﻿ 冷却条件下超临界CO2在突扩管中流动及其换热的数值模拟 Numerical Simulation on the Flow and Heat Transfer of Supercritical CO2 in Sudden Expansion Pipe under Cooling Condition

Applied Physics
Vol.05 No.12(2015), Article ID:16693,7 pages
10.12677/APP.2015.512030

Numerical Simulation on the Flow and Heat Transfer of Supercritical CO2 in Sudden Expansion Pipe under Cooling Condition

Chao Wang1, Xinrong Zhang2*, Hao Bai1

1School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing

2College of Engineering, Peking University, Beijing

Received: Dec. 11th, 2015; accepted: Dec. 26th, 2015; published: Dec. 31st, 2015

ABSTRACT

The flow and heat transfer law of supercritical CO2 in sudden expansion duct has important meaning on efficient design of technology and devices of new energy conversion system and recycling of waste resources. In this paper, the numerical method is finite volume method. The flow and heat transfer law of supercritical CO2 in sudden expansion duct under cooling condition is studied in this paper by using numerical method of finite volume method. It is founded that the flow situation of supercritical CO2 in sudden expansion pipe under cool condition is the same as that of under heat condition in this study. Compared with the condition of heating, the bifurcation phenomenon is easier to appear under cooling. And with the increase of wall cooling heat flux, the length of recirculation regions becomes smaller. It is a comparison and supplement to the previous studies, and sheds some light on the application of the law of flow and heat transfer of supercritical CO2 as working fluid material in sudden expansion duct.

Keywords:Supercritical CO2, Sudden Expansion Pipe, Flow and Heat Transfer, Flow Bifurcation

1北京科技大学冶金与生态工程学院，北京

2北京大学工学院，北京

1. 引言

2. 数值计算模型

2.1. 物理模型

2.2. 数学模型

(1)

(2)

(3)

(4)

2.3. 边界条件

3. 计算结果与讨论

3.1. 流动雷诺数的影响

Figure 1. Physical model

Figure 2. Streamline chart q = −100 W/m2, ER = 2

3.2. 热流密度的影响

Table 1. Recr and Retr of supercritical CO2 in sudden expansion duct under different heat transfer conditions (ER = 2)

Figure 3. Streamline chart q = 100 W/m2, ER = 2 [15]

Figure 4. Variation of reattachment length with Reynolds at different wall flux under cooling condition

Figure 5. Variation of reattachment length with Reynolds at different wall flux under heating condition [15]

4. 结论

1) 冷却条件下，与超临界CO2加热条件下的规律基本一致，随着流动雷诺数的增大，流动由对称发展为不对称，进而出现第三个或者更多的回流区。这是对常规流体流动规律和超临界CO2加热条件下流动规律的补充。

2) 在冷却条件下超临界CO2的流动情况，和在加热条件下对应的情况比较，临界雷诺数和转换雷诺数都明显减小。这意味着在冷却条件下超临界CO2流动更易失稳，易发生流动分叉。

3) 在冷却条件下，随着冷却热流密度的增大，回流区长度减小。

Numerical Simulation on the Flow and Heat Transfer of Supercritical CO2 in Sudden Expansion Pipe under Cooling Condition[J]. 应用物理, 2015, 05(12): 216-222. http://dx.doi.org/10.12677/APP.2015.512030

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*通讯作者。