摘 要

目前，世界面临能源短缺的局面，大力发展节能技术已成为当前工业生产和人民生活中一个重要课题。翅片管换热器作为高效的换热设备，广泛应用于能源动力、暖通空调、冶金化工、石油、车辆船舶等领域中。本文研究的KLQ518型翅片管式换热器是大型低速船舶涡轮增压柴油机的中冷器，用于冷却进入柴油机的空气，进而实现提高柴油机功率、改善动力性、降低油耗的目的。翅片的片型有平直型、百叶窗型、波纹型等，其中平直型翅片结构简单、加工制造方便，使用过程中不易发生变形，因而应用广泛。

本文通过ANSYS软件对翅片管换热器的换热和流动进行了数值模拟研究，得到了翅片管换热器空气侧的温度、速度以及压力分布云图。结果显示基管背风侧温度要低于迎风侧温度，且在基管背风侧出现卡门涡街现象。同时对不同的入口速度进行了仿真，发现随着雷诺数Re的增大，进出口的温度差减小，而压降和换热量都在增加。也就是说雷诺数Re的增加，导致有很多空气未能及时换热便以流出，使得出口温度增加；同时，雷诺数Re的增加，增强了湍流强度进而增加了换热，而Re的增加也伴随着阻力的增加，进而使得压降ΔP增加。通过j/f因子发现Re的增加不利于换热器综合性能的提高。

然后，本文对翅片间距和基管直径对翅片管换热器的换热和流动性能的影响进行了研究。通过设置多组不同的翅片间距和管直径来观察它们对换热器性能的影响。仿真结果表明，在翅片间距和入口速度一定时，随着基管直径的增加，翅片管换热器的换热性能增加，而流动性能下降；而在基管直径和入口流速一定时，随着翅片间距的增加，翅片管换热器的换热性能下降，而流动性能增加。因为换热器的换热性能和流动性能通常是相互对立的，因而本文采用j/f因子来综合评价换热器性能。研究结果发现，在翅片间距和入口速度一定时，管直径较大时，翅片管换热器的综合性能较好；而管直径和入口速度一定时，较大的翅片间距也使翅片管换热器的综合性能得到提高。最后对所有的翅片管结构尺寸进行对比分析，发现在基管直径D=16mm、翅片间距H=2.4mm时，翅片管换热器的综合性能最好。

关键词：翅片管式换热器；数值模拟；强化传热；结构参数优化；

Abstract

At present, the world is facing energy shortage, thus striving to develop energy-saving technology has become an important issue in the industrial production and people’s lives. As a highly efficient heat transfer equipment, fin and tube heat exchanger widely used in energy and power, HVAC, metallurgy and chemistry, petroleum, vehicles and ships, and other domain. In this paper, we study the KLQ518 type fin and tube heat exchanger. This heat exchanger is the intercooler of a large low speed turbo-charging diesel engine, and be used to cool the intake air of the diesel engine, thus it achieved the purpose of increasing diesel engine power, improving power performance, reducing the fuel consumption. The shapes of fin and tube have straight fin, louver fin, corrugated fin, and so on. Because the straight fin has a simple straight fin structure and easy in assembly and not easy to deform in the use process, thus it is widely used in many fields.

This thesis conducted numerical simulation study for the heat transfer and fluid flow of fin and tube heat exchanger by using ANSYS software, and obtained contour of temperature, velocity and pressure on the air side of the fin and tube heat exchanger. The results showed that the leeward side of tube temperature is lower than the windward side of the temperature, and the Karman vortex street phenomena happened in the leeward side of the tube. This thesis also simulated different inlet velocity, and found that with the increase of Reynolds number Re, the temperature difference between inlet and outlet is decreasing, but the pressure drop and heat exchange amount are increasing. The reason is the increasing of Reynolds number Re results a lot of air fail to heat transfer then flow out, so that the outlet temperature is increasing. At the same time, the increasing of Reynolds number Re enhance the strength of the turbulence which increases heat transfer and resistance, thus making the pressure drop ΔP increase. By j/f factor found with the increasing of Reynolds number Re, the overall performance of the heat exchanger is decreased.

Then the thesis studied fin spacing and pipe diameter of the impact of the fin and tube

heat exchanger for heat transfer and fluid flow. By setting different sets of fin spacing and tube diameter to observe their effects on the performance of the heat exchanger. Simulation results show that when the fin spacing and inlet velocity are constants, with the increasing of the tube diameter, the heat transfer performance of the fin and tube heat exchanger is increased, but the flow performance is decreased. When the tube diameter and inlet velocity are constants, with the increasing of the fin spacing, the heat transfer performance of the fin and tube heat exchanger is decreased, but the flow performance is increased. Because the heat transfer and flow performance of the heat exchanger are often contradictory, thus the thesis used j/f factor to evaluate the overall performance of the heat exchanger. The results found that in certain fin spacing and inlet velocity, with the increasing of tube diameter the overall performance of fin and tube heat exchanger is increased. When the tube diameter and inlet velocity are constants, the larger fin spacing also makes the overall performance of the fin and tube heat exchanger is increased. Finally the thesis analyzed all of the fin and tube structure size, and it was found that when the tube diameter D=16mm, the fin spacing H=2.4mm the overall performance of fin and tube heat exchanger is best.

Key Words: fin and tube heat exchanger; numerical simulation; enhancing heat transfer; structural parameter optimization

目录

第1章 绪论 1

1.1研究的背景及意义： 1

1.2翅片管换热器 2

1.2.1翅片管换热器的分类 3

1.2.2翅片管的特点 6

1.3国内外研究现状 6

1.3.1国内研究现状 7

1.3.2国外研究现状 7

1.4本文研究内容 8

第2章 翅片管换热器传热和流动基本理论 10

2.1传热过程的基本理论 10

2.1.1热传导 10

2.1.2 热对流 11

2.1.3 热辐射 11

2.2 流体流动控制方程 12

2.3翅片管式换热器的传热计算 13

2.3.1传热方程 13

2.3.2 干工况总传热系数 14

2.4翅片管换热器的性能评价标准 15

2.5 本章内容小结 16

第3章 翅片管换热器空气侧数值模拟 17

3.1模型的构建 17

3.1.1几何模型的构建 17

3.1.2网格的划分 18

3.2数学模型的建立与求解 20

3.2.1基本假设 20

3.2.2边界条件设置 20

3.2.3物性参数 21

3.2.4求解算法 21

3.2.5参数定义 22

3.3数值仿真结果分析 23

3.3.1 雷诺数Re=2183时模拟结果分析 23

3.3.2不同入口工况下的模拟结果分析 26

3.4 本章内容小结 31

第4章不同翅片间距和管直径的影响分析 32

4.1基管直径对换热和流动的影响 32

4.2 翅片间距对换热和流动的影响 35

4.3本章内容小结 41

第5章 结论与展望 43

参考文献 45