超低温温区热连接方式试验研究

为验证超低温温区不同热连接方式对深冷辐射源的降温影响程度,搭建了超低温温区真空热试验系统,对三种型式的热连接件的超低温导热特性进行了试验.结果表明:40K以下高纯铜与铝呈现出极好的超低温导热特性;在结构允许的前提下,可通过增大热连接件导热截面积、缩短导热路径、降低热连接件热容的方式来降低冷屏降温时间;同时可通过采用柔性...     

夏热冬冷地区能源总线系统的区域能源规划方法

本文提出一种适于夏热冬冷地区、采用能源总线进行区域能源规划的普遍方法。利用分布式变频水泵的水力解耦特性,通过冷、热线将多个冷(热)源和多个用户(楼宇)连接成能源网。在冷(热)源处采用制冷或供热设备控制总线供水温度,在用户处采用制冷机组和热泵等为用户提供冷水、热水或生活热水。该能源总线组态方式具有热力解耦能力,源和用户都可根据本地负荷变化灵活调整设备运行。本文建立了一整套水力、热力数学模型,用于规划冬季供暖且夏季供冷的区域供能场合,以实际案例说明了能源总线的区域能源规划的具体方法。结果表明:结合地源热泵、水源热泵及蒸气型溴化锂等供能设备,该方法具有良好的低品位能源利用率,在夏季和冬季的系统综合性能系数COP分别为3.85和3.17。     

Thermal behavior of a cryogenic loop heat pipe for space application

This paper discusses a prototype of cryogenic loop heat pipe (CLHP) working around 80 K with nitrogen as the coolant, developed at CEA-SBT in collaboration with the CAS/TIPC and tested in laboratory conditions. In addition to the main loop it features a pressure reduction reservoir and a secondary circuit which allow cooling down the loop from the room temperature conditions to the nitrogen liquid temperature and transferring the evaporator heat leaks and radiation heat loads towards the condenser. The general design, the instrumentation and the experimental results of the thermal response of the CLHP are presented, analyzed and discussed both in the transient phase of cooling from room temperature (i) and in stationary conditions (ii). During phase (i), even in a severe radiation environment, the secondary circuit helped to condense the fluid and was very efficient to chill the primary evaporator. During phase (ii), we studied the effects of transferred power, filling pressure and radiation heat load for two basic configurations of cold reservoir of the secondary circuit. A maximum cold power of 19 W with a corresponding limited temperature difference of 5 K was achieved across a 0.5 m distance. We evidenced the importance of the filling pressure to optimize the thermal response. A small heating power (0.1 W) applied on the shunted cold reservoir allows to maintain a constant subcooling (1 K). The CLHP behaves as a capillary pumped loop (CPL) in such a configuration, with the cold reservoir being the compensation chamber of the thermal link. The radiation heat loads may affect significantly the thermal response of the system due to boiling process of liquid and large mass transfer towards the pressure reduction reservoir.     

Cooling processes and effects of crushed rock embankment along the Qinghai–Tibet Railway in permafrost regions

Crushed rock embankment (CRE) was most prevalent embankment structure with cooling measures along the Qinghai–Tibet Railway in permafrost regions. Ground temperature dataset from embankment construction (in 2002) to 2010 at nine monitoring sites along the railway were compiled to study long term cooling processes and cooling effects of CRE. Monitoring results indicated that the heat stored in filling materials could dissipate out in two cold seasons after embankment construction. Under cooling effect of CRE, permafrost tables beneath CRE moved upwards significantly during the first three years after embankment construction and then maintain almost constant. But underlying permafrost experienced different thermal process in relative warm and cold permafrost regions. In cold regions, underlying permafrost up to 14 m in depth experienced considerable cooling trends during the first five to sixth years after embankment construction. While in warm regions, the uppermost permafrost layer warmed after upwards movement of permafrost table, and underlying deep permafrost had no obvious cooling trends with time. Finally, differences in freezing and thawing seasons of, and differences in ground thermal regimes of cold and warm permafrost regions were investigated based on ground temperature from natural borehole. Then, the different cooling effects of CRE in two regions were interpreted based on these differences.     

