摘要
相变散热器在有效保障功率瞬变、间歇性工作电子器件安全运行方面具有极大潜力.针对现有相变散热器性能亟需进一步提升的问题,本文通过改变加热位置和添加泡沫铜,实验探究了石蜡在导热+自然对流、导热、导热增强+自然对流抑制以及导热增强4种作用条件下的定向熔化特性.研究发现,在导热和自然对流同时作用条件下,石蜡的温度经历缓慢上升、极速上升、缓慢波动和继续上升4个阶段,自然对流的作用可将相变散热器的有限保护时间从导热作用时的483 s延长至4400 s.虽然添加泡沫铜能降低石蜡内部的温度梯度,但会延长自然对流作用的起始时间、缩短作用时长以及削弱作用强度,导致自然对流的作用权重比从8.1降至0.72,有效保护时间仅提升80 s.因此,采用相变材料(phase change material, PCM)散热器冷却低热流密度的电子器件时,应优先强化工质熔化过程中的自然对流,随着热流密度的增加,再逐渐强化其导热性能.
At present,electronic devices are increasingly prone to severe heat dissipation problems owing to higher integration and miniaturization.Generally,the performances and service lives of electronic devices both decrease with increase in the working temperatures.In contrast,the failure rates of electronic devices rapidly increase when the working temperature increases gradually.For instance,the working temperatures of insulated gate bipolar transistor(IGBT)modules and missile-borne radar systems should be maintained below 150°C.Moreover,the heat fluxes of these systems present transient and intermittent characteristics.This indicates that the traditional finned radiators are increasingly failing to meet the cooling demands of these systems.Generally,the melting process of phase change materials(PCMs)requires a nearly constant temperature(or limited within a temperature range)and absorbs a large amount of latent heat;this hints that the PCM heat sink may possibly help prevent high-power thermal shock and ensure safe operation of electronic devices with variable heat fluxes.To further improve the thermal shock resistances of PCM heat sinks,an experimental system(consisting of a heating unit,an experiment unit,and a measuring unit)was established to explore the directional melting characteristics of paraffin under four conditions(thermal conduction and natural convection,thermal conduction,thermal conduction enhancement and natural convection suppression,and thermal conduction enhancement)by changing the heating positions and adding copper foam.Specifically,paraffin with a phase change temperature of 56.9–63.6°C was adopted as the working medium.Moreover,copper foam of dimensions 58 mm×20 mm×95 mm and porosity 15 PPI was used to enhance the heat conduction performance of paraffin.It should be noted here that the natural convection in the melting process of paraffin is driven by buoyancy,i.e.,natural convection can be ignored when paraffin is heated from the top.Besides,the maximum thermal loss and maximum uncerta
作者
方健
冯文创
丁斌
朱传勇
巩亮
Jian Fang;Wen-Chuang Feng;Bin Ding;Chuan-Yong Zhu;Liang Gong(College of New Energy,China University of Petroleum(East China),Qingdao 266580,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2021年第21期2758-2765,共8页
Chinese Science Bulletin
基金
国家自然科学基金(51906257)
山东省自然科学基金(ZR2019ZD11)资助。
关键词
石蜡
相变散热器
自然对流
熔化
paraffin
PCM heat sink
natural convection
melting
