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Thermoelectric generators (TEGs) are a promising solution for waste-heat-recovery system as they can generate power when there is a temperature difference, i.e., temperature difference between the waste heat, Tsource, and heat sink, Tsink. While there are many studies on TEGs for waste-heat recovery, most works optimize their performance based on the hot- and cold-side temperatures, Thot and Tcold, respectively, of the TEGs which are different than those of the available waste-heat and coolant temperatures, i.e., Tsource and Tsink. This work proposes a model for estimating the maximum power output of TEGs based on heat-source and heat-sink conditions without taking extra steps to extract Thot and Tcold out of the conditions. From given heat-source and heat-sink conditions, i.e., temperature and flow rate, the model can determine the optimal TEG and heat exchanger geometry for maximum power generation. This model is valid for cases where the heat transfer rate of the heat sink is much greater than that of the heat source. Finally, a TEG system is optimized for marine engine waste-heat recovery, generating about 157% more power than an unoptimized system. This newly proposed model offers a simple and quick estimation of the maximum power generation of a TEG system for waste-heat recovery. [ABSTRACT FROM AUTHOR]

The current two-dimensional (2D) numerical study presents the melting phenomenon and heat transfer performance of the nanocomposite phase change material (NCPCM) based heat sink. Metallic nanoparticles (copper: Cu) of different volume fractions of 0.00, 0.01, 0.03, and 0.05 were dispersed in RT–28HC, used as a PCM. Transient simulations with conjugate heat transfer and melting/solidification schemes were formulated using finite–volume–method (FVM). The thermal performance and melting process of the NCPCM filled heat sink were evaluated through melting time, heat storage capacity, heat storage density, rate of heat transfer and rate of heat transfer density. The results showed that with the addition of Cu nanoparticles, the rate of heat transfer was increased and melting time was reduced. The reduction in melting time was obtained of − 1.36%, − 1.81%, and − 2.56% at 0.01, 0.03, and 0.05, respectively, compared with 0.00 NCPCM based heat sink. The higher heat storage capacity enhancement of 1.87% and lower reduction of − 7.23% in heat storage density was obtained with 0.01 volume fraction. The enhancement in rate of heat transfer was obtained of 2.86%, 2.19% and 1.63%; and reduction in rate of heat transfer density was obtained of − 6.33%, − 21.05% and − 31.82% with 0.01, 0.03, and 0.05 volume fraction of Cu nanoparticles, respectively. The results suggest that Cu nanoparticles of 0.01 volume fraction has the lower melting rate, higher heat storage capacity and heat transfer rate, lower heat storage density and heat transfer rate density which is preferable for passive cooling electronic components. [ABSTRACT FROM AUTHOR]

Thermal interface materials (TIMs) play a pivotal role in the transfer of heat from high‐temperature sources, such as CPUs, to heat sinks in power electronics. The effectiveness of grease‐type TIMs is determined by their effective thermal impedance (REFF), which hinges on optimizing both the specific bulk (RB) and contact (RC) thermal resistances. Achieving concurrent optimization of these resistances poses a significant challenge, especially in high filler loading TIMs, typically above 76 vol%. This research leverages interface engineering through Self‐Assembled Monolayers (SAMs) to address this challenge. A substantial decrease in REFF is realized to 0.169 K cm2 W−1, a tenfold enhancement compared to non‐SAM treated TIMs, which exhibit REFF values of 2.265 K cm2 W−1. This leap in performance is primarily ascribed to the reduced surface energy of SAM treated Al2O3, leading to lower particle‐to‐particle Van der Waals forces, thereby improving particle dispersion and strengthening interfacial bonds. Furthermore, longer carbon chains in SAMs result in increased RB, yet a decrease in RC, due to the chains' capacity for enhanced energy absorption and molecular entanglement. The investigation underscores the significance of shorter‐chain SAMs in fine‐tuning thermal resistance, highlighting the crucial role of molecular architecture in the design of advanced TIMs. [ABSTRACT FROM AUTHOR]

Heat sinks are used as heat exchangers to dissipate heat from electronic equipment due to their high functionality and viability. However, heat dispersion is the main obstacle to improving the heat sinks thermal efficiency. This paper has two main parts. The first part of this study focuses on the thermal design of the heat sink, encompassing several factors such as heat dissipation devices using natural convection, heat sinks with various geometries, locations of intake and outlet, materials of the core, flat fins (especially FPFHS and PFHS fins), and porosity fins. Heat sinks that are single-layered or multi-layered and heat sinks that use different cooling liquids. The second part examines interior heat transmission by investigating various indoor geometries, including cylindrical, circular, rectangular, and hexagonal shapes, and assessing their effect on the transport of heat. Additionally, interior structures influence various fin arrangements for any type of heat convection, including actual trials conducted on enclosures using diverse fin designs, are considered. The current study aims to collect research literature that studies the heat sink and various enclosures. The research has been divided into groups to simplify the research process for activities that use cavitation-based technology to improve heat transfer for heat sinks, especially heat exchangers used to cool electrical equipment. These advantages can be attributed to their outstanding features, which include ease of production, cost-effectiveness, and effective heat dissipation. [ABSTRACT FROM AUTHOR]

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The utilization of microchannel heat sinks stands as one of the most reliable solutions for dissipating heat generated in electronic chips. In this numerical study, a fractal microchannel heat sink employing three nanofluids Cu-water, Al2O3-water, and TiO2-water with variable volume fractions of 2 and 4 percent as the cooling fluid within the microchannels was investigated. The fluid flow inside the microchannels was analyzed from both hydrodynamic and thermal perspectives. The parameters such as pump power, Nusselt number, and performance evaluation criterion (PEC) were studied. Results demonstrate that heat transfer increases with an increase in the flow rate and volume fraction of nanoparticles. The maximum temperature reduction for the Cu-water nanofluid at an inlet flow rate of 200 ml/min and a volume fraction of 4% is 2.41%, the highest among the investigated nanofluids. However, this nanofluid also exhibits the highest pressure drop, reaching 25% at a 4% volume fraction. The PEC number analysis reveals an overall performance increase for all three microchannels. The Cuwater nanofluid exhibits the best comprehensive performance, providing an 8% overall enhancement, followed by Al2O3-water and TiO2-water nanofluids, which increase the system performance by 5% and 4%, respectively. Furthermore, the study introduced fins and cavities to the microchannel branches to enhance heat transfer and overall performance. Results indicate an increase in heat transfer for both modified geometries. The microchannel with fins exhibits a 3.5% lower maximum temperature compared to the original geometry at an inlet flow rate of 200 ml/min, while the microchannel with cavities showed a 1% reduction. However, the microchannel with fins experiences a 400% higher pressure drop than the initial geometry, while the microchannel with cavities has a 4% increase. PEC number analysis demonstrated that the microchannel with cavities improves system performance by 8%, whereas the microchannel with fins reduced system performance by 4%. [ABSTRACT FROM AUTHOR]

