摘要
试验对真空冷凝锅炉中的叉排水平换热管的管束效应进行了研究。为了解真空锅炉中冷却水流速、进出口温度、热通量、不凝性气体等参数对管束效应的影响规律,试验设置了不同的工况,得到换热管束中各单管的冷凝传热系数,结果呈现出一定的规律。分析试验结果得出,真空环境下的叉排管束冷凝换热规律与Nusselt模型相差较大,当热通量较大时,模型预测值偏低。不凝性气体含量的多少对换热效率的影响很大,当含量增加约100%时,冷凝传热系数降低约70%。叉排换热管束第5、6排处于换热薄弱地带,对其进行强化换热如在第5、6排管加装翅片或将其换成强化管等,以提高局部冷凝传热系数,从而提高管束整体的传热系数和锅炉的换热效率。
We experimentally addressed the tube bundle effect of the vacuum condensation boiler with horizontal bundle of staggered heat-transfer tubes. The influence of the operation conditions,including the flow-rate,inlet /outlet temperatures and heat-flux of cooling water,concentration of non-condensable gases,on the heat-transfer coefficient of individual tube-row was measured and calculated in steady-state heat-transfer equations and with Nusselt model,respectively. The results show that Nusselt model does a poor job,especially at a large heat flux,in predicting the heat-transfer of the boiler,and that the concentration of non-condensable gases strongly affects the condensation heat-transfer efficiency. For example,100% increase of the concentration reduced the coefficient by 70%. Since the 5th and 6th rows have smaller heat transfer coefficients than the other rows of the staggered tube bundle,we suggest that substitution of the enhanced tubes for those of the 5th and 6th rows and / or installation of fins may improve the total condensation heat-transfer efficiency.
出处
《真空科学与技术学报》
EI
CAS
CSCD
北大核心
2016年第3期263-267,共5页
Chinese Journal of Vacuum Science and Technology
基金
国家自然科学基金面上项目(51276171)
浙江省教育厅一般科研项目(Y201534825)
关键词
真空锅炉
叉排管束
管束效应
冷凝换热
Vacuum boiler
Staggered tube bundle
Tubebundle effect
Condensation heat transfer
