【作者】 李鹏；

【导师】 何理； 孙金猛；

【作者基本信息】 华北电力大学(北京) ， 动力工程（专业学位）， 2018， 硕士

【摘要】 在过去的30年间,数值模拟技术已经广泛用于管壳式换热器领域。在本文中,将用数值计算的方法对不同挡板类型管壳式换热器壳侧流体的流动传热性能进行研究。首先对弓形挡板管壳式换热器的壳侧流场的流动传热进行数值计算。基于模拟结果,使用热力学第二定律和焓(火用)理论对(火用)利用效率进行定量分析。结果表明,与能量分析相比,(火用)分析法是更加科学地分析能量回收利用程度的方法。增加壳侧热水的质量流量可以增加管侧冷水的品质且增大壳侧传热系数,但是降低了热水的利用程度。最后,该部分对不同缺口高度的弓形挡板进行了研究,结果表明,随着挡板缺口高度的增加,壳侧传热系数和压降都逐渐下降,但是性能参数α/ρ会显著增大。然后,研究了双管程的管壳式换热器。首先,在相同的输入条件下比较了单管程和双管程弓形挡板管壳式换热器。结果表明,双管程换热器中回收热量的品质几乎是单管程换热器中的两倍,而在两种换热器中它们的壳侧传热系数几乎是相同的。在所有的换热器中,增加壳侧热水的质量流量可以提高管侧冷水的品质及增大传热系数,但是会降低热水的利用程度。为了研究不同挡板类型的双管程管壳式换热器的流动传热性能,特此比较了在相同输入条件下弓形挡板、螺旋形挡板及花瓣形挡板换热器的数值模拟结果。结果表明,在相同的条件下,花瓣形挡板换热器的壳侧压降和传热系数都是最小的。为了更好地评估三种不同类型换热器的经济性,引入了新的评价指标,即单位有效泵做功下的热流量QH/Po。数值模拟结果显示,三种换热器在相同的输入条件下,花瓣形挡板换热器的QH/Po是最高的,而弓形挡板换热器的QH/Po是最低的。因此,花瓣形挡板换热器在平衡壳侧传热系数与壳侧压降方面做得最好。在某种程度上,花瓣形挡板管壳式换热器也是最经济的。更多还原

【Abstract】 CFD simulation has been widely used in shell-and-tube heat exchangers over last 30 years.In this article,Thermo-hydraulic performances of shell-and-tube heat exchangers with different baffle types will be studied using CFD methods.First,an attempt has been made to study hydraulic-thermal performances in the shell side of a segmental baffled shell-and-tube heat exchanger(SB-STHE)Furthermore,the second law of thermodynamics and the exergy theory are adopted on the simulation results to give a quantitative analysis of exergy utilizing efficiency.The results reveal that the exergy analysis is a more scientific means to analyze the utilization of energy compared with energy analysis.Increasing the mass flow rate of shell side water can increase the recovered quality and heat transfer coefficient,but decrease the utilization degree of hot water.Lastly,STHEs with different height of baffle cuts are studied,with the increase of the height of baffle cut,both the heat transfer coefficient and pressure drop decreases,but the performance ratio α/P increases prominently.Then,double-tube-pass shell-and-tube heat exchanger(DTP-STHE)is proposed to improve the recovered heat quality from the point of the exergy theory.To prove this point,single-tube-pass shell-and-tube heat exchanger(STP-STHE)and DTP-STHE with segmental baffles are compared under the same conditions.The conclusion is surely made that the recovered heat quality in DTP-STHE is almost twice as that in STP-STHE.Furthermore,the heat transfer rate in both heat exchangers are nearly the same.In all heat exchangers,increasing the mass flow rate of water in shell side can increase the cold water quality and heat transfer rate,but decrease the utilization degree of hot water y.In order to investigate thermo-hydraulic performances of different DTP-STHEs,three kinds of DTP-STHEs with segmental,helical and flower baffles respectively are compared under same conditions.The results show that flower baffles produce the lowest pressure drop and lowest heat transfer coefficient.In order to better evaluate the economy of these three kinds of heat exchangers,heat transfer rate per effective pumping power QH/Po is introduced.The simulated results show that QH/Po of the flower baffle is the highest and QH/Po of the segmental baffle is the lowest.Therefore,heat exchangers with flower baffles balance the heat transfer rate and effective pumping power,thus it is the most economical.更多还原