太阳能发电用高温混凝土储热材料的制备及性能研究

论述太阳能热发电储热材料的分类及太阳能热发电储热混凝土的优势,介绍太阳热发电储热混凝土高温实验过程,经过对样品力学性能和热导率做了相关测试后,对实验结果进行了分析,论证了实验室制太阳能热发电高温储热混凝土在工业实际中的可行性。     

Assessment of Thermal Properties via Nanosecond Thermoreflectance Method

Nanosecond time-domain thermoreflectance (ns-TDTR) is an all optical method of determining independently a variety of thermal parameters of both homogeneous and layered materials. Despite its relative experimental simplicity, the sensitivity of the temperature decay (measured by the transient reflectivity signal) to the relevant thermal properties has yet to be fully characterized. In principle, it is possible to simultaneously extract multiple thermal parameters from a single measurement. In practice, however, changes to several of these parameters may result in experimentally indistinguishable variations to the transient reflectivity signal. In this work, we focus on investigating thermal properties of bulk material and the contact resistance between the thin-film coating that is needed for the ns-TDTR method and the bulk substrate. To extract multiple properties from one temperature decay trace, we divide the data into temporal sub-regions known to be influenced to different degrees by each individual thermal parameter and iteratively fit with a 1-D heat conduction model to independently determine the contact resistance and cross-plane thermal conductivity.     

管道保温计算数学模型研究

采用有限差分法和焓降法相结合的方法数值模拟三维方管保温温度场,研究提高保温计算精度的途径和方法。研究结果表明：管内空气出口温度测试结果与考虑保温层热导率随温度变化及管内壁传热热阻时的数值模拟结果误差〈2．1％;保温材料热导率随温度变化和管内壁传热热阻对短管管内介质出口温度的影响可以忽略;管长〉2．35km时管内介质出口温度计算要考虑保温层热导率随温度变化;忽略保温层热导率随温度变化的管外壁散热损失误差〉11％,表明管外壁散热损失和长管管内介质出口温度计算必须考虑保温层热导率随温度变化,但可忽略管内壁综合表面传热热阻。     

高温条件下接触热阻的数值模拟与试验研究

接触热阻是衡量接触界面间传热效率的重要指标之一。利用ANSYS有限元软件对高温条件下高温合金GH4169界面间的接触热阻进行了研究。通过光学显微镜获得高温合金表面的真实形貌,并在ANSYS有限元软件中重建其表面模型,基于结构力学理论对接触界面微观结构的弹塑性变形进行模拟,以及传热学分析获得接触界面间的接触热阻值。研究了界面温度与接触压力对接触热阻的影响,同时考虑了高温条件下接触界面间辐射换热的影响,最后利用试验测试装置进行验证。结果表明：理论模拟与试验测试的结果两者之间的最大误差为12.6%,高温合金界面间的接触热阻随着界面温度和接触压力的增加而减小;接触界面温差随着界面温度的增加出现先增大后减小的趋势。     

高温熔融盐纳米固液相变复合材料研究进展

熔融盐是一种非常有前景的高温液体传热蓄热工质,在太阳能热发电、余热回收及工业热利用方面有显著的优势,但是熔融盐本身存在导热性能不高等问题。本文对纳米复合相变材料固液相变储能过程的若干最新研究进行了回顾,综述了熔融盐纳米固液相变复合材料国内外研究现状及发展趋势,最后对纳米复合相变材料固液相变储能过程的未来发展和重点研究方向进行了展望,认为主要解决纳米复合材料内熔化相变传热双温度模型的建立及求解、NC-PCM的制备工艺、金属纳米粒子的团聚性及NC-PCM蓄热器的热循环实验等方面的问题是未来研究的重点。     

工业水管锅炉对流受热面受压元件壁温的选取

提出了确定锅炉对流受热面中金属壁温的新思路、新方法.同时,验证了GB/T9222中确定金属温度的经验式是安全的.该方法可用于强度计算中的金属壁温的确定.     

Reference data sets for vertical borehole ground heat exchanger models and thermal response test analysis

Ground source heat pump systems often use vertical boreholes to exchange heat with the ground. Two areas of active research are the development of models to predict the thermal performance of vertical boreholes and improved procedures for analysis of in situ thermal conductivity tests, commonly known as thermal response tests (TRT). Both the models and analysis procedures ultimately need to be validated by comparing them to actual borehole data sets. This paper describes reference data sets for researchers to test their borehole models. The data sets are from a large laboratory “sandbox” containing a borehole with a U-tube. The tests are made under more controlled conditions than can be obtained in field tests. Thermal response tests on the borehole include temperature measurements on the borehole wall and within the surrounding soil, which are not usually available in field tests. The test data provide independent values of soil thermal conductivity and borehole thermal resistance for verifying borehole models and TRT analysis procedures. As an illustration, several borehole models are compared with one of the thermal response tests.     

