Micro Thermal Devices and Their Applications

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

Deadline for manuscript submissions: closed (30 October 2024) | Viewed by 11953

Special Issue Editor


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Guest Editor
Department of Engineering and Architecture, University of Parma, Parco Area delle Scienze 181/A, 43124 Parma, Italy
Interests: microfluidics; fluid flow; heat transfer; micro thermal devices; microfabrication techniques
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Special Issue Information

Dear Colleagues,

Microsystems are widely used in the microelectronics, biomedical, pharmaceutical, chemical, automotive, and aerospace fields, among others. Among the microcomponents that are commonly used in these fields, devices with improved heat exchange capacities due to their very large surface-to-volume ratio are represented by microchannel heat transfer devices.

Although the performances of microchannel heat transfer devices have been investigated by many authors, more research is required to better understand the thermal phenomena acting at the microscale and to evaluate new scenarios.

In particular, more accurate methodologies are needed to generate sufficient knowledge of the fluid flow and the heat transfer mechanism in microdevices, thus providing accurate correlations between the performances of these apparatuses and the relevant parameters that affect their performance.

On the other hand, the advent of new microfabrication technologies and additive manufacturing have enabled innovative geometries. In particular, new fabrication technologies can be used to obtain simple, novel geometries, while additive manufacturing enables the user to build highly complex polymer and metal parts due to the layer-wise process.

This Special Issue seeks to showcase research papers, short communications, and review articles that focus on the investigation of the performances of novel microchannel geometries, novel developments in microfabrication techniques and novel experimental approaches. Moreover, comparisons between different cooling techniques (such as micro heat pipes, micro heat sinks, and micro heat exchangers) are welcome.

Dr. Pamela Vocale
Guest Editor

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Keywords

  • microsystems
  • new microfabrication techniques
  • additive manufacturing
  • micro thermal devices
  • microscale cooling techniques
  • heat transfer enhancement

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Related Special Issue

Published Papers (5 papers)

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Research

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20 pages, 7025 KiB  
Article
Numerical Investigation of Enhanced Heat Transfer with Micro Pin Fins in Heat Exchangers
by Qin Zhou, Hongyan Wang, Fuyuan Wu, Shengfei Liu, Huafeng Wei and Guoqing Hu
Micromachines 2024, 15(9), 1120; https://doi.org/10.3390/mi15091120 - 31 Aug 2024
Viewed by 875
Abstract
Pin-fin and flat-tube heat exchangers (PFFTHXs) offer a promising alternative to traditional louvered-fin and flat-tube heat exchangers (LFFTHXs), especially when used as evaporators. The streamlined structure of pin fins helps to effectively remove condensate and defrost water. In this study, we conducted a [...] Read more.
Pin-fin and flat-tube heat exchangers (PFFTHXs) offer a promising alternative to traditional louvered-fin and flat-tube heat exchangers (LFFTHXs), especially when used as evaporators. The streamlined structure of pin fins helps to effectively remove condensate and defrost water. In this study, we conducted a numerical analysis of 60 different pin-fin configurations across three pin diameters to enhance heat transfer in PFFTHXs. Our investigation focused on how pin pitch affects both airflow and heat transfer efficiency. The results show that a closer pin pitch increases both the heat transfer rate per unit area and the pressure drop for a given airflow velocity. We evaluated the overall performance of these configurations using the heat transfer rate per unit frontal area obtained at equivalent fan power levels. The analysis identified optimal configurations for each pin diameter, with the 0.2 mm diameter configuration demonstrating the highest heat transfer efficiency—this was on par with louvered fins but used fewer resources. This makes it an ideal choice for evaporative applications in PFFTHXs. Full article
(This article belongs to the Special Issue Micro Thermal Devices and Their Applications)
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14 pages, 5989 KiB  
Article
Analysis of Flow Characteristics between Tandem Flexible Structures Based on PIV: Substantial Applications for the Removal of Microplastics
by Hyeonjin Lee, Bongliba T. Sangtam, Heejoong Seong, Jeong Jae Kim and Hanwook Park
Micromachines 2024, 15(1), 100; https://doi.org/10.3390/mi15010100 - 4 Jan 2024
Viewed by 2257
Abstract
This study emphasizes the potential risk posed by microplastics, particularly in tap water. Numerous studies have reported the removal of microplastics, but the limitations in addressing this issue remain challenging. To tackle this problem, a new method is introduced using tandem flexible structures [...] Read more.
This study emphasizes the potential risk posed by microplastics, particularly in tap water. Numerous studies have reported the removal of microplastics, but the limitations in addressing this issue remain challenging. To tackle this problem, a new method is introduced using tandem flexible structures (FSs) for microplastic removal. The present study focused on understanding the hydrodynamic characteristics between FSs to utilize microplastic removal. This comprehension of fluid flow and FSs offers valuable insights for improving the efficiency of microplastic removal methods. Therefore, the optimal conditions for removing microplastics were experimentally investigated inside the FSs gap region. Based on the gap distance and height, the flow structures between FSs were investigated. A small secondary vortex structure that could trap particles from upstream was continuously maintained behind the upstream FSs under certain geometric conditions. It is shown that this vortex structure has an effective way of confining the particles from upstream. The persistency of a small secondary vortex was also evaluated. This study may be helpful to researchers working on microplastic removal and FSs with a tandem arrangement. Full article
(This article belongs to the Special Issue Micro Thermal Devices and Their Applications)
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11 pages, 3469 KiB  
Article
Thermal Characterization of Rarefied Flows in Rhombic Microchannels
by Pamela Vocale and Gian Luca Morini
Micromachines 2023, 14(12), 2222; https://doi.org/10.3390/mi14122222 - 10 Dec 2023
Cited by 2 | Viewed by 1001
Abstract
This work aimed to numerically investigate the dynamic and thermal behavior of a fully developed, laminar, gaseous flow in a microchannel featuring a rhombic cross-section. Due to new fabrication techniques, microducts with rhombic cross-sections have recently received more attention. The momentum and energy [...] Read more.
This work aimed to numerically investigate the dynamic and thermal behavior of a fully developed, laminar, gaseous flow in a microchannel featuring a rhombic cross-section. Due to new fabrication techniques, microducts with rhombic cross-sections have recently received more attention. The momentum and energy balance equations were solved by using a commercial CDF code and assuming the slip and the H2 boundary conditions. The temperature jump between the wall and the adjacent fluid was also taken into account. The accuracy of the numerical results was checked by using the data available in the literature in terms of velocity profiles in the slip flow regime and the Nusselt number in the continuum flow regime. To also investigate the geometry effects on the fluid behavior, several values of the side angle of the rhombus were considered. The numerical results revealed that the rarefaction degree and geometrical properties significantly affected the Nusselt number. Full article
(This article belongs to the Special Issue Micro Thermal Devices and Their Applications)
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Review

