太阳能空气集热器吸热板结构优化及其数值模拟

文章提出了一种新型抛物线型吸热板结构的太阳能空气集热器,建立其数学模型和物理模型,运用ANSYS数值模拟软件,对不同入口流速和倾角下集热器内空气换热特性进行数值模拟。结果表明:随着流速的增加,3种吸热板集热器瞬时效率逐渐增加;随着倾角的增加,集热器瞬时效率先增加后减小,在倾角30°时最大;对比传统平板和三角波纹吸热板结构,抛物线型空气集热器具有较高的瞬时效率和较小的压损。     

平板式太阳能空气集热器流道改进的试验研究和数值模拟

对传统平板式太阳能空气集热器的流道进行了改进,把对角型进出口流道改为多进出口式流道。对改进的集热器的性能进行了试验测试。新的进出口流道消除了吸热板和空气换热不均的现象,出口温度提升明显。在相同条件下,集热器的瞬时效率增加约20%。用CFD方法对集热器内部的流场结构和传热进行的数值模拟对比表明,传统集热器内部存在流动死区,中心截面温度分布不均匀,吸热板上有局部的高温区域,改进后的集热器流场和温度场分布得较均匀。     

平板式太阳能集热器稳态热性能数值模拟研究

采用有限容积法研究了平板式太阳能集热器的稳态热性能,分析了环境温度、工质入口温度、集热管间距及集热管管径对平板式太阳能集热器热性能的影响。建立翼管式平板式太阳能集热器的物理模型,对该模型进行数值模拟,并将模拟结果与实验研究结果进行对比分析。研究结果表明:随环境温度升高,工质入口温度降低,可显著提高集热器的瞬时效率。太阳辐射强度为740 W/m2,环境风速为4 m/s时,环境温度从0℃增加到30℃时,集热器的瞬时效率从35.85%增加到82.19%;工质入口温度从50℃降低到10℃时,集热器的瞬时效率从23.24%增加到79.78%。减小集热管间距,增加集热管管径都有利于提高集热器的瞬时效率。太阳辐射强度为740 W/m2,环境风速为4 m/s时,集热管间距从180 mm减小到40 mm时,集热器瞬时效率从58.23%增加到65.78%;集热管管径从8 mm增加到20 mm时,集热器瞬时效率从59.47%增加到66.78%。该研究结果有利于对平板式太阳能集热器的设计参数进行优化设计。     

不同吸热涂层平板集热器的热性能衰减研究

为分析不同吸热涂层平板集热器的热性能衰减,以蓝膜、阳极氧化和黑铬集热器为研究对象,基于太阳集热器热性能测试平台,对集热器热性能及空晒老化性能进行测试。分别测试吸热涂层样品的吸收比和发射比,分析空晒前后平板集热器吸收比、发射比和瞬时效率的变化情况及影响因素。研究结果表明:在温度约为18℃的工况下,蓝膜集热器热性能为75.5%,黑铬为73.4%,阳极氧化为69.3%,吸热涂层的光学性能是影响平板集热器热性能的主要因素。平板集热器瞬时效率、吸收比和发射比变化情况的依存关系为Δη≈9.553Δα-1.213Δερ,该式可衡量平板集热器的热性能衰减度。通过空晒老化性能实验可知,提高平板集热器吸热涂层的抗腐蚀、抗氧化能力,可延长集热器的使用寿命。     

波纹丝网型太阳能空气集热器热性能特性研究

提出一种新型波纹丝网型太阳能空气集热器,根据集热器的传热关系,用Matlab建立数学模型,并搭建实验系统进行测试,验证模型的准确性。利用模型研究关键结构参数和运行参数对集热器热性能的影响规律。结果表明:出口温度和集热量的模拟值与实验值最大偏差分别为2.3 K和4.43%,当温度系数介于0.01~0.05时,波纹丝网型太阳能空气集热器的热效率比波纹填料型和丝网填料型集热器的热效率最大提升9.8%和18%,具有广阔的应用前景和发展潜力。     

多功能太阳能采暖集热器研究

本研究设计了一种可转换冬季与夏季功能的太阳空气集热器,该集热器的集热板为一组叶片,叶片由传动装置联接在一起,吸热板叶片可以转动,并且能够跟踪太阳能运行,最大限度吸收太阳辐射。吸热板背面涂以热反射涂层,夏季叶片翻转180,°反射红外辐射隔热降温。文章分析了影响太阳空气集热器的瞬时集热效率的各种因素,并对其热性能进行了试验。     

