Flow boiling heat transfer of phase separation structure microchannels under pulsating pressure

doi:10.11949/0438-1157.20250570

Abstract

Abstract:

Phase separation structure microchannels have attracted considerable attention due to their high heat transfer efficiency and minimal pressure fluctuations. The effect of phase separation structure on the heat transfer property and temperature uniformity of microchannel was studied, this paper conducts research on three types of phase separation hole counts: 10-hole N1 type, 20-hole N2 type and 30-hole N3 type, as well as three types of phase separation arrangement positions: midstream and downstream (Type A), upstream and downstream (Type B), and upstream, midstream, and downstream (Type C). Ethanol is used as the working fluid, and flow boiling experiments are conducted in a rectangular counterflow microchannel with a cross-section of 2 mm×2 mm under conditions of heat flux density ranging from 15.05 to 124.89 kW/m², inlet temperature of 40℃, and mass flow rate of 102.50 kg/(m²·s). Pulsating pressure is applied to the forward channel to achieve gas phase separation. The effects of the phase separation structure were analyzed by introducing parameters such as the heat transfer enhancement factor, along-line wall temperature distribution, average wall temperature, and temperature standard deviation. The research results indicate that, at a constant transmembrane pressure, the heat transfer coefficient reaches its maximum when the number of phase separation holes is 20, and further increasing the number to 30 does not significantly enhance the heat transfer effect. In comparison with the non-phase-separation operational conditions, the maximum heat transfer enhancement factor in the microchannel with phase separation structures reaches 1.92, while the maximum standard deviation of two-phase wall temperature along the path is reduced by 44%. This suggests that phase separation microchannels can effectively improve the heat transfer efficiency and temperature uniformity in microchannels.

Key words: pulsating pressure, phase separation structure, counterflow, microchannels, heat transfer enhancement, temperature uniformity

摘要：

为了探究相分离结构对微细通道流动沸腾传热性能和均温性的影响，对三种相分离孔数（10孔N1型、20孔N2型、30孔N3型）和三种布置位置（中下游A型、上下游B型、上中下游C型）开展了研究。实验采用乙醇作为工质，在热通量15.05~124.89 kW/m²、工质入口温度40℃、质量流率102.50 kg/（m²·s）条件下，对2 mm×2 mm矩形逆流微细通道进行流动沸腾实验，通过脉动压力实现气相分离。引入强化传热因子、沿程壁温分布、壁面平均温度和温度标准差等参数分析相分离结构的影响。结果表明，跨膜压力一定时，相分离孔数为20时传热系数最大，孔数增加至30对传热提升有限。与无相分离工况相比，相分离结构使传热强化因子最大达1.92，沿程壁温标准差最大降低44%。这表明，相分离微细通道有效提升了传热效率和均温性。

关键词: 脉动压力, 相分离结构, 逆流, 微细通道, 强化传热, 均温性

CLC Number:

TK 124

Xiaoping LUO, Lan XIAO, Jiayu ZHANG. Flow boiling heat transfer of phase separation structure microchannels under pulsating pressure[J]. CIESC Journal, 2025, 76(11): 5877-5889.

罗小平, 肖岚, 张嘉宇. 脉动压力作用下相分离结构微细通道流动沸腾传热[J]. 化工学报, 2025, 76(11): 5877-5889.

Figures/Tables 23

Fig.1 Schematic diagram of experimental system

Fig.2 Pressure difference between adjacent channels

Fig.3 Explosion diagram of experimental section

Fig.4 Microchannel plate

Fig.5 Location of temperature measuring hole and pressure measuring hole in test section

Table 1 Physical properties of ethanol

饱和温度

T_sat/℃

液相密度

$ρ l$ /(kg/m³)

气相密度

$ρ g$ /(kg/m³)

液相黏度

$μ l$ /(mPa·s)

液相热导率

$λ l$ /(W/(m·K))

液相比热容

c_p_,_l /(J(kg·K))

汽化潜热

h_f,g/(J/kg)

表面张力

$γ$ /(mN·m)

Table 1 Physical properties of ethanol

饱和温度

T_sat/℃

液相密度

$ρ l$ /(kg/m³)

气相密度

$ρ g$ /(kg/m³)

液相黏度

$μ l$ /(mPa·s)

液相热导率

$λ l$ /(W/(m·K))

液相比热容

c_p_,_l /(J(kg·K))

汽化潜热

h_f,g/(J/kg)

表面张力

$γ$ /(mN·m)

78.34

736.49

1.65

0.44

0.15

2.93

846.75

16.75

Fig.6 Microchannel with phase separation structure

Fig.7 Specification of stainless steel fixing plate

Fig.8 Heat loss fitting curve

Table 2 Instrument accuracy

测量仪器	测量值	设备型号	量程	精度
热电阻	温度/℃	PT-100	0~200	0.1℃
转子流量计	流量/(L/h)	LZB-WS-10	6~60	2.5%
压力传感器	压力/kPa	HY-131	0~100	0.2%
直流高压静电发生器	电压/kV	DW-P503	0~50	0.5%

Table 3 Maximum relative error of indirect physical quantities

测量物理参数	最大不确定度/%
热通量q_eff	3.31
单相段长度L_sp	2.76
质量流率G	2.50
局部饱和传热系数h	6.29

Fig.9 Time domain characteristics of saturated boiling heat transfer coefficient under fluctuating pressure

Fig. 10 Heat transfer coefficient of saturated boiling under the synergistic effect of different types of fluctuating pressure and phase separation structure

Fig.11 Variation of inlet pressure of forward flow channel with time

Fig.12 Effect of gas phase separation holes on saturated boiling heat transfer coefficient

Fig.13 Heat transfer factors for different number of gas phase separation holes

Fig.14 Effect of gas phase separation position on saturated boiling heat transfer coefficient

Fig.15 Heat transfer enhancement factors at different gas phase separation positions

Table 4 Operating range of heat flux density

工况	热通量/(kW/m²)	工况	热通量/(kW/m²)
A	15.05	H	77.58
B	23.27	I	87.61
C	32.33	J	97.08
D	40.62	K	105.36
E	50.85	L	114.86
F	60.02	M	124.89
G	68.29

Fig.16 Temperature distribution along the wall under the synergistic effect of fluctuating pressure and phase separation structure

Fig.17 Average wall temperature

Fig.18 Standard deviation of wall temperature

Fig.19 High speed photography of exhaust phase

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