怎样确定“测定冰的熔化热”实验中水的初温

“测定冰的熔化热”是中专物理热学部分的一个重要实验,为了提高测量精度,水的初温的确定非常重要。 程川吉先生编的中专《物理实验》第二版。在“测定冰的熔化热”实验中要求水的初温比室温高10～20℃,水的质量一般为100g左     

稳态“冷源”法对冰的导热系数测量系统研究

本文基于稳态“冷源”法设计了一种实现在常温环境下测量冰的导热系数的实验装置.结果表明,该系统对冰的导热系数测量准确,重复性好,操作简单,成功率高,应用前景广阔.该研究也是大学物理实验教学中“物体导热系数的测定”实验的拓展,对促进实验教学以及冰这一物质的研究具有重要意义.     

稳态法测量冰的导热系数

基于保护热板法原型,使用干冰-乙醇和乙二醇混合浴制造不同温度稳定低温环境之间的传热代替传统的加热传热,设计了冰的导热系数测量装置,在较大的温度范围(-70～-30℃)内实现了冰的导热系数稳定可靠的测量.同时充分借助电子式温度计高效测量数据,测得了冰在不同温度下和含有不同杂质情况下的导热系数变化规律,实验结果与参考值符合较好.利用杂质对冰的导热系数的影响规律,可以按需求调节冰的导热系数.     

稳态法测量冰导热系数的实验研究

测量固体导热系数的方法有很多，但能直接应用于冰的测量方法并不多.考虑到冰的零下低温环境等问题，本实验基于稳态法，根据傅里叶导热定律对相关细节进行了设计与改进，先后研究了待测冰直径与厚度的比值、环境温度和含盐率对冰的导热系数的影响.结果表明待测冰的直径厚度比值为12时，导热系数有最佳值2.25 W/m·K,且最佳测量环境温度为-10℃;不同浓度盐水冰的导热系数相比于纯水冰显著下降，且随着含盐率的升高降幅逐渐减小.     

基于用D I S系统对晶体凝固和熔化的研究

本文采用D I S数字化信息系统对晶体的熔化与凝固实验进行了研究. 在按照初中物理教材的实验安 排, 用海波水浴加热法测量晶体的熔化曲线的基础上, 本文做了两个改进, 一是选择用水替代海波, 先让水凝固成 冰, 然后再利用空气浴法让冰在空气中自然熔化, 从而测量冰的凝固与熔化过程温度 时间曲线( 即凝固曲线和熔 化曲线) , 全程观察冰的凝固与熔化过程其温度及状态的变化; 二是采用D I S温度传感器来替代液体温度计人工测 量温度, 实时记录了冰的凝固曲线和熔化曲线. 实验结果表明, 采取上述改进后, 既提高了该实验的准确性、 可靠性 和直观性, 也增强了实验的说服力     

基于现场图像处理的输电线路覆冰测量系统

对于电力系统而言,高压输电线路及绝缘子在冬季覆冰容易造成短路、闪络等问题.已有的基于图像的输电线路覆冰厚度测量技术,需要将图像数据回传,运行适用范围小且成本较高.本文提出一种基于现场图像处理的输电线路覆冰的监测系统,并详细介绍系统组成.系统通过摄像机采集覆冰图像,传感器监测微气象信息,图像处理获得实时的线路覆冰厚度,并将覆冰厚度和微气象信息通过全球移动通信系统传输回监控中心.搭建了基于气候实验室的标定系统,对测量系统进行了标定和实验.监测系统能够实现覆冰在线监测和微气象在线监测,性能稳定重复性好.     

冰的熔解热实验中冰水质量比的探讨

冰与温水质量比对冰的熔解热实验的成败起着关键作用。文章对冰水质量比进行测量和分析,得出了冰的熔解热实验中最适合的冰水质量比的范围约为1／12-1／5。     

外推法计算冰的熔解热的理论依据及Matlab实现方案

本文基于牛顿冷却规律给出了“冰的熔解热实验”中用外推法修正温度的完整的理论依据.采用Matlab编程实现了修正温度时面积补偿的要求,将其用于数字温度计所得实验数据的处理,计算得到的熔解热值基本符合预期.通过理论分析和数值计算发现,采用外推法处理实验数据基本上不依赖于冰、水质量以及投冰时水温等实验参数的设置,而环境温度测量虽然影响散热系数的计算,但对温度的修正与熔解热的计算影响很小,因此,基于该方法的熔解热测量很适合在实验条件要求不高的物理实验教学中推广应用.     

冰的熔解热测定的实验改进

冰在熔解过程中需要吸取热能,根据热力学第一定律,将冰与水混合的过程中系统的总能量守恒。混合法测定冰的熔解热作为大学物理中一个经典实验,在大学物理实验的教学中具有重要的地位。本文从细节出发对传统实验冰的熔解热的测定进行改进,包含对量热器进行改造、改良实验数据的处理等方法,提高了实验结果的精确度,节约了实验器材的成本。最后测得的冰的熔解热的数值误差仅为标准值的0.299%,对今后我校在本实验上的教学有深远的意义。     

冰的熔解热实验装置的改进

将保温杯引入到测定冰熔解热的实验中,提高了实验装置的保温性能;利用马达和风扇自制了搅拌装置,保证了搅拌均匀性;利用单片机、传感器模块和液晶屏实现了温度数显功能,提高了实验精度.通过对比改进前后的实验装置的实验数据可知,改进后的实验装置有效地减小了实验误差.     

Experimental Investigation and Theoretical Modeling of Ice-Melting Processes

In this article, ice-melting phenomena have been investigated experimentally. The geometrical shapes studied were cylindrical and right circular truncated cones. Ice blocks were left floating on a large water container in order to be melted. The rate of melting was measured experimentally. A relation was developed for the remaining mass of the ice in respect to time, considering the turbulent boundary layer around the ice block. Based on the experimental results, this assumption is confirmed, and a relation for a heat transfer coefficient between air and ice and water and ice has been developed in a dimensionless form. Using this relation, the ice-melting process can be presented by a single dimensionless number Kazeroon (Kz). This dimensionless parameter includes all of the effective parameters in ice-melting phenomena. A relation is presented between the mass of remaining ice and the Kz number. The mass of the remaining ice is calculated using this relation and is compared with the experimental results. Eighteen cylindrical and 15 right circular truncated cones have been experimentally examined. The results of the experimental studies have, with reasonable matching, been compared with those of the developed theoretical model.     

CO2激光热熔法除冰的研究

介绍了CO2激光在高压线除冰中的实验研究情况.由于直接热融法除冰效率较低,提出了激光热融加上冰块自身重力脱落法除冰的实验方案.利用功率为35 W的CO2激光照射冰块与绝缘子的接触面,降低其粘结力以致整体脱落从而达到除冰的目的,测得除去1 kg冰需要90kJ的能量,耗时26 min.     

测量条件对掺锡氧化铟薄膜电学测量结果的影响

用van der Pauw方法测量磁控溅射制备的掺锡氧化铟(ITO)薄膜的电学性能,研究了在室温和冰水混合条件下测量电流大小对电阻率测量结果的影响;在室温条件下测量电流和磁场的大小对载流子浓度和迁移率测量结果的影响.实验结果显示,测量电流为5 mA和测量磁场为0.5 T时,测量结果最佳.     

Study of Phase Change and Supercooling in Micro-Channels by Infrared Thermography

The present work presents a fast and simple new experimental method, designed to enhance the observation and characterization of thermal phenomena at microscale. Supercooling of water was carried out in micro-channels and recorded with a high-frequency infrared camera. The method is based on the coupling of microfluidics, infrared thermography, and inverse techniques. The objective is to extract a maximum of information from the experiment to perform advanced characterization of the system. First, a thermal modeling of such a system was written, then the image processing from infrared recordings allowed estimating the thermal properties (diffusivity) and the source term (energy released by the phase change). The novelty of the approach is the ability of measuring the heat released by the phase change and using this displacement to calculate the ice front propagation velocity and thermal properties. This method is appropriate for many other applications and is mainly devoted to the characterization of fluids during phase change at microscale.     

