TURBO-B类强化换热管沸腾换热性能实验与理论研究

VIP免费

3.0 侯斌 2024-11-19 4 4 3.22MB 68 页 15积分

侵权投诉

摘要

目前中央空调冷水机组中，强化换热高效管已代替光滑管，应用非常的广泛。

TURBO-B 管是一种后兴起的强化换热管，由于强化管表面结构复杂，影响强化管

换热性能的因素比较多，目前对于管外沸腾强化换热性能的研究主要以实验为主，

并更换不同的工况。一个工况则需要做很多实验来进行分析，大大增加了人力、

物力方面的成本。通过实验和理论模型的结合，可以减少这方面的成本。

本课题首先对两种用于池沸腾换热的强化换热管 TURBO-B 管进行了水平管

外换热性能实验。然后，利用威尔逊图解法和 Origin 软件处理实验数据，推导出

这两种管型的管内外换热系数的关联式，同时，根据实验测得的数据比较这两种

管型的换热性能。最后在此基础上，结合制冷剂物性参数，表面张力，接触角和

强化管的表面结构，建立了管外沸腾强化换热管的物理模型。

两种实验管子均为管内外双侧强化管，管外表面同属于 TURBO-B 类，但具体

表面形状有所区别。根据金相显微镜拍摄的管外形状，分析强化管表面尺寸结构

对强化换热管的换热性能的影响。试验工况为：管内为水，管外为制冷剂 R134a，

蒸发温度为 5℃，水速为 1.0-2.5m/s。在相同工况下，管内为准三角形螺纹的强化

管的管内换热性能要比梯形的好，管内螺纹数越多，换热性能越好；在实验的热

流密度范围内，管外换热系数随着热流密度的增加而变大，管外换热性能与管外

表面结构的凹穴半径、凹穴开口尺寸、次级表面通道的宽度和形状等因素有关，

且翅顶表面刻画的浅槽有利于池沸腾换热性能的提高。管内换热系数的简单计算

关联式分别为：

A管：

8.0

iu4400h 

B管：

8.0

iu9390h 

管外换热系数的简单计算关联式分别为：

A管：

591.0

oA q205.27h 

B管：

588.0

oB q53.38h 

从微液层理论和气泡动力学出发，结合实验结果建立了管外沸腾换热的模型，

并对两种 TURBO-B 管的模型应用进行分析。管外换热系数的理论值与实验处理得

到的值偏差在 30%以内，对强化管的开发和应用具有一定的理论指导意义。

针对整个实验过程出现的问题，如实验不能做到高热流密度值，水速调节范

围不够宽泛，提出试验台整改方案，提升了强化换热实验台性能测试的能力。

关键词：池沸腾管外沸腾换热强化传热 TURBO-B 管换热关联式

ABSTRACT

At present, enhanced heat transfer tube took the place of smooth tube has been

used widely in the central air-conditioning chiller. As a new kind enhanced tube,

TURBO-B has different geometry size and sub channel. Because the structure of

enhanced surface is very complicated, there are a lot of facts affected the performance

of heat transfer. The study on the boiling enhanced heat transfer focus on experiment

under different conditions, which increase the cost on human and money. With the

combination of experiment and theory, the cost will cut down.

First, the experiment about the pool boiling heat transfer of two enhanced heat

transfer tubes TURBO-B is done. Secondly, after experimental data are analyzed with

the Wilson graphic method and the software Origin, the heat transfer coefficients on

both sides are deduced, and the heat transfer performance of the two enhanced are

compared. At last, the model of boiling heat transfer outside tube is built based on the

refrigerant parametric, surface tension, contact angle and the surface structure.

The two tubes are both enhanced on the two sides and belong to the TURBO-B. It

is analyzed that the surface structure has influence on the performance of enhanced heat

transfer tube according to the surface shape photographed by metalloscope. The

experimental condition is following: the water is in the tube, the refrigerant R134a is

outside the tube, the evaporating temperature is 5℃, and the water velocity is from1.0

to 2.5 m/s. Under the same condition, the heat transfer performance of triangle shape is

higher than trapezoid, the more the ridge is, the higher the inside heat transfer

coefficient is. In a range of heat flux, the outside heat transfer coefficient enhance as the

increase of the heat flux, which is related to the size of reentrant cavity, the width and

shape of sub channel. The notched surface favors to pool boiling heat transfer. The

simple correlation of heat transfer coefficient inside tube is following:

Tube A：

8.0

iu4400h 

Tube B：

8.0

iu9390h 

The simple correlation of heat transfer coefficient outside tube is following:

Tube A：

591.0

oA q205.27h 

Tube B：

588.0

oB q53.38h 

Based on the micro liquid layer theory and bubble dynamic, the model of pool

boiling is built combined with the experiment. The model application of the two tubes is

analyzed too. The deviation of the experimental vale and the vale calculated by model is

in 30%，the model is useful for the development and application of enhanced tube.

