Experimental studies on a novel roof pond configuration for the cooling of buildings

A new evaporation based passive cooling technology was tested. The technology is based on the exposure of “floating” wetted cloth to the ambient air. It was compared to various other passive cooling techniques, with very favorable results. Two identical shallow ponds were constructed. One of them was covered with white cotton towels stretched on a densely perforated PVC panel supported by pieces of waterproof polystyrene keeping it just floating on the water surface. Five comparable experiments of different cooling techniques have been carried out. The results indicate that the new cooling technique performed slightly better than the pond with movable insulation, which is widely considered as one of the best roof cooling techniques based on evaporation. It seems that the higher efficiency of the tested technique is due to the thermal stratification created in the water inside the pond, which more effectively resists the transfer of heat gains from the sun and ambient air into the deep water of the pond. In turn, the water temperature near the floor of the pond is lower, thus heat flow from the building to the pond is increased. During the experiment, all the ponds which were compared were ranked according to performance (from best to worse): shaded pond with towels floated on it, pond with towels floated on it and pond with movable insulation, shaded open pond, open pond, covered pond.     

煤质对水煤浆气化性能的影响研究

煤质与气流床气化炉的匹配性至关重要,其不但影响气化炉的运行条件,也影响气化性能。本文选择了10种来自新疆和陕西北部的煤样进行了工业分析、元素分析、灰组成分析、灰熔点分析以及成浆性测试,并筛选出适合水煤浆气化的煤样。同时借助Aspen Plus软件对适合水煤浆气化的煤样在相同的煤浆浓度、碳转化率及操作压力条件下开展煤质对水煤浆气化性能影响的模拟分析。结果表明煤中灰含量越高,冷煤气效率和有效气含量越低,比氧耗和比煤耗越高;煤中O/C质量比和H/C质量比的增加也会导致冷煤气效率和有效气含量降低,比氧耗和比煤耗增加。因此从水煤浆气化经济性考虑,建议水煤浆气化煤质灰含量小于9.0wt%,煤中O/C质量比小于0.173,H/C质量比小于0.065。     

CFD modeling of large-scale LH2 spills in open environment

In earlier work the three-dimensional time dependent fully compressible CFD code ADREA-HF was applied against large-scale LH2 release experiments in the vicinity of buildings. In the present contribution the ADREA-HF code is applied to simulate large-scale LH2 spill tests in open, unobstructed environment. A series of simulations were performed to investigate on the effects of the source model (jet or pool), the modeling of the earthen sides of the pond around the source and the inclusion of a contact ground heat transfer. The predicted hydrogen concentrations (by vol.) are compared against the experimental at the available sensor locations. In addition the predicted structure of the concentration field is compared against the experimental, which was originally derived from temperature measurements. Modeling the source as a two-phase jet pointing downwards, including the modeling of the earthen sides of the pond as a fence and the contact heat transfer to the ground gave the best agreement with respect to experimental behavior.     

Modelling of two phase solid-liquid flow in horizontal pipe using computational fluid dynamics technique

In this paper three-dimensional fluid flow characteristics of slurry pipeline has been studied using commercial Computational Fluid Dynamics (CFD) code FLUENT at different velocities and solid concentrations. An Euler-Lagrange multiphase approach was used to simulate the flow of bottom ash slurry in a 50 mm diameter straight pipeline. Simulations were carried out with bottom ash at velocity range of 1–3 ms^–1. The solid concentration of bottom ash particles was varied from 40 to 60% (by weight). The simulations were carried out using SST k-ω turbulence model and the results obtained were compared with experimental results. It was found that the SST k-ω turbulence model shows good agreement with experimental data. Numerical simulation results show that the pressure drop in pipeline increases non-linearly with increase in velocity and solid concentration.     

Assessment of Mixture and Eulerian Multiphase Models in Predicting the Thermo-Fluidic Transport Characteristics for Fly Ash-Water Slurry Flow in Straight Horizontal Pipeline

The thermo-fluidic transport characteristics of the fly ash–water slurry flow in a straight horizontal pipe are predicted by deploying two different multiphase modeling strategies, viz. the mixture and the Eulerian multiphase models. Comparisons between the two model predictions in terms of the pressure drop and heat transfer coefficient are done along with the comparisons between the single (water) and the two phase system (slurry). Spherical fly ash particles, with diameter of 13 µm for an average inflow velocity ranging from 1 to 5 m/s and particle concentrations within 0–40% by volume for each velocity are considered as the dispersed phase carried by the carrier phase water. Significant differences between the two model predictions can be observed both from the qualitative and quantitative perspectives. This finally leads to the appropriate choice of the multiphase model for predicting the thermo-fluidic transport characteristics in slurry flow.     

