Numerical study on heat transfer characteristics of a novel rectangular printed circuit heat exchanger

doi:10.11949/0438-1157.20250568

Abstract

Abstract:

A mathematical model was established based on a sample of a novel rectangular printed circuit board heat exchanger (RM-PCHE). The coupled heat transfer characteristics of supercritical CO₂ within the RM-PCHE were investigated through numerical simulation. The reliability of the numerical model was validated against experimental data, with the maximum relative error in heat transfer performance quantified at 11.2% under the tested conditions. This result demonstrates the credibility of the simulation outcomes. Numerical analysis results show that under typical low-temperature regenerator operating conditions, the heat transfer performance of supercritical CO₂ is influenced by both specific heat and thermal conductivity. On the hot side, due to the approximately constant thermal conductivity, the heat transfer performance of supercritical CO₂ is primarily dominated by specific heat. Moreover, compared with turbulence intensity, the thermophysical properties of supercritical CO₂ are the primary factor affecting its heat transfer, leading to the heat transfer coefficient of supercritical CO₂ on the cold side of rectangular printed circuit heat exchanger consistently being higher than that on the hot side. Additionally, due to the baffle in rectangular printed circuit heat exchanger enhancing the fluid's turbulent diffusion capacity, the existing correlation consistently underestimates the heat transfer performance of supercritical CO₂. Therefore, based on simulated data and incorporating the effects of thermophysical property variations and turbulence intensity on heat transfer, modified heat transfer correlations for supercritical CO₂ were developed. Under the simulated conditions, the maximum deviations of the hot-side and cold-side correlations for the rectangular printed circuit heat exchanger using supercritical CO₂ as working fluid were 2.3% and 6.8%, respectively.

Key words: supercritical carbon dioxide, turbulent flow, printed circuit heat exchanger, heat transfer, numerical analysis

摘要：

根据新型矩形印刷电路板式换热器（RM-PCHE）的试样建立了数学模型，通过数值模拟对RM-PCHE内超临界CO₂的耦合传热特性展开了研究。通过实验数据验证了数值模型的可靠性，换热量的最大相对误差为11.2%，模拟结果可靠。数值分析结果表明，在低温回热器的典型工况下，超临界CO₂的传热性能由比热容和热导率共同影响。在热侧，由于热导率近似恒定，超临界CO₂的传热性能主要由比热容主导。与湍流强度相比，超临界CO₂的热物理性质是影响其传热性能的更主要因素，这导致RM-PCHE冷侧超临界CO₂的传热系数总是大于热侧。基于模拟数据，综合考虑物性变化和湍流强度对传热的影响，建立了修正的超临界CO₂传热关联式，在模拟工况下，热侧关联式的最大偏差为2.3%，冷侧关联式的最大偏差为6.8%。

关键词: 超临界二氧化碳, 湍流, 印刷电路板式换热器, 传热, 数值分析

CLC Number:

TK 172

Shaogeng ZHONG, Hong ZHANG, Ronggang ZHANG, Yan REN, Weidong WU. Numerical study on heat transfer characteristics of a novel rectangular printed circuit heat exchanger[J]. CIESC Journal, 2025, 76(11): 5911-5922.

钟绍庚, 张宏, 张荣刚, 任燕, 武卫东. 新型矩形印刷电路板式换热器的数值研究[J]. 化工学报, 2025, 76(11): 5911-5922.

Figures/Tables 16

Fig.1 Structure and flow mode of RM-PCHE

Fig.2 Geometric models and mesh structure

Table 1 Simulated operating conditions of RM-PCHE

工况	热侧温度/℃	热侧压力/MPa	热侧质量流量/(kg·s^-1)	冷侧温度/℃	冷侧压力/MPa	冷侧质量流量/(kg·s^-1)
组1	80~190	8.5	0.002	50	20	0.002
组2	120	8~9	0.002	50	20	0.002
组3	120	8.5	0.002	50~80	20	0.002
组4	120	8.5	0.002	50	19~21	0.002
组5	120	8.5	0.001~0.006	50	20	0.001~0.006

Table 2 Comparison of turbulence model calculation results

湍流模型	热侧出口温度/℃	相对误差/%	冷侧出口温度/℃	相对误差/%
实验值	50.4	—	63.3	—
标准k-ω	54.4	7.9	58.5	7.6
SST k-ω	53.0	5.2	61.7	2.5
标准k-ε	54.8	8.7	59.3	6.3
RNG k-ε	53.9	6.9	61.1	3.5

Table 3 Grid schemes and results

方案	网格数	y⁺值	高压侧传热系数/(W·m^-2·℃^-1)	相对偏差/%
1	3207852	0.532	4782.0	5.73
2	4176820	0.539	4704.6	4.02
3	5196750	0.545	4621.4	2.18
4	5911124	0.561	4541.7	0.42
5	6693236	0.569	4522.8	0.00

Table 4 The verification conditions for RM-PCHE model

工况点	(T_h_,_i /T_c_,_i)/℃	(P_h,o/P_c,o)/MPa	(m_h/m_c)/(kg·s^-1)
1	66.4 / 44.2	8.2 / 18.5	0.001466 / 0.001467
2	70.4 / 44.8	8.2 / 18.5	0.001434 / 0.001480
3	73.8 /45.7	8.2 / 18.4	0.001466 / 0.001467
4	79.0 / 46.4	8.2 / 18.4	0.001425 / 0.001459
5	84.0 / 46.5	8.2 / 18.7	0.001410 / 0.001462
6	92.2 / 47.2	8.1 / 18.7	0.001358 / 0.001472

Fig.3 Verification of the simulation results for RM-PCHE

Fig.4 Effect of hot-side inlet temperature and pressure on heat transfer coefficients of both sides

Fig.5 Effect of cold-side inlet temperature and pressure on heat transfer coefficients of both sides

Fig.6 Variation of thermal physical properties for SCO2 at different pressures

Fig.7 Effect of mass flow rate on local heat transfer coefficients

Fig.8 Contour of turbulence kinetic energy on hot side of the RM-PCHE at x=213 mm

Fig.9 Contour of turbulence kinetic energy on cold side of the RM-PCHE at x=213 mm

Table 5 Heat transfer correlations from different literature

公式	文献
$N u b = 0.0183 R e b 0.82 P r b 0.5 ρ b ρ w - 0.3$	[31]
$N u b = 0.022126 R e b 0.8 P r b 0.3 ρ b ρ w - 1.4652 c p b c p w 0.0832$	[32]
$N u b = 0.0183 R e b 0.82 P r b 0.5 ρ w ρ b 0.3 c p ¯ c p b 0.4$	[33]
$N u b = 0.023 R e b 0.8 P r b 0.4 c p ¯ c p b n ρ w ρ b 0.3$ $n = 0.4, f o r T b < T w < T p c a n d 1.2 T p c < T b < T w 0.4 + 0.2 T w T p c - 1, f o r T b < T p c < T w 0.4 + 0.2 T w T p c - 1 1 - 5 T b T p c - 1, f o r T p c < T b < 1.2 T p c$	[34]

Table 5 Heat transfer correlations from different literature

公式	文献
$N u b = 0.0183 R e b 0.82 P r b 0.5 ρ b ρ w - 0.3$	[31]
$N u b = 0.022126 R e b 0.8 P r b 0.3 ρ b ρ w - 1.4652 c p b c p w 0.0832$	[32]
$N u b = 0.0183 R e b 0.82 P r b 0.5 ρ w ρ b 0.3 c p ¯ c p b 0.4$	[33]
$N u b = 0.023 R e b 0.8 P r b 0.4 c p ¯ c p b n ρ w ρ b 0.3$ $n = 0.4, f o r T b < T w < T p c a n d 1.2 T p c < T b < T w 0.4 + 0.2 T w T p c - 1, f o r T b < T p c < T w 0.4 + 0.2 T w T p c - 1 1 - 5 T b T p c - 1, f o r T p c < T b < 1.2 T p c$	[34]

Fig.10 Comparison between simulation data and present correlation results

Fig.11 Comparison between simulation data and the modified correlation results

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