For the problems in the experiment, such as not attached the higher heat flux,

regulated water rate not in wide range, the improving solution on the experimental

instrument is putted forward to raise the ability of testing the performance of heat

transfer.

Key word: Pool boiling, Boiling heat transfer outside, Enhanced heat

transfer, TURBO-B, Heat transfer relation

中文摘要

ABSTRACT

第一章绪论·················································································1

§1.1 课题研究背景及意义······························································1

§1.2 强化沸腾换热技术国外的现状与发展·········································1

§1.3 强化水平管外冷凝换热技术的现状与发展·································· 6

§1.4 沸腾换热理论模型的现状与分析············································· 10

§1.5 本课题的主要研究内容························································· 12

§1.6 本章小结··········································································· 14

第二章换热表面的沸腾换热机理······················································· 15

§2.1 影响沸腾换热的液体参数······················································ 15

§2.2 影响沸腾换热的表面结构参数················································ 16

§2.3 气泡的经典核化理论···························································· 18

§2.4 气泡动力学········································································ 20

§2.5 沸腾换热机理模型······························································· 21

§2.6 本章小结··········································································· 27

第三章池沸腾实验及数据处理·························································· 28

§3.1 实验管型··········································································· 28

§3.2 实验装置原理及实验系统图··················································· 31

§3.2.1 实验装置原理································································ 31

§3.2.2 实验系统图··································································· 32

§3.3 实验原理及数据处理方法······················································ 34

§3.4 实验结果与分析·································································· 36

§3.4.1 管内换热性能的比较分析················································· 36

§3.4.2 管外换热性能的比较分析················································· 38

§3.5 实验小结··········································································· 40

§3.6 本章小结··········································································· 40

第四章 Turbo-B 管沸腾换热理论模型研究············································ 42

§4.1 管外沸腾研究的内容···························································· 42

§4.2 管外沸腾换热模型的建立······················································ 43

§4.3 模型的稳态计算及分析························································· 48

§4.4 本章小结··········································································· 55

第五章结论与展望········································································· 56

§5.1 完成的主要工作及结论························································· 56

§5.1.1 完成的主要工作····························································· 56

§5.1.2 本课题结论··································································· 56

§5.2 进一步工作和展望······························································· 57

参考文献························································································ 59

在读期间公开发表的论文和承担科研项目··············································64

致谢······························································································ 65