石门电厂灰场土工布反滤试验及渗流场计算

通过对土工布垂直渗透试验和反滤试验，了解不同规格的土工布在垂向水流作用下的渗透性，并判断土工布作为粉煤灰滤层时是否会产生淤堵。为进一步优化坝型，保证灰场的安全、经济运行、节约投资，利用有限元方法计算灰坝二维渗流场，并对结果进行分析，确定最优灰坝的筑坝方案。     

Study of an indian biogas plant with a water pond

To overcome the problem of reduced biogas production, due to low ambient temperatures during the winter months of northern India, a novel concept of a shallow solar pond (SSP) water heater has been put forward and studied theoretically. The pond is proposed to be integrated with the dome of the conventional Indian (KVIC) biogas design. The results of the study show that system is capable of providing hot water upto a temperature of 40°C which, in turn, can be used for hot charging of the slurry besides reducing the heat losses from slurry to the ambient. Simultaneously, it helps in enhancing the slurry temperature from 20°C to 27°C.     

水煤浆燃烧飞灰含碳量的影响因素及控制

水煤浆是一种很有市场潜力的清洁燃料,控制飞灰含碳量是非常重要的。本文通过对茂名热电厂25℃炉燃烧水煤浆试验,针对飞灰含碳量大小影响因素进行分析,具体从水煤浆燃料的浓度、雾化状况、燃料特性、燃烧方式、锅炉负荷、空气过量系数等方面进行分析。     

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.     

相变微胶囊悬浮液传热特性实验研究

相变微胶囊(microencapsulated phase change material,MPCM)在建筑节能领域应用广泛,为研究其传热特性,搭建了以水为换热流体(heat transfer fluid,HTF),微胶囊悬浮液为储能介质的潜热储能(latent thermal energy storage,LTES)系统。在实验过程中,通过改变换热流体的进口初始温度以及搅拌器的搅拌速率,获得了MPCM悬浮液的温度变化规律并计算了MPCM悬浮液的平均充放冷速率。实验结果表明:在充冷过程中,MPCM相变时温度变化速率减缓,相变温度区间较大,而在放冷过程中,MPCM相变时温度保持恒定,相变温度区间较小;未搅拌时,MPCM悬浮液中温度梯度较大,传热能力较差;搅拌时,MPCM悬浮液混合均匀,其温度梯度很小,传热能力较强;增加搅拌器的搅拌速率及水与相变微胶囊悬浮液的温差均可以提高MPCM的充放冷速率。     

Field testing on nonsalt solar ponds

A new type of nonsalt solar pond was investigated by field testing. The roof of the solar pond was formed using a transparent double film. Three kinds of tests were carried out under the following conditions: (1) insulating pellets were packed between the layers of the transparent double film of the roof at sunset; (2) the water surface of the pond was insulated using only the two transparent films; (3) the water surface of the pond was covered by the double film with the top surface blackened on which solar energy can be collected, while pond water was circulated using a solar cell powered submerged water pump. The warm water stored in the solar pond by the above methods was utilized as a heat source for a gas engine powered heat pump used to heat a greenhouse. In this report, the results of the field tests on the above solar ponds and greenhouse heating system are discussed. Also the utility of a combination plant using a solar pond and underground borehole storage system is evaluated.Important conclusions on performance are as follows: (1) collection efficiencies of these solar ponds become 9–54% corresponding to the weather conditions and pond temperatures; (2) maximum temperature of the pond water under weather conditions at Osaka is about 80°C; (3) the solar pond can be effectively utilized for heating a greenhouse; (4) the combination plant using the solar pond and the underground storage layer can store heat of 1119 MJ m⁻² yr⁻¹.     

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.     

高含水开发后期优化补孔措施挖潜剩余油实践

阐述了通过补孔完善注采关系进行剩余油挖潜的做法。对萨北开发区近年来的补孔井效果进行了详细分析,包括对限流法压裂投产的低效井进行限流段重射补孔、通过补孔完善不同层系水驱注采关系、水驱井补孔完善聚驱单砂体注采关系等,确定了经济有效的措施类型。实践表明,通过补孔措施,灵活运用水驱低产井完善水驱不同井网、聚驱注采关系,挖潜不完善井区的剩余油,可以取得较好开发效果。     

