Ali M. H. Al-Obaidy^*, Ekhlas M. Fayyadh, Amer M. Al-Dabagh

Frontiers in Heat and Mass Transfer, Vol.22, No.5, pp. 1421-1442, 2024, DOI:10.32604/fhmt.2024.055063 - 30 October 2024

Abstract High heat dissipation is required for miniaturization and increasing the power of electronic systems. Pool boiling is a promising option for achieving efficient heat dissipation at low wall superheat without the need for moving parts. Many studies have focused on improving heat transfer efficiency during boiling by modifying the surface of the heating element. This paper presents an experimental investigation on improving pool boiling heat transfer using an open microchannel. The primary goal of this work is to investigate the impact of the channel geometry characteristics on boiling heat transfer. Initially, rectangular microchannels were prepared… More > Graphic Abstract

Fujian Zhang¹, Ziyang Wang¹, Xiang Gao¹, Zhongqiang Zhang^1,*

The International Conference on Computational & Experimental Engineering and Sciences, Vol.29, No.2, pp. 1-1, 2024, DOI:10.32604/icces.2024.011736

Abstract Spontaneous droplet transport has broad application prospects in fields such as water collection and microfluidic chips. Despite extensive research in this area, droplet self-transport is still limited by issues such as slow transport velocity, short distance, and poor integrity. Here, a novel cross-hatch textured cone (CHTC) with multistage microchannels and circular grooves is proposed to realize ultrafast directional long-distance self-transport of multi-scale droplets. The CHTC triggers two modes of fluid transport: Droplet transport by Laplace pressure difference and capillary suction pressure-induced fluid transfer in microchannels on cone surfaces. By leveraging the coupling effect of the… More >

Elena Mosheva^1,*, Ivan Krasnyakov²

FDMP-Fluid Dynamics & Materials Processing, Vol.20, No.8, pp. 1743-1758, 2024, DOI:10.32604/fdmp.2024.049146 - 06 August 2024

Abstract Continuous-flow microchannels are widely employed for synthesizing various materials, including nanoparticles, polymers, and metal-organic frameworks (MOFs), to name a few. Microsystem technology allows precise control over reaction parameters, resulting in purer, more uniform, and structurally stable products due to more effective mass transfer manipulation. However, continuous-flow synthesis processes may be accompanied by the emergence of spatial convective structures initiating convective flows. On the one hand, convection can accelerate reactions by intensifying mass transfer. On the other hand, it may lead to non-uniformity in the final product or defects, especially in MOF microcrystal synthesis. The ability… More > Graphic Abstract

Zongjun Yin^*, Rong Su, Hui Xu

FDMP-Fluid Dynamics & Materials Processing, Vol.20, No.3, pp. 487-504, 2024, DOI:10.32604/fdmp.2023.042631 - 12 January 2024

Abstract In this study, numerical simulations of the pinching-off phenomena displayed by the dispersed phase in a continuous phase have been conducted using COMSOL Multiphysics (level-set method). Four flow patterns, namely “drop flow”, “jet flow”, “squeeze flow”, and “co-flow”, have been obtained for different flow velocity ratios, channel diameter ratios, density ratios, viscosity ratios, and surface tension. The flow pattern map of two-phase flow in coaxial microchannels has been obtained accordingly, and the associated droplet generation process has been critically discussed considering the related frequency, diameter, and pinch-off length. In particular, it is shown that the More > Graphic Abstract

Muataz S. Alhassan¹, Ameer A. Alameri², Andrés Alexis Ramírez-Coronel³, I. B. Sapaev^4,5,6, Azher M. Abed^7,*, David-Juan Ramos-Huallpartupa⁸, Rahman S. Zabibah⁹

FDMP-Fluid Dynamics & Materials Processing, Vol.20, No.2, pp. 311-323, 2024, DOI:10.32604/fdmp.2023.026782 - 14 December 2023

Abstract In line with recent studies, where it has been shown that nanofluids containing graphene have a stronger capacity to boost the heat transfer coefficient with respect to ordinary nanofluids, experiments have been conducted using water with cobalt ferrite/graphene nanoparticles. In particular, a circular channel made of copper subjected to a constant heat flux has been considered. As nanoparticles are sensitive to the presence of a magnetic field, different conditions have been examined, allowing both the strength and the frequency of such a field to span relatively wide ranges and assuming different concentrations of nanoparticles. According More >

