competitive compared with traditional solar energy systems. Copyright © 2016 John Wiley & Sons, Ltd.