大型空分装置换热器冷箱管道布置论述

介绍了空分装置换热器冷箱设备布置及管道布置的基本要点。首先介绍了换热器冷箱的工作原理和结构,然后分析了正确且优化的管道布置对冷箱的安全运行、成本控制的重要性;最后详细介绍了换热器冷箱管道布置的设计方法和原则。     

冷氦换热器数值建模及性能仿真研究

采用基于集总参数法的AMESim仿真软件对某型号运载火箭冷氦换热器进行建模,模型考虑了管外的高温燃气凝结换热、管内的强制对流换热及换热管沿轴向、径向的导热。在此基础上,开展了冷氦换热器的单元无关性分析、换热器性能仿真及参数影响性分析。仿真模型有效性通过搭载发动机地面试车试验数据进行验证。计算结果表明:仿真模型能较好地模拟冷氦换热器的性能,且随着冷氦进口温度升高,出口温度也基本线性递增;随着冷氦流量增大,出口温度逐渐降低,而工作压力对换热器性能影响较小。     

杭钢6500m~3/h空分设备冷箱跑冷原因分析及处理

杭钢6500 m3/h空分设备在运行8年后出现了冷箱跑冷结冰现象,采取临时措施后,空分设备又维持运行了4年。随着冷箱跑冷结冰和冷箱钢板的裂纹面积越来越大,空分设备无法维持正常运行,对空分设备进行了扒砂检修处理。介绍冷箱跑冷的现象和危害以及采取的临时措施,分析跑冷原因,阐述扒砂检修过程和从中获得的经验、体会。     

空分设备冷箱内配管优化设计

随着空分设备向大型化、多样化发展,冷箱内部管道不断增多,配管难度也越来越高。对冷箱内配管进行优化设计,以提高空分设备运行的安全性和经济性。文章从单元设备、阀门及冷箱板开孔位置布置,与单元设备相连管道布置,换热器热端管道布置,水平管道敷设和排放管道引出方式等10方面,介绍杭氧对冷箱内配管所做的优化设计,旨在提高空分设备的经济性和运行安全性。     

LNG工程用大截面高压板翅式换热器的技术发展与现状

随着国内外LNG工业的高速发展,对铝制板翅式换热器提出了新的要求,以往小截面、多只并/串连的板翅式换热器组合方案已不能满足大、中型液化天然气工业发展的需要。大截面高压板翅式换热器的换热单元个数少,承压能力高,能够尽量减少气流分配的不均性。大截面高压板翅式换热器的应用,也使得LNG冷箱内管道布置简单,安全性、可靠性大大提高,冷箱体积减小,满足了液化天然气工业发展的需要,也降低了用户投资成本。简介板翅式换热器的技术发展与现状,阐述大截面高压板翅式换热器的热力设计与结构优化。     

冷箱内管道支架在珠光砂影响下的荷载设计

空分设备冷箱内管道荷载大部分由塔器承受,合理设计管道支架荷载对容器选择经济的壁厚及空分设备安全运行有较大影响。冷箱内的管道除了自重外,荷载受保温材料珠光砂的影响较大,通过力的平衡分析,介绍了冷箱中管道荷载在珠光砂影响下的计算方法。     

中温热管换热器内传热特性的研究

采用有效度-传热单元数(ε-NTU)法,建立了中温热管换热器的离散型数学模型。研究了中温热管换热器冷侧和热侧的传热特性。建立了单根热管的传热模型来修正计算热管热阻时所产生的温度误差,分析了单根热管的传热过程对整个换热器换热的影响。研究成果为安全衔接热管不同温度区域内的每排热管和强化中温热管换热器的传热性能以及中温热管换热器的进一步结构优化提供了理论依据。     

间接蒸发冷却板式换热器换热性能的数值模拟

应用计算流体力学(CFD)方法建立了间接蒸发冷却板型换热器内三维层流流动与传热的数学物理模型;对影响蒸发冷却换热器换热性能的主要因素进行了数值计算和预测;通过计算表明,换热器通道间距、空气的迎面风速,以及一次风的干球温度的变化对换热器效率有很大的影响;分析了不同参数时通道内流场、能量场以及换热器效率的变化.     

空分设备筛板塔内珠光砂的清理

空分设备冷箱内管道断裂,珠光砂会进入塔体或板翅式换热器内部,影响空分设备的正常运行。详细介绍珠光砂进入筛板塔的清理方法和步骤,阐述鼓风机自动吸砂和吸尘器人工吸砂相结合的清砂方案的效果,提出空分设备冷箱日常安全管理的措施。     

南方供暖室内设计温度的研究

平均辐射温度、室内空气温度、空气流速和相对湿度是影响人体热舒适的重要因素,人体热舒适是其影响因素综合作用的结果。各地采暖室外计算温度不同,由于不同室外温度对建筑围护结构壁面温度影响,采用理论计算的方法,得出壁面冷辐射换热对人体热舒适的影响。从而探讨了在室内供暖设计时,目前冬季室内热环境研究较少的非传统供暖区域南方舒适节能的供暖室内设计温度情况。     

脉管制冷机冷端换热器的改进

为了进一步提高脉管制冷机在液氮温区（７７Ｋ）的制冷量,本文对脉管冷端换热器进行了改进,同时还对脉管冷端气流的平均温度进行了测量。实验结果表明,常规脉管制冷机冷端换热器中的换热面积是不足的,脉管制冷机冷端换热器的传热损失较大,在设计计算中不应忽视。采用高目数的换热器填料有利于降低脉管冷端壁面与冷端气体之间的温差,从而提高冷端换热器效率,进而提高液氮温区脉管制冷机效率。     

Concept for thermal insulation arrangement within a flexible cryostat for HTS power cables

The successful application of high temperature superconducting power cables requires improved flexible cryostats with respect to their thermal heat load between environment (300 K) and LN₂ (77 K) operating temperature. Heat transfer through the thermal insulation consists of thermal radiation, solid and residual gas conduction. Considering this heat load contributions, a new concept for the thermal insulation arrangement is presented in this paper. The main advantage of this concept consists in a separation of the thermal insulation and the supporting structure. This separation protects the thermal insulation from degradation by mechanical load. The fraction of solid heat conduction through this support structure is minimised by small contact areas and high heat conduction lengths. Heat transfer due to residual gas conduction is reduced by improved evacuation conditions close to the cold wall. Finally the structure allows subdivision of the multilayer insulation ensuring an optimal number of layers with respect to their insulation thickness, i.e. an optimal layer density.     