第一章绪论

§1.1 课题研究背景及意义

能源不仅与社会经济有着重要关系，而且与人类的生存也是密不可分的。在

这个大背景下，各行各业都在积极寻找相关的节能方案。无论能源、石油、化工、

冶金、材料、制冷、动力等工程领域，还是航天、电子、核能等高科技领域，都

不可避免地涉及到加热、冷却等热量传递的问题。换热器是用于热量传递的载体，

其性能优越与否对能源合理利用来说，有着非常重要意义。

管壳式换热器处理能力大、可靠性高，适应性强。因此，它广泛应用于大型

制冷设备中，如大型活塞式冷水机组、螺杆式冷水机组、以及离心式冷水机组。

换热管是换热器的核心部分，其效率的高低直接决定换热器的性能好坏。换热性

能好的换热管有利于减小换热器尺寸或者增加原有换热器的热负荷，减小泵的功

率，降低金属消耗，节约能源，非常符合当代“节能、环保、低碳”的理念。大

量的实验数据已经证明机械加工表面多孔管的换热性能比光管优越，在冷水机组

的两器当中已经很少见到光滑管的踪影。强化水平管管外沸腾换热技术尽管在工

程中广泛应用，但是由于强化沸腾换热管表面的复杂性和多样性，人们对它的管

外沸腾换热特性还没有深刻的认识，换热机理、换热计算及许多其它重要沸腾现

象的分析也还存在着分歧，到目前为止还没有形成一个令人满意的理论来解释强

化换热管表面与沸腾换热现象之间的定量关系。

另一方面，近十多年来，随着人们环保意识的加强，特别是对臭氧层保护的

关注，一些传统的卤代烃制冷剂已逐近被新的环保制冷剂取代。本实验工质采用

R134a，因为它现在广泛用于中央空调系统中，不像氟利昂 R22 一样对臭氧层有

破坏作用，是当前世界绝大多数国家认可并推荐使用的环保制冷剂，虽然 R134a

的温室效应指数 GWP 为1300，但仍有很长的使用年限，为制冷设备生产厂家

所青睐。制冷剂 R134a 作为 R12 替代物广泛用于中央空调系统中，各种不同工况

下的试验数据有待更新，为研究出更贴近的沸腾换热现象理论提供依据，为设计

高效节能的壳管式换热器提供可靠数据，为进行表面换热计算和优化设计，进一

步改善换热性能以适应工程需要提供分析数据。

因此，结合环保制冷剂 R134a，对水平强化换热蒸发管进行实验和理论研究是

一个非常有意义的课题。

§1.2 强化沸腾换热技术国外的现状与发展

相对冷凝换热，沸腾换热的研究起步比较晚，理论研究分析还不够完善。据

TURBO-B 类强化换热管沸腾换热性能实验与理论研究

可供考证的史料记载，开始于十八世纪中叶。1756 年Leidenfrost,1888 年Lang 两

位科学家都通过实验发现了沸腾热流密度 q与壁面过热度ΔT之间的变化规律，沸

腾热流密度存在着最高值与最低值[1]。到了 1935 年，日本科学家 Nukiyama[2]通过

系统全面的研究，描绘了大家所熟悉的大容器饱和沸腾曲线（图 1-1），这是沸腾

换热研究领域的一个重大发现，该曲线精确地反映了饱和水在水平加热面上沸腾

热流密度随壁面过热度的变化规律。在核态沸腾的范围内，由于气泡的形成、长

大以及脱离加热壁面所引起的各种扰动，水沸腾时的热流密度可以高达

105-106W/m2的数量级，比相同温差变化范围内水的强制对流传热密度至少高一个

数量级。

图1-1 饱和水在水平加热面上的沸腾曲线(P=1.013×105Pa)

在整个沸腾过程中，随着壁面过热度

sw ttt 



升高，会出现自然对流，核态

沸腾，过度沸腾，稳定膜态沸腾 4个不同换热规律的区域。起初阶段，壁面过热

度（图 1-1 中过热度 t<4℃）较小,还没有开始沸腾，换热服从单相自然对流规律。

从起始沸腾点后，进入核态沸腾阶段，加热面上的某些地方（汽化核心处）开始

产生汽泡，这些气泡并不相互干扰，称孤立气泡区（沸腾现象如图 1-2 所示）。随

着壁面过热度的增加，汽化核心数也相应增加，气泡相互影响，慢慢会合成气块

和气柱，剧烈扰动，换热系数和热流密度近似线性比例急剧增加。核态沸腾具有

温差小，换热大的特点，绝大多数沸腾换热在此阶段进行。第三阶段是过渡沸腾，

气泡汇聚覆盖在加热壁面，蒸汽排除过程越趋恶化。热流密度不仅不随壁面过热

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

15 积分 4人已下载

立即下载 VIP免费下载

摘要：

摘要目前中央空调冷水机组中，强化换热高效管已代替光滑管，应用非常的广泛。TURBO-B管是一种后兴起的强化换热管，由于强化管表面结构复杂，影响强化管换热性能的因素比较多，目前对于管外沸腾强化换热性能的研究主要以实验为主，并更换不同的工况。一个工况则需要做很多实验来进行分析，大大增加了人力、物力方面的成本。通过实验和理论模型的结合，可以减少这方面的成本。本课题首先对两种用于池沸腾换热的强化换热管TURBO-B管进行了水平管外换热性能实验。然后，利用威尔逊图解法和Origin软件处理实验数据，推导出这两种管型的管内外换热系数的关联式，同时，根据实验测得的数据比较这两种管型的换热性能。最后在此基础上...

展开>> 收起<<

TURBO-B类强化换热管沸腾换热性能实验与理论研究.pdf

共68页,预览7页

还剩页未读，继续阅读

TURBO-B类强化换热管沸腾换热性能实验与理论研究

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

推荐作者

热门标签

举报选择: