地热能道路融雪化冰过程实验研究

建立了一套小型地热能道路融雪实验系统,进行了不同工况下的融化实验.结果表明,路面融化面积比曲线可以分为3个阶段:静止期、启动期和加速期.临界融化面积比与冰雪物理特性有关.当流体加热温度和环境条件相同时,平均融化速率大小顺序为:碎冰>实冰>人工雪>自然雪.当冰雪面积和厚度相同时,融化时间快慢顺序为:自然雪>人工雪>碎冰>实冰.与提高流体加热温度相比,合理设置待融时间可以更有效地缩短融化时间.采用35～40℃的地热尾水来实现道路融雪化冰是完全可行的,且有利于能量梯级利用.     

太阳能和地表热能道路融雪化冰系统

我国北方的高速公路、城市道路、港口码头和机场等特殊混凝土路面，因降雪结冰，给道路畅通和行车安全带来了严重的影响，甚至造成道路和机场关闭，给客货运输带来不便。为了保障道路畅通和行车安全，在恶劣的气候条件下最大限度地改善道路状况，必须采取措施对混凝土路面进行融雪化冰。     

基于浅层地热能流体加热技术的机场道面融雪方案

在利用浅层地热能流体加热技术为机场道面融雪化冰时,因传统埋管方案埋深较浅难以和机场道面施工结合,且在换热时会在道面结构内引起较大的温度应力,因此该文提出一种将管道铺设于面层和基层的交界处的新型埋管方案,以提高施工便利性、减小面层混凝土中的温度应力。建立COMSOL Multiphysics三维有限元数值模型,重点比较其在传热规律和融雪性能上与传统方案的差异,并分析入口温度和流速对融雪效果的影响。结果表明,新方案可有效利用浅层地热能提高路表温度,有效传热率为85.9%,融雪效果较好;新方案温度梯度仅为传统方案的40%,温度分布更均匀,可降低温度应力而减小路表开裂的风险;提高入口温度可有效提升融雪效果,而流速对传热性能和融雪效果的影响较小。     

太阳能-地热道路融雪系统路面传热特性的数值研究

初步建立了道路融雪系统的路面传热模型,并基于典型年逐时气象数据与复合边界条件,进行了稳态传热数值模拟,分析了不同埋管深度和加热温度对道路融雪性能的影响,得到了最大和待融热负荷与降雪量、环境温度、相对湿度以及风速等因素之间的关系,可为工程设计应用提供必要的参考依据。     

道路积雪后非预热式主动过程融雪特性实验研究

针对新型道路热融雪过程,开展三种不同埋管节距道路实验。研究主动融雪过程中道路热融雪特性和路面融雪形态和传热规律,分析道路路面温度、单位面积耗热量和单位流程温差的变化规律,探索融雪过程因素影响特征,认知道路埋设盘管热流体循环融雪过程。实验研究表明:积雪和降雪的融化过程分为四个阶段,由于埋管节距的不同,密距型道路在四个阶段所需时间最少;同时,埋管节距越小,其表面无雪率越大,融雪能力越强,单位面积耗热量也越大,但单位流程温差存在一定的增长限度。     

太阳能及土壤源耦合融雪化冰系统特性研究

道路雪后结冰对道路的使用率和安全性带来极大的负面影响,因此,道路融雪受到广泛关注。采用道路融雪系统可以解决道路结冰的问题,与传统的机械清除和加入融雪剂的方式相比,应用太阳能蓄热和土壤源热泵耦合的形式进行融雪,可以节省大量的人力物力,并且起到了环保的作用。文中主要研究了道路融雪系统的融雪机理,并且在稳态模型的条件下,进行负荷计算和系统的设计。以北京市为例,进行融雪负荷的具体计算,分析了融雪负荷与气象参数和管道参数之间的关系,从而为融雪化冰系统提供了理论基础。     

气液两相流动及沸腾传热流体模化分析

基于制冷剂类物质热物性表与水和水蒸气热力性质图表,计算并比较了R12、R22、R123、R134a在相同气液密度比条件下模化水热力过程的能力;应用相似原理与量纲理论分析了流体模化方法在研究气液两相流动特性、高温高压传热过程、临界热流密度现象以及近临界和超临界传热方面的优势与方法.结果表明:制冷剂类物质具有良好的热力性质,其中R134a在相同气液密度比条件下的压力值仅约为水的1/5,而且其臭氧消耗潜能值为0,是环境友好的理想模化流体.提出并探讨了从本质上革新准则数以及基于模型探索新的模化条件和发展新的准则关系式的流体模化技术发展思路.     

HAT循环饱和器传热传质过程及相似分析

以HAT循环中饱和器为研究对象,讨论了实验研究的相似条件。在简化条件下建立了饱和器内部多相流的控制方程,并给出了相应的边界条件;对这些方程进行了无量纲化处理．根据微分方程的不变性原理,得到了饱和器实验研究中应遵循的相似准则,并对这些准则在实验中作用进行说明,指出了饱和器实验设计中应注意的主要问题。     

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。     

Heat transfer analysis of a field-scale melting experiment

Heat transfer analysis was used to evaluate conceptual models of processes associated with In Situ Vitrification (ISV). ISV is a phase-change process used to melt contaminated soil sites into more stable configurations for environmental restoration. Using data from a field-scale ISV test we develop relations that allow us to estimate the temperature of the melt voltage and amperage measurements. The calculated temperatures are in excellent agreement with measured values. A global heat balance calculation is used to account for heats several processes that occur as soil is heated up and melted during ISV. This analysis yields an efficiency of 33% for the ISV process. Most of the heat is lost from the surface of the melt, and heat transfer concepts confirm that radiative heat transfer is the dominant process.     

