A comparative study on thermo-economic performance between subcritical and transcritical Organic Rankine Cycles under different heat source temperatures

In this paper, the net power output, exergy efficiency and levelized energy cost of system were selected as performance indicators for assessing Organic Rankine Cycle （ORC）. Firstly, the turbine inlet temperature and pressure meeting the requirement of pinch point temperature difference of evaporator in transcritical ORC （trans-ORC） were determined based on performance opti- mization. Subsequently, the thermo-economic performance of a subcritical ORC （sub-ORC） using R601 as working fluid and a trans-ORC using R134a as working fluid were compared under different heat source temperatures and a fixed outlet temperature of flue gas. Results show that for trans-ORC, when the pinch point temperature difference of evaporator lies between the inlet and outlet of evaporator, a lower inlet pressure of turbine is favorable; when the pinch point temperature difference of evaporator is located at the outlet of evaporator, there exists an optimal inlet pressure of turbine. Either for sub-ORC or trans-ORC, the net power output increases and levelized energy cost decreases with the increase in heat source temperature. For sub-ORC, exergy efficiency of system increases monotonously with heat source temperature, while for trans-ORC, exergy efficiency of system grows up firstly and then reduces （or keeps constant） with the increasing of heat source tem- perature. Moreover, for net power output and exergy efficiency of system, there exist a range of heat source temperatures making trans-ORC better than sub-ORC, and the heat source temperature region extends with the increase in pinch point temperature difference of evapo- rator. For levelized energy cost of system, the sub-ORC is always superior to trans-ORC.     

基于热传导设计的LED器件散热研究

大功率LED(Light Emitting Diode)散热技术已成为半导体照明产业发展的一项关键技术。本文设计了一种含热导管的LED散热器,分析了工作原理和结构特点。利用热电类比的方法对该散热器的热阻进行了详细的分析,并且推出了散热器总传热系数的方程式,最后通过实验测试了散热器各特征点的温度,验证了该散热结构设计的可行性与正确性。     

热处理炉助燃风机变频自动控制节能研究与应用

本文主要对风机变频控制节能进行分析,并通过修改PLC程序及优化变频器参数,利用较为先进的模糊PID控制技术,实现助燃风机压力和流量自动控制.     

LBE–DEM simulation of inter-phase heat transfer in gas–solid cross jets

Lattice-Boltzmann equation(LBE)–Discrete element method(DEM)coupled simulation of a twodimensional gas–solid cross jet is performed,focusing on the gas-particle two-way coupling effect on heat transfer characteristics.The Reynolds number is 1000,and particle Stokes numbers are 10,25,and 50 under the same number flow rate of particles.The gas phase temperature field and particle distribution as well as the inter-phase heat transfer characteristics are studied and analyzed.The dominating effects,i.e.the mean temperature difference and mean heat transfer coefficient between the gas–solid phases,for the pre-and post-collision stages of the cross jets are illustrated respectively.The change of dominating roles is related to the dynamical response characteristics of particles.     

泌尿外科本科实习中的微创教学体会

随着医疗技术的进步,泌尿外科已经入微创时代。为适应时代的发展,我们改进了实习教学方案。通过结合微创手术系统的复习解剖、强化膀胱镜训练、观摩和讨论经典手术录像、规范化的模拟器训练、积极参与临床手术等措施,取得了满意的教学效果。     

微生物活细胞固定化技术在硝铵炸药废水处理中的应用

本研究采用驯化后的生长在醛化维纶软性填料上的自然菌以接触氧化法对硝铵炸药废水进行生化处理。处理后,毒物TNT去除率达90%以上,COD去除率达80%以上。工艺流程简单,费用较低,为硝铵炸药废水的处理提供了实用的方法。     

予估——校正法在相变导热求解中的应用

本文将予估——校正法应用于焓法方程的异步迭代求解,减少了迭代次数,加速了收敛。数值实例就计算精度和计算时间进行了比较。最后就一食品冷冻问题进行了计算,并与实验进行了对比。     

热学教材中的一处谬误及其纠正

本文指出了现行热学教材上对“理想气体定律的推证”一节内容中的逻辑循环问题;探讨了由此产生的热学教学过程中的危机;同时又举出了另一种简便的推证法,并论证了该推证法不存在,也不隐含逻辑循环。用它替代后,能避免危机的出现。     

热胁迫下不结球白菜耐热感热品种超微结构的差异

通过透射电镜方法，研究不结球白菜的耐热品种和感热品种在自然高温胁迫下（３８—３９℃）叶片细胞超微结构的差异，结果表明：耐热品种叶肉细胞结构受高温胁迫后变化较小，细胞结构基本保持完好；感热品种受热伤害程度较为严重，细胞中的膜结构受到不同程度损伤。特别是叶绿体结构变化较大，包括叶绿体变形，类囊体膨大，排列紊乱，被膜模糊不清，叶绿体内脂质球数目增多且体积大；核糖体呈凝集状态；细胞壁出现降解现象，壁周围出现散乱的纤维细丝；胞间连丝有断裂现象；细胞核膜膨大、断裂，核仁消失。     

Heat balance modelling

The only way to describe the effects of the thermal environment on the human body completely is to do it by means of an energy balance equation. In such an equation all relevant meteorological parameters, behavioral characteristics (activity and clothing) and body measurements can be considered. Using Fanger's comfort equation and the models MEMI and IMEM as examples, the problems of energy balancing and ways of solving them are described. The value of energy balance models is documented by examples from the field of application.