Siham Hammid¹, Khatir Naima², Omolayo M. Ikumapayi³, Cheikh Kezrane¹, Abdelkrim Liazid⁴, Jihad Asad⁵, Mokdad Hayawi Rahman⁶, Farhan Lafta Rashid⁷, Naseer Ali Hussien⁸, Younes Menni^2,9,*

CMES-Computer Modeling in Engineering & Sciences, Vol.138, No.1, pp. 273-299, 2024, DOI:10.32604/cmes.2023.028951 - 22 September 2023

Abstract The objective of this investigation is to assess the effect of obstacles on numerical heat transfer and fluid flow momentum in a rectangular microchannel (MC). Two distinct configurations were studied: one without obstacles and the other with alternating obstacles placed on the upper and lower walls. The research utilized the thermal lattice Boltzmann method (LBM), which solves the energy and momentum equations of fluids with the BGK approximation, implemented in a Python coding environment. Temperature jump and slip velocity conditions were utilized in the simulation for the MC and extended to all obstacle boundaries. The… More >

Zihuan Ma¹, Xiang Ma¹, Chengyu Hu¹, Jinjia Wei^1,2,*

The International Conference on Computational & Experimental Engineering and Sciences, Vol.26, No.2, pp. 1-1, 2023, DOI:10.32604/icces.2023.08963

Abstract Flow boiling in microchannel heat sinks is considered as a promising cooling solution for electronic components. Higher heat flux can be effectively dissipated by the utilization of the latent heat of vaporization. However, most of the current studies on flow boiling in microchannels are mainly experimental investigations and two-dimensional numerical studies. In this paper, the Volume of Fluid (VOF) model combined with the Lee evaporation-condensation phase change model is used to simulate the flow boiling of HFE7100 in horizontal microchannels by three-dimensional conjugate numerical simulation. The numerical simulation results are compared with the experimental results… More >

Mohamed Shaimi^* , Rabha Khatyr, Jaafar Khalid Naciri

Frontiers in Heat and Mass Transfer, Vol.20, pp. 1-14, 2023, DOI:10.5098/hmt.20.23

Abstract This paper presents an exact analytical solution to the extended Graetz problem in microchannels and microtubes, including axial heat conduction, viscous dissipation, and rarefaction effects for an imposed constant wall temperature. The flow in the microchannel or microtube is assumed to be hydrodynamically fully developed. At the same time, the first-order slip-velocity and temperature jump models represent the wall boundary conditions. The energy equation is solved analytically, and the solution is obtained in terms of Kummer functions with expansion constants directly determined from explicit expressions. The local and fully developed Nusselt numbers are calculated in… More >

Ningbo Guo, Xianming Gao^*, Duanling Li, Jixing Zhang, Penghui Yin, Mengyi Hua

CMES-Computer Modeling in Engineering & Sciences, Vol.136, No.3, pp. 3061-3082, 2023, DOI:10.32604/cmes.2023.026657 - 09 March 2023

Abstract Computational fluid dynamics was used and a numerical simulation analysis of boiling heat transfer in microchannels with three depths and three cross-sectional profiles was conducted. The heat transfer coefficient and bubble generation process of three microchannel structures with a width of 80 μm and a depth of 40, 60, and 80 μm were compared during the boiling process, and the factors influencing bubble generation were studied. A visual test bench was built, and test substrates of different sizes were prepared using a micro-nano laser. During the test, the behavior characteristics of the bubbles on the More >

Mehdi Moslemi¹, Motahare Mahmoodnezhad¹, S. A. Edalatpanah^1,*, Sulima Ahmed Mohammed Zubair², Hamiden Abd El-Wahed Khalifa^2,3

CMES-Computer Modeling in Engineering & Sciences, Vol.134, No.3, pp. 1957-1973, 2023, DOI:10.32604/cmes.2022.021481 - 20 September 2022

Abstract In this research, a numerical study of mixed convection of non-Newtonian fluid and magnetic field effect along a vertical wavy surface was investigated. A simple coordinate transformation to transform wavy surface to a flat surface is employed. A cubic spline collocation numerical method is employed to analyze transformed equations. The effect of various parameters such as Reynolds number, volume fraction 0-, Hartmann number, and amplitude of wave length was evaluated in improving the performance of a wavy microchannel. According to the presented results, the sinusoidal shape of the microchannel has a direct impact on heat More >