Background: Thermal ablation (TA) with radiofrequency (RFA) or cryoablation (CA) are established treatments for small renal masses (≤4 cm). Microwave ablation (MWA) has several potential benefits (decreased ablation time, less susceptibility to heat-sink, higher lesion temperatures than RFA) but is still considered experimental considering the available small-sample studies with short follow-up. Purpose: To evaluate technique efficacy and complications of our initial experience of renal tumors treated using percutaneous MWA with a curative intent. Material and Methods: A total of 105 renal tumors (in 93 patients) were treated between April 2014 and August 2017. MWA was performed percutaneously with computed tomography (CT) guidance under conscious sedation (n=82) or full anesthesia. Patients were followed with contrast-enhanced CT scans at six months and yearly thereafter for a minimum of five years. The mean follow-up time was 2.1 years. The percentage of tumors completely ablated in a single session (primary efficacy rate) and those successfully treated after repeat ablation (secondary efficacy rate) were recorded. Patient and tumor characteristics as well as complications were collected retrospectively. Results: The median patient age was 70 years and median tumor size was 25 mm. Primary efficacy rate was 96.2% (101/105 tumors). After including two residual tumors for a second ablation session, secondary efficacy was 97.1% (102/105). Periprocedural complications were found in 5.2% (5/95) sessions: four Clavien-Dindo I and one Clavien-Dindo IIIa. One postprocedural Clavien-Dindo II complication was found. Conclusion: MWA has high efficacy rates and few complications compared to other TA methods at a mean follow-up of two years. [ABSTRACT FROM AUTHOR]

The utilization of cold plate radiators as a prevalent method for indirect liquid cooling has been extensively investigated and implemented in server cooling systems. However, there is a lack of comprehensive study on the application of this technology at the chip size, indicating a need for more development and exploration in this area. A proposal was made for a grid-channel chip cold plate heat sink to facilitate the dissipation of heat from a chip. tests were conducted to investigate the impact of the flow rate of the cold plate and the layout of the inlet and outlet on various thermal parameters, including the average temperature, maximum temperature, thermal resistance, and uniformity coefficient of the cold plate. The tests were specifically conducted under a chip power of 150W, and the accuracy of the simulation was confirmed through the use of FLUENT. The findings indicate that the cold plate effectively regulates the temperature of the chip, ensuring it remains below 85 °C throughout all experimental groups. In contrast to the single in single out configuration, the single-in multiple-out layout exhibits a higher degree of temperature uniformity within the cold plate. Nevertheless, it is important to note that augmenting the quantity of exits does not guarantee an improvement in heat transfer efficiency. This outcome is contingent upon the presence of a longitudinal flow channel shared by the outlet and intake, as well as the dispersion characteristics of the outlet. Enhancing the dispersion of the exit can significantly enhance the thermal transfer efficiency of the cold plate. Furthermore, a strategy for adjusting the aperture of the orifice is proposed as a solution to address the challenges related to flow uniformity and the issue of high pressure drop in the cold plate. [ABSTRACT FROM AUTHOR]

An experimental investigation of the effect of random vibration on the melting behavior of a phase change material (PCM) and the thermal performance of a PCM-based heat sink is presented. While random vibration from 2 to 16 g rms for the frequency range from 15 to 2000 Hz was applied to a rectangular enclosure, which contains paraffin wax and the heat sink, a constant heat flux was imposed on the heat sink to melt the PCM. The experimental results showed that the random vibration has no effect on the melting behavior early in the melting process during which conduction is the primary mode of heat transfer. However, the random vibration significantly affected the melting behavior later in the process during which natural convection is the primary mode of heat transfer. The random vibration augmented heat transfer in the molten PCM and increased the Nusselt number, 1.56 times greater under the vibration of 16 g rms than without vibration. The augmented heat transfer accelerated PCM melting and delayed the rise in temperature of the heat sink. The time for the temperature of the heat sink to rise to a threshold increased as the intensity of random vibration increased, 5.9 times longer under the vibration of 16 g rms than without vibration. [ABSTRACT FROM AUTHOR]

This paper investigates the current sink capacitor technique as a method to minimize the turn-off power losses of SiC MOSFETs operated with zero-voltage switching (ZVS). The method is simple and is based on adding auxiliary capacitors in parallel to the transistors, allowing the sink capacitor to take over part of the channel current, thus limiting the power loss while also advantageously lowering the d v d s / d t ratio. The technique is validated and experimentally studied based on a single-pulse test setup with 1200 V-rated SiC MOSFETs, with several capacitances and gate resistance values, at various switched currents up to roughly 60 A. It is shown that by employing even very small capacitances, in the range of nanofarads, the turn-off power loss can be reduced by over tenfold, with a negligible impact on the volume and complexity of the system. Thus, the presented method can be effectively employed to improve soft-switched power converters. [ABSTRACT FROM AUTHOR]

Thermoelectric coolers are preferred in many areas because of their simple mechanism and no need for a refrigerant. In this study, an air-to-water mini thermoelectric cooler system was designed and produced. Experiments were performed by placing different numbers of thermoelectric modules on the liquid-cooling heat sink and applying different voltages. The cooling capacity and COP values of the system under different operating conditions were analyzed and discussed. In addition, the effect of fluid flow rate on system performance and temperature difference between inlet and outlet sections has been presented. The heat transfer and flow behavior of the fluid in the liquid-cooling heat sink were determined using CFD simulation methods. Moreover, the heat loss from the system was tried to be reduced by using extra foam insulation and the results were compared with single foam and the effect of the insulation on the temperature drop inside cooler was discussed. At 0.011 kg s−1 mass flow rate and 12 V voltage conditions, when the number of TE modules is increased from 1 to 3 in the TE cooler, a maximum increase of 35% in cooling load is obtained. Also, if the cases with 3 TE modules and 0.011 kg s−1 flow rate are compared in terms of cooling load, 12 V has 80% higher cooling load than 4 V. According to the numerical results, flow structures that negatively affect the heat transfer interactions and reduce the cooling performance of the TE cooler have been determined in the liquid-cooled heat exchanger. Additionally, a significant decrease in the temperature of the cooling chamber has also been achieved with additional insulation. [ABSTRACT FROM AUTHOR]

