太阳光光催化降解弱酸性大红的动力学研究

采用自制的反应装置,研究了负载型TiO2膜太阳光光催化降解弱酸性大红的动力学.结果表明:在所研究的范围内,太阳光光催化降解弱酸性大红符合一级动力学反应,可用L-H动力学方程描述,且反应速率常数(K)与C0-1.50、pH-1.147和V成正比;太阳光光催化对染料的降解无选择性且弱酸性大红染料能够被完全矿化为CO2和H2O;一年四季降解实验中,由于冬季太阳光光强太弱,应考虑人工光源作为补偿.     

太阳能光催化染料污水脱色研究

以太阳光中近紫外光激发催化剂ＴｉＯ２将染料污水光催化脱色，探讨催化剂用量，催化剂活性、曝气、污水流速、光催化反应器受辐射面积、太阳辐照度等条件对染料污水脱色效率的影响。结果表明，在一般晴天经２ｈ的太阳光照射，阳离子蓝Ｘ－ＧＲＲＬ的脱色效率在８０－９３％之间，即使在阴天多云条件下，脱色效率亦可达到６６％，表明太阳能光催化染料污水脱色处理是一种经济、实用、高效的污水脱色处理技术。     

太阳能光催化废水处理反应器发展

对太阳能光催化废水处理反应器的研制及应用情况进行了回顾，并对其未来的发展进行了展望。复合抛物面聚集器是现有设计中性能最优越的太阳光收集器，固定相催化剂是光催化反应器发展的必然趋势。基于光纤负载光催化剂的太阳能光催化反应器在废水处理方面具有广泛的应用前景。     

太阳光TiO2薄层光催化降解有机磷农药的研究

研究了在太阳光的照射下，ＴｉＯ２薄层光催化降解有机磷农药的可行性。结果表明，０．６５×１０－４ｍｏｌ·Ｌ－１的久效磷、甲拌磷农药光照他可完全降解至ＰＯ４３－；加入微量的Ｈ２Ｏ２或通入空气可大大提高光解率；有机磷农药初始浓度增加，其光解率下降；光照１２０ｈ后ＴｉＯ２薄层的光催化活性没有减弱，可以连续使用。初步探讨了有机磷农药光催化降解的机理，认为·ＯＨ和Ｏ２２－是最主要的氧化剂。     

不同类型染料化合物太阳光催化降解研究

针对四大类八种水溶性染料和一种化学指示剂，在相同实验条件下，进行了ＴｉＯ２悬浆体系太阳光催化氧化降解规律的研究。在ＵＶ辐照度２１．２８Ｗ／ｍ２的晴天，染料初始浓度均为２０ｍｇ／Ｌ，催化剂投加量１ｇ／Ｌ，溶液平均温度２０℃，经太阳光照射４ｈ，各料染料脱色和总有机碳去除明显。根据表观速率常数算出不同染料光催化降解的难易程度，实验证实了多相光催化氧化技术用于染料废水处理工艺的可行性。     

Cu_20/Ti0_2异质结复合薄膜的光催化性能研究

采用溶胶-凝胶法和磁控溅射技术制备Cu_2O/TiO_2半导体异质结构的光催化复合薄膜。以钛酸丁酯为原料溶胶浸渍提拉制备均匀透明的TiO_2薄膜,以金属Cu为靶源在TiO_2薄膜表面反应溅射p型Cu_2O薄膜,利用SEM、XRD、UV-Vis等分析技术对催化剂进行表征,通过染料的降解实验考查异质结复合薄膜在模拟太阳光下的光催化活性,并对其机理进行探讨。结果表明,TiO_2与Cu_2O复合后形成的异质结薄膜在模拟太阳光下具有较好的光催化活性,异质结复合扩展了催化剂的光响应范围及光响应强度,提高了量子效率,是一种充分利用太阳能的光催化复合薄膜。     

太阳能光导采光的传光过程

太阳能光导采光可利用太阳能作为能源，利用光学玻璃纤维作为传光线路，把太阳光引入阴暗处进行照明，既节约大量的常规能源，又可以起到阳光浴的作用，具有显著的经济效益。对太阳光在光学纤维中传输的物理过程进行了分析。     

能发电的窗玻璃

日本产业技术综合研究所最近研制了一种透明型的太阳能电池 ,据悉用专门技术将其粘贴在玻璃上 ,便有可能让窗玻璃发出电能。众所周知 ,目前已普及的硅太阳能电池由于吸收的是太阳光中的所有光线 ,故应呈黑色 ;而新近开发的透明型太阳能电池却仅仅靠吸收太阳光中的紫外线来发电 ,故可以透过其它光线 ,自然呈透明的了。不过 ,传统太阳能电池利用的是太阳光中高占 9成以上的可视光线 ;但透明型太阳能电池仅仅能利用太阳光中少量的紫外线 ,故对光与电的转换机制的效率要求无疑特高。日本专家为此开发成功了一种能和紫外线发生反应的无色透明又高…     

