共查询到19条相似文献,搜索用时 140 毫秒
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磁回路参数测量方法的研究 总被引:4,自引:2,他引:2
磁回路的多项参数(电学的、几何的)之间会互相影响,利用这一特性可以有许多的应用.但在测量某一特定参数时,要想提高测量精度,就要避免其他参数对测量结果的影响.本文在进一步研究回路特性的基础上,提出一个能避开其他参数的影响从而提高测量精度的测量方法. 相似文献
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一、前言 参数估计提供了有效地利用数据去估计数学模型中的参数的方法。可如图1所示。 通常的热物性测试原理都是基于导热微分方程的一个反问题,即由一定单值性条件下的解来确定方程中的某些系数,即热物性。本文以激光脉冲法为例,说明参数估计在测量热物性中的应用具有良好的前景。 相似文献
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地源热泵地下换热系统的实验研究 总被引:1,自引:0,他引:1
地源热泵地下换热系统对于地源热泵系统的稳定运行和地源热泵系统的投入成本起着关键的作用.为了对地下换热系统换热效果和周围土壤的温度场进行实验研究,我们在北京工业大学高科技能源楼建立了一套包含60套不同结构地下换热系统的实验台.利用温度及流量测试装置获得运行过程中温度变化并计算换热量,探求不同结构地下换热系统的换热情况.本实验台还可以收集系统运行过程中地下换热系统的传热温度扩散半径,实验系统不仅为地源热泵的设计提供了数据,而且为地源热泵的深入研究提供了平台.本文给出的部分实验结果证明,根据当地地质情况、负荷需求及系统运行模式配置能源井是至关重要的. 相似文献
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A simplified heat transfer model is proposed for conveniently determining the thermal properties of deep ground soil at worksites and other associated engineering applications. The model does not need exact information of the U-tube location, spacing between up and down tubes, the properties of the tube and the backfill, and other parameters in the borehole as usual cases and greatly eliminates the errors caused by measuring the parameters mentioned. A practical site test was conducted to obtain heat flux imposed on the buried loop, water flow rate, and temperatures at the outlet and inlet of the loop by an in-situ test apparatus. The simplified model, together with optimal estimation algorithm, was used to determine the thermal conductivity of the deep ground soil in the worksite. 相似文献
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Ground source heat pump (GSHP) systems have been applied widely because of their environmental-friendly, energy-saving, and sustainable nature. In this work, heat transfer performance of a single vertical small-scale U-shaped tube ground heat exchanger under hot climatic condition is addressed considering the influences of inlet water temperature, Reynolds number, and backfill materials (raw soil; soil–polyacrylamide (PAM) blend (0.27% blending ratio for PAM). The backfill materials had an important effect on the heat transfer of the ground heat exchanger. At an inlet water temperature of 45°C and Reynolds numbers of 3104 and 4656, the temperature drops of water in the tube in the soil–PAM blend increased by about 0.3 and 0.4°C compared to that in the raw soil. Within Reynolds number from 3104 to 6208, the average surface heat transfer coefficients of the water in the tube in the soil–PAM blend and raw soil at an inlet water temperature of 45°C were 411 and 231 W m?2K?1, respectively. The results suggest that adding the PAM into soil can be an effective manner for enhancing the heat transfer of the ground heat exchanger. The dimensionless surface heat transfer correlation of the water in the U-tube heat exchanger in the soil–PAM blend was obtained. The model could better fit the experimental data within ±10% deviation. 相似文献
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Single crystals of CeS, CeSe and CeTe have been investigated by means of measurements of the specific heat, the thermal expansion, the magnetic susceptibility and the magnetization at low temperatures. Crystal-field effects on some of these properties are used to derive the crystal-field splitting of the 4f electron ground state. It is found that chemical composition and crystal perfection strongly influence the magnetic properties of these compounds. 相似文献
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Yu. V. Khrustalyov O. S. Vaulina 《Journal of Experimental and Theoretical Physics》2013,116(5):876-885
New data on heat transfer in two-dimensional Yukawa systems have been obtained. The results of a numerical study of the thermal conductivity for equilibrium systems with parameters close to the conditions of laboratory experiments in dusty plasma are presented. The Green-Kubo relations are used to calculate the heat transfer coefficients. The influence of dissipation (internal friction) on the heat transfer processes in nonideal systems is studied. New approximations are proposed for the thermal conductivity and diffusivity for nonideal dissipative systems. The results obtained are compared with the existing experimental and numerical data. 相似文献
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With the size reduction of nanoscale electronic devices, the heat generated by the unit area in integrated circuits will be increasing exponentially, and consequently the thermal management in these devices is a very important issue. In addition, the heat generated by the electronic devices mostly diffuses to the air in the form of waste heat, which makes the thermoelectric energy conversion also an important issue for nowadays. In recent years, the thermal transport properties in nanoscale systems have attracted increasing attention in both experiments and theoretical calculations. In this review, we will discuss various theoretical simulation methods for investigating thermal transport properties and take a glance at several interesting thermal transport phenomena in nanoscale systems. Our emphasizes will lie on the advantage and limitation of calculational method, and the application of nanoscale thermal transport and thermoelectric property. 相似文献
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在环路热管系统工作中,存在因补偿腔温度过高而造成的蒸发器烧干现象。在常规环路热管系统中设计了补偿腔支路,以带走热源向补偿腔传递的径向热量,并对设计的环路热管系统进行实验测试,分析补偿腔支路对环路热管传热特性的影响。实验结果表明:补偿腔支路开启后,在热流密度14 W/cm2时,系统稳定启动所需时间从4 min减少到3 min,表明系统稳定启动所需时间减小,有利于快速启动;在热流密度18 W/cm2下,对应的壁面温度从88.2℃降至85.4℃,系统热阻从0.56 K/W减小到了0.49 K/W,表明系统所能承受的最大热流密度更大,系统热阻也更低,因此系统的传热性能更好。 相似文献
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The sorption heat pipe (SHP) is a new heat transfer device, which can be used as a sorption cooler or as a heat pipe. The SHP has a sorbent bed (adsorber/desorber and evaporator) at one end and a condenser+evaporator at the other end. This device is insensitive to some “g” acceleration and could be suggested for space and ground application. The most crucial feature of this device is that in different cases it can be used, for example, as a loop heat pipe, because they have the same evaporator and condenser, or as a SHP. The SHP can be used also as a cryogenic cooler. The SHP is convenient for cryogenic fluid storage, when the system does not work at low pressure and room temperature, and for use in the active cryogenic thermal control systems of spacecraft in orbit (cold plates for infrared observation of the Earth or space), or as an efficient electronic component cooling device. 相似文献