The research conducted deals with the use of an aluminum heat sink, which is usually used to cool electronic cores and integrated circuits, to cool a solar cell and study the effect of microprocessors and integrated circuits on the performance and temperature of the cell. In this study, an experiment was carried out and simulated using computational fluid dynamics. The results showed that increasing the temperature of the solar cell leads to an accelerated decrease in the open circuit voltage, but when a heat sink is used, the increasing temperature of the cell is reduced more slowly over the same period. Thus, the open circuit voltage drop is reduced more slowly as well, which means the cell operates more efficiently under the same conditions. The temperatures are 290 K at the lowest point and 350 K at the highest point, which shows that heat is being dissipated from the solar cell to the heat sink. It is evident that as the heat sink's number of fins increases, the rate at which heat is transferred increases because the enhanced heat transfer that results from having more fins lowers the heat sink's temperature. These findings can help improve the efficiency of solar power generation and increase the efficiency of solar cells in converting solar energy into electrical energy. [ABSTRACT FROM AUTHOR]

As the junction temperature of a light-emitting diode (LED) is inversely proportional to its lifespan and efficiency, it is necessary to maintain it at a lower temperature using different heat transfer techniques. This study investigates, the thermal performance of a heat sink-based model with a drop-shaped pin fin connected with plate fin under natural convection. The study focuses on the basic design parameters of pin fin configuration such as fin array, pin fin shape and vertical fin spacing (Sv). Three distinct pin fin shapes with variable vertical fin spacing (Sv = 25, 50 and 75 mm) are considered for study. Several experimental trials are performed for the validation purpose of the traditional plate fins and circular pin fins type heat sink. The standard correlations are used for the comparison of experimental results. A qualitative investigation is also performed utilising experimental research to investigate heat transfer enhancement for various configurations. For different fin shape and vertical fin spacing, a Nusselt number, convective heat transfer coefficient and the temperature difference between the base plate and ambient temperature are assessed. Experimental results revealed that, for any heat input, with an increase in vertical fin spacing, the Nusselt number, convective heat transfer coefficient and temperature difference between the base plate and ambient temperature are increased. The maximum heat transfer coefficient was found to be 11.97 W/m2K for drop shape pin fins with vertical fin spacing (Sv) equal to 75 mm and heat input of 200 W. Similarly, the Nusselt number was found 88.66 for same configuration. This comparison will help to understand the effect of vertical fin spacing in vertical orientation. Also, it will help to determine innovative passive cooling technology with combined drop shape and plate fin type heat sink for electronic devices such as LED streetlights. [ABSTRACT FROM AUTHOR]

Introduction : High irrigation rates are commonly used during ureteroscopy and can increase intrarenal pressure (IRP) substantially. Concerns have been raised that elevated IRP may diminish renal blood flow (RBF) and perfusion of the kidney. Our objective was to investigate the real-time changes in RBF while increasing IRP during Ureteroscopy (URS) in an in-vivo porcine model. Methods: Four renal units in two porcine subjects were used in this study, three experimental units and one control. For the experimental units, RBF was measured by placing an ultrasonic flow cuff around the renal artery, while performing ureteroscopy in the same kidney using a prototype ureteroscope with a pressure sensor at its tip. Irrigation was cycled between two rates to achieve targeted IRPs of 30 mmHg and 100 mmHg. A control data set was obtained by placing the ultrasonic flow cuff on the contralateral renal artery while performing ipsilateral URS. Results: At high IRP, RBF was reduced in all three experimental trials by 10–20% but not in the control trial. The percentage change in RBF due to alteration in IRP was internally consistent in each porcine renal unit and independent of slower systemic variation in RBF encountered in both the experimental and control units. Conclusion: RBF decreased 10–20% when IRP was increased from 30 to 100 mmHg during ureteroscopy in an in-vivo porcine model. While this reduction in RBF is unlikely to have an appreciable effect on tissue oxygenation, it may impact heat-sink capacity in vulnerable regions of the kidney. [ABSTRACT FROM AUTHOR]

Thermoelectric cooling (TEC) reverses the electrical energy to temperature caused by the Peltier effect, where a temperature difference occurs between two conductors, that is, hot and cold junctions. This article presents the enhanced heat transfer of a TEC module using a TEC1‐12710 model integrated with a wavy channel heat sink using ferrofluid as a coolant under continuous and pulsating flows, where the differences in the distance of the magnetic field are considered. Square permanent magnets measuring 30 mm × 20 mm × 4 mm (width × length × height) are used to transmit a magnetic field to the heat sink and then tested under a magnetic distance of 10–30 mm. The test is performed at a water flow rate from 0.0083 to 0.028 kg/s and supplied with a constant TEC voltage of 12 V. By applying a magnetic field to the TEC module with a magnetic distance of 20 mm and a ferrofluid concentration ratio of 0.015%, the cooling efficiency increases by approximately 18.64%. Hence, using pulsating flow may improve thermal efficiency by approximately 23%. The results show an exponential increase in the cooling efficiency when both passive and active cooling techniques are used. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thermal management technology is a major challenge in high-end equipment. The demand for high-efficiency heat sinks has increased. In this study, a controllable aspect ratio (AR) fractal channel (CARFC) heat sink is proposed to enhance thermal performance. First, a parameterized modeling method for the CARFC is constructed. Fractal networks are constructed using control points and bifurcation points. The geometric size of each level channel is determined by considering the AR of each level channel. A mathematical relationship is established between the two parts. Under constant heat flow boundary, the effect of aspect ratio on the fractal channel performance is studied by numerical simulation. The influence of the inlet AR on the performance of the fractal channels is studied. Then, the impact of the AR of each level channel on the performance of the CARFC is studied. The results show that the AR of the inlet has an obvious effect on the performance of the fractal channel. The CARFC results show that the AR of each level channel influences the thermal performance of the heat sink, especially the aspect ratio k 0 and k 1 . Compared with only changing the aspect ratio of the inlet, the CARFC has better performance; the peak temperature and temperature difference are reduced by 9.62% and 26.57%, respectively. The CARFC requires less coolant to meet the same thermal demand, which is of great significance in the development of lightweight equipment. [ABSTRACT FROM AUTHOR]