管内对流换热过程的热优化分析

对管内对流换热过程的温差换热和粘性摩擦引起的熵产进行了分析和优化计算 ,对换热设备和传热技术的设计和优化组织具有一定的指导意义。     

Experimental study of slab solar collection on the hydronic system of road

This paper studied the slab solar collection (SSC) process, which is one of the essential compositions of road hydronic ice-snow melting (HISM) system that stores solar energy in summer to melt ice and snow on the road in winter. Its aim is to find out the heat transfer characteristic of the SSC and heat collecting efficiency and the influence of pipe spacing and flow rate by experiment. As shown in experimental results, the average heat collecting capacity is about 150–250 W/m² in natural summer condition, while the solar radiation intensity is about 300–1000 W/m². It is shown that the increment of fluid flow results in the increment of heat collection efficiency, while the increment of pipe spacing results in the decrement of the efficiency in experiment modes. The results show that the road slab can obtain about 30% solar heat in summertime, and the solar collection can lower the pavement temperature and reduce the insolation weathering.     

Heat transfer model of slurry ice melting on external surface of helical coil

This research studies the heat transfer phenomenon of melting slurry ice on external surface of a copper helical coil. There is water flowing inside the tube coil and exchanging heat with the slurry ice. In this experiment, the coil diameters are 6.35 mm and 9.53 mm each of 4.2 m coil length. The mass flow rate of water in the helical coil is between 0.0149–0.0562 kg/s, while the inlet temperature of water is varied in the range of 23–27 °C. The slurry ice has 60% ice and 40% water by mass at the starting.     

Heat and mass transfer coefficients of falling-film absorption process

This paper deals with the method to calculate heat and mass transfer coefficients of falling film absorption process over vertical tube or plate type surface employed in absorption refrigeration system. The conventional log mean temperature/concentration difference method is criticized for lack of physical rationality, and for incorrect results from the calculation. A new method based on a simplified model is proposed and demonstrated by numerical simulations and comparison analysis.     

Heat and mass transfer during mixed convection melting of glacial ice in saline water

An analysis of laminar mixed convection melting of a vertical wall of pure water ice submerged in saline water is presented. The analysis shows that melt rates at saline water temperatures below 4^oC are still of the order of centimeters per hour.     

微细管壳式换热器传热性能分析

对微细管管壳式换热器的流动与传热性能进行了实验研究。根据实验获得的微细圆管换热器对流传热努谢尔特数准则式与流动阻力系数的准则式,分析了微细管管壳式换热器的传热流动综合性能,并与传统的管壳式换热器进行了分析对比。结果表明:微细管管壳式换热器传热流动综合传热性能是传统管壳式换热器的2到5倍,且在实验范围内随着雷诺数的增加而增加。     

Heat transfer in dusty fluid with suspended hybrid nanoparticles over a melting surface

The melting effect with the magnetic field performs a significant role in various manufacturing and industrial applications, such as welding, casting, magma-solidification, nuclear engineering, and so forth. The present study focuses on the impact of the melting effect and magnetic field with inhomogeneous heat origination and sink. The formulation of the mathematical model is done by considering fluid with hybrid nanoparticles and dust particles in two different phases. We have considered Fe₂SO₄ and Cu as nanoparticles dispersed in the base fluid water along with suspended dust particles. The set of partial differential equations is reduced by using apt similarity variables and boundary conditions to obtain ordinary differential equations. The numerical solution is approximated using MATLAB-bvp4c adopting the shooting technique. The impact of numerous pertinent physical parameters on the velocity and thermal profiles is plotted and deliberated. Furthermore, the rate of heat flow and friction factor is also tabulated and visualized through the graphs. Streamlines are also drawn to know the behavior of the fluid flow. The rise in values of M_E quickly increases the velocity of the fluid motion but declines the thermal gradient and thickness of its related boundary layer. Also, inclining values of Pr enhance the thermal profile due to the impact of melting.     

Heat transfer analysis of soil heating systems

Heat transfer from a pipe in a soil heating system has been numerically examined in this study. The Brinkman-extended Darcy equations are used to model the flow in the soil while Navier--Stokes equations are used for that above the soil. A parametric study has been performed to investigate the effects of Rayleigh number, Darcy number, and air layer thickness on the flow patterns and heat transfer rates. The results show that heat transfer increases with the Rayleigh number, but the convective strength decreases with a reduction in the Darcy number. The present results confirm the existence of a critical fluid layer thickness that leads to a minimum heat transfer from the pipe. However, the critical layer thickness is a more complicated function of Rayleigh number and Darcy number than that reported in the previous studies.