Abstract: This paper presents an experimental investigation on nucleate pool boiling of saturated deionized water from uncoated and self-made sintered coated porous tubes with the heat flux from 0.1 to 160 kW·m^-2.The influences of the orientation(vertical and horizontal)and diameter(20,25 and 32 mm)of the heating tube and the coating particle size(between 30 and 105 μm)on the nucleate pool boiling were investigated.The results show that the sintered porous coatings can lower the incipient boiling superheat and enhance nucleate boiling heat transfer coefficient compared with smooth surfaces.The incipient boiling superheat of deionized water drops from 4-5 K with the smooth tubes to 1-2.5 K with the porous coated tubes.And the nucleate heat transfer coefficient on porous coating tubes are 3-4.5 times those of smooth tubes.It is found that,at high heat flux,the horizontal tube presents better boiling performance than the vertical tube due to the decrease in bubble slug formation on the tube surface and easy access of liquid to the surface.In addition,the influence of tube orientation on boiling performance is smaller for the porous tube than for smooth tubes.The heat transfer coefficients on smooth tubes and porous tubes decrease as the tube diameter increases.The data for different porous coatings suggest that small particle has slight effect on boiling heat transfer and greater enhancement is found with larger particle size.

Key words: sintered porous coating surface, nucleate boiling, incipient boiling superheat, heat transfer enhancement

摘要： 实验研究了热通量为0.1~160 kW·m^-2时,去离子水在光管及烧结型多孔表面管管外的池沸腾传热特性,分析了换热管布置方式(垂直与水平)、管径大小(20、25和32 mm)与多孔层颗粒尺寸(30~105 μm)对池沸腾传热特性的影响规律。结果表明:去离子水在多孔管表面的起始沸腾过热度小于光管,比光管低3 K左右;多孔表面管可明显强化核态沸腾传热,其沸腾传热系数可达光管的3~4.5倍;大热通量下,换热管水平布置时的传热效果较垂直布置佳,且布置方式对多孔管换热效果的影响比对光管的影响小;随管径增大,光管与多孔表面管的沸腾传热系数降低;大颗粒尺寸多孔层的强化效果优于小颗粒尺寸多孔层。

关键词: 烧结多孔表面, 核态沸腾, 起始沸腾过热度, 强化传热