共查询到16条相似文献,搜索用时 156 毫秒
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本实验对不锈钢管内CaCO_3污垢的沉积过程进行了分段研究。测得传热系数后,获得了污垢热阻,并用电镜扫描(SEM)获得了污垢分布随时间的变化.实验结果表明:在不锈钢管内CaCO_3污垢沉积的初始阶段,传热系数增大而非减小,出现负污垢热阻,说明CaCO_3污垢初始阶段的沉积有利于传热,经过一段时间的沉积后才会出现正污垢热阻。电镜扫描(SEM)结果表明,污垢沉积的初始阶段,污垢结晶以星状点分布于管内壁,随着沉积时间的增长星状点变得密实,这种不完全覆盖使得流体在流经污垢时产生扰流,增强了传热效果。随着时间推移,结晶污垢的覆盖面积逐渐增大,污垢热阻逐渐增加,传热系数减小。 相似文献
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工业烟气含尘的特点易导致换热器积灰,进而制约烟气余热的高效回收。本文针对一种具有超大拓展表面的三维微肋管换热器的对流换热与积灰特性进行了研究。首先,对比研究了光管与三维微肋管的对流换热特性;接着,基于所建立的积灰数值模型,探究了三维微肋管的积灰特性,并揭示了烟气流速与飞灰粒径对其积灰特性的影响规律。结果表明,相对于传统光管,三维微肋管的换热面积可增大约2.9倍;换热性能平均能提高16%;积灰后渐进污垢热阻最大能减小70%;同时,清灰周期更长,运行经济性更佳。综合而言,三维微肋管相比传统光管,在增强换热的同时,还能有效减轻积灰,因此可作为高效的抗积灰传热元件,应用于含尘烟气的余热回收场合。 相似文献
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Abstract The objective of the present study was to investigate the mechanism of a physical water treatment (PWT) technology used to mitigate mineral fouling in a heat exchanger. The PWT method tested utilized a solenoid coil to produce induced electric fields in a feed pipe prior to the heat exchanger. Fouling experiments were conducted using well water circulated through a laboratory cooling tower over 270 h with no blowdown, and fouling resistances were determined over time. Compared with the fouling resistance for the baseline case, those obtained with the PWT technology showed high efficacy for maintaining a low fouling resistance value. Samples of circulating well water were collected and analyzed using a laser particle counter over time. After 4 days of operation, the total number of particles was approximately 1 million per cc for the untreated case, whereas the case with PWT produced 3.5 million per cc. The present data on the particle counting provide empirical support for the bulk-precipitation hypothesis for the mechanism of PWT generally and electro-flocculation mechanism for solenoid coil techniques in particular. 相似文献
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