铝排管集热器吸收太阳能、空气能和环境能研究

对无透光和保温材料封装的新型铝排管平板集热器进行吸热特性分析,建立了吸收太阳能、空气能和环境能的数学模型,并分析了流体滞止特性对平板集热器吸收空气能的影响。进一步针对铝排管平板集热器的设计参数,通过TRNSYS软件进行仿真。在TRNSYS软件中对于影响集热器吸热性能的参数进行了单一变量分析。仿真结果显示:该平板集热器集热效率相比普通集热器大大提高。风速对空气能吸收量影响较大,风速越大,滞止温度越高,空气能吸收量越多;辐射量对太阳能吸收量影响作用明显,但对环境能吸收有减小趋势;集热面积增大和集热器整体性能提升有很大的关联作用;环境温度对环境能吸收量有很大的决定作用;入口流量对集热性能的提升存在峰值影响力,而进口温度的增加会降低集热器的集热效率。该平板集热器通过实际应用表明,其性能与仿真结果相符,且能够大大提高集热器效率。     

整体式太阳能空气集热器热性能研究

对一种新型的整体式太阳能空气集热器,根据简化的物理模型利用CFD软件对集热器内部的流场、压力场和温度场进行数值模拟分析,并与传统拼装式集热器阵列进行对比。结果表明,传统拼装式集热器阵列内部存在流动的滞留区,内部温度分布不均匀,吸热板有局部的高温区域;整体式空气集热器内部流场、压力场和温度场分布比较均匀,有明显的温度梯度,吸热板与空气能够更好的进行对流换热。因此,整体式空气集热器的热性能优于传统拼装式空气集热器阵列。     

全年用热管式真空管太阳能热水系统

BT2-Ⅱ型热管式真空管集热器是北京市太阳能研究所最新研制的高科技专利产品(专利号:9022255320)。真空管中吸热板采用国外引进的新型结构材料,在板上磁控溅射高温选择性吸收涂层,玻璃与金属封     

吸热板参数对平板太阳集热器热性能的影响

建立单层盖板平板太阳集热器的一维稳态数学模型,用Visual Basic语言编写程序模拟研究吸热板各参数对平板太阳集热器热性能的影响。在综合考虑集热器效率因子与金属消耗量的基础上,设集热器总热损失系数为变量,对铜铝复合平板太阳集热器的吸热板厚度与管间距进行了优化。研究表明,用导热系数大的铜板代替铝板的优势并不明显;吸热板厚度在0.3 mm以上增加时,平板太阳集热器热性能的提升很小;随着管间距的增加,平板太阳集热器性能下降;吸热板涂层的改进对于平板太阳集热器热性能的提高至关重要;排管内/外径、盖板透过率、涂层吸收率分别为0.0108/0.012 m、0.916、0.89时,在全年运行的平均工况下,保证集热器效率因子为0.9,优化得到吸热板厚度、管间距分别为0.25 mm、11 cm时,金属材料消耗量最小,为2.27 kg/m2。     

余热回收用热管及热管式换热器的研究

简要介绍了热管及热管式换热器的工作原理,热管式换热器在工业余热回收中的应用,以及热管式换热器运行过程中防止积灰和低温腐蚀等问题的有效措施。     

On the steady‐state modelling of a two‐stage evaporator system

We develop and validate against experimental measurements a steady‐state two‐stage flooded refrigerant evaporator model for a heat pump drying system. A prototype two‐stage heat pump dryer test facility was designed, built and instrumented to provide the required measurements for the validation of the model. Repeatability and data quality tests were conducted to evaluate the accuracy of measurements. Experimental data could be reproduced to within ±6.5 per cent of replicated air and refrigerant side measurements for the same evaporator's air inlet conditions while the discrepancy of energy balance at the air‐side and refrigerant‐side was observed to be within ±8.9 per cent. The two‐stage evaporator model predicted the air‐side total heat and latent heat transfer of the two‐stage evaporator to within (?6.3 per cent, 7.6 per cent) and (?11.5 per cent, 9.5 per cent), respectively. On the refrigerant‐side, the model enabled the calculation of the degree of superheat to within (?10.6 per cent, 1.7 per cent). The model has shown that there is significant improvement in the heat recovered from a two‐stage evaporator system compared to a single evaporator system. In addition, the model demonstrated that the improvement in total heat recovery could be as high as 40 per cent over its base‐value when the latent to total load at the two‐stage evaporator is increased. Copyright © 2001 John Wiley & Sons, Ltd.     

显热储热材料的制备及性能研究

采用水泥作为材料的胶凝剂,添加热容、热导率大的物质作为骨料来制备混凝土储热材料。研究表明:当铝酸盐水泥含量为10%时,材料的抗压、抗折强度能满足工业需求;材料的比热容随温度的升高先增大,在500℃时达到最大,后随着温度的升高反而降低;材料的热导率随着石墨粉含量的增加几乎成直线上升,当石墨含量为5%时材料的热导率大于1.7W/(m·K)。     

Quantification of the European industrial heat demand by branch and temperature level