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.     

地下水渗流对垂直埋管换热器换热性能影响的实验研究

地埋管换热器的换热性能是地源热泵空调系统设计的关键问题之一。建立了地源热泵砂箱实验台,实验研究了地下水渗流对地源热泵地埋管换热器换热性能的影响。研究结果表明:地下水渗流可以强化地埋管的换热,且随着渗流速度的增大,强化换热作用越明显。另外,实验结果也表明,U型管周围温度峰值的位置会沿渗流方向向下游偏移,地埋管群布置时应避开该位置,以强化埋管的换热。     

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...     

A calorimeter for multilayer insulation (MLI) performance measurements at variable temperature

Here we describe a concentric cylindrical calorimeter with radiation guards developed to measure the thermal performance of multilayer insulation (MLI) for low temperature applications. One unique feature of this calorimeter is its ability to independently control the boundary temperatures between room temperature and about 15 K using two single-stage Gifford–McMahon cryocoolers. Also, unlike the existing calorimeters that use the evaporation rate of a liquid cryogen to measure the heat load, in the present system the total heat transfer through the MLI is measured by recording the temperature difference across a calibrated heat load support rod that connects the cold inner cylinder to the lower temperature cryocooler. This design allows the continuous mapping of MLI performance over a much wider temperature range with independently controlled boundary conditions. The calorimeter is also suitable for performing a variety of radiation heat transfer experiments including the determination of the temperature dependence of the total emissivity.     

Experimental study of the influence of cold heat exchanger geometry on the performance of a co-axial pulse tube cooler

Improving the performance of the pulse tube cooler is one of the important objectives of the current studies. Besides the phase shifters and regenerators, heat exchangers also play an important role in determining the system efficiency and cooling capacity. A series of experiments on a 10 W @ 77 K class co-axial type pulse tube cooler with different cold heat exchanger geometries are presented in this paper. The cold heat exchangers are made from a copper block with radial slots, cut through using electrical discharge machining. Different slot widths varying from 0.12 mm to 0.4 mm and different slot numbers varying from around 20–60 are investigated, while the length of cold heat exchangers are kept the same. The cold heat exchanger geometry is classified into three groups, namely, constant heat transfer area, constant porosity and constant slot width. The study reveals that a large channel width of 0.4 mm (about ten times the thermal penetration depth of helium gas at 77 K, 100 Hz and 3.5 MPa) shows poor performance, the other results show complicated interaction effects between slot width and slot number. These systematic comparison experiments provide a useful reference for selecting a cold heat exchanger geometry in a practical cooler.     

On the performance of copper foaming metal in the heat exchangers of pulse tube refrigerator

As key components in pulse tube refrigerators (PTRs), heat exchangers have great influence on the performance of the PTRs, especially the cold end heat exchangers which dominate the cooling effect between the cold gas and heat load. Filling copper screens are widely used to improve the performance of heat exchange and laminar flow. Whereas, the heat transfer rate of copper screens is still not good enough for the actual requirements of PTRs. Furthermore, the flow resistance of the copper screen is growing up quickly with the increase of screen mesh. In this paper, we propose a new type of copper foaming metal with high heat transfer area and low flow resistance in the heat exchanger instead of the copper screens. The heat transfer performances of the copper screens and the copper foaming metal are firstly compared by theoretical calculation, which shows that the performance of the copper foaming metal with 600 μm pore size is better than that of 20 and 80 mesh copper screens, verified by experimental results. A four valve pulse tube refrigerator (FVPTR) with copper foaming metal of 600 μm pore size as filling material of the heat exchanger achieved 69.5 K, 2.5 K lower than that of using 20 mesh copper screens, 1.7 K lower than that of using 80 mesh copper screens.     

Heat exchangers for he II cooling loops with self-sustained fountain effect pumps

A cooling cycle with He II convection driven by self-sustained fountain effect pumps is being investigated. Special attention is drawn to the problem of heat transfer at both ends of the superfilter of this loop. The heat exchanger requirements are derived from theoretical considerations on the degradation of the cooling characteristic effected by non-perfect heat exchangers. A shell and tube type heat exchanger, optimized for the warm end of the filter has been operated in this loop with a thermal load of up to 9 W, with 2.8 g s⁻¹ maximum helium flow rate and with inlet temperatures between 1.8 and 3.4 K. Its performance is well described by computations. A different heat exchanger design with finned Cu walls is suggested for the cold end of the pump. Some considerations on its optimization are given.     

换热器热传递的有限元分析

 换热器的设计涉及许多因素,而热传递能力是检验换热器结构设计成功与否的重要标准.从理论上难以准确计算出换热器的传热效率,所以提出利用ANSYS有限元分析软件来研究换热器的热交换过程.剖析系统的热传递原理,对换热器进行优化建模,加载热载荷,并得到换热器的温度场分布;由分析结果可以看出换热器能够满足系统要求,使系统重新达到热平衡.换热器的换热性能得以肯定,继而说明了换热器的结构设计是可行的,并为后一步的优化设计奠定了基础.