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57 pages, 13215 KiB  
Review
An Overview of Innovative Surface-Modification Routes for Pool Boiling Enhancement
by José Pereira, Reinaldo Souza, António Moreira and Ana Moita
Micromachines 2024, 15(3), 302; https://doi.org/10.3390/mi15030302 - 22 Feb 2024
Cited by 2 | Viewed by 1570
Abstract
This overview intends to provide a comprehensive assessment of the novel fluids and the current techniques for surface modification for pool boiling enhancement. The surface modification at macro-, micro-, and nanoscales is assessed concerning the underlying fluid routing and capability to eliminate the [...] Read more.
This overview intends to provide a comprehensive assessment of the novel fluids and the current techniques for surface modification for pool boiling enhancement. The surface modification at macro-, micro-, and nanoscales is assessed concerning the underlying fluid routing and capability to eliminate the incipient boiling hysteresis and ameliorate the pool boiling heat-transfer ability, particularly when employed together with self-rewetting fluids and nanofluids with enriched thermophysical properties. Considering the nanofluids, it is viable to take the profit of their high thermal conductivity and their specific heat simultaneously and to produce a film of deposited nanoparticles onto the heating surface, which possesses enhanced surface roughness and an increased density of nucleation sites. Whilst the diverse improvement scales are found to achieve distinct levels of success regarding the nucleate boiling heat-transfer capability enhancement, it is also shown that the micro–nanoscale boiling surface features are susceptible to blockage, leading to the degradation of the improvement with time. Furthermore, topics relating to the heat transfer thermal behavior, ease of manufacture, cost-effectiveness, reliability, and durability are reviewed whenever available and challenges and recommendations for further research are highlighted. Full article
(This article belongs to the Special Issue Micro Thermal Devices and Their Applications)
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41 pages, 8330 KiB  
Review
Review on Bubble Dynamics in Proton Exchange Membrane Water Electrolysis: Towards Optimal Green Hydrogen Yield
by Bongliba T. Sangtam and Hanwook Park
Micromachines 2023, 14(12), 2234; https://doi.org/10.3390/mi14122234 - 12 Dec 2023
Cited by 5 | Viewed by 5546
Abstract
Water electrolysis using a proton exchange membrane (PEM) holds substantial promise to produce green hydrogen with zero carbon discharge. Although various techniques are available to produce hydrogen gas, the water electrolysis process tends to be more cost-effective with greater advantages for energy storage [...] Read more.
Water electrolysis using a proton exchange membrane (PEM) holds substantial promise to produce green hydrogen with zero carbon discharge. Although various techniques are available to produce hydrogen gas, the water electrolysis process tends to be more cost-effective with greater advantages for energy storage devices. However, one of the challenges associated with PEM water electrolysis is the accumulation of gas bubbles, which can impair cell performance and result in lower hydrogen output. Achieving an in-depth knowledge of bubble dynamics during electrolysis is essential for optimal cell performance. This review paper discusses bubble behaviors, measuring techniques, and other aspects of bubble dynamics in PEM water electrolysis. It also examines bubble behavior under different operating conditions, as well as the system geometry. The current review paper will further improve the understanding of bubble dynamics in PEM water electrolysis, facilitating more competent, inexpensive, and feasible green hydrogen production. Full article
(This article belongs to the Special Issue Micro Thermal Devices and Their Applications)
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