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Experimental study of a rectangular microchannel printed circuit heat exchanger using supercritical carbon dioxide and water cooling

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APPLIED THERMAL ENGINEERING 2025年 262卷

作者： Ren, Yan Jiang, Ruowen Wang, Peidong Wu, Weidong Yang, Yingying Yang, Qiguo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai Elect Power Generat Equipment Co Ltd Turb Shanghai 200240 Peoples R China

Printed circuit heat exchangers with rectangular microchannels (RM-PCHEs) have attracted interest in recent years owing to their excellent heat-transfer performance and efficient and convenient processing methods. However, experimental studies on RM-PCHE using supercritical carbon dioxide (SCO2) and cooling water as working fluids are still scarce. This study established an experimental system to investigate the flow and heattransfer characteristics of an RM-PCHE. The experiment considered inlet temperature ranges of 343.13-371.1 K for SCO2 and 283.13-293.13 K for the cooling water. The results showed that the SCO2 inlet temperature had the most significant effect on the heat-transfer performance. With a 1 % increase in the SCO2 inlet temperature, the test sample Qave increased by 2.18 %, and thermal performance decreased by 2.62 %. Decreasing the SCO2 inlet temperature or increasing the cooling-water inlet temperature improved the hot-side flow performance. The cold-side pressure drop and effectiveness were most significantly affected by the cooling-water mass flow rate and minimally affected by the cooling-water inlet temperature. The effectiveness increased to 96.9 % with an increase in the cooling-water mass flow rate to 1500 kg & sdot;h- 1. These results provide theoretical and data support for the structural design and performance optimization of SCO2 microchannel water coolers.

关键词： Printed circuit heat exchanger Supercritical carbon dioxide Cooling water Flow and heat-transfer characteristics rectangular microchannel

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Optimization of fin for rectangular microchannel printed circuit heat exchanger using supercritical CO2 as working fluid

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JOURNAL OF SUPERCRITICAL FLUIDS 2025年 219卷

作者： Ren, Yan Zeng, Le Zhong, Shaogeng Wu, Weidong Yang, Yingying Yang, Qiguo Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Fujian Polytech Normal Univ Sch Elect & Mech Engn Fuzhou 350300 Peoples R China

To improve the performance of printed circuit heat exchanger (PCHE) in the supercritical carbon dioxide (SCO2) Brayton cycle system, the mathematic-physical model of the heat exchange unit was established, based on a newtype rectangular microchannel PCHE (RM-PCHE) manufacturing by total-etching technology in this study. And the influence mechanism and laws on the flow and heat transfer of the different fin distributions and shapes were numerically investigate. Results showed average simulation deviations of 0.9 % for outlet temperature and 13.3 % for heat transfer quantity, meeting accuracy requirement. Uniform fin distribution at 10 mm intervals significantly reduced pressure drop and improved comprehensive heat transfer performance by 14.8 %. When elliptical and airfoil fins were selected for the hot-side and cold-side channels, the flow characteristic significantly improved and the heat transfer process became more stable, improving the single-side performance by 15.9 % and 12.3 %, respectively.

关键词： Supercritical carbon dioxide Printed circuit heat exchanger rectangular microchannel Flow and heat transfer characteristics Optimization of fin distribution and shape

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Flow regimes of the immiscible liquids within a rectangular microchannel

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Acta Mechanica Sinica 2021年第10期37卷 1544-1556,I0003页

作者： Xiang Wang Yan Pang Yilin Ma Yanlin Ren Zhaomiao Liu College of Mechanical Engineering and Applied Electronics Technology Faculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China Beijing Key Laboratory of Advanced Manufacturing Technology Beijing University of TechnologyBeijing100124China

Flow regimes of two immiscible liquids at the cross junction within a rectangular microchannel are experimentally *** of the flow regimes including critical conditions and interfacial deformations are *** is found that the occurrence of the tubing regime is favored by increased viscosity of the dispersed phase or reduced cross-sectional aspect ratio,leading to the shrinkage of the flow rate range that could produce *** order to reveal the physical mechanism,the force analysis is carried out based on the tunnel structure formed between the interface and channel side walls within the rectangular *** reshaping stage and pinch-off stage are mainly driven by the interfacial tension,leading to far larger neck thinning rate compared to the superficial velocity of either *** filling stage and squeezing stage are dominated by the pressure drop across the dispersed tip while the role of the shear force becomes more important with increasing tunnel *** filling period is estimated as t2≈kHwn02/Qd with k=1.34 and the squeezing period is expressed as t3/Tc=0.3Cac−*** to the force analysis,the critical tip velocity under dripping scales with three key parameters,which can be expressed as(utip/U)*~QcLtip/wtunnel3.

