1、2023 年第 1 期总第 251 期低温工程CRYOGENICSNo.1 2023SumNo.251超临界氮气在规则球床堆中的流动与传热特性分析陈煜尧1,2程帅3童念雪3陈亚春1,2魏健健1,2张德志3金滔1,2(1浙江大学制冷与低温研究所杭州 310027)(2浙江省制冷与低温技术重点实验室杭州 310027)(3西北核技术研究所西安 710024)摘要:采用计算流体力学方法模拟高温高压工况下规则球床堆内超临界氮的流动与传热特性,系统分析了入口流量、填充颗粒直径、堆积床高径比对流动和传热性能的影响规律。结果表明:堆积床内相邻颗粒层间存在流动滞止区,该区域流体温度高于其它低阻力区域。随着液氮
2、入口流量和堆积床高径比的增大以及填充颗粒直径的缩小,气体流动阻力逐渐升高,气体与堆芯的换热更加充分,进而出口氮气温度变高。关键词:规则堆积床超临界氮气换热性能数值模拟中图分类号:TB663文献标识码:A文章编号:1000-6516(2023)01-0037-06收稿日期:2022-10-26;修订日期:2023-02-09作者简介:陈煜尧,男,24 岁,硕士研究生。通讯作者:魏健健,男,34 岁,副教授,Simulation and analysis of supercritical N2flow andheat transfer in a regular spherical pebble b
3、edChen Yuyao1,2Chen Shuai3Tong Nianxue3Chen Yachun1,2Wei Jianjian1,2Zhang Dezhi3Jin Tao1,2(1Institute of Refrigeration and Cryogenics,Zhejiang University,Hangzhou 310027,China)(2Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province,Hangzhou 310027,China)(3Northwest Institute
4、of Nuclear Technology,Xian 710024,China)Abstract:A pebble-bed-type high-temperature and pressure gas preparation system by liquidnitrogen reheating involves heat transfer between liquid nitrogen and pebble bed core.It is signifi-cant to study the flow and heat transfer characteristics of supercritic
5、al nitrogen in the pebble bedunder high pressure for its design,operation and safety analysis.Computational fluid dynamics isused to simulate the flow and heat transfer of supercritical nitrogen in a regularly arranged pebblebed under high temperature and pressure.The effects of the inlet flow,parti
6、cle diameter,andheight-to-diameter ratio of the pebble bed on the flow and heat transfer performance are analyzed.The results show a flow stagnation region between adjacent particle layers in the pebble bed,andthe fluid temperature in this region is higher than in other low-resistance regions.Meanwh
7、ile,withthe increase of the inlet flow rate of liquid nitrogen and the ratio of height-to-diameter of pebblebed,and the decrease of the diameter of filling particles,the gas flow resistance rises,the heat ex-change between the gas and the core is intensified,and the nitrogen temperature at the outle
8、t rises.Key words:regular spherical pebble bed;supercritical N2;heat transfer characteristics;nu-merical simulation低温工程2023 年1引言近临界态流体的热物性在类临界点变化剧烈,流体物性一旦超过临界点,一种无结构的、均匀的、连续的超临界流体在状态空间中普遍存在。由于超临界流体的独特物性,近年来在多孔介质换热、高温气冷堆、催化反应器、蒸汽循环发电等领域备受青睐。在某复热型高温高压气体制备系统实验平台中,需要产出压力 215 MPa,温度 0450 的气体。常规的工业管路换热系统,
9、受限于系统的加压、加热和输运能力,难以实现快速产气、充气的目标。Osof-sky 等1研制了液氮复热式高温高压气体制备系统,用于提供稳定可靠驱动气体且实现对生产过程的有效调控。系统中采用卵石堆积床作为复热部件,堆积床的致密堆积结构能够有效加强气固元件间的换热,流体与堆积颗粒换热越充分,越有助于后期的温度精准调控。高压条件下超临界流体在堆积床内的复杂流动换热特性决定着堆积床内温度分布,会影响堆积床的设计、性能乃至安全运行。为了解堆积床中流体的复杂流动特性,相关学者针对堆积床流 动传热过 程开展 了 大 量 实 验 研 究。Ergun等2对空气、氮气、二氧化碳等不同流体工质流经固体颗粒堆积床的实验
10、结果进行了详细的讨论,给出经典的固定床压降经验关联式(Ergun equation),关联式表明,压降与表面速度之比是质量流量的线性函数,关联式的系数取决于固定床孔隙率、流体与颗粒接触的表面积和流体粘度,但该压降公式仅适用于低雷诺数工况(Re 1 000)。Kerntechnischer 等3通过实验提出了著名的压降预测关联式(KTA equa-tion),该式适用于更高雷诺数范围(Re/(1-)280 mm 后,圆形通道内平均对流换热系数和平均无量纲 Nu 数显著高于矩形,表明圆形通道内沿流动方向对流换热能力更强,冷却效果优于矩形。参考文献1 Sobel D R,Spadaccini L J
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