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Micromachines
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Heat Transfer and Fluid Flow in Micromachines, Volume II
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Heat Transfer and Fluid Flow in Micromachines, Volume II

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "A：Physics".

Deadline for manuscript submissions: closed (31 July 2022) | Viewed by 18543

Special Issue Editors

Dr. Jinyuan Qian

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Guest Editor
Institute of Process Equipment, College of Energy Engineering, Zhejiang University, Hangzhou 310027, China
Interests: flow control; heat transfer; hydraulics; computational fluid dynamics
Special Issues, Collections and Topics in MDPI journals
Dr. Zan Wu

E-Mail Website
Guest Editor
Department of Energy Sciences, Lund University, 221 00 Lund, Sweden
Interests: boiling and condensation; heat transfer; microfluidics; surface modification
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Junhui Zhang

E-Mail Website
Guest Editor
State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China
Interests: flow control; aviation hydraulic; hydraulic robot
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Bengt Sunden

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Guest Editor
Department of Energy Sciences, Lund University, 221 00 Lund, Sweden
Interests: PEMFC; SOFC; batteries; hydrogen production and storage; renewable energy
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

With the advances in manufacturing technology, more and more micromachines have been successfully developed, such as microchannel, micro mixer, micro pump, micro reactor, micro valve, microfluidics, and MEMS. In recent years, micromachine applications have also experienced rapid development in many industries.  In micromachines, due to the large surface-to-volume ratio, heat transfer and fluid flow characteristics inside have obvious differences, compared with those at normal size, e.g., different cavitation phenomena, different boiling, and condensation characteristics.  Thus, heat transfer and fluid flow characteristics in micromachines have been attracting many researchers, with the purpose of innovative heat transfer enhancement and smart fluid control flow. Many new innovative findings and enabling technologies have appeared. Accordingly, it is important to collect and present these recent advances. This Special Issue on “Heat Transfer and Fluid Flow in Micromachines”, welcomes review articles and original research papers, fundamental or applied, theoretical, numerical, or experimental, on heat transfer and fluid flow in micromachines. Topics of interest include but are not limited to the following: 

  • Boiling
  • Cavitation
  • Compressible flow
  • Condensation
  • Flow control
  • Flow rate
  • Fluid dynamics
  • Fluid flow
  • Fluid power
  • Heat transfer
  • Heat exchanger
  • Hydraulics
  • Lab-on-a-chip
  • Mass transfer
  • MEMS
  • Microchannel
  • Microfluidics
  • Micro mixer
  • Micro pump
  • Micro reactor
  • Micro valve
  • Multiphase flow
  • Nanofluidics
  • Nanofluids

Dr. Jin-yuan Qian
Prof. Dr. Zan Wu
Prof. Dr. Junhui Zhang
Prof. Dr. Bengt Sunden
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

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Published Papers (9 papers)

