二元混合氯化盐的配制及热物性研究

在太阳能热发电技术中,硝酸盐类相变材料是使用最多的一种相变材料,但其最高使用温度仅为600 ℃,因此找到一种热容量大、工作温度范围宽、热损失低、价格便宜的相变储热材料是目前的研究重点。选取氯化锂和氯化钠两种高温熔盐相变材料按照不同的质量比混合制备了9种二元熔盐混合物,利用差式扫描量热仪（DSC）对其在600 ℃范围内的相变温度和相变潜热进行了研究。实验结果显示：由于氯化钠的熔点较高,当氯化锂和氯化钠的二元混合物中氯化钠的含量较多时,即氯化锂的含量较少时,少量的氯化锂不能将混合物的熔点降低至600 ℃以下,混合材料无法熔化;当氯化钠和氯化锂发生熔融时,无论何种比例其相变温度均保持在540 ℃左右,浮动±15 ℃;以质量配比为90%氯化锂-10%氯化钠的二元混合物的熔融温度与结晶温度相差较大,所以该二元混合熔盐可以应用于太阳能发电的传热和蓄热技术中。     

Performance of a solar air composite heat source heat pump system

For the shortcoming of air source heat pump in heating condition, a composite heat exchanger was designed which integrates fin tube and tube heat exchanger, and it can achieve synchronous and composite heat exchange in one heat exchanger between working fluids, gaseous and liquid heat source. With the above composite heat exchanger as the core component, the Solar Air Composite Heat Source Heat Pump System (SACHP) was developed which has three working modes, including single solar heat source mode, single air heat source mode and solar air dual heat sources mode. A SACHP experiment table was established and conducted a comprehensive experimental study of three working modes of this system in the standard enthalpy difference laboratory. The results show that when the ambient temperature was −15 °C, compared to the single air heat source mode, the dual heat source mode increased 62% in heat capacity and 59% in COP; when the temperature difference of combined heat transfer was 5 °C, compared to the single air heat source mode, the dual heat source mode increased 51% in heat capacity and 49% in COP. Experimental results demonstrate that the application of the solar air composite heat pump technology can accelerate the application process of the solar heat pump in air conditioners for buildings.     

The EU internal electricity market: Done forever?

Taking a quarter-century to build Europe's internal market for electricity may seem an incredibly long journey. The aim of achieving a European-wide market might be reached, but we went through – and should continue to go through – a process subject to many adverse dynamics. The EU internal market may derail greatly in the coming years from the effects of a massive push for renewables, as well as a growing decentralization of the production–consumption loop. Moreover, a serious concern is the risk of a definitive fragmentation of the European electricity market due to uncoordinated national moves with respect to renewable support and capacity mechanisms.     

癸酸—月桂酸二元复合相变储能材料循环热稳定性

以研究癸酸—月桂酸二元复合相变储能材料在循环相变过程中的热稳定性为目的,搭建了实现相变材料加速热循环过程的实验平台,并利用差示扫描量热仪(DSC)测定了经过0,800,1 600,2 400,3 200,4 000次加速热循环后相变材料的相变温度和相变潜热。经过4 000次循环后,相变温度下降了0.8℃,相变潜热降低为初始值的92.08%。结果表明:随着循环次数的增加,该相变材料的相变温度变化微小,相变潜热有所降低,其热稳定性比较好。基于实验结果,讨论了此种相变材料在太阳能及建筑节能领域的应用前景。     

Orientation effect on heat transfer of a shrouded LED backlight panel with a plate-fin array

This study reports thermal performance of a shrouded 348 mm × 558 mm aluminum plate-fin heat sink subject to various input powers and orientations. Effects of clearance (C) and the orientation on the heat transfer of the heat sink were investigated. Results show that the clearance effect is detectable only in a “window region” between 5 mm and 10 mm where an appreciable rise of heat transfer coefficient is encountered. As the tilted angle (θ) of the LED panel is increased, the heat transfer coefficient is reduced and the clearance effect on heat transfer becomes more pronounced. The heat transfer coefficients are similar between two cases in which the tilted angles of the LED panel are supplementary irrespective of clearance and input power. Except the cases of a horizontal heat sink, heat transfer coefficient of the shrouded heat sink having a fin array facing downward is usually slightly higher than that having supplementary tilted angle.     