We present the first comprehensive estimate of the final energy demand for heat in all EU28 member states for the reference year 2012, differentiated by temperature levels, comparing two different approaches. Two different calculation approaches based on different data sets yielded estimates of the total final energy demand for heat in the EU28 of 8150 PJ and 8518 PJ in 2012, respectively. Approach 1 distinguishes between three different process heat (PH) temperature levels and results in final energy demand for heat <100°C: 2077 PJ, 100–400°C: 2214 PJ and >400°C: 3859 PJ. The second approach distinguishes between low temperature space heat and hot water (<100°C: 1161 PJ) and four different PH temperature levels with a resulting energy demand of <100°C: 1027 PJ, 100–500°C: 1785 PJ, 500–1000°C: 1679 PJ and >1000°C: 2865 PJ. The high share of high‐temperature heat illustrates the limits to the potential decarbonisation of industrial thermal processes with renewable energy sources such as (non‐concentrating) solar thermal, geothermal or environmental heat. Therefore specific information on required temperature levels is of the essence. This, in turn, points out the relevance of renewable electricity and synthetic fuels based on renewable power for a significant reduction of CO₂ emissions from the industry sector in Europe. Considering current data quality, it is recommended to develop a consistent, comprehensive methodology to significantly improve the data basis on industrial heat demand. Copyright © 2015 John Wiley & Sons, Ltd.     

间歇式热处理炉传热计算与分析

建立了台车式热处理炉炉膛传热数学模型和辐射换热器工作模型,分析了换热器的传热特性（空气预热温度、壁温、传热系数）随炉况的变化。结果表明,辐射换热器的传热特性随炉子的升温及保温过程变化而波动很大,因而对炉子的热工性能产生了影响。     

Heat pump dryer Part 1: Simulation of the models

Heat pump dryer is a complex system because of the interaction of heat and mass transfer of the working fluids. Since the system cannot be completely close, ambient conditions (temperature and humidity) influence the performance of the system. To investigate the performance of the heat pump dryer thoroughly, simulation models of heat pump dryer components have been developed. The finite-difference method was employed in the simulation to examine the state of the working fluids and heat and mass transfer. The simulation of each component can be used to construct different system configurations the results of which are reported in Part 2.     

国内分离式热管概况与热环研究的小结及展望

本文对我国分离式热管技术的研究进行了简要概况,针对工程中热源在上,冷源在下及冷热源相距较远时的热量传递问题,在分析了一般分离式热管及“水回路”等技术的基础上,对一种新型分离式热管－泵或风机驱动的动力型分离式热管（简称热环）的研究进行了小结和展望。     

Field test of a novel combined system of a high-efficiency heating/cooling heat pump and a clathrate cool storage unit

The Research Laboratory of Kyushu Electric Power Co., Inc. (KEPCO) installed a novel system in March 1992 which is a combination of a super heat pump with about twice the performance of a conventional one and a compact chemical storage-type clathrate cool storage unit. A field test was implemented by integrating these units into an actual air-conditioning system. As a result of the test, system performance was determined and the effectiveness of the system was confirmed. © 1998 Scripta Technica. Heat Trans Jpn Res, 26(6): 410–418, 1997     

Heat-spreading analysis of a heat sink base embedded with a heat pipe

A simplified model predicting the heat transfer performance of a heat sink base with a high thermal conductivity was developed. Numerical analysis was performed using the commercial software FLUENT. The investigation indicates that for heat sink bases with a high effective thermal conductivity, such as the base embedded with a typical heat pipe, the entire heat sink can be modeled as a flat plate with a uniform temperature and an effective convection heat transfer coefficient. This simplified model can be used to determine the heat transfer performance of a heat sink embedded with a typical heat pipe or vapor chamber.     

Augmentation of heat transfer through passive techniques

The thermal performance of energy preservation systems is greatly improved by increasing miniaturization and boosting. These are imaginative (or Promethean) techniques to enhance heat transfer. Enhancement methods of heat transfer draw great attention in front of the industrial sector because of their ability to provide energy savings and raise the economic efficiency of thermal systems. Three techniques these methods are categorized; those are active, passive, and compound. Different types of components are used in passive methods because of the transfer/working fluid flow path to the enhancement of the heat transfer rate. In this article, the subject of the review was the passive heat transfer enhancement methods including inserts (conical strips, winglets, twisted tapes, baffles), porous materials, coil/helical/spiral tubes, rough surfaces (corrugated/ribbed surfaces), extended surfaces (fins) and nanofluids (mono and hybrid nanofluid). Recent passive heat transfer enhancement techniques are studied in this article as they are cost-effective and reliable, and also comparably passive methods do not need any extra power to promote the energy conversion systems' thermal efficiency than active methods. In the passive approaches, various components are applied to the heat transfer/working fluid flow path to improve the heat transfer rate. The passive heat transfer enhancement methods studied in this article include inserts (twisted tapes, conical strips, baffles, winglets), extended surfaces (fins), porous materials, coil/helical/spiral tubes, rough surfaces (corrugated/ribbed surfaces), and nanofluids (mono and hybrid nanofluid). From the pioneers' research work, it is clear that a lower twist ratio and lower pitch, lesser winglet angles can provide more heat transfer rate and a little bit more friction factor. In the case of nanofluids, a little bit of pumping power is enhanced. Finally, heat transfer enhancement is compared with the thermal performance factor, which is more than unity.