Design Configurations and Operating Limitations of an Oscillating Heat Pipe

Passive and compact heat dissipation systems are and will remain vital for the successful operation of modern electronic systems. Oscillating heat pipes (OHPs) have been a part of this research area since their inception due to their ability to passively manage high heat fluxes. In the current investigation, different designs of tubular, flat plate, and multiple layer oscillating heat pipes are studied by using different operating parameters to investigate the operating limitations of each design. Furthermore, selective laser melting was demonstrated as a new OHP manufacturing technique and was used to create a compact multiple layer flat plate OHP. A 7-turn tubular oscillating heat pipe (T-OHP) was created and tested experimentally with three working fluids (water, acetone, and n-pentane) and different orientations (horizontal, vertical top heating, and vertical bottom heating). For vertical, T-OHP was tested with the condenser at 0°, 45° and 90° bend angle from the y-axis (achieved by bending the OHP in the adiabatic) in both bottom and top heating modes. The results show that T-OHP thermal performance depends on the bend angle, working fluid, and orientation. Another design of L-shape closed loop square microchannel (750 x 750 microns) copper heat pipe was fabricated from copper to create a thermal connector with thermal resistance \u3c 0.09 ˚C/W for electronic boards. The TC-OHP was able to manage heat rates up to 250 W. A laser powder bed fusion (L-PBF) additive manufacturing (AM) method was employed for fabricating a multi-layered, Ti-6Al-4V oscillating heat pipe (ML-OHP). The 50.8 x 38.1 x 15.75 mm3 ML-OHP consisted of four inter-connected layers of circular mini-channels, as well an integrated, hermetic-grade fill port. A series of experiments were conducted to characterize the ML-OHP thermal performance by varying power input (up to 50 W), working fluid (water, acetone, NovecTM 7200, and n-pentane), and operating orientation (vertical bottom-heating, horizontal, and vertical top-heating). The ML-OHP was found to operate effectively for all working fluids and orientations investigated, demonstrating that the OHP can function in a multi-layered form, and further indicating that one can ‘stack’ multiple, interconnected OHPs within flat media for increased thermal management

Strategies to improve the thermal performance of heat pipe solar collectors in solar systems: A review

Invention of evacuated tube heat pipe solar collectors (HPSCs) was a huge step forward towards resolving the challenges of conventional solar systems due to their unique features and advantages. This has led to their utilization in a wide range of solar applications surpassing other conventional collectors. However, relatively low thermal efficiency of heat pipe solar (HPS) systems is still the major challenge of solar industry evidenced by numerous studies conducted mainly during the last decade to improve their efficiency. To date, several review papers have been published summarizing studies relevant to utilization of HPSCs in various thermal applications. However, to the authors\u27 knowledge, a comprehensive review which surveys and provides an overview of the studies undertaken to improve the thermal performance of HPS systems (mainly during the last decade) by implementing different strategies has not been published to date. This review paper summarizes all the proposed strategies to improve the thermal efficiency of different industrial, domestic, and innovative HPS systems. First, the concept, structure, and operational principles of HPSCs are introduced concisely. Then, novel structures and designs of HPSCs aiming to increase the thermal efficiency of the collector as the most important component of the solar system is reviewed. This is followed by a comprehensive review of various methods to store solar energy more efficiently, increase solar system’s operation time, increase overall efficiency by turning the solar system into a multi-purpose system, enhance heat transmission in the solar system, and implement new solar loop and heat pipe working fluids with better heat transfer characteristics. Finally, research gaps in this field are identified and some future research trends and directions are recommended

A Review of Recent Passive Heat Transfer Enhancement Methods

[EN] Improvements in miniaturization and boosting the thermal performance of energy conservation systems call for innovative techniques to enhance heat transfer. Heat transfer enhancement methods have attracted a great deal of attention in the industrial sector due to their ability to provide energy savings, encourage the proper use of energy sources, and increase the economic efficiency of thermal systems. These methods are categorized into active, passive, and compound techniques. This article reviews recent passive heat transfer enhancement techniques, since they are reliable, cost-effective, and they do not require any extra power to promote the energy conversion systems' thermal efficiency when compared to the active methods. In the passive approaches, various components are applied to the heat transfer/working fluid flow path to improve the heat transfer rate. The passive heat transfer enhancement methods studied in this article include inserts (twisted tapes, conical strips, baffles, winglets), extended surfaces (fins), porous materials, coil/helical/spiral tubes, rough surfaces (corrugated/ribbed surfaces), and nanofluids (mono and hybrid nanofluids).Ajarostaghi, SSM.; Zaboli, M.; Javadi, H.; Badenes Badenes, B.; Urchueguía Schölzel, JF. (2022). A Review of Recent Passive Heat Transfer Enhancement Methods. Energies. 15(3):1-55. https://doi.org/10.3390/en1503098615515