冰浆储存与融化及流动换热特性研究现状及展望

冰浆具有良好的流动性、传输性以及传热性能,在电力削峰填谷上有着很大的应用前景。文中主要对冰浆制取方式的优劣性进行对比,着重介绍了国内外冰浆储存与融化的研究进展,对冰浆流动换热的动态特性进行分析,并根据研究现状对下一步研究工作进行了展望。     

Modeling of Ice-Water Phase Change in Horizontal Annulus Using Modified Enthalpy Method

Phase change in ice-water systems in the geometry of horizontal cylindrical annulus with constant inner wall temperature and adiabatic outer wall is modeled with an enthalpy-based mixture model. Solidification and melting phenomena under different temperature conditions are analyzed through a sequence of numerical calculations. In the case of freezing of water, the importance of convection and conduction as well as the influence of cold pipe temperature on time for the complete solidification is examined. As for the case of melting of ice, the influence of the inner pipe wall temperature on the shape of the ice-water interface, the flow and temperature fields in the liquid, the heat transfer coefficients and the rate of melting are analyzed. The results of numerical calculations point to good qualitative agreement with the available experimental and other numerical results.     

分离式螺旋热管管外融冰放冷特性分析

在提出分离式螺旋热管蓄冷空调系统的基础上,建立了螺旋热管管外融冰放冷过程的理论模型;分析了蓄冷桶内融冰量及放冷量随时间的变化关系。研究结果表明,在蓄冷桶进口水温一定的情况下,外融冰的循环水流量越大,其融冰放冷过程就越快;在外融冰循环水流量一定的情况下,放冷过程随蓄冷桶进口水温的升高而加快。     

Liquid-liquid critical point in heavy water

According to the liquid-liquid critical-point hypothesis about water, two liquid waters exist at low temperatures and are supposed to be merged at a critical point. The low-temperature metastable melting curves of D2O ices have been measured. It is found that the melting curve of D2O ice III is smoothly curved around 25 MPa and 238 K, whereas the melting curve of D2O ice IV undergoes an abrupt change of slope at 100 MPa and 220 K. This is consistent with the existence of a liquid-liquid critical point in the region between the melting curve of D2O ice III and the melting curve of D2O ice IV.     

Experimental Investigations on Latent Heat Storage Unit using Paraffin Wax as Phase Change Material

Thermal performance of a latent heat storage unit is evaluated experimentally. The latent heat thermal energy storage system analyzed in this work is a shell-and-tube type of heat exchanger using paraffin wax (melting point between 58°C and 60°C) as the phase change material. The temperature distribution in the phase change material is measured with time. The influence of mass flow rate and inlet temperature of the heat transfer fluid on heat fraction is examined for both the melting and solidification processes. The mass flow rate of heat transfer fluid (water) is varied in the range of 0.0167 kg/s to 0.0833 kg/s (1 kg/min to 5 kg/min), and the fluid inlet temperature is varied between 75°C and 85°C. The experimental results indicate that the total melting time of the phase change material increases as the mass flow rate and inlet temperature of heat transfer fluid decrease. The fluid inlet temperature influences the heat fraction considerably as compared to the mass flow rate of heat transfer fluid during the melting process of the phase change material.     

Formation of circular rings on the snow-covered ice field of Lake Baikal

Satellite images taken from the ice surface of Lake Baikal show dark rings 7–8 km in diameter. Physically, this phenomenon can be explained by the emission of warm natural gas from the sedimentary thickness on the Lake Baikal bed. When the natural gas ascends toward the surface, it cools down but has time to heat ambient cold water. This gives rise to toroidal convection around the site of natural gas emission in the water column. Convection carries the warmed water to the surface (to the lower surface of ice) clear of the natural gas column. The heat reaches the upper surface of ice by means of heat conduction, where snow starts intensely melting. As a result, a thaw hole in the form of a ring arises on the snow-covered ice.