直接接触冷凝器流动特性及传热研究

发布时间：2018-05-08 19:33

  本文选题：静态混合器 + 直接接触冷凝器　； 参考：《天津大学》2015年硕士论文

【摘要】：本文利用SV型和SK型静态混合器,并以纯金属钛粉末烧结的微泡发生器作为气体分布器,开发出一种新型直接接触冷凝器。本文首先在空气-水体系中对两种新型直接接触冷凝器的流体力学性能进行测试,测量并观察气液两相流体在新型直接接触冷凝器中的流动状态、气泡形态、气含率以及压降情况。实验结果表明,在装有SV型静态混合器的冷凝器中,气泡尺寸较小,气含率较大且随气相流量的增大呈先增大后保持不变的趋势;气含率随液相流量的增大基本保持不变。在两种直接接触冷凝器中,压降均随气相及液相流量的增大而增大。装有SV型静态混合器的冷凝器中,压差较大于SK型。这是由于,SV型直接接触冷凝器对于分散相气泡具有较强的破碎作用,使气泡尺寸更小,分布更均匀。且SV型静态混合器具有较大的比表面积,气泡上升孔道小,路径长。气泡在上升过程中受到阻力大,停留时间长。在空气-水实验基础上,本研究在水蒸气-水体系中,进一步测试并比较两种新型直接接触冷凝器的流体力学性能及冷凝传热性能。测试气体分布器对于冷凝传热性能的影响,包括换热效率、温度的轴向分布情况、连续相与分散相的平均传热温差、体积传热系数以及临界液相温度。实验结果表明,在新型直接接触式凝结器中,由于使用了钛金属烧结成的多孔介质作为气体分布器,使水蒸气稳定均一地进入水相中,有效地避免了蒸汽凝结时产生的振动与噪音。水蒸气的冷凝过程主要集中在冷凝器的气相进口位置,冷凝段高度与流体流量有关。新型直接接触冷凝器在空气-水体系下具有较大的平均体积传热系数(35-40 kW·m-3·℃-1),装有SV型静态混合器的直接接触冷凝器略高于SK型。SK型静态混合器具有较小压降以及临界液相温度,因此SK型冷凝器具有更大操作范围。本研究从实际应用角度出发,考虑到直接接触冷凝在天然气接收站中具有重要应用,是天然气接收站稳定、安全运行的关键技术。本研究在之前所做研究的基础上,对两种新型直接接触冷凝器在低温流体下的流动及传热性能进行研究。考虑到安全、环保等问题,本研究选在氮气-液氮体系下,对两种新型直接接触冷凝器的性能进行研究。实验结果表明,新型直接接触冷凝器在低温流体体系下同样表现出良好的性能。正常工作条件下,其平均体积传热系数在25-40 kW·m-3·℃-1范围内,SV型冷凝器传热性能优于SK型,但具有较小的操作范围。结果表明:装有SV型静态混合器的新型直接接触冷凝器较装有SK型静态混合器的新型冷凝器对分散相气体的分布更加均匀,具有更好的吸收效果,钛曝气器的利用可有效提高换热效率,并降低水蒸气冷凝所引起的振动与噪声。
[Abstract]:In this paper, a new direct contact condenser is developed by using SV and SK static mixers and using pure titanium powder sintered microbubble generator as gas distributor. In this paper, the hydrodynamic properties of two new direct contact condensers are tested in the air-water system, and the flow state and bubble morphology of the gas-liquid two-phase fluid in the new direct contact condenser are measured and observed. Gas holdup and pressure drop. The experimental results show that in the condenser with SV type static mixer, the bubble size is smaller, the gas holdup is larger, and the gas holdup increases first and then remains unchanged with the increase of the gas flow rate, and the gas holdup remains basically unchanged with the increase of the liquid flow rate. In both direct contact condensers, the pressure drop increases with the increase of gas and liquid flow. In the condenser with SV type static mixer, the pressure difference is larger than SK type. This is due to the fact that the SV-type direct contact condenser has a strong fragmentation effect on the dispersed bubble, which makes the bubble size smaller and the distribution more uniform. The SV type static mixer has large specific surface area, small rising pore channel and long path. The bubble is subjected to large resistance and long residence time during the rising process. On the basis of air-water experiments, the hydrodynamic properties and condensing heat transfer properties of two new direct contact condensers were further tested and compared in water vapor water system. The effect of gas distributor on condensing heat transfer performance including heat transfer efficiency axial distribution of temperature average heat transfer temperature difference between continuous phase and dispersed phase volume heat transfer coefficient and critical liquid temperature were measured. The experimental results show that in the new direct contact condenser, because the porous medium sintered by titanium is used as the gas distributor, the water vapor enters the water phase stably and uniformly. The vibration and noise caused by steam condensation are effectively avoided. The condensing process of water vapor is mainly concentrated at the inlet position of the condenser, and the height of the condensing section is related to the flow rate of the condenser. The new direct contact condenser has a large average volumetric heat transfer coefficient of 35-40 kW m-3 鈩，

本文编号：1862774