High-intensity focused ultrasound (HIFU) is a recent, non-ionizing and non-invasive technology of focal destruction. Independence from the heat-sink effect of blood flow makes HIFU an interesting technique for focal ablation of liver tumors. Current available technology is based on extracorporeal treatment that limits use of HIFU for the treatment of liver tumors, as elementary ablations are small and must be juxtaposed to treat tumors, resulting in long-duration treatment. We developed an HIFU probe with toroidal technology, which increases the volume of ablation, for intra-operative use, and we assessed the feasibility and efficacy of this device in patients with colorectal liver metastasis (CLM) measuring less than 30 mm. This study was an ablate-and-resect, prospective, single-center, phase II study. All ablations were performed in the area of liver scheduled for liver resection to avoid loss of chance of recovery. The primary objective was to ablate CLM with safety margins (>5 mm). Between May 2014 and July 2020, 15 patients were enrolled and 24 CLM were targeted. The HIFU ablation time was 370 s. In total, 23 of 24 CLM were successfully treated (95.8%). No damage occurred to extrahepatic tissues. HIFU ablations were oblate shaped with an average long axis of 44.3 ± 6.1 mm and an average shortest axis of 35.9 ± 6.7 mm. On pathological examination, the average diameter of the treated metastasis was 12.2 ± 4.8 mm. Intra-operative HIFU can safely and accurately produce large ablations in 6 min with real-time guidance (ClinicalTrials.gov identifier: NCT01489787). [ABSTRACT FROM AUTHOR]

Flat heat pipe (HP)-phase change material (PCM) hybrid system used for thermal regulation of simulated PV is investigated experimentally. Three PCMs; Rubitherm RT-25 H (RT25), Rubitherm RT-35 H (RT35), and Rubitherm RT-44 H (RT44) coupled with the HP are tested for best cooling system. Impact of using one or two heat sinks compared with PCM only is studied. The results show that RT25 achieves lowest PV temperature, while RT44 achieves highest energy storage. Compared to RT25 and RT44, RT35 is considered the best for PV cooling and PCM energy storage. Including heat sinks reduces PV temperature and melting time and increases energy storage rate. [ABSTRACT FROM AUTHOR]

This study represents Computational Fluid Dynamics (CFD) analyses to improve the heat transfer on the two sides of a thermoelectric generator (TEG) by utilizing heat sinks to recover the waste heat of hot air. In this respect, the temperature difference between the hot and cold sides of the TEG, the heat transfer rate on the hot and cold sides and the pressure drop between the inlet and outlet of the hot and cold air are investigated for varying hot air inlet temperature and Re number in terms of improving the heat transfer and accordingly the output power of the TEG. According to the numerical results, the maximum temperature difference between the hot and cold sides of the TEG concerning hot air inlet temperature of 600 °C and Re number of 16800 is specified as 418.9 °C and 478.1 °C, respectively. In terms of heat transfer, maximum heat transfer rate on the hot side for hot air inlet temperature of 600 °C and Re number of 16800 is specified as 180.4 W and 205.1 W, respectively, while the maximum heat transfer rate on the cold side is specified as 168.0 W and 192.6 W. The maximum pressure drop occurs as 304.4 Pa for the Re number of 16800. As a result, increasing hot air inlet temperature and Re number yields an increase in the temperature difference, the heat transfer rate on the hot side, and the heat transfer rate on the cold side. Besides, pressure drop increases with increasing Re number. [ABSTRACT FROM AUTHOR]

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Significant circulating currents in the modular multilevel converter (MMC) increase system losses and complicate heat-sink design. Conventional PI and PR controllers can achieve steady-state error adjustment, but are sensitive to parameter changes and model uncertainty, heavily relying on coordinate transformations and careful design of model parameters. Model predictive control (MPC) has the characteristics of simple design, good robustness, and excellent dynamic response; however, it encountered the complexity of adjusting weighting factors. This paper proposed circulating the current model predictive proportional integral control (MPPIC) method in abc reference frame. This hybrid control solution utilized the predictive model and traditional PI algorithm to combine the advantages of nonlinear and linear control. Compared with existing suppression methods, this method avoided complex mathematical operations and a selection of weight coefficients, was easy to implement, and can effectively suppress circulating currents under different modulation ratios. Simulations were conducted on MATLAB/Simulink to verify the effectiveness of the proposed control strategy. MPPIC can not only distinctly suppress the circulating currents, but also reduce the overall voltage fluctuation of sub-modules capacitors under different modulation ratios, and had almost no any adverse effect on the performance of MMC. [ABSTRACT FROM AUTHOR]

A common heat exchange method used for most new designs is the use of heat sinks such as short pin fins. This experimental study investigated the static pressure characteristics developed in a short pin fin. Different fin array arrangements, fin longitudinal and transverse spacing ratios and individual slot heights in the fin were investigated. It was found that the row removed arrangement has superior flow efficiency, but to enhance heat transfer the staggered array is a better choice; the greater the fin spacing and slot height in each fin are, the less the pressure loss was experienced in the array. [ABSTRACT FROM AUTHOR]

Quad Small Form-factor Pluggable-Double Density (QSFP-DD) is the smallest high-speed (>14 Tb/s) interconnect system and is widely used in cloud computing and 5G network. However, the high-speed feature comes at the cost of large power dissipation. The QSFP-DD system contributes 400 to 960 W per rack unit, which necessitates its thermal management. The authors, having identified a knowledge gap in the existing literature, humbly hope to pioneer a thermal-hydraulic study for QSFP-DD. The study starts with experiments in a wind tunnel wherein temperature, power, fan speed, and pressure are measured. The experimental data are used to validate computational fluid dynamics (CFD) models. Both lumped fan and multiple reference frame fan models have been studied with comparisons versus experimental data. Subsequently, the focus of CFD study is shifted to the QSFP-DD system's thermal-hydraulic structures, including variation in fins' height, quantity, and the grille free area ratio. Finally, the CFD results are processed into an empirical Nusselt number correlation for thermal performance prediction. The study reveals that optimum thermal performance could be achieved by balancing heat sink fin area and pressure drop of the system. [ABSTRACT FROM AUTHOR]

Ultrathin vapor chambers (VCs) are the most typically used heat-sink components in the development of thin and light electronic products. In this study, microgrooved aluminum wicks with multi-scale structures fabricated by two-step laser processing are developed to enhancing the performance of ultrathin VCs. The multi-scale microgroove wick is composed of the main groove and the multi-scale microstructures that include cluster particles, the gradient structure, and holes formed between cluster particles. The effects of the second step laser processing scan interval and the scan number on the surface morphology, wettability, capillary rise rate, and capillary performance parameters of the multi-scale microgroove structured wicks are investigated. The second-step laser processing changes the morphology of the main groove surface, which affects the wettability of the multi-scale microgroove structure. When the scan interval of second step laser processing is 0.05 mm and the scan number is 1, the droplets on the surface of the multi-scale microgrooves are completely immersed within 23.5 ms, which is 80.6% less than all the time of A1. In addition, the capillary rise velocity of the two-step laser processing multi-scale microgroove structure in the initial 3 s is 150% higher than that of the one-step laser processed microgroove wick, and the capillary performance parameters K/Reff improves by 114.15%. [ABSTRACT FROM AUTHOR]

