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141.
Mohamed I. Hassan Pawan K. Singh Waka Tesfai Youssef Shatilla 《International Journal of Green Energy》2015,12(3):225-229
Heat pipe cooling is widely used in computer processors. Advances in microprocessor technology have resulted in reduced heat transfer surface area. Maintaining an efficient cooling process is therefore challenging. The main goal of this experimental study is to perform a parametric study on heat pipe performance using nanofluids. Nanofluids of 1 and 3 vol% of alumina nanoparticles of 20–50 nm diameters in deionized water versus deionized water as a base fluid were considered in the present study. The nanofluids are prepared in our laboratory using two-step method. The nanofluids thermal properties are measured to confirm the properties enhancement that could indicate a corresponding performance enhancement of the heat pipe. A 10 mm inner diameter, 200 mm long brass tube with 50 mm long evaporator, and 50 mm long water cooled condenser were used. Heat pipe wall temperature is reduced with nanofluids as is the temperature difference between the evaporator and condenser. The thermal diffusivity of the nanofluids is increased by 10%. The pipe pressure in case of deionized water was higher than the corresponding one for the nanofluids by 20–32%. 相似文献
142.
143.
Ashutosh Mittal Tarun Kataria Gautam K. Das 《International Journal of Green Energy》2013,10(4):347-368
Evaporative cooling of water in a small porous clay vessel was studied under controlled humidity conditions. In steady-state experiments performed at an ambient temperature of 23 °C, the cooling effect increased from 4.7 to 8.3 °C as the ambient relative humidity decreased from 60 to 15%. External heat and mass transfer coefficients, estimated from the steady-state measurements, were used in mathematical models to predict the experimentally observed transient temperature variation of the water under ramp changes of the ambient relative humidity. With a prototypical cool chamber containing water tested in Kolkata, India under an ambient temperature of 34.5–35 °C, the cooling effect reached a maximum of 7 °C between 3 and 3:30 PM and then declined to 4.5 °C around 6 PM. 相似文献
144.
《International Journal of Green Energy》2013,10(1):65-77
Abstract Heating and air-conditioning systems have very low exergetic efficiency as they dissipate primary energy resources at low temperatures usually between 90 and 60°C. This compounds the problem that buildings spend approximately 30% of all the energy consumed in the U.S. for heating and air-conditioning. The overall result is a large entropy production and long-term environmental degradation that can be resolved only by substituting primary energy resources by low-temperature, waste, or alternative energy resources, usually available below 50°C. For such a replacement to be feasible the environmental cost of exergy production must be factored into calculations and compatible HVAC systems must be developed without any need for temperature peaking or equipment oversizing. This article addresses environmental and often-conflicting problems associated with exergy production by HVAC systems and presents an analytical optimization and control algorithm. Results indicate that when a careful design optimization is accompanied by a dynamic control of the split between radiant and convective means of satisfying thermal HVAC loads, exergy efficient sustainable buildings may be cost effective and environmentally benign. 相似文献
145.
棉花阴燃和明火燃烧特性的对比研究 总被引:1,自引:0,他引:1
利用锥形量热仪,选取不同辐射强度,分别在使用和不使用点火器条件下,对棉花进行了热辐射引燃实验,发现在热辐射强度大于6kW/m2的情况下,使用点火器时棉花发生明火燃烧,不使用点火器时棉花发生阴燃燃烧。实验分别测得了在两种燃烧形式下的引燃时间、热释放速率、质量损失速率一氧化碳生成率,结果表明:无论是发生阴燃还是明火燃烧,引燃时间均随着辐射强度的增加而减小,且引燃时间平方根的倒数与辐射强度成线性关系;热释放速率、质量损失速率的峰值和平均值均随辐射强度的增加而增加,但在同一辐射强度下,明火燃烧的峰值和均值均比阴燃燃烧时的大;明火燃烧的一氧化碳平均生成率随着辐射强度的增加而减小,阴燃燃烧的一氧化碳平均生成率随着辐射强度的增加而增加。 相似文献
146.
甲醛生产在化学工业生产中属于能耗较多的产品之一,回收甲醛生产过程中的化学反应热量不但节省大量能源,对于降低甲醛生产成本,改善生产环境都具有现实意义。 相似文献
147.
James L. Hanson Nazli Yeşiller Michael T. Onnen Wei-Lien Liu Nicolas K. Oettle Janelle A. Marinos 《Waste management (New York, N.Y.)》2013,33(10):1993-2000
A numerical modeling approach has been developed for predicting temperatures in municipal solid waste landfills. Model formulation and details of boundary conditions are described. Model performance was evaluated using field data from a landfill in Michigan, USA. The numerical approach was based on finite element analysis incorporating transient conductive heat transfer. Heat generation functions representing decomposition of wastes were empirically developed and incorporated to the formulation. Thermal properties of materials were determined using experimental testing, field observations, and data reported in literature. The boundary conditions consisted of seasonal temperature cycles at the ground surface and constant temperatures at the far-field boundary. Heat generation functions were developed sequentially using varying degrees of conceptual complexity in modeling. First a step-function was developed to represent initial (aerobic) and residual (anaerobic) conditions. Second, an exponential growth-decay function was established. Third, the function was scaled for temperature dependency. Finally, an energy-expended function was developed to simulate heat generation with waste age as a function of temperature. Results are presented and compared to field data for the temperature-dependent growth-decay functions. The formulations developed can be used for prediction of temperatures within various components of landfill systems (liner, waste mass, cover, and surrounding subgrade), determination of frost depths, and determination of heat gain due to decomposition of wastes. 相似文献
148.
掘进工作面围岩散热的有限元计算 总被引:3,自引:1,他引:3
掘进工作面的围岩散热是至今尚未解决的一个重要问题。笔者根据掘进工作面围岩温度场的特点 ,分析了移动柱坐标下的导热微分方程 ,合理地确定了温度场边界、划分了单元格 ;推导了该特定导热微分方程的变分方程 ,阐述了有限元解算的原理 ;论述了由温度场解算结果计算围岩散热量的方法。由此原理和方法 ,编制了计算机程序 ,以一个简单的实例 ,分析了掘进工作面围岩温度场及其散热的特点和规律 相似文献
149.
CuZnAl形状记忆合金在井下火灾防预系统上的应用初探 总被引:3,自引:0,他引:3
司乃潮 《中国安全科学学报》1998,(3)
应用CuZnAl形状记忆合金的感温——驱动原理,制作井下火灾防预系统装置,具有较大的实用性。探讨该系统的设计原理及方法,研究复合细化、热处理工艺对形状记忆合金的影响 相似文献
150.
一种新型的环保节能采暖系统——地源热泵空调系统 总被引:1,自引:0,他引:1
本文简介了地源热泵采暖系统的结构、技术特点及原理,以及在国内外的使用情况和应用现状,该系统设备的合理配制,安全保证问题,经济性分析,环保,节能效果。 相似文献