A review of novel heat transfer materials and fluids for aerospace applications

The issue of thermal control for space missions has been critical since the early space missions in the late 1950s. The demands in such environments are heightened, characterized by significant temperature variations and the need to manage substantial densities of heat. The current work offers a comprehensive survey of the innovative materials and thermal fluids employed in the aerospace technological area. In this scope, the materials should exhibit enhanced reliability for facing maintenance and raw materials scarcity. The improved thermophysical properties of the nanofluids increase the efficiency of the systems, allowing the mass/volume reduction in satellites, rovers, and spacecraft. Herein are summarized the main findings from a literature review of more than one hundred works on aerospace thermal management. In this sense, relevant issues in aerospace convection cooling were reported and discussed, using heat pipes and heat exchangers, and with heat transfer ability at high velocity, low pressure, and microgravity. Among the main findings, it could be highlighted the fact that these novel materials and fluids provide enhanced thermal conductivity, stability, and insulation, enhancing the heat transfer capability and preventing the malfunctioning, overheating, and degradation over time of the systems. The resulting indicators will contribute to strategic mapping knowledge and further competence. Also, this work will identify the main scientific and technological gaps and possible challenges for integrating the materials and fluids into existing systems and for maturation and large-scale feasibility for aerospace valorization and technology transfer enhancement.This work has been funded by FCT/MCTES (PIDDAC) through the base funding from the following research units: UIDP/50009/2020-FCT and UIDB/50009/2020-FCT, UIDB/00532/2020, LA/P/0045/2020, UIDB/04077/2020, and UIDP/04077/2020. The authors are also grateful for FCT funding through 2022. 03151.PTDC, PTDC/EME-TED/7801/2020, POCI-01-0145-FEDER-016861, POCI-01-0145-FEDER-028159, 2022. 02085.PTDC (https://doi.org/10.54499/2022.02085.PTDC, accessed on 25 March 2024), funded by COMPETE2020, NORTE2020, PORTUGAL2020, and FEDER. Glauco Nobrega was supported by the doctoral grant PRT/BD/153088/2021, financed by the Portuguese Foundation for Science and Technology (FCT), under the MIT Portugal Program. Pinho D. and Susana O. Catarino thank FCT for her contract funding provided through 2021.00027.CEECIND, 2020.00215.CEECIND (DOI: https://doi.org/10.54499/2020.00215.CEECIND/CP1600/CT0009, accessed on 25 March 2024), respectively. The authors are also grateful to the Fundação para a Ciência e a Tecnologia (FCT), Avenida D. Carlos I, 126, 1249–074 Lisboa, Portugal, for partially financing the Project “Estratégias interfaciais de arrefecimento para tecnologias de conversão com elevadas potências de dissipação”, ref. PTDC/EMETED/7801/2020, Associação do Instituto Superior Técnico para a Investigação e o Desenvolvimento (IST-ID). José Pereira also acknowledges FCT for his PhD fellowship (Ref. 2021. 05830.BD). The authors are also grateful for FCT funding through 2022.03151.PTD and LA/P/0083/2020 IN + -IST-ID. The authors are also grateful for FCT funding through 2022.03151.PTD and LA/P/0083/2020 IN + -IST-ID and through UIPD/50009/2020-FCT and UIDB/50009—FCT. Ana Moita also acknowledges FCT for partially financing her contract through CEECINST/00043/2021/CP2797/CT0005, doi:https://doi.org/10.54499/CEECINST/00043/2021/CP2797/CT0005, accessed on 25 March 2024. The authors also acknowledge Exército Português for their support through projects CINAMIL Desenvolvimento de Sistemas de Gestão Térmica e Climatização de equipamento NBQ and COOLUAV—Sistema de arrefecimento da componente eletrónica e baterias em veículos militares não tripulados

Workshops Proceedings

The idea behind the Workshops Proceedings document is to collect in an eBook the information of all the Nanouptake Working Group (WG) Workshops before April 2019 where the participants have been presenting their last research work in nanofluids

Overview on the hydrodynamic conditions found in industrial systems and its impact in (bio)fouling formation

Supplementary data to this article can be found online at https://doi.org/10.1016/j.cej.2021.129348.Biofouling is the unwanted accumulation of deposits on surfaces, composed by organic and inorganic particles and (micro)organisms. Its occurrence in industrial equipment is responsible for several drawbacks related to operation and maintenance costs, reduction of process safety and product quality, and putative outbreaks of pathogens. The understanding on the role of operating conditions in biofouling development highlights the hydrodynamic conditions as key parameter. In general, (bio)fouling occurs in a higher extension when laminar flow conditions are used. However, the characteristics and resilience of biofouling are highly dependent on the hydrodynamic conditions under which it is developed, with turbulent conditions being associated to recalcitrant biodeposits. In industrial settings like heat exchangers, fluid distribution networks and stirred tanks, hydrodynamics play a dual function, affecting the process effectiveness while favouring biofouling formation. This review summarizes the hydrodynamics played in conventional industrial settings and provides an overview on the relevance of hydrodynamic conditions in biofouling development as well as in the effectiveness of industrial processes.This work was financially supported by: Base Funding - UIDB/00511/2020 of LEPABE and UIDB/00081/2020 of CIQUP funded by national funds through the FCT/MCTES (PIDDAC); Project Bio cide_for_Biofilm - PTDC/BII-BTI/30219/2017 - POCI-01-0145-FEDER 030219, ABFISH – PTDC/ASP-PES/28397/2017 - POCI-01-0145- FEDER-028397 and ALGAVALOR - POCI-01-0247-FEDER-035234, fun ded by FEDER funds through COMPETE2020 – Programa Operacional Competitividade e Internacionalizaçao ˜ (POCI) and by national funds (PIDDAC) through FCT/MCTES; Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER 000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte; FCT/ SFRH/BD/147276/2019 (Susana Fernandes) and SFRH/BSAB/150379/2019 (Manuel Simoes).info:eu-repo/semantics/publishedVersio