In this study, the effect of the fin surface on the electrical performance of passively cooled photovoltaics (PV) modules equipped with flat (PVf) and tread (PVt) surface finned heat sinks was experimentally investigated. PVf and PVt modules were fabricated with heat sinks by filling phase change material (paraffin)/aluminum chip mixture between the PV module and heat sink. The mean ambient temperature, solar radiation, and solar power during the experiment were about 13°C, 864 W/m2 , and 247, respectively. The electrical power of the PVf and PVt modules was increased by 10.84% and 17.2%, respectively, while the average temperature was decreased by 11.78% and 16.5%, respectively, compared to the PV module. The PVt module provided 5.37% more effective cooling and a 5.74% higher electrical power than the PVf module. The electrical efficiency of the PV module was 11.35%, and the rate of increase was 1.21% and 1.95% for the PVf and PVt modules via cooling. Compared to the PV module, the electrical exergy of the PVf and PVt modules increased by 10.84% and 17.2%, respectively, at an average solar exergy of 230.61 W, while their thermal exergy decreased by 23.64% and 32.3%, respectively. Compared to the PVf module, the thermal exergy of the PVt module was reduced by 11.34%, and the electrical exergy was increased by 5.74%. The increase in exergy efficiency is 3.14% and 4.51% for PVf and PVt modules versus the PV module. A small part of solar energy is converted into electricity, while a significant part is converted into heat and increases the temperature of the PV cells. An increase in the temperature of PV cells harms conversion efficiency and causes an increase in the share of converted heat and a decrease in electricity generation. The conversion efficiency can be improved by removing the accumulated heat of the module. In practice, there are various examples of passive and active cooling. Active cooling methods enhance heat transfer by forcing the fluid flow with a fan or pump to facilitate heat removal. Active cooling applications are heavy, expensive, and complicated. Natural heat convection can be maximized with heat spreaders or heat sinks during passive cooling. Passive cooling may not dissipate heat as effectively as active cooling. Passive cooling systems are cheap, lightweight, and uncomplicated, and they can become even more valuable as their thermal efficiency increases. This study addresses the effect of the heat sink fin surface on the cooling and electrical performance of flat and tread finned heat sinks coupled PV modules that are paraffin/aluminum chips blend backplane filled. 1st and 2nd law PV module efficiencies improved by about 1.21% and 1.95% and 3.14% and 4.51% with flat and tread finned heat sinks, respectively. [ABSTRACT FROM AUTHOR]

Thermal emission is an informative tool to study materials' properties at high temperatures under laser irradiation. The kinetics decay of laser-induced thermal emission from carbon microparticles deposited on heat-sink surfaces of transparent dielectrics (glass and sapphire) was studied. A Q-switched YAG:Nd3+ laser (pulse duration τi = 20 ns, energy/power density 0.5 J·cm-2, 25 MW·cm-2) was employed to excite thermal emission. In calculations, the classical heat conduction equation was used. With increasing the thermal conductivity of substrate (from glass to sapphire), reduction in the emission pulse duration has been observed. [ABSTRACT FROM AUTHOR]

Herein, three material approaches, for the fabrication of thermally conductive and yet electrically insulating parts via additive manufacturing (AM) technologies, are described. Samples are prepared from light‐curable resins, sol–gel‐hybrid polymers, and thermoplastic materials using thermally conductive particles as fillers. AM sample preparation is done using vat photo‐polymerization and material extrusion with subsequent measurements of thermal conductivity and electrical insulation properties. The main goal herein in addition to material development is the demonstration of manufacturing applicability including usage properties. Use cases are heat sinks for power electronics, which have to be thermally conductive to spread the generated heat and electrically insulating to ensure general functionality and long‐term operation. [ABSTRACT FROM AUTHOR]

Heatsinks have a prime role in the thermal management of energy systems and electronic devices. Miniaturization and the high power requirement of modern electronic equipment make them more compact and more heat-generating. For the efficient operation of modern electronic equipment, efficient thermal management system is required. Microchannel heatsinks (MCHS) are the best choice for efficient thermal management of electronic devices because of their high compactness and large heat-dissipating capacity. The attention of most of the researchers is on the improvement of the performance of the MCHS. In the present work, the augmentation of the performance of MCHS by incorporating the phase change material (PCM) was analysed. Six novel designs of PCM-based hybrid MCHS are modelled using ANSYS FLUENT. The computational model implemented for the present work was validated with both experimental and numerical works in the literature, and a good agreement was observed. The performance of six models of PCM-based MCHSs is analysed and compared with the heatsink without PCM. The heatsink model with the best thermal performance is presented. The variation of thermal resistance, liquid fraction, and temperature uniformity coefficient (TUC) with Reynolds number are analysed. A maximum of 15.26% lower TUC and 7.3% lower thermal resistance was found in hybrid MCHS with PCM compared to the MCHS without PCM. The influence of the liquid fraction and position of the PCM on the performance of MCHS were also studied. [ABSTRACT FROM AUTHOR]

The electrical resistivity of solid-state tungsten (W) and rhenium (Re) was experimentally measured at high pressures up to 5 GPa and temperatures up to ∼2273 K using a four-wire resistivity method. For both metals, the resistivity decreased as a function of pressure and increased as a function of temperature, in excellent agreement with 1 atm data. The Wiedemann–Franz law was used to calculate the total thermal conductivity from the resistivity. Thermal conductivity increased as a function of pressure for both metals, but decreased as a function of temperature for W and increased for Re. Values of thermal conductivity at high pressures and temperatures are consistent with most recommended previous experimental studies at 1 atm. [ABSTRACT FROM AUTHOR]

Interfacial thermal resistance between metal and dielectric materials is a bottleneck of the thermal management for modern integrated circuits as interface density increases with thinner films. In this work, we have observed that the interfacial resistance across gold and aluminum oxide can be reduced from 4.8 × 10 − 8 m 2 K / W to 1.4 × 10 − 8 m 2 K / W after adding a nickel layer in between, which represents a 70% reduction. The two temperature model is applied to explain the reduction of interfacial resistance, and the results show that the nickel layer functions as a bridge that reduces the phonon mismatch between gold and aluminum oxide. Moreover, nickel has strong electron-phonon coupling, which reduces the thermal resistance caused by the weak electron-phonon coupling in gold. [ABSTRACT FROM AUTHOR]

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This study experimentally investigates a Regenerative Organic Rankine Cycle (RORC) system that operated under varied cryogenic conditions using liquid nitrogen (LN2) as the heat sink. A three-fluid heat exchanger (TFHE) is applied to this system instead of a condenser and regenerator to realize the RORC system. The condensing pressure changes between 0.08 MPa and 0.6 MPa, and applying the R290 as the working fluid. The condensing pressure effect on system performances, including electrical power output, cold thermal efficiency, and exergetic efficiency, are investigated under different LN2 flow rates. The comparisons between basic ORC (BORC) and RORC under the same working conditions are conducted. The results demonstrate that as the condensing pressure remains constant, the higher LN2 flow rate is beneficial to the overall performance of the RORC system. The maximum cold thermal efficiency and power generation obtained in the RORC system are 13.35% and 738.81 W, which are obtained at the LN2 flow rate of 120 kg/h and the condensing pressure of 0.25 MPa. Additionally, the RORC shows improved performance with an exergetic efficiency of 10.68%. The results would be a technological guide for the construction and improvement of the system with cold energy recovery. [ABSTRACT FROM AUTHOR]

This paper addresses the use of a geothermal heat-sink to remove the heat released in domestic-sized single and double-effect water–LiBr absorption chillers operating in hot climates. This study is the continuation of a previous work, which demonstrated the operational constraints of these absorption chillers working in hot Algerian climate-zones. After localizing the non-operation zones for both systems, the thermo-physical properties of the soil at several depths are investigated for the implementation of the underground heat-exchanger. This heat-exchanger is connected to the condenser and the absorber of both systems, to supply cooling water at inlet temperatures of 33 °C in hot climate conditions, with ambient temperatures varying from 38 °C to 42 °C. The results show a steady operation for both absorption chillers in climate conditions which had not previously allowed the two systems to operate in water or air-cooled modes. A maximum coefficient of performance of 0.76 and 1.25 is obtained for single- and double-effect absorption cycles, respectively, with chilled water at 7 °C. The underground-tube length required is between 4.5 and 18 m, depending on the absorption-cycle configuration and the temperature of the chilled water. [ABSTRACT FROM AUTHOR]

This paper presents an auxiliary passive circuit and control design for wireless power transfer (WPT) systems in DC microgrids to achieve optimal power transfer efficiency while maintain accurate output voltage regulation. An auxiliary inductance is added at the transmitter resonator to form a current sink to ensure zero voltage switching (ZVS) of the primary-side full-bridge inverter with even extremely light load conditions. Moreover, an adaptive proportional–integral (PI) controller is adopted to track the output voltage references by regulating the phase shift angle of the phase shift control for the full-bridge inverter. The coefficients of the adaptive PI controller are determined by the inductance of the auxiliary inductance. Both simulation and experimental results validated the effectiveness of the proposed circuit and control design in achieving optimal efficiency and output voltage regulation for WPT systems in DC microgrids with source and load variations. [ABSTRACT FROM AUTHOR]

The purpose of this study is to analyse and evaluate the function of interventional radiology in such instances by evaluating several elements of each procedure, such as its influence on survival rates, recurrence, tumour response, and complications. The following databases were searched: PubMed, Web of Science, Science Direct, EBSCO, and the Cochrane Library. Using Rayyan QCRI, study papers were screened by title and abstract before being subjected to a full-text evaluation. This review included 13 studies with participants of varying ages and genders; more than half were males. All included studies discussing the role of interventional radiology in hepatoma cases in diagnosis and treatment. We included Sex studies that were systematic reviews; two were randomized controlled, one was a case-control study, one was a prospective study, two were retrospective studies, and one was a pilot study. In the ablation therapy of hepatocellular carcinoma nodules, we determined that microwave ablation had greater complete ablation and lower local tumour growth than radiofrequency ablation. In large tumors (up to 6 cm), mwa is preferred, and cryoablation is preferred in recurrent disease. Because of a lesser heat-sink effect, mwa and cryoablation are preferred to RFA in perivascular disease. Chemoablation can be used in smaller lesions (<3 cm). In intermediate-stage, multifocal lesions (>3), tace, debs, and tare are to be used. [ABSTRACT FROM AUTHOR]

The 2020 National Building Code of Canada (NBCC) seismic hazard model (SHM) marks a comprehensive update over its predecessor (NBCC 2015). For different regions in Canada, this will have an impact on the design of new buildings and performance assessment of existing ones. In the present study, a recently developed hybrid building system with reinforced concrete (RC) moment-resisting frames and cross-laminated timber (CLT) infills is assessed for its seismic performance against the latest SHM. The six-story RC-CLT hybrid system, designed using the direct displacement-based method, is located in Vancouver, Canada. Along with very high seismicity, southwestern British Columbia is characterized by complex seismotectonics, consisting of subduction, shallow crustal, and in-slab faulting mechanisms. A hazard-consistent set of 40 ground motion pairs is selected from the PEER and KiK-net databases, and used to estimate the building's seismic performance. The effects of using steel slit dampers (associated with large hysteresis loops) and flag-shaped energy dissipators (associated with the recentering capability) are investigated. The results indicate that the hybrid system has good seismic performance with a probability of collapse of 2–3% at the 2475-year return period shaking intensity. The hybrid building with steel slit dampers exhibits a collapse margin ratio of 2.8, which increases to 3.5–3.6 when flag-shaped dissipators are used. The flag-shaped dissipators are found to significantly reduce the residual drift of the hybrid building. Additionally, the seismic performance of the hybrid building equipped with flag-shaped dissipators is found to improve marginally when the recentering ratio is increased. [ABSTRACT FROM AUTHOR]

Radiofrequency ablation (RFA) is a minimally invasive form of thermotherapy with great potential in cancer care, having the capability of selectively ablating tumoral masses with a surface area of several cm2. When performing RFA in the proximity of a blood vessel, the heating profile changes due to heat dissipation, perfusion, and impedance changes. In this work, we provide an experimental framework for the real-time evaluation of 2D thermal maps in RFA neighboring a blood vessel; the experimental setup is based on simultaneous scanning of multiple fibers in a distributed sensing network, achieving a spatial resolution of 2.5 × 4 mm2 in situ. We also demonstrate an increase of ablating potential when injecting an agarose gel in the tissue. Experimental results show that the heat-sink effect contributes to a reduction of the ablated region around 30–60% on average; however, the use of agarose significantly mitigates this effect, enlarging the ablated area by a significant amount, and ablating an even larger surface (+15%) in the absence of blood vessels. [ABSTRACT FROM AUTHOR]