纵向通风下隧道速度场及温度场的模拟研究

在隧道火灾研究中,将临界速度作为衡量纵向通风效率的标准已被广泛认可.然而,对于排烟口位于火源两侧,两端都是进风口的情况,临界速度并不能有效地衡量通风效率.对此,研究人员提出了“限制性速度”的概念,并将其作为标准,但到目前为止,对于限制性速度的研究依然很少.本文中的CFD模型以0.Vauquelin的实验为基础,通过CF...     

Thermodynamic evaluation and optimization of LiNO3–KNO3–NaNO3 ternary system

The phase diagram of LiNO₃–KNO₃ system was investigated with differential scanning calorimetry. Phase transitions data of LiNO₃–KNO₃ system were obtained. Using the measured phase equilibrium data as well as other available phase equilibrium and thermodynamic data in literature, the thermodynamic optimization of parameters for all phases and compounds in the LiNO₃–NaNO₃–KNO₃ system was performed. The Modified Quasichemical Model was applied for the liquid phase, and Compound Energy Formalism was used for the NaNO₃–KNO₃ solid solutions. The compound KNO₃·LiNO₃ was treated with Neumann-Kopp rule. The optimized parameters were used to predict the phase diagram of LiNO₃–NaNO₃–KNO₃ ternary system and the predicted ternary invariant points were experimentally verified.     

相变材料蓄能式吊顶辐射供冷系统热性能模拟研究

本文将单位体积蓄能密度较大的相变材料与毛细管网格栅埋入到建筑吊顶中,设计出了一种相变材料蓄能式吊顶辐射供冷末端形式,建立了分析该吊顶在间歇运行工况下热性能的数学模型,利用该模型可以分析不同相变材料物性对该相变材料蓄能式吊顶的表面平均热流密度和蓄能比的影响。通过对影响因素的敏感性分析,得出了影响吊顶热性能的主要因素。此外,对比分析了相变材料蓄能式吊顶与混凝土蓄能式吊顶热性能的差异,指出相变材料蓄能式吊顶辐射供冷方式具有蓄能比更高的特点。     

Energy and Power Engineering,Environmental Engineering,and Mining Engineering Building dynamic thermal simulation of low-order multi-dimensional heat transfer简

Multi-dimensional heat transfers modeling is crucial for building simulations of insulated buildings, which are widely used and have multi-dimensional heat transfers characteristics. For this work, state-model-reduction techniques were used to develop a reduced low-order model of multi-dimensional heat transfers. With hot box experiment of hollow block wall, heat flow relative errors between experiment and low-order model predication were less than 8% and the largest errors were less than 3%. Also, frequency responses of five typical walls, each with different thermal masses or insulation modes, the low-order model and the complete model showed that the low-order model results agree very well in the lower excitation frequency band with deviations appearing only at high frequency. Furthermore, low-order model was used on intersection thermal bridge of a floor slab and exterior wall. Results show that errors between the two models are very small. This low-order model could be coupled with most existing simulation software for different thermal mass envelope analyses to make up for differences between the multi-dimensional and one-dimensional models, simultaneously simplifying simulation calculations.     

Experiment investigation on visualization and operating characteristics of closed loop plate oscillating heat pipe with parallel channels

Using ethanol or acetone as the working fluid, visualization of oscillations in steady state was observed visually by high-speed cameras, and temperature oscillating and heat transfer characteristics of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying liquid filled ratios(50%, 70%, 85%), section scales(1 mm×1 mm and 1 mm×1.5 mm), inclination angles, working fluids and heating inputs. It was found that during operating there was mixed flow consisting of plug flow and annular flow in channels of oscillating heat pipe at steady-state. There was an equilibrium position for working fluid of condenser during oscillating, and periodic oscillations occurred up and down in the vicinity of equilibrium position. With heat input increasing, equilibrium position rose slowly as a result of vapor pressure of evaporation.Evaporation temperature oscillating amplitude possessed a trend of small-large-small and frequency trend was of small-large during steady-state. It may be generally concluded that temperature, whether evaporator or condenser, fluctuated sharply or rose continuously when oscillating heat pipe coming to dry burning state. Simultaneously, it was found that temperature difference of cooling water possibly dropped with heat input rising during dry burning state. Thermal resistance of No. 2 with acetone was lower than that of No. 1 during experiments, but No. 2 achieving heat transfer limit was earlier than No. 1. However, with ethanol, thermal resistance of No. 1 and No. 2 were similar with the heating input less than 110-120 W and filling ratios of 50% and 70%. And with filling ratio of 85%, heating transfer performance of No. 2 was better compared to No. 1 during all the experiments.