410 t/h循环流化床锅炉煤焦混烧热力性能试验研究

在额定蒸发量为410t/h的循环流化床锅炉上进行以烟煤、石油焦混合物为燃料的锅炉热力性能试验,根据ASME锅炉性能规程计算了锅炉热效率,并对温度、汽水流量、气态污染物排放、灰渣含碳量等多个参数进行了测试,整理得到了一些规律性的结果。结果表明,锅炉以烟煤、石油焦为燃料,添加石灰石脱硫,采用尾部飞灰再循环,额定负荷下锅炉热效率可达92.8%;炉内密相区温度分布均匀;床温、分离器入口温度、排烟温度和排渣温度等各温度稳定;主蒸汽流量、给水流量、减温水流量等汽水流量波动小;气态污染物均可控制在较低水平。这对我国循环流化床锅炉燃用煤焦混合物的设计和运行工作有一定借鉴意义。     

尾矿坝中土工织物滤层反滤试验研究

土工织物作为滤层在尾矿坝排渗设施中已得到广泛应用,但由于工作条件复杂,土工织物经常发生淤堵,导致其排渗能力不足,严重影响尾矿坝的安全.为进一步认识尾矿坝中土工织物滤层的反滤特性,通过改进的梯度比试验装置,对无纺土工织物和不同孔径的有纺土工织物开展了一系列梯度比试验,对比分析了其保土性、防淤堵性和透水性.结果 表明,在满...     

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.     

Agglomeration of Makarwal coal using soybean oil as agglomerant

The study was carried out for beneficiation of Makarwal coal using soybean oil as agglomerant. The effect of six parameters – pH, mesh size of coal particles, slurry ratio, stirring speed, soybean oil concentration, and time of agglomeration – was investigated to reduce ash and sulfur from Makarwal coal and to enhance the gross calorific value. In the cleaned product obtained after the agglomeration process, the gross calorific value was increased from 4900 to 7115 Kcal/kg. The ash of agglomerates was reduced from 30% to 7.5% and sulfur was reduced from 5.4% to 2.0% The optimum operating conditions were concentration of soybean oil 10 mL, pH 9, stirring speed 2800 rpm, mesh size 200, coal to water ratio of 15:450 (W/V), and time of agglomeration 20 min. Significant reduction in ash and sulfur showed the effectiveness for agglomeration of Makarwal coal using soybean oil as the agglomerant. The final product thus obtained may be used efficiently in various energy recovery schemes.     

隔热层和黑色吸收膜对海水制盐的影响

对采用气泡塑料隔热板和黑色吸收膜的太阳能制盐效果进行数值模拟分析，讨论了盐池在蒸发海水过程中的动态特性和卤水的深度、天气条件、风速等参数对制盐效率的影响。与传统制盐方法相比，土壤对制盐的影响变小，卤水向地表渗漏损失可以避免，蒸发效率可提高１０％。     

气力输送状态下利用高活性吸收剂的循环流化床烟气脱硫模型

利用以工业石灰、粉煤灰和添加剂制备的高活性吸收剂在循环流化床上进行了脱硫实验.通过对床内流场和温度场的分析,建立了气力输送状态下循环流化床物理模型.在此基础上,针对床内喷水增湿活化脱硫时吸收剂的三种不同物态：新鲜干燥颗粒、干燥再循环颗粒、含水颗粒,分别建立了与之对应的表面覆盖模型、气固反应模型、浆滴脱硫模型,并总结出气力输送状态下利用高活性吸收剂的循环流化床总脱硫模型.同时通过实验数据对模型进行了校核,校核结果误差在5.5%以内,较以往模型具有更高的精度.图8表1参18     

CFD modeling for slurry flow through a horizontal pipe bend at different Prandtl number

The present work shows the slurry flow characteristics of bottom ash particulates having density 2219 kg/m³ at different Prandtl number through horizontal pipe bend. The simulation is carried out by adopting Eulerian two-phase model in conjunction with RNG k-ε turbulence model using available commercial software ANSYS Fluent. The transportation of solid particulates has the settling behaviour in the slurry pipeline and that leads to the sedimentation and blockage of the pipeline resulting more power and pressure drop in the pipeline. Therefore, it is important to know the transport capability of the solid particulates at different Prandtl fluids to minimise the pressure loss. The fluid properties at four Prandtl numbers i.e., 1.34, 2.14, 3.42 and 5.83 are used to carry the bottom ash concentration ranging from 40 to 60% (by weight) at mean flow-velocity ranging from 1 to 5 ms^?1. The obtained computational results for pressure drop are validated with the published data in the literature and found in good agreement. The findings show that the pressure drop rises with escalation in flow velocity and Prandtl number for chosen efflux concentration range. The bottom ash particulates flowing at higher Prandtl fluid experiences less pressure drop through bend cross section in comparison to bottom ash particulates flowing at low Prandtl fluid. Finally, the contours of granular pressure, granular temperature and wall shear stress are predicted and discussed in details through the bend cross section to understand the complex slurry flow for chosen Prandtl numbers.