Embedded cooling is a promising solution to address thermal challenges of power electronics. The present work investigates heat spreading effect on the optimal geometries of cooling structures within a single-phase manifold heat sink in laminar regime by integration of topology optimization (TO) and Bayesian optimization (BO). Such integration is for the manual parameter tuning issue in the density-based TO of conjugate heat transfer, and the TO process is accelerated by using a dual-level simulator and the optimality criteria optimizer combined with the stochastic gradient descent method. The heat spreading effect significantly alters the optimal geometries, due to the change of thermal resistance constitutions. Physical analyses on the BO-TO-generated geometries give two guidelines for improving the cooling structures here: (a) Heat source-coolant distance should increase properly for narrow heating area and small Biot number; (b) Highly-thermal-conductivity solid can be filled into low-velocity regions directly connecting to hot area. As an example, a fabrication-friendly cooling structure is devised in the case of concentrating heating following these guidelines, avoiding the computationally-expensive optimization process and the over-complicated geometries. The CFD simulations show this design can significantly reduce the thermal resistance with minor increase of pressure loss as the Reynold number from 50 to 300. • BO is utilized to replace manual parameter tuning process in density-based TO of conjugate heat transfer. • TO process is accelerated through using a dual-level simulator with SGD-OC optimizer. • Heat spreading effect alters optimal geometries due to the change of thermal resistance constitutions. • Two practical design guidelines are proposed based on physical analyses over the BO-TO-generated structures. [ABSTRACT FROM AUTHOR]

Pin-fin heat sinks are widely employed to dissipate heat from power devices under natural convection conditions. To improve heat dissipation performance, optimization of the fin height distribution was conducted in this study. In order to enhance optimization efficiency, we propose a dynamic surrogate model that integrates machine learning, iteratively sampling and training until the convergence criterion is met. Compared with traditional surrogate models, the dynamic surrogate model significantly reduces the prediction error of the optimal result, proving more efficient and yielding superior outcomes with fewer samples. By optimizing the fin height distribution, the heat sink thermal resistance was minimized without increasing mass. Subsequently, an experimental bench was developed to compare the heat sink's total thermal resistance pre- and post-optimization under natural convection conditions. Experimental results demonstrate that within the input heat flux range of q = 500–1200 W/m2, the optimized heat sink's total thermal resistance is diminished by 6.08% to 8.01%, without any mass increment, which confirms the dynamic surrogate model's efficacy in natural convection scenarios. This study elucidates the design principles governing the height distribution of pin-fins of heat sinks under natural convection, and provides a significant insight for guiding the design of pin-fin heat sinks. • Pin-fin height distribution of heat sinks was optimized and experimentally verified. • A dynamic surrogate heat transfer optimization model with constraints is developed. • A non-equal-height pin-fin design to enhance heat sink natural convection is proposed. • Optimized heat sink reduces thermal resistance by about 7% under natural convection. [ABSTRACT FROM AUTHOR]

Constructal theory is used to build a hybrid heat-sink model with rectangular microchannel and porous fin in a 3D electronic device. Firstly, constructal design is conducted with objective of minimizing linear weighted sum of maximum temperature-difference and pump power consumption with fixed total volumes of 3D electronic device, porous fin and microchannel. The optimal microchannel aspect ratio and elemental number are gained. Secondly, multi-objective-optimization is conducted based on NSGA-II, which uses the "gamultiobj" function of Matlab's artificial neural-network toolbox. The findings indicate that when microchannel aspect ratio and elemental number are 0.29 and 38, respectively, complex function achieves its double minimum of 0.810, which is decreased by 19.0% compared to its original value. Therefore, optimizing microchannel aspect ratio and elemental number simultaneously contributes to improving the comprehensive performance of 3D electronic device. Based on LINMAP, TOPSIS and Shannon Entropy decision-making strategies, the multi-objective solution set is compared. The third decision-making method has the smallest deviation index. The corresponding optimal microchannel aspect ratio and elemental number are 0.35 and 32, respectively, which can be used as the optional structure design scheme. The research findings can serve as a new theoretical reference for designing hybrid cooling system in a 3D electronic device. • Hybrid heat-sink model with rectangular microchannel and porous fin in a 3D electronic device. • Constructal designs with fixed total volumes of 3D electronic device, porous fin and microchannel. • It is to minimize maximum temperature-difference and pump power consumption objectives. • The first is to minimize linear weighted sum of two optimization objectives. • Then to minimize two objectives with ANN, NSGA-II and three decision-making methods. [ABSTRACT FROM AUTHOR]

Improving the cooling performance of heat sink is critical for providing better thermal management to compact electronic devices. Thus, analyzing various cavity shapes for a heat sink containing Nano-enhanced Phase Change Material is of utmost necessity. The present study focuses on a two-dimensional conjugate heat propagation in a Heat sink with Rectangular (HRC), Trapezoidal (HTC), and Wavy (HWC) cavities. Various cavity shapes are examined to identify the ideal shape for a heat sink containing nano-enhanced Phase Change Material (Ne-PCM). The copper oxide (CuO) nanoparticle enhanced paraffin is considered as Ne-PCM. The analysis encompasses identification of the potent cavity shape, its optimum geometric parameters, the dominant mode of heat transfer and ultimately the desirable thermophysical properties of the Ne-PCM. Among HRC, HTC, and HWC, the heat sink with HRC performs the best by maintaining the lowest base temperature. The HTC, has a better initial performance than the HRC, though HTC has low PCM content. Nevertheless, as time progresses, HTC fails to inhibit the base temperature rise. In contrast, due to increased contact surface area, PCM in HWC experiences a stronger opposing viscous force. Consequently, HWC has conduction-dominated heat transfer and the slowest melting of PCM that elevates the base temperature, accumulating heat near cavity walls. Shortening the relative pitch distance and elongating the relative height of the HRC further lowers the base temperature of the heat sink. Notably, the heat transfer mode analysis reveals that in the cavity with maximum height, heat diffusion dominates convective heat transfer. Heat diffusion increases away from the cavity walls towards the middle of the cavity. Ultimately, it is noted that a denser PCM with high thermal conductivity and low viscosity effectively maintains a low heat sink base temperature. A denser PCM imparts more sensible and latent heat absorption capability and maintains a lower base temperature. On complete melting, the convective heat transfer is much higher in a denser PCM. A PCM with higher thermal conductivity marginally lowers the base temperature with a small increase in PCM melting rate. [ABSTRACT FROM AUTHOR]