关键词： Cross junction Flow regime Liquid interface Force analysis rectangular microchannel

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Numerical study of liquid flow and heat transfer in rectangular microchannel with longitudinal vortex generators

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APPLIED THERMAL ENGINEERING 2015年 78卷 576-583页

作者： Ebrahimi, Amin Roohi, Ehsan Kheradmand, Saeid Ferdowsi Univ Mashhad Fac Engn Dept Mech Engn High Performance Comp HPC Lab Mashhad Iran Malek Ashtar Univ Technol Dept Mech & Aerosp Engn Shahin Shahr Isfahan Iran

The liquid flow and conjugated heat transfer performance of single phase laminar flow in rectangular microchannels equipped with longitudinal vortex generators (LVGs) are numerically investigated. Deionized-water with temperature-dependent thermo-physical properties is employed to conduct the simulations. Three dimensional simulations are performed using an open-source flow solver based on finite volume approach and SIMPLEC algorithm. Five different configurations of the microchannel with different angles of attack of the LVGs are considered. Simulation results are compared with available experimental data and a deviation below 10% is achieved. The results show that for Reynolds number ranged from 100 to 1100, there is a 2-25% increase in the Nusselt number for microchannels with LVGs, while the friction factor increased by 4-30%. Except one at Re = 100, the overall performance of the all configurations of microchannels with LVGs is higher than ones without LVG's. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： rectangular microchannel Vortex generators Laminar liquid flow Heat transfer

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An experimental investigation on characteristics of liquid film thickness of gas-liquid Taylor flow in square/rectangular microchannel applied in microreactor

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2024年 234卷

作者： Fu, Dengwei Hu, Yifei Li, Zhaoyu Dang, Chaobin Hong, Sihui Sun Yat Sen Univ Sch Phys & Astron Zhuhai 519082 Peoples R China Zhejiang Univ Coll Elect Engn Hangzhou 310027 Peoples R China Univ Tokyo Dept Human & Engn Environm Studies 5-1-5 Kashiwanoha Kashiwa Chiba 2778563 Japan Univ Fukui Grad Sch Engn 3-9-1 Bunkyo Fukui Fukui 9108507 Japan

microchannel reactors employing Taylor flow is 1 - 3 orders of magnitude higher than traditional reactor in handling gas-liquid reaction processes, which has found important applications in oxidation, hydrogenation, chlorination, fluorination and absorption involved in chemical industry. Liquid film thickness of gas-liquid Taylor flow in circular microchannel has been widely investigated, whereas the variation and distribution of liquid film thickness in square/rectangular microchannel are lack of comprehension. In the present work, experiments were conducted to investigate the variation of liquid film thickness in square channels with hydraulic diameter Dh h = 0.3, 0.5, 0.7, 1.0 mm, and rectangular channels with a depth of 0.5 mm and widths of 0.3, 0.5, 0.7, 1.0 mm under the condition of air-water and the addition of surfactant Tween-20. The liquid film thicknesses were measured using a laser focus displacement meter (LFDM), the bubble shapes and velocities were compared using high speed photography. The experimental results illustrate that the dimensionless bubble diameter in square/rectangular microchannels can be divided into initial stage, reduction stage and stable stage with the increasing of capillary number Ca . The initial, reduction and stable stage of the dimensionless bubble diameter are all influenced by the channel hydraulic diameter, aspect ratio, asymmetry effects and surface tension coefficient of working fluid. In square channels with D-h = 0.3, 0.5, 0.7, and 1.0 mm, the dimensionless bubble diameter enters the reduction stage at Ca = 0.019, 0.015, 0.011, and 0.009, respectively. Besides, an empirical formula of dimensionless bubble diameter was developed using the dimensionless groups Ca, Re, Bo , and Li/Dh i / D h to describe the characteristics of liquid film thickness in square/rectangular microchannel.

关键词： Liquid film thickness Gas-liquid two-phase flow Square microchannel rectangular microchannel Precision measurement

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AC electroosmotic flow of generalized Maxwell fluids in a rectangular microchannel

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JOURNAL OF NON-NEWTONIAN FLUID MECHANICS 2011年第21-22期166卷 1304-1314页

作者： Jian, Yong-jun Liu, Quan-sheng Yang, Lian-gui Inner Mongolia Univ Sch Math Sci Hohhot 010021 Peoples R China

Many biofluids such as blood and DNA solutions are viscoelastic and exhibit extraordinary flow behaviors, not existing in Newtonian fluids. In the present investigation, analytical series solutions for the time periodic EOF flow of the generalized Maxwell fluids through a two-dimensional rectangular microchannel are found under the Debye-Huckel linear approximation. A linearized Poisson-Boltzmann equation governing the electrical double layer (EDL) field, together with the Cauchy momentum equation and the general Maxwell constitutive equation are included in the analysis. Numerical results are presented for the velocity profiles and volumetric flow rates in the rectangular microchannel for different parametric values that characterize this flow. (C) 2011 Elsevier B.V. All rights reserved.