太阳光Fenton氧化-混凝联合处理含酚废水

研究了煤气含酚废水和模拟苯酚废水的太阳光Fenton氧化-混凝联合处理技术,比较了混凝法、太阳光Fenton氧化法及其联合技术对含酚废水的处理效果。结果表明,太阳光Fenton体系可有效地氧化降解含酚废水,但废水完全矿化所需的H2O2用量较大,导致处理成本较高。含酚废水直接采用混凝处理的效果不理想,CODCr和挥发酚去除率较低(6.5%～28.7%)。采用太阳光Fenton氧化-混凝联合技术处理中等浓度的煤气含酚废水,使其CODCr和挥发酚浓度达到国家二级排放标准,只需投加700mg/L的H2O2,而单纯采用太阳光Fenton氧化所需消耗的H2O2大于2800mg/L,即联合技术可节约H2O2用量3倍以上。结果还表明晴天下太阳光Fenton氧化反应45min与人工电紫外光Fenton氧化反应30min对含酚废水的处理效果相当。太阳光Fenton氧化-混凝联合技术具有能耗低、处理效率高、处理量大等特点,在环境治理领域具有更广阔的应用前景。     

光催化在有机合成反应中的应用研究进展

光催化有机合成开辟了一条新的合成路线.光催化有机合成反应通常在常温、常压下进行,易操作,不仅可以在温和条件下实现以往需要苛刻反应条件的合成,而且能够有效减少副反应的发生,控制反应进行的程度,在绿色环保的同时,提升反应的安全性和可控性.因此,光催化作为一种绿色合成手段,在有机合成中的应用越来越受到人们的重视,并已在脂肪烃...     

Effect of the gap spacing on the shallow solar pond performance

It is stated by Garg et al. [Energy Convers. Mgmt 22, 117 (1981)] that, for a shallow solar pond where the gap spacing is large (300 mm), the convective heat loss is somewhat lower than for a conventional collector with a shorter gap spacing (20 mm). How much the total heat transfer coefficient is lowered, and what is the effect of the gap spacing on the performance of the shallow solar pond were not mentioned. In this study, the effect of gap spacing on shallow solar pond performance is studied. For this purpose, a computer program is constructed and is experimentally tested using a shallow solar pond of 6.6 m² area. It is concluded from the results that the effect of gap spacing on the top loss coefficient is independent of the temperature difference between the upper film of the water bag and the glazing of the shallow solar pond. The results also show that the change in gap spacing of the shallow solar pond has not an important effect on the pond performance. Hence, the large gap spacing in the conventional design shallow solar pond (300 mm) cannot be considered as a major difference with the flat plate collector design (20 mm), as Garg et al. stated.     

The effect of a baffle plate on the transient performance of a shallow solar pond water heater

A straightforward transient analysis of a shallow solar pond (SSP) water heater fitted with a baffle plate has been presented. In order to study the performance of the system, numerical calculations have been made for a typical cold day in Delhi, viz. 18 Dec. 1984. It is concluded that the SSP can also be used as a built-in storage water heater, with better performance being achieved with the use of a baffle plate.     

Salt gradient stabilized solar pond collector

This paper presents a theoretical analysis of a salt gradient solar pond as a steady state flat plate solar energy collector. We explicitly take into account the convective heat and mass flux through the pond surface and evaluate the temperature and heat fluxes at various levels in the pond by solving the Fourier heat conduction equation with internal heat generation resulting from the absorption of solar radiation as it passes through the pond water. These evaluations, in combination with energy balance considerations, enable the derivation of the expressions for solar pond efficiency of heat collection as well as the efficiency of heat removal. The efficiency expressions are Hottel-Whillier-Bliss type, prevalent for flat plate collectors. Numerical computations are made to investigate the optimization of geometrical and operational parameters of the solar pond. For given atmospheric air temperature, solar insolation and heat collection temperature, there is an optimum thickness of nonconvective zone for which the heat collection efficiency is maximum. The heat removal factor is also similar to that of a flat plate collector and the maximum efficiency of heat removal depends on both the flow rate and the temperature in the nonconvective zone.     

Transient behaviour of collector/storage solar water heaters for generalised demand patterns

This communication presents a simple transient model for predicting the thermal performance of collector/storage solar water heaters for generalised demand patterns. These heaters consist of either (i) an insulated rectangular metallic tank whose top surface is blackened and suitably glazed (i.e. a built-in storage solar water heater) or (ii) an insulated open shallow tank with black bottom.inner sides and a glass plate at the surface in contact with the water (i.e. a shallow solar pond water heater). The time dependence of the water temperature for the withdrawal of hot water from the system at constant flow rates constantly or intermittently has been explicitly evaluated. Numerical results for the operation of the system in industrial and community service applications are discussed.     