动态冰蓄冷在牛奶行业的节能应用

动态冰蓄冷技术在国内首次应用于牛奶加工工艺冷却过程,通过改造原有冷水机组,利用普通水制备的0℃冰浆,针对不同乳品加工冷却过程分别提供1℃的低温冷水和10℃高温冷水。这改变了牛奶行业固有的统一供低温冷水的格局,达到了能源梯级利用,节能减排的目的。系统增设一台170RT双工况螺杆式制冷机,研制相应制冰设备,蓄冰槽体积为98m3。总蓄冷量为1020RT·h,实现转移高峰电量22.29万kWh,年节约电费38.04万元,单位产品吨耗下降9.90元/吨。     

锂离子电池仿生树状通道液冷板数值优化

目的 将锂离子电池在5C放电倍率、环境温度298.15 K的工作条件下的最大温度和温差控制在适宜范围内。方法 在锂电池两侧插入带通道的仿生树状液冷板,建立电池模块液冷散热模型。首先验证液冷数值模型的准确性,然后通过正交试验设计研究分支流道角度、入口流速、分支流道宽度和液冷板厚度对冷板散热性能的影响,并通过极差分析对4种影响因素进行重要程度排序,确定最佳的参数组合。结果 经优化后,锂电池的最高温度为302.4 K、温差为3.4 K,满足设计要求,但冷却剂在流动循环过程中存在泄漏风险。结论 提出的树状液冷板满足锂电池热管理性能的要求,优化后电池模块的表面温度在安全范围内,同时电池的温度均匀性显著提高。应选择导热系数高的冷板材料,并注重冷板结构设计,防止冷却剂泄漏。     

铝带冷轧机工作辊分段冷却热辊型调控功效分析

目的研究铝带冷轧机轧辊热辊型调控功效对分段冷却流量分布的影响。方法利用ANSYS有限元软件及其APDL参数化编程语言,建立工作辊温度场和热辊型轴对称仿真模型,对轧辊温度场仿真结果和实测数据进行对比分析,对轧辊基本冷却和分段局部冷却2种模式的热辊型调控效应进行了仿真分析。结果轧辊温度场仿真模型计算结果与实测结果误差较小。热辊型调控功效分析表明,二次基本冷却模式能改善轧辊中部冷却效果,减少板边处轧辊局部冷却能有效改善板边处轧辊的温降,得到了二肋浪位置附近喷嘴对二肋浪处热辊型的调控效应系数相对比例。结论热辊型调控功效分析研究结果为二肋浪等局部板形控制的分段冷却流量的确定提供了依据。     

Storage of solar energy

A framework is presented for identifying appropriate systems for storage of electrical, mechanical, chemical, and thermal energy in solar energy supply systems. Classification categories include the nature of the supply system’s setting; the type of energy supplied ; the type of solar energy collection system used (including ‘ indirect ’ solar energy, such as wind and hydropower) ; the type of energy stored ; and some other characteristics of the storage system. A global insolation summary is used to exhibit the diversity of requirements for solar energy storage in different settings. Comments are then made on the need and opportunities for 24 hr storage of electrical energy in batteries; backup systems that use stored chemical fuel derived from solar energy; storage of intermediate temperature heat as heat of hydration of compounds such as sulfuric acid; annual storage of low temperature heat in fresh water ponds or aquifers; and annual storage of ice produced in places with cold winters. Arguments are presented for using a systems approach to the selection of solar energy storage methods appropriate for use in specific types of settings.     

Experimental investigation of startup characteristics of R290 rotary compressor under low ambient temperature heating condition

The cold and warm startup characteristics of an R290 heat pump system and its rotary compressor were experimentally investigated under a low ambient temperature heating condition. These startup characteristics included the temperatures in the compressor shell and system and the pressures in the cylinder and system. The results showed that the minimum suction gauge pressure (−48 kPa) during a cold startup was lower than that during a warm startup (155 kPa) under a low ambient temperature heating condition. In addition, the time required for the R290 heat pump system to reach a steady pressure was much longer than that of a system using R410A as the refrigerant. Compared with that of the cooling condition, smaller amounts of liquid were generated in the cylinder at the beginnings of both the cold and warm startup processes under the low ambient temperature heating condition.     