A study of heat transfer in high‐performance hydrogen bell‐type annealing furnaces

The mechanisms of heat transfer in high‐performance hydrogen bell‐type annealing furnaces are discussed in this paper. It examines two important parameters, the convective heat transfer coefficient and the equivalent radial thermal conductivity, which have large effects on the overall heat transfer in the furnace. The calculated annealing curves are in good agreement with experimental data. © 2001 Scripta Technica, Heat Trans Asian Res, 30(8): 615–623, 2001     

商用太阳电池改造的光伏-光热组件传热性能分析

介绍了将传统晶体硅商用太阳电池加装水冷器,改造为光伏-光热集成组件后的结构;通过热阻分析的方法,分析了该光伏-光热组件的传热特性;并通过实验,实际测量了该光伏-光热组件的传热性能,得到了导热热阻及其有效热导率,可为组件的进一步开发提供参考。     

新型传热工质纳米流体的研究与应用

介绍了一种在强化传热领域具有广阔应用前景的新型传热（冷却）工质——纳米流体,分析了纳米流体的导热机理、导热性能以及影响其导热系数的各种因素,阐述了纳米流体对流换热性能的研究、纳米流体的制备及其稳定性和应用前景。     

地热换热器的传热模型及其分析

讨论了地源热泵的地热换热器的三种传热模型,给出了各自的解析式,并进行了比较,指明了各自的适用范围与条件,指出准三维模型能够提供更准确的数据。     

Thermal contact resistance between an element and a housing in an aluminum electrolytic capacitor

Cooling performance of an aluminum electrolytic capacitor, whose element pressed on the inner bottom surface of the capacitor housing in order to decrease thermal contact resistance between the element and the housing, was measured and improved. It was found that a thermally conductive elastomer decreases this contact resistance. The elastomer with a thickness ranging from 0.5 to 1.5 mm was inserted between the bottom surface of the capacitor element and the plain metal surface. Experimental measurements show that the contact resistance with the 0.5‐mm‐thick elastomer is smaller than that without an elastomer. A simple analysis was also developed for predicting the thermal contact resistance with different elastomer thicknesses, and these predicted resistances agree reasonably well with the experimental measurements. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(3): 268–277, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10090     

Convective‐radiative fins with simultaneous variation of thermal conductivity,heat transfer coefficient,and surface emissivity with temperature

This paper is a numerical study of thermal performance of a convective‐radiative fin with simultaneous variation of thermal conductivity, heat transfer coefficient, and surface emissivity with temperature. The convective heat transfer is assumed to be a power function of the local temperature between the fin and the ambient which allows simulation of different convection mechanisms such as natural convection (laminar and turbulent), boiling, etc. The thermal conductivity and the surface emissivity are treated as linear functions of the local temperature between the fin and the ambient which provide a satisfactory representation of the thermal property variations of most fin materials. The thermal performance is governed by seven parameters, namely, convection–conduction parameter Nc, radiation–conduction parameter Nr, thermal conductivity parameter A, emissivity parameter B, the exponent n associated with convective heat transfer coefficient, and the two temperature ratios, θ_a and θ_s, that characterize the temperatures of convection and radiation sinks. The effect of these parameters on the temperature distribution and fin heat transfer rate are illustrated and the results interpreted in physical terms. Compared with the constant properties model, the fin heat transfer rate can be underestimated or overestimated considerably depending on the values of the governing parameters. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20408     

多片平板微热管阵列运行特性

将多片平板微热管阵列进行堆叠可以提高传热量。实验研究了不同叠加片数下平板微热管阵列在不同加热功率下的热阻、传热极限、温度分布及变化规律、不同层热管传热等运行特性。实验表明,随热管片数增加,热管整体的传热量增加,最大传热量由单片的60W提升至5片的180W;传热热阻降低,最小传热热阻由单片的1.09℃/W下降为5片的0.24℃/W。而且,随着片数增加,热管间的传热热阻开始影响多片平板微热管阵列的整体运行：外侧热管的传热量高于内侧热管,热阻低于内侧热管,且当片数为4片及以上时,热管整体性能提升会越来越不明显。在相同的加热功率下,多片平板微热管阵列的外侧蒸发段、外侧冷凝段和内侧蒸发段温度均随片数增加而降低,但内侧冷凝段温度先升高后降低。最理想的热管叠加片数为3-4片。     

用于现场测量深层岩土导热系数的简化方法

为便于工程上实现应用现场测量确定实际介质的物性,采用一种简化的传热分析方法确定深层岩土导热系数。该方法不需要测量钻孔中埋管的具体位置、上升管和下降管之间的距离以及埋管和回填材料的特性等参数,可消除上述参数测量带来的误差。通过现场测量地下埋管回路的加热热流、回路循环水流量以及回路出入口水温度随时间的变化,利用简化分析和最优化估计方法,确定了某工地地下岩土的导热系数,检验证实了该方法的实用性和可靠性。     

Thermal analysis of a longitudinal fin with variable thermal properties by recursive formulation

The present study supplies a new approach to calculate thermal performance of a singular fin with variable thermal properties. With discrete model, the singular fin can be divided into many sections. Then, each section can be combined together to obtain the whole solution of the fin by recursive numerical formulation. The recursive formulas for both conditions with and without heat transfer on fin tip are derived in the present study. Finally, several examples including composite and boiling mode of a fin have been successfully simulated to demonstrate the validity of the present approach.     

Developing a temperature‐dependent Kersten function for soil thermal conductivity

This paper describes the development of the Kersten function (Ke), which depends on soil temperature and the degree of saturation. The new Kersten function enables the prediction of thermal conductivities of moist soils also including high temperatures. The eight soils used in this paper represent three distinct textural groups, each having a comparable shape of Kersten function. The soil thermal conductivity is obtained from a linear interpolation between the dryness and saturation states with the Ke as the slope. The new Kersten function is valid when the degree of saturation (S_r) is greater than 0.125 and soil temperature is between 30 and 90°C. At a lower degree of saturation (i.e. 0<S_r<0.125), a linear approximation is applied to Ke. The new Ke function gives particularly good agreement with experimental data for temperatures of 30 and 50°C and for low moisture contents at all temperatures. At higher temperatures (i.e. 70 and 90°C) and moisture contents above the permanent wilting point, generally good or acceptable results were obtained. Copyright © 2000 John Wiley & Sons, Ltd.