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Research

21 pages, 12157 KiB  
Article
Effect of Couple Stress and Mass Transpiration on Ternary Hybrid Nanoliquid over a Stretching/Shrinking Sheet with Heat Transfer
by Kolkar Nanjappa Sneha, Gadabanahalli Puttasiddappa Vanitha, Ulavathi Shettar Mahabaleshwar and David Laroze
Micromachines 2022, 13(10), 1694; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13101694 - 09 Oct 2022
Cited by 13 | Viewed by 1342
Abstract
The present article describes the unsteady flow of a couple stress via a ternary hybrid nanofluid on a stretching surface with porous media. The nanofluid exhibits important properties for increasing heat transmission, and it is widely used in manufacturing and industrial applications. The [...] Read more.
The present article describes the unsteady flow of a couple stress via a ternary hybrid nanofluid on a stretching surface with porous media. The nanofluid exhibits important properties for increasing heat transmission, and it is widely used in manufacturing and industrial applications. The basic similarity equations have been discovered to accommodate both stretching/shrinking surfaces. Ternary hybrid nanofluid is a colloidal combination of three types of microspheres: Al2O3, single wall carbon nanotubes, and graphene. For investigating spherical, cylindrical, and platelet nanoparticles, the governing partial differential equations are converted into ordinary differential equations, expending appropriate transformations. The analytical solution can then be carried out using various forms of nanoparticles, such as spherical, cylindrical, and platelet, to obtain the solution domain. Heat transfer is used in an electrically conducting fluid and also including thermal radiation, as calculated with the Biot number. The focus of the present effort is the evaluation of the flow of ternary hybrid nanofluid over a porous media via thermal radiation, with couple stress, using an analytical process. For various physical parameters, the velocity and temperature conditions are shown graphically. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines, Volume II)
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16 pages, 2084 KiB  
Article
Influence of Thermal Boundary Conditions and Number of Channels on the Performance of Heat Sinks with Rectangular Minichannels
by Pamela Vocale
Micromachines 2022, 13(8), 1236; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13081236 - 31 Jul 2022
Viewed by 1356
Abstract
This paper aims to contribute to the analysis of a heat sink designed for the active cooling of small flat surfaces. The heat transfer device investigated here consists of a flat square substrate and a cover, separated by parallel channels with a rectangular [...] Read more.
This paper aims to contribute to the analysis of a heat sink designed for the active cooling of small flat surfaces. The heat transfer device investigated here consists of a flat square substrate and a cover, separated by parallel channels with a rectangular cross-section. The cold air flowing in the channels is sucked from the environment, and the bottom of the substrate adheres closely to the hot surface of the device to be cooled. The thermal problem is tackled by considering two different conditions: the first one assuming one long side of the channel is heated and the three other sides are adiabatic (version 1L) and the second one assuming high conductivity of the walls (version 4), in both the H1 and H2 boundary conditions. Moreover, to investigate the effect of the number of channels on the performance of the heat sink, the number of channels is changed between 1 and 20. The results, presented in terms of the f Re product, Nusselt number, maximum surface temperature, and thermal resistance, reveal that both the thermal boundary conditions and the number of channels significantly affect the performance of the investigated heat transfer device. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines, Volume II)
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16 pages, 4212 KiB  
Article
Study on the Motion Characteristics of Solid Particles in Fine Flow Channels by Ultrasonic Cavitation
by Mu Yuan, Chen Li, Jiangqin Ge, Qingduo Xu and Zhian Li
Micromachines 2022, 13(8), 1196; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13081196 - 28 Jul 2022
Cited by 3 | Viewed by 1599
Abstract
Microjets caused by the cavitation effect in microchannels can affect the motion trajectory of solid particles in microchannels under ultrasonic conditions. The optimal parameters for an observation experiment were obtained through simulations, and an experiment was designed to verify these parameters. When the [...] Read more.
Microjets caused by the cavitation effect in microchannels can affect the motion trajectory of solid particles in microchannels under ultrasonic conditions. The optimal parameters for an observation experiment were obtained through simulations, and an experiment was designed to verify these parameters. When the cavitation bubbles collapse in the near-wall area, the solid particles in the microchannel can be displaced along the expected motion trajectory. Using fluent software to simulate the bubble collapse process, it can be seen that, when an ultrasonic sound pressure acts on a bubble near the wall, the pressure causes the top of the bubble wall to sink inward and eventually penetrate the bottom of the bubble wall, forming a high-speed microjet. The maximum speed of the jet can reach nearly 28 m/s, and the liquid near the top of the bubble also moves at a high speed, driving the particles in the liquid towards the wall. A high-speed camera was used to observe the ultrasonic cavitation process of bubbles in the water to verify the simulation results. A comparison of particle motion with and without ultrasonic waves proved the feasibility of using the ultrasonic cavitation effect to guide small particles towards the wall. This method provides a novel experimental basis for changing the fluid layer state in the microchannel and improving precision machining. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines, Volume II)