转子系统瞬态热启动过程动力学特性研究

摘 要：某型航空发动机在停车后的冷却过程中,其高压转子会产生较大的热弯曲。当再次启动时,高压转子会产生较大的热振动,进而威胁到发动机的安全运行。采用流-热-固-动力学开放式半耦合系统,对停车后不同时刻的瞬态温度场对某航空发动机高压转子系统的瞬态热启动特性的影响进行了探讨并和试验值进行了比较。结果表明,高压转子的停车时间位于65~90min时,其转子的最大振速超过了最大临界安全振速80mm/s,因此,热启动时应当尽量避开这一时间段,或者在这一时间段冷运转后再启动减小热弯曲对瞬态振动的影响。计算结果为航空发动机高压转子系统的优化设计和热弯曲故障诊断提供了理论依据。     

Thermal energy reservoir capacities for solar absorption cooling systemsCapacité des accumulateurs d'énergie thermique pour les systèmes frigorifiques à absorption solaires

It is essential to incorporate both hot and cold energy storage for a solar absorption cooling system in order to maximize the saving of conventional electrical power. The paper correlates the thermal energy storage requirements with the daily cooling demand pattern of a building. The other parameters which affect the choice of the two storage volumes are the effective sunshine hours, the chiller cooling capacity, its daily operation period and the two storage temperature differentials. The results have been obtained in a generalized manner and applied to an actual building in Kuwait.     

Comparative thermal analysis of different rotor types for a high-speed permanent-magnet electrical machine

A thermal analysis of three different rotor constructions for a high-speed permanent-magnet electrical machine is performed. The first type of rotor has a carbon-fibre sleeve for retaining the magnets against the centrifugal forces and an aluminium shield for eddy currents. The other two rotors have retaining sleeves made of different titanium alloys and do not have additional eddy-current shields. The thermal analysis of the rotor types is performed using two completely different approaches. The first implemented method is a numerical-multiphysics one that couples computational fluid dynamics equations with heat-transfer equations. For better reliability of the analysis, a traditional thermal-network method is also implemented for estimation of the temperature distribution in the examined rotors. The accuracy of the aforementioned methods is verified using experimental results for the average temperature rise of the permanent magnets. The results obtained from the implemented methods show that although the rotor with a retaining sleeve made of titanium alloy Ti?6%Al?6%V?2%Sn does not have any eddy-current shield, it fulfils the thermal constraints and can be implemented for high-speed applications.     

液化天然气(LNG)冷能用于斯特林发动机和燃气轮机的联合系统研究

利用LNG冷能具有较好的节能潜力和经济效益,通过流程的创新设计,提出了一种将LNG冷能用于燃气轮机和斯特林发动机的联合系统。基于热力学第一、第二定律,对联合系统进行热力学分析,结果表明:在环境温度35℃条件下,联合系统的输出功率为5715.48kW,热效率为31.62%,效率为43.65%;相比燃气轮机系统和直接冷却进气系统,联合系统的输出功率分别提高了7.84%和0.78%,热效率分别提高了3.16%和1.18%,效率分别提高了4.23%和1.63%。联合系统在不同环境温度下,可将燃气轮机的进气温度降低10℃左右,系统的输出功率和效率随着进气温度的降低均有所提高。     

Thermal energy reservoir capacities for solar absorption cooling systems

It is essential to incorporate both hot and cold energy storage for a solar absorption cooling system in order to maximize the saving of conventional electrical power. The paper correlates the thermal energy storage requirements with the daily cooling demand pattern of a building. The other parameters which affect the choice of the two storage volumes are the effective sunshine hours, the chiller cooling capacity, its daily operation period and the two storage temperature differentials. The results have been obtained in a generalized manner and applied to an actual building in Kuwait.     

