Effect of axial heat conduction on heat transfer performance of plate fin heat exchanger under different thermal boundary condition

doi:10.11949/0438-1157.20200922

Abstract

Abstract:

Based on MATLAB program and by implementing the distributed parameter method, the 2-D model of reverse-flow plate fin heat exchanger(PFHE) was constructed. The numerical results were compared with the experimental results in a multi-stream PFHE used in liquefier in Claude cycle, and the numerical results were in good agreement with the experimental results. The effect of the axial conduction on heat transfer performance of PFHE was investigated, and it was observed that the effectiveness of PFHE considering axial conduction decreased by 21.8%, compared with that without considering axial conduction. Moreover, the influence of the adiabatic boundary condition on the cold and hot ends of separating plate of PFHE was transferred to the inner domain of PFHE by axial conduction effect, which resulted in the fluid temperature distortion in near-inlet domain. When the boundary conditions of constant wall temperature or constant heat flux were adopted on hot and cold ends of separating plate respectively, the fluid temperature distortion in near-inlet domain almost disappeared. When considering axial heat conduction, compared with the adiabatic boundary conditions at both ends of the partition, the effectiveness of the constant wall temperature boundary conditions increases by 35.8%( $ε_{c}$ ) and 31.7%( $ε_{h}$ ), and the effectiveness of the constant heat flow boundary conditions increases by 22.8%( $ε$ ).

Key words: thermal boundary condition, plate fin heat exchanger, axial conduction, cold end of separating plate, hot end of separating plate, effectiveness

摘要：

基于MATLAB编程，采用分布参数法构建了逆流板翅式换热器的二维计算模型，并与Claude循环氦液化器中多股流板翅式换热器的实验结果进行比较，数值结果和实验结果的吻合程度很好。研究了轴向导热对板翅式换热器换热能力的影响，发现考虑轴向导热的有效度相较于不考虑轴向导热降低了21.8%，且由于轴向导热将隔板冷端和热端的绝热边界条件施加的影响向换热器计算域内部传递，引发了换热器入口区域流体温度的畸变。而在隔板的冷端和热端分别采取定壁温或定热流的边界条件时，流体入口区域温度畸变几乎消失。在考虑轴向导热时，与隔板两端绝热边界条件相比，定壁温边界条件有效度增加35.8%（ $ε_{c}$ ）和31.7%（ $ε_{h}$ ），定热流边界条件有效度增加22.8%（ $ε$ ）。

关键词: 热边界条件, 板翅换热器, 轴向导热, 隔板冷端, 隔板热端, 有效度

CLC Number:

TK 124

LI Ke, WEN Jian, WANG Simin. Effect of axial heat conduction on heat transfer performance of plate fin heat exchanger under different thermal boundary condition[J]. CIESC Journal, 2021, 72(4): 1956-1964.

李科, 文键, 王斯民. 不同热边界条件下板翅式换热器轴向导热对换热的影响[J]. 化工学报, 2021, 72(4): 1956-1964.

Figures/Tables 8

Fig.1 Model of reverse-flow plate fin heat exchanger

Fig.2 Interaction effects between different nodes

Fig.3 Calculation process

Table 1 Comparison between experimental results and numerical results

制冷模式		液化模式
T_out,exp/K	T_out,num/K	T_out,exp/K	T_out,num/K
12.5	12.82	13.3	13.72
44.4	44.03	51.1	50.73
13.1	12.91	14.9	14.72

Table 2 Operation condition of reverse-flow plate fin heat exchanger

流体编号	工质	质量流量/(g/s)	入口温度/K	入口压力/MPa	总层数
1	N₂	1	80	0.11	1
2	N₂	1	311	0.11	1

Fig.4 Distribution of axial fluid temperature (adiabatic boundary condition)

Fig.5 Distribution of axial fluid temperature (constant wall temperature boundary condition)

Fig.6 Distribution of axial fluid temperature (constant heat flux boundary condition)

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