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11 pages, 4301 KiB  
Article
Quantitative Analysis of Drag Force for Task-Specific Micromachine at Low Reynolds Numbers
by Qiang Wang and Zhen Wang
Micromachines 2022, 13(7), 1134; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13071134 - 18 Jul 2022
Cited by 3 | Viewed by 1542
Abstract
Micromotors have spread widely in order to meet the needs of new applications, including cell operation, drug delivery, biosensing, precise surgery and environmental decontamination, due to their small size, low energy consumption and large propelling power, especially the newly designed multifunctional micromotors that [...] Read more.
Micromotors have spread widely in order to meet the needs of new applications, including cell operation, drug delivery, biosensing, precise surgery and environmental decontamination, due to their small size, low energy consumption and large propelling power, especially the newly designed multifunctional micromotors that combine many extra shape features in one device. Features such as rod-like receptors, dendritic biosensors and ball-like catalyzing enzymes are added to the outer surface of the tubular micromotor during fabrication to perform their special mission. However, the structural optimization of motion performance is still unclear. The main factor restricting the motion performance of the micromotors is the drag forces. The complex geometry of a micromotor makes its dynamic behavior more complicated in a fluid environment. This study aimed to design the optimum structure of tubular micromotors with minimum drag forces and obtain the magnitude of drag forces considering both the internal and external fluids of the micromotors. By using the computational fluid dynamics software Fluent 18.0 (ANSYS), the drag force and the drag coefficient of different conical micromotors were calculated. Moreover, the influence of the Reynolds numbers Re, the semi-cone angle δ and the ratios ξ and η on the drag coefficient was analyzed. The results show the drag force monotonically increased with Reynolds numbers Re and the ratio η. The extreme point of the drag curve is reached when the semi-cone angle δ is 8° and the ratio ξ is 3.846. This work provides theoretical support and guidance for optimizing the design and development of conical micromotors. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines, Volume II)
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11 pages, 6392 KiB  
Article
Flow Regulation Performance Analysis of Microfluidic Passive Valve for High Throughput Liquid Delivery
by Qi Su, Weiran Chen, Weiping Chen, Zhijiang Jin and Zhenhao Lin
Micromachines 2022, 13(5), 687; https://0-doi-org.brum.beds.ac.uk/10.3390/mi13050687 - 28 Apr 2022
Cited by 1 | Viewed by 1560
Abstract
A microfluidic passive valve (MPV) is important for precise flow control, and it determines the reliability of the microfluidic system. In this paper, a novel MPV capable of delivering a constant flow rate independently of inlet pressure changes is proposed. The flow rate [...] Read more.
A microfluidic passive valve (MPV) is important for precise flow control, and it determines the reliability of the microfluidic system. In this paper, a novel MPV capable of delivering a constant flow rate independently of inlet pressure changes is proposed. The flow rate of the MPV is adjusted by the difference between the fluid force on the upper surface of the valve core and the spring force. The constant flow rate of the MPV is maintained by automatically changing the size of the gap channel formed by the groove on the valve core and the baffle on the valve body. The nearly constant flow rate of the MPV is 6.26 mL/min, with a variation of 6.5% under the inlet pressure varied from 1.25 kPa to 3.5 kPa. In addition, the flow characteristics of the MPV are analyzed by numerical simulation. With the increase in the inlet pressure, the maximum velocity gradually increases, while the increment of the maximum velocity decreases. In the movement process of the valve core, the region of pressure drop becomes larger. This work has a certain reference value for the design and research of the MPVs with high throughput liquid delivery. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines, Volume II)
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15 pages, 3907 KiB  
Article
Influence of Thermophoretic Particle Deposition on the 3D Flow of Sodium Alginate-Based Casson Nanofluid over a Stretching Sheet
by Bheemasandra M. Shankaralingappa, Javali K. Madhukesh, Ioannis E. Sarris, Bijjanal J. Gireesha and Ballajja C. Prasannakumara
Micromachines 2021, 12(12), 1474; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12121474 - 29 Nov 2021
Cited by 39 | Viewed by 1661
Abstract
The wide range of industrial applications of flow across moving or static solid surfaces has aroused the curiosity of researchers. In order to generate a more exact estimate of flow and heat transfer properties, three-dimensional modelling must be addressed. This plays a vital [...] Read more.
The wide range of industrial applications of flow across moving or static solid surfaces has aroused the curiosity of researchers. In order to generate a more exact estimate of flow and heat transfer properties, three-dimensional modelling must be addressed. This plays a vital role in metalworking operations, producing plastic and rubber films, and the continuous cooling of fibre. In view of the above scope, an incompressible, laminar three-dimensional flow of a Casson nanoliquid in the occurrence of thermophoretic particle deposition over a non-linearly extending sheet is examined. To convert the collection of partial differential equations into ordinary differential equations, the governing equations are framed with sufficient assumptions, and appropriate similarity transformations are employed. The reduced equations are solved by implementing Runge Kutta Fehlberg 4th 5th order technique with the aid of a shooting scheme. The numerical results are obtained for linear and non-linear cases, and graphs are drawn for various dimensionless constraints. The present study shows that improvement in the Casson parameter values will diminish the axial velocities, but improvement is seen in thermal distribution. The escalation in the thermophoretic parameter will decline the concentration profiles. The rate of mass transfer, surface drag force will reduce with the improved values of the power law index. The non-linear stretching case shows greater impact in all of the profiles compared to the linear stretching case. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines, Volume II)