Thermal performance of a shallow solar-pond integrated with a baffle plate

A shallow solar-pond integrated with a baffle plate is investigated theoretically and experimentally under Tanta prevailing weather conditions. A transient mathematical model is presented for the pond. The energy-balance equations for various parts of the pond are solved analytically using the elimination technique. In order to validate the theoretical model, experiments are performed under the batch mode of heat extraction with a black painted baffle plate made of stainless steel, with and without vents in the plate, for different masses of water in the upper and lower layers. It is found that the pond-water temperature decreases with increasing vent area; therefore, the baffle plate should be used without vents with shallow depths of the upper water-layer. Experiments have also been carried out using baffle plates made from Al and mica in order to study the effect of the thermal conductivity of the baffle plate on the pond’s performance. The average temperature of the pond water is found to be less dependent on the thermal conductivity of the baffle plate. It is also inferred that the present system could provide 88 L of hot water at a maximum temperature of 71 °C at 3:00 pm with a daily efficiency of 64.3% when the baffle plate is used without vents. The pond can retain hot water until 7:00 am of the next day at a temperature of 43 °C, which can be used for most domestic applications. Comparisons between experimental and theoretical results indicated that the theoretical model could be used for estimating the pond’s performance with good accuracy.     

Effect of heat exchanger on the performance of a shallow solar pond water heater

In this communication, a mathematical model has been developed to predict the performance of a shallow solar pond water heater with a heat exchanger. Explicit heat balance equations are written for the plate temperature and water tank temperature, as well as for the heat extracting fluid temperature, by properly taking into account the absorption of solar radiation in the body of pond water. It is seen that efficiencies may be achieved as high as 60% at water flow rates of 0.1 – 0.2 kg/s m². Thereafter, the efficiency becomes almost constant at higher flow rates.     

Spectral calculation of the thermal performance of a solar pond and comparison of the results with experiments

This paper deals with a method and the result of the spectroscopic calculation on heat balance of a salt-gradient solar pond under the conditions of spectral solar radiation. Furthermore, reflection of the ray incident upon the surface of the pond water, refraction of the rays within the salt-water layer and diffusion of salt in the pond water are considered. On the other hand, in order to make a clear mechanism of the heat collection and heat storage of the solar pond, we conducted an indoor experiment and a numerical analysis on a small scale model of the salt-gradient solar pond with 2 m² surface area and 1.6 m depth, under the incident rays from a Xe-lamp solar simulator. According to the above experimental analysis, we made a simulation model of thermal performance for a solar pond and carried out the calculation from the heat balance. We found that the simulation calculations correspond well to the experimental results, so that our thermal simulation model and method might be correct. We also did the thermal calculation by changing the incident rays from a Xe-lamp into natural ray (Moon’s spectrum) and Halogen lamp. As a result, it was found that the temperature distributions in the solar pond were notably different due to spectral characteristics of the incident ray. Therefore, the spectroscopic consideration for thermal performance of any solar pond is necessary to obtain a correct solution under the spectral incidence with special wavelength distributions.     

Effect of Buoyancy on the Perfomance of Solar Air Collectors with Different Structures

In order to study the effect of buoyancy on the performance of solar air collector, the theoretical analysis and experimental tests of four solar air collectors with different structures under natural convection and mixed convection are carried out. The results show that the air temperature rise of the protrusion-corrugated plate air collector is the highest in the natural convection, which is 9.17 Chigher than that of the flat plate collector, and the air outlet velocity is 0.19 m/s, increasing by 16.88% than that of the flat plate collector. Observing the effects on the heat transfer performance of mixed convection, it can be found, in addition to the protrusion-corrugated plate air collector, the buoyancy plays a positive role on the other three solar air collectors in the upward flow, while the buoyancy plays a negative role on the other three solar air collectors in the downward flow, and the enhanced degree of the buoyancy to the corrugated plate air collector is the largest, while the enhancement degree of the flat plate collector is the least.     

Study on shallow solar pond applications at Tehran

In this study, a theoretical model which is validated experimentally is used to predict the performance of a shallow solar pond in Tehran. The theoretical and experimental results show good agreement. The maximum hourly water temperature of the shallow solar pond is found to lag behind the maximum hourly ambient temperature and solar radiation by 1–2 and 3.5 h, respectively.The maximum monthly daily-average water temperature follows the trend of the monthly daily-average solar radiation but leads the monthly daily-average ambient temperature in one month. The shallow solar pond, with 10-cm water depth, cannot be used as a thermal source in winter but can be used for many thermal applications in summer. With 5-cm water depth, the shallow solar pond can be used as a thermal source for low heat applications in most of the winter but can be used, even for moderate applications, where high temperature up to 95°C is obtained in summer. Using a reflector makes the 10-cm depth shallow solar pond useful for low heat applications and the 5-cm depth useful for moderate heat applications in most of the winter. Using a double cover top glazing is found to have no effect on improving the system performance.     

Performance of Shallow Solar Ponds

This investigation is devoted to study the performance of a shallow solar pond composed of two zones, a convective zone and a non-convective zone. Finite difference techniques and a comprehensive iterative procedure were employed to solve the realistic transient energy equations subjected to temperature dependent heat transfer coefficients. Actual solar insolation, wind speed, and ambient temperature were used to evaluate the performance of this shallow solar pond at various time intervals for Alexandria all the year round. Lastly, the effect of varying the percentage of the non-convective zone was also investigated under various environmental and operating conditions.