• Manufacturing of various variants of heat pipes and heat sinks. • Experimental analysis of cooling effects of these innovative variants. • Preparation of nanofluids and hybrid nanofluids. • Performance comparison of all heat sinks and heat pipes under the influence of nanofluids and hybrid nanofluids. • Use of advanced energy materials (nanofluids), fins and external liquid-based cooling for thermal management. • Results validation from previous studies. • Future recommendations for following researchers. Heat sinks and heat pipes have vast applications including industrial domains requiring high heat flux. Due to numerous uses of these heat transfer devices, there have been great advancement in this area through innovation. This study focuses use of nanofluids and hybrid nanofluids for thermal performance enhancement of heat pipes and heat sinks. There are five different arrangements finless sintered copper wicked heat pipe, water based TiO 2 filled heat pipe, TiO 2 and SiO 2 based hybrid nanofluid filled heat pipe, water cooled cylindrical pin finned heat sink and Fe 2 O 3 and TiO 2 hybrid nanofluid cooled heat sink. There are two test rigs one for testing heat pipe configurations and other for heat sinks. All the five elements are tested at constant heat flux ranging from 900 W/m2 to 3600 W/m2, in four equal steps. It's observed that nanofluids play a very significant role in thermal performance augmentation, the affect is even more significant in heat pipes compared to heat sinks. Interestingly, nanofluids based heat pipes are proved more significant for high heat flux applications, although, nanofluid cooled heat sinks have slight better performance compared to the said but at a higher expense of weight, auxiliaries, space and cost. At 3600 W/m2 nanofluid based heat pipes have 33 % lower thermal resistance compared to water cooled heat sink. Therefore, nanofluid based heat pipes are primarily significant unless use of heat sink deemed dire. Nusselt number of heat sink is calculated at various heat flux and at variable mass flux conditions and found increasing with both parameter. [ABSTRACT FROM AUTHOR]

The foremost method to exhaust heat sourced from electronic devices is to use heat sinks. However, in practice, these structures behave as actual antennas and cause interference problems. The selected heat sink like many others is performing like a real antenna whose gain at 4.9 GHz is ~ 7 dBi both in simulation and measurement. In this study, a novel gain (radiation pattern) controlling belt made up of a metamaterial (MTM) structure was designed and dressed to the heat-sink antenna. The effect of the position of the belt on the antenna pattern is investigated. The sliding position of the belt which allows for dynamic gain control varies the antenna gain between 3.38 and 7.36 dBi (~ 7 dB in ${\theta }$ angle and ~ 9 dB in ${\emptyset }$ angle). Maximum gain enhancement reaches up to 18.43 dB and maximum suppression ratio reaches up to 21.36 dB for the entire angle. [ABSTRACT FROM AUTHOR]

The data from the Planck and Herschel space observatories revealed that the cosmic rays at L2 orbit can have a significant impact on the performance of scientific instruments. In this paper, we present our simulation results of such impacts on SAFARI/SPICA, a far-infrared spectrometer equipped with transition-edge sensors (TESs). These TESs are fabricated on SiN membranes and suspended by long and thin SiN legs that thermally isolate them from the surrounding silicon structure (wafer). Cosmic rays that pass through this surrounding structure deposit a portion of their energy, leading to temperature fluctuations in the wafer. These temperature fluctuations are sensed by the TES detectors as an effective bath temperature and result in additional noise. To simulate the impact, we generate a 2D model of the wafer and the suspended TESs in COMSOL 5.4. This 2D model is bombarded with 128 randomly generated cosmic rays according to the observed energy distributions at L2. Subsequently, the temperature fluctuations at different points on the wafer are estimated. Our results show that these thermal fluctuations, as well as the calculated additional TES noise caused by them, depend strongly on the heat-sink design of the wafer. We study the impact of the different heat sink designs on the noise profile of the system. Later, these results are compared to the SAFARI instrument noise requirements. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the validation of the usefulness of cooling systems containing Peltier modules for cooling power devices based on measurements of the influence of selected factors on the value of thermal resistance of such a cooling system. Design/methodology/approach: A cooling system containing a heat-sink, a Peltier module and a fan was built by the authors and the measurements of temperatures and thermal resistance in various supply conditions of the Peltier module and the fan were carried out and discussed. Findings: Conclusions from the research carried out answer the question if the use of Peltier modules in active cooling systems provides any benefits comparing with cooling systems containing just passive heat-sinks or conventional active heat-sinks constructed of a heat-sink and a fan. Research limitations/implications: The research carried out is the preliminary stage to asses if a compact thermal model of the investigated cooling system can be formulated. Originality/value: In the paper, the original results of measurements and calculations of parameters of a cooling system containing a Peltier module and an active heat-sink are presented and discussed. An influence of power dissipated in the components of the cooling system on its efficiency is investigated. [ABSTRACT FROM AUTHOR]

The chips present unsteady and highly concentrated heat fluxes and the available volume for cooling solution is significantly constrained with the trend of miniaturization and integration. Traditional liquid cooling techniques fail to regulate the coolant distribution according to the changing thermal environment and remove the unevenly distributed thermal loads effectively. In this article, embedded cooling with self-adaptive microchannel/pin-fin hybrid heat sink is proposed. Hybrid channels with thermal-sensitive hydrogels at the outlet are designed and integrated into the substrate. A numerical model is established and an iteration procedure is designed to investigate the flow regulation behavior. The hydrogel downstream of the hotspot undergoes volume reduction and the local coolant flow rate is enlarged, illustrating the autonomous flow regulation effect. Various nonuniform heat load distributions are considered. Taking advantage of the current self-adaptive cooling solution, heat flux of up to 500 W/cm2 can be dissipated and the peak temperature is reduced by 12.2 K with a pressure drop of 34.0 kPa. The embedded self-adaptive cooling provides both effective and intelligent thermal management for densely integrated electronics. [ABSTRACT FROM AUTHOR]

Introduction: Endoscopic submucosal dissection (ESD) using underwater technique has been developed to make colorectal ESD easier and safer. We have carried out a novel technique of colorectal ESD using gas-alternating-water infusion method for en-bloc resection of large colorectal tumors. Aim: To evaluate the feasibility and safety of colorectal ESD using the gas-alternating-water infusion method (GAWESD) with or without internal traction assistance depending on the level of exposure of the submucosal space, for large colorectal tumors (≥ 3 cm in size). Material and methods: All 8 patients were kept in the left lateral position during GAW-ESD as follows: (1) C-shaped mucosal incision. (2) The colorectal lumen was instilled with normal saline. Then the mucosal flap on the lower side of gravity was created with the help of buoyancy, followed by a V-shaped dissection both below and above the liquid surface, if necessary, assisted by internal traction using one-matching-many repositionable clips attached to one rubber band. (3) The post-ESD defect was closed underwater using repositionable clips. Results: GAW-ESD was performed successfully in 8 patients, five without internal traction, three with internal traction. The en-bloc resection rate was 100%. No perforation occurred. Only 1 patient suffered from post-ESD bleeding, which was resolved by endoscopic clipping. Conclusions: GAW-ESD with/without internal traction is safe and effective for en-bloc resection of large colorectal tumors, with the advantages of quick gas/liquid switch, stable platform, fixed position, buoyancy effect, counteraction design, dissection acceleration, heat-sink effect, optical zoom effect, and downsizing effect. [ABSTRACT FROM AUTHOR]