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16 pages, 4267 KiB  
Article
A Novel Dielectric Barrier Discharge (DBD) Reactor with Streamer and Glow Corona Discharge for Improved Ozone Generation at Atmospheric Pressure
by Pu Liu, Yongxin Song and Zhitao Zhang
Micromachines 2021, 12(11), 1287; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12111287 - 21 Oct 2021
Cited by 5 | Viewed by 3112
Abstract
Discharge mode is an important parameter for ozone synthesis by dielectric barrier discharge (DBD). Currently, it is still challenging to stably generate glow discharge with oxygen at atmospheric pressure. In this paper, a DBD reactor with a layer of silver placed between the [...] Read more.
Discharge mode is an important parameter for ozone synthesis by dielectric barrier discharge (DBD). Currently, it is still challenging to stably generate glow discharge with oxygen at atmospheric pressure. In this paper, a DBD reactor with a layer of silver placed between the electrode and the dielectric layer (SL-DBD) was developed. Experimental results show that both streamer and glow corona discharge were stably generated under sinusoidal excitation with a 0.5 mm discharge gap in a parallel-plate DBD, due to the increased electric field strength in the discharge gap by the silver layer. It was also found that, in the SL-DBD reactor, glow corona discharge enhances the discharge strength by 50 times. The spectral peak of O at 777 nm in SL-DBD is increased to 28,800, compared with 18,389 in a reactor with a streamer only. The SL-DBD reactor produces ozone with a concentration of as high as 150 g/m3 and shows good stability in an 8 h durability test. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines, Volume II)
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15 pages, 3065 KiB  
Article
Active Pressure Ripple Reduction of a Self-Supplied Variable Displacement Pump with Notch Least Mean Square Filter
by Xiaochen Huang, Bing Xu, Weidi Huang, Haogong Xu, Fei Lyu and Qi Su
Micromachines 2021, 12(8), 932; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12080932 - 05 Aug 2021
Cited by 2 | Viewed by 3629
Abstract
As the power sources in hydraulic systems, variable displacement axial piston pumps generate flow fluctuation. Unfortunately, it results in pressure pulsation which excites the system vibration and emitted noise. The majority of studies try to eliminate the pulsation via a passive technique and [...] Read more.
As the power sources in hydraulic systems, variable displacement axial piston pumps generate flow fluctuation. Unfortunately, it results in pressure pulsation which excites the system vibration and emitted noise. The majority of studies try to eliminate the pulsation via a passive technique and the active control methodology has not been discussed in detail. In this research, the feasibility of reducing the pressure ripple by properly controlling the proportional valve has been investigated, which also supports the miniaturization of the active control system. A mathematical model of the self-supplied variable displacement pump including the control system has been developed. The filtered-X least mean square algorithm with time-delay compensation is utilized to calculate the active control signal. Simulation results show the effectiveness of the active control technique. The effect of the active control signal on the flow rate from different chambers of the pump has been analyzed. It demonstrates that the variation of the pressure pulsation should be ascribed to the comprehensive reaction of different flow rates. The major reason is that the flow of the actuator piston neutralizes the peak value of the flow ripple, generated by the nine pistons. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines, Volume II)
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16 pages, 6489 KiB  
Article
Topology Optimization of Passive Cell Traps
by Zhiqi Wang, Yuchen Guo, Eddie Wadbro and Zhenyu Liu
Micromachines 2021, 12(7), 809; https://0-doi-org.brum.beds.ac.uk/10.3390/mi12070809 - 09 Jul 2021
Cited by 2 | Viewed by 1721
Abstract
This paper discusses a flexible design method of cell traps based on the topology optimization of fluidic flows. Being different from the traditional method, this method obtains the periodic layout of the cell traps according to the cell trapping requirements by proposing a [...] Read more.
This paper discusses a flexible design method of cell traps based on the topology optimization of fluidic flows. Being different from the traditional method, this method obtains the periodic layout of the cell traps according to the cell trapping requirements by proposing a topology optimization model. Additionally, it satisfies the cell trapping function by restricting the flow distribution while taking into account the overall energy dissipation of the flow field. The dependence on the experience of the designer is reduced when this method is used to design a cell trap with acceptable trapping performance. By comparing the influence of the changes of various parameters on the optimization results, the flexibility of the topology optimization method for cell trap structure optimization is verified. The capability of this design method is validated by several performed comparisons between the obtained layouts and optimized designs in the published literature. Full article
(This article belongs to the Special Issue Heat Transfer and Fluid Flow in Micromachines, Volume II)
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