关键词： EDL Time periodic EOF Generalized Maxwell fluids rectangular microchannel Oscillating reynolds number Relaxation times

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Experimental study of interfacial mass transfer in a slug flow of ethanol - CO2 mixture in a rectangular microchannel

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THERMOPHYSICS AND AEROMECHANICS 2023年第3期30卷 475-486页

作者： Bartkus, G. V. Filatov, N. A. Bukatin, A. S. Kuznetsov, V. V. Kutateladze Inst Thermophys SB RAS Novosibirsk Russia Alferov St Petersburg Acad Univ RAS St Petersburg Russia Inst Analyt Instrumentat RAS St Petersburg Russia

The structure of a slug gas-liquid flow and interfacial mass transfer during the flow of ethanol-N2 and ethanol-CO(2 )mixtures in a horizontal rectangular microchannel have been experimentally studied. The experiments were carried out in a straight microchannel with a cross section of 380 x 190 mu m. To determine a change in the volume of a gas bubble along the microchannel length, the method of high-speed visualization with digital processing was applied. In a wide range of gas flow rates, the bubble frequency and the volume of gas bubbles and their velocity were measured, and the volumetric coefficient of mass transfer from liquid was determined for the ethanol-CO2 mixture. A physically substantiated model of interfacial mass transfer for a slug flow in a channel of rectangular cross section, which takes into account the circulation flow in a liquid slug, was proposed.

关键词： rectangular microchannel gas-liquid flow interfacial mass transfer CO2 dissolution

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Thermally fully developed electroosmotic flow through a rectangular microchannel

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2012年第21-22期55卷 6285-6290页

作者： Su, Jie Jian, Yongjun Chang, Long Inner Mongolia Univ Sch Math Sci Hohhot 010021 Inner Mongolia Peoples R China Inner Mongolia Finance & Econ Coll Sch Math & Stat Hohhot 010051 Inner Mongolia Peoples R China

This study investigates the velocity and temperature distributions of the thermally fully developed electroosmotic flow through a rectangular microchannel. Based on linearized Poisson-Boltzmann (PB) equation, Navier-Stokes equation and thermally fully developed energy equation, analytical solutions of normalized velocity, temperature and Nusselt number are derived. They greatly depend on the ratio K of characteristic scale of the rectangular microchannel to Debye length, width to height ratio alpha and Joule heating to heat flux ratio S. By numerical computation, we found that for prescribed electrokinetic width K, increased S yields greater temperature. For small K, the variations of the temperature Dare larger than those of large K. The dependence of temperature on S is more significant for a small K, while at a larger K the temperature profiles are almost identical. In addition, we illustrate the Nusselt number Nu variations with S, alpha and K. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： rectangular microchannel Electroosmotic flow Fully developed Joule heating

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Experimental study of interfacial mass transfer for the transition from slug to bubbly flow in a rectangular microchannel

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THERMOPHYSICS AND AEROMECHANICS 2024年第3期31卷 513-522页

The structure of a gas-liquid flow and interfacial mass transfer during the transition from the slug to the bubbly flow of ethanol-CO2 mixture in a horizontal straight microchannel were experimentally studied. The experiments were performed for a channel with a rectangular cross section of 141x385 mu m in the range of superficial gas and liquid velocities J(G) = 0.16-0.8 m/s and J(L) = 0.22-0.5 m/s. To determine a change in the volume of the elongated bubble along the microchannel length due to CO2 absorption, the method of high-speed visualization with subsequent image processing was applied. The bubble frequency, velocity, size, and change in the volume of gas slugs and bubbles along the channel were measured, and volumetric coefficient of mass transfer from liquid kLa was calculated. The measured volumetric mass transfer coefficient was compared with the known correlations and a new correlation was proposed for the transition from the slug to the bubbly flow due to interfacial mass transfer.

关键词： rectangular microchannel gas-liquid flow interfacial mass transfer CO2 absorption

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The effect of rib shape on the behavior of laminar flow of oil/MWCNT nanofluid in a rectangular microchannel

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JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY 2018年第3期134卷 1611-1628页

作者： Gholami, Mohammad Reza Akbari, Omid Ali Marzban, Ali Toghraie, Davood Shabani, Gholamreza Ahmadi Sheikh Zarringhalam, Majid Islamic Azad Univ Aligoudarz Branch Dept Mech Engn Aligoudarz Iran Islamic Azad Univ Khomeinishahr Branch Young Researchers & Elite Club Khomeinishahr Iran Islamic Azad Univ Khomeinishahr Branch Dept Mech Engn Khomeinishahr 84175119 Iran Islamic Azad Univ South Tehran Branch Young Researchers & Elite Club Tehran Iran

In this research, the laminar and forced flow and heat transfer of oil/multi-walled carbon nanotubes nanofluid in a microchannel have been numerically investigated. The studied geometrics is a two-dimensional rectangular microchannel with the proportion of length to height of 150 (L/d=150). The purpose of this research is to investigate the effect of using rectangular, oval, parabolic, triangular and trapezoidal rib shapes on behavior and heat transfer of nanofluid flow in the rectangular microchannel. This research has been simulated in Reynolds numbers of 1, 10, 50 and 100 and volume fractions of 0, 2 and 4% of nanoparticles by using finite volume method. The results of this research indicate that the existence of ribs enhances the friction factor and Nusselt number, significantly. Also, the shape of rib is one of the most important factors for determining the behavior and heat transfer of cooling fluid flows. Among the investigated rib shapes, the parabolic rib, comparing to the augmentation of friction factor, has the best proportion of Nusselt number enhancement.

关键词： Nanofluid rectangular microchannel Laminar flow Rib Multi-walled carbon nanotubes (MWCNT)

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