Conference Proceedings: 1st International Conference on Nanofluids (ICNf2019), 2nd European Symposium on Nanofluids (ESNf2019)

Conference proceedings of the 1st International Conference on Nanofluids (ICNf2019) and 2nd European Symposium on Nanofluids (ESNf2019), 26-28 June 2019 in Castelló (Spain), organized by Nanouptake Action (CA15119) and Universitat Jaume

Experimental study on the flow and heat transfer characteristics of nanofluids in double-tube heat exchangers based on thermal efficiency assessment

Thermal performance and pressure drop of TiO2-H2O nanofluids in double-tube heat exchangers are investigated. The influence of the thermal fluid (water) volume flow rates (qv = 1–5 L/min), nanoparticle mass frictions (ω = 0.0%, 0.1%, 0.3% and 0.5%), nanofluids locations (shell-side and tube-side), Reynolds numbers of nanofluids (Re = 3000–12000), and the structures of inner tubes (smooth tube and corrugated tube) is analyzed. Results indicate that nanofluids (ω = 0.1%, 0.3% and 0.5%) can improve the heat transfer rate by 10.8%, 13.4% and 14.8% at best compared with deionized water respectively, and the number of transfer units (NTU) and effectiveness are all improved. The pressure drop can be increased by 51.9% (tube-side) and 40.7% (shell-side) at best under the condition of using both nanofluids and corrugated inner tube. When the nanofluids flow in the shell-side of the corrugated double-tube heat exchanger, the comprehensive performance of nanofluids-side is better than that of the smooth double-tube heat exchanger

A Flexible 3D Architecture for Cooling Future Generation Devices

Systems that consume and convert energy produce thermal energy as a byproduct. This generation of thermal energy, if not dissipated properly, contributes to the significant temperature rise of the overall system. This temperature rise can lead to reduced efficiency and system-level failure. Future technologies will continue to face such thermal challenges. In fact, next-gen devices will demand flexible thermal management architectures for high-performance operation. To tackle these challenges, innovative liquid cooling technologies and high-speed thermal diagnostic systems must be developed simultaneously. Active and passive pulsation-liquid-cooling techniques are currently an attractive thermal management solution. In an active cooling mode, the influence of pulsation on heat transfer enhancement using liquid jets is understood, fairly well both theoretically and experimentally. However, the thermal diagnostic systems for characterizing these cooling methods fall short for many reasons including that the conventional thermal cameras have limited temporal and spatial resolutions. To solve this problem and capture high thermal transients, a low-cost thermal mapping technique using Quantum-dots is developed. In parallel to active cooling solutions, passive cooling technologies have come a long way due to their capability of hot spot mitigation. However, challenges remain in thermal diagnostics and the fabrication methodologies – especially for the next-gen of flexible and 3D electronic packages. To solve these problems, firstly, research efforts are pursued to come up with i) a fabrication process that is easy, cheap and repeatable and ii) an innovative design with modular features that makes it suitable for double-sided cooling configuration. Secondly, experimental testing is pursued to reveal the flow and thermal kinetics for different condensation conditions. This work identified many design, fabrication, and thermal performance limitations tied to planar, flexible and stacked-3D pulsating heat pipes that can also incorporate multi-phase coolants such as the combination of paraffin wax and water-ethanol fluid mixtures

Polymer and Composite Materials in Two-Phase Passive Thermal Management Systems: A Review

The application of polymeric and composite materials in two-phase passive heat transfer devices is reviewed critically, with a focus on advantages and disadvantages of these materials in thermal management systems. Recent technology developments led to an increase of the power density in several applications including portable electronics, space and deployable systems, etc., which require high-performance and compact thermal management systems. In this context, passive two-phase systems are the most promising heat transfer devices to dissipate large heat fluxes without external power supply. Usually, heat transfer systems are built with metals due to their excellent thermal properties. However, there is an increasing interest in replacing metallic materials with polymers and composites that can offer cost-effectiveness, light weight and high mechanical flexibility. The present work reviews state-of the-art applications of polymers and composites in two-phase passive thermal management systems, with an analysis of their limitations and technical challenges.</jats:p