摘要
水平降膜蒸发器是机械蒸汽再压缩结晶(MVRC)系统的关键设备,在MVRC系统中可以用来蒸发废水并从含盐废水中回收二次蒸汽能量。然而,喷洒在水平降膜蒸发器管外的含盐废水的物性参数与普通水明显不同,其传热流动特性也必然不同。本文建立了MVRC系统中水平降膜蒸发器的三维数值模型,用水和硫酸钠混合物模拟含盐废水。用VOF模型跟踪蒸发器水平管上的液气界面,研究了不同硫酸钠含量、热流密度、喷淋密度和喷淋温度对传热系数hθ的影响,并建立了无量纲关联式。结果表明:1)传热特性可分为三个区域;2)在热发展区域,局部传热系数随硫酸钠含量的增加而降低;3)局部传热系数随喷淋密度和喷淋温度的增加而增加,在热发展区域受热流密度的影响很小。
The horizontal falling film evaporator is a key component of the mechanical vapor recompression crystallization(MVRC) system, in which it can be used to evaporate wastewater and recover secondary vapor energy from salty wastewater. However, the heat transfer and flow characteristics of the salty wastewater sprayed outside the horizontal falling film evaporator tube are obviously different from ordinary water as the spray medium. In this paper, a three-dimensional numerical model was established for a horizontal falling film evaporator in the mechanical vapor recompression crystallization system, and a mixture of water and sodium sulfate was used to simulate the real salty wastewater. The VOF model was applied to track the liquid-gas interface of salty wastewater spray falling film over a horizontal tube in the evaporator. The effects of different sodium sulfate content,heat flux, spray density and spray temperature on the heat transfer coefficient hθwere investigated,and a dimensionless correlation equation was established. The results show that: 1) the heat transfer characteristic can be divided into three regions around the tube;2) the local heat transfer coefficient decreases with increase of sodium sulfate content in the thermal developing region;3) the local heat transfer coefficient increases with the increase of the spray density and spray temperature, and is little affected by heat flux in the thermal developing region.
作者
曹艳美
王瑜
CAO Yanmei;WANG Yu(College of Urban Construction,Nanjing Tech University,Nanjing 211816,China)
出处
《工程热物理学报》
EI
CAS
CSCD
北大核心
2022年第10期2751-2763,共13页
Journal of Engineering Thermophysics
基金
国家自然科学基金(No.51806096)。
关键词
数值模拟
喷淋降膜
传热系数
含盐废水
机械蒸汽再压缩结晶系统
numerical simulation
spray falling film
heat transfer coefficient
salty wastewater
mechanical vapor recompression system