LOCA工况下锆合金包壳的行为概述

LOCA作为反应堆运行过程中比较严重的事故,是反应堆基准设计事故;而作为确保裂变产物不泄露的第一道屏障,锆合金优异的性能对于保障LOCA工况下的核安全具有重要意义。阐述了LOCA工况下锆合金的高温氧化行为、抗热冲击性能和力学性能及显微组织等方面的内容,为反应堆用锆合金的研发提供了技术支持。     

小型风冷型装配式冷库热回收改装

现有的小型风冷型装配式冷库制冷系统一般将高温高压的制冷剂蒸汽通过冷凝器把热量排到大气中达到制冷的目的。但是这对环境造成＂热污染＂,同时也浪费了能源。本文中介绍了一项对小型风冷型装配式冷库制冷系统的改造,将压缩机产生的冷凝热有效的进行回收从而产生50～60℃的热水提供生活用水。从而达到节能环保的目的。     

Three-dimensional rail cooling analysis for a repetitively firedrailgun

A three-dimensional rail cooling analysis for fabrication and demonstration of a stand-alone, repetitive-fire, compulsator-driven 9 MJ gun system has been performed to assure that the entire rail can be maintained below its thermal limit for multiple shots. The three-dimensional rail thermal model can predict the temperature, pressure, and convective heat transfer coefficient variations of the coolant along the 10 m long copper rail. The 9 MJ projectiles are fired every 20 s for 3 min. Water cooling was used in the model for its high cooling capacity. Single liquid phase heat transfer was assumed in the cooling analysis. For multiple shots, the temperature difference between the rail and the water was enhanced due to accumulated heat in the rail. As a result, the heat removal by water increased from shot to shot. The rail temperature initially increased and finally stabilized after a number of shots     

A new viscoelastic method of calculation of low-temperature thermal stresses in asphalt layers of pavements

The paper presents a new method of calculation of thermal stresses in asphalt layers of pavements induced by cooling or heating. The method, developed by the author, is based on the analytical solution for the linear viscoelastic Burgers model extended numerically for the case of asphalt layers whose rheological parameters are strongly dependent on temperature. The coefficient of thermal expansion and Poisson’s ratio may optionally be taken either as constant or varying with temperature. Two equivalent numerical methods have been developed, named as ‘the incremental method’ and ‘the stress increase and relaxation method’. The computer program was developed for calculation of thermal stresses in several different cases of temperature impact, included constant rate cooling and heating, change of temperature and relaxation and a cycle of first cooling, relaxation and second cooling. What the most important practically, the solution for any change of temperature, modelling real winter changes in long period of time, was also developed. Several examples of calculations are presented. The results obtained with use of this method are promising and appear to be acceptable. The advantages of the new method in comparison with existing methods are that it takes fully into account the viscoelastic properties of a layer and the method is correct if the material does not meet the time–temperature superposition principle.     

Thermal and morphological skin-core effects in processing of thermoplastic composites

During thermostamping, the processing method where preconsolidated laminates are preheated in an oven and then transferred to a ‘cold’ mould for forming and solidification, the transfer from the oven to the mould as well as the initial cooling upon contact with the mould surface may cause high and/or unbalanced cooling on the two sides of a part. These conditions generate internal stresses as well as corresponding morphological features. This work focused on analysing the morphology through the thickness of a part using our process simulated laminate (psl) technique, which allows evaluation of a laminate through its thickness in relation to the processing conditions employed. Specifically, the degree of crystallinity and storage shear moduli were examined as a function of thickness for balanced and unbalanced cooled peek/AS-4 process simulated laminates. The resulting curvature for the unbalanced cooled laminates was measured in order to estimate the process-induced stress level. A methodology is in place to assess the importance of these phenomena for a variety of manufacturing processes. Thus, this study reveals through both differential scanning calorimetry and dynamic mechanical analysis that pronounced thermal and morphological ‘skin-core’ phenomena may be induced in thermoplastic composite laminates by high production rate processing techniques.     

On the character of low temperature discontinuous plastic deformation of metals

A ‘thermal model’ is proposed in order to explain the discontinuous plastic deformation observed at low temperatures. Certain trends can be observed from experimental studies of the effects of variations in coolant and strain rate on discontinuities in plastic deformation, which can be satisfactorily explained using this thermal model.