Increased Heat Dissipation Research Articles

Transient thermal analysis and optimization of convective-radiative porous fin under the influence of magnetic field for efficient microprocessor cooling

With the continuous evolution of the electronics industry, the trend towards miniaturization in consumer electronic imposes serious challenge of excess heat. Moreover, increasing the microprocessor performance require an increase in the power density which is associated with increased heat dissipation. Porous fins are widely established as viable thermal candidate to achieve effective cooling. In this work, transient thermal analysis and optimization of a longitudinal porous fin under magnetic field subjected to a conductive-convective-radiative mechanism is presented. The developed model is solved using the finite volume method (FVM). Optimization of key fin performance parameters is carried out using particle swarm optimization technique. From the present study, it is established that increase in thermal conductivity parameter enhances heat transfer from the base of the fin to its tip influenced by the radiative diffusion process. Moreover, the study shows that an increase in the porosity effect reduces the overall fin efficiency. Furthermore, the fin thermal behaviour improves in the convective and radiative heat transfer as well as in the magnetic field. The practical implication of the present study is the effective thermal management of various single and multi-layer microprocessor-based consumer electronics.

Numerical Study of Performance of Porous Fin Heat Sink of Functionally Graded Material for Improved Thermal Management of Consumer Electronics

The ever-increasing demand for high-performance electronic and computer systems has unequivocally called for increased microprocessor performance. However, increasing microprocessor performance requires increasing the power and on-chip power density of the microprocessor, both of which are associated with increased heat dissipation. In recent times, thermal management of electronic systems has gained intense research attention due to increased miniaturization trend in the electronics industry. In this paper, we present a numerical study on the performance of a convective–radiative porous heat sink with functionally graded material (FGM) for improved cooling of various consumer electronics. For the theoretical investigation, the thermal property of the FGM is assumed as a linear and power-law function. We solved the developed thermal models using the Chebyshev spectral collocation method (CSCM). The effects of inhomogeneity index of FGM and convective and radiative parameters on the thermal behavior of the porous heat sink are investigated. This paper shows that increase in the inhomogeneity index of FGM and convective and radiative parameters improves the thermal efficiency of the porous fin heat sink. Moreover, for all values of Nc and Rd, the temperature gradient along the fin of FGM is negligible compared to HM fin in both linear and power-law functions. For comparison, the thermal predictions made in this paper using CSCM agree excellently with the established results of Runge–Kutta with shooting and homotopy analytical method.

Mitigation of thermal distortion in wire arc additively manufactured Ti6Al4V part using active interpass cooling

ABSTRACTIn this study, active interpass cooling using compressed CO2 was innovatively employed in the wire arc additively manufactured Ti6Al4V process with the aim of mitigating part distortion. A comparative analysis between simulation and experimental results was performed to explore the effects of active interpass cooling on the thermal behaviours, geometric features and distortion levels of deposit. The results show that active interpass cooling with CO2 gas is an effective means of reducing Wire arc additive manufacturing (WAAM)-part distortion by increasing heat dissipation and reducing heat accumulation within the deposition. It can contribute to a maximum reduction of 81% in longitudinal distortion and 69% in transverse distortion for the wall structures produced in this study. Compared to the cooling gas flow rate, cooling time alternation is more effective in mitigating WAAM-part distortion due to more effective heat dissipation per unit time. The findings reveal that using active interpass cooling in WAAM can offer significant cost and build-time savings, as well as providing conditions for the improvement of WAAM-part quality.

Thermal transport in molecular beam epitaxy grown Si1 − xGex alloy films with a full spectrum of composition (x = 0–1)

The thermal properties of Si1 – xGex alloys are important for two major reasons: one is their applications in high-temperature thermoelectrics and the other is the increasing heat dissipation demand for high power density devices. However, the large lattice mismatch between silicon and germanium leads to tremendous difficulties to obtain high-quality Si1 – xGex thin films, especially when x > 0.5. In this study, we obtained a series of high crystalline quality Si1 – xGex thin films with x covering all the way from 0 to 1 on Si substrates by molecular beam epitaxy. The out-of-plane thermal conductivities of these Si1 – xGex films were measured by the time-domain thermoreflectance approach. Results show that while the thermal conductivity can vary significantly with composition, it only changes marginally in the temperature range of 100 K–300 K for a specific Ge content x. A theoretical analysis indicates that alloy and boundary scatterings are the dominant mechanisms for the thermal transport in these Si1 – xGex (x = 0–1) alloy films.

The Models of Permafrost for Arid and Alpine Regions

Stationary models of the thermal regime of permafrost taking into account water evaporation and ice sublimation within upper layer of soil are submitted. The results of Chinese researchers in mountainous Tibet and theoretical approach of Russian scientists for Northern Tien Shan are discussed. The thickness of the frozen rocks may reach an unexpectedly very large depth up to 100 m and more. Traditional stationary model of permafrost (Model Problem #0) was examined. The authors of the paper theoretically based the thermal regime of formation permafrost of cryolithozone in the highlands (two-stratum Model Problem #1). The new mechanism of formation of the thermal regime caused evaporation and sublimation processes in dispersed rocks in conditions of arid (high land) climate are suggested. Evaporation when filtering moisture in the upper soil layers is like heat sink. Then this process becomes the primary for the temperature field variations inside coarse clastic sediments. Additionally ice sublimation can increase heat dissipation in dispersed rocks. Three-stratum Model Problem #2 with a certain subsurface volumetric layer under frost desiccation was introduced. This soil layer being between the upper one of evaporation and the deep one of permafrost may generate a significant heat effect on the depth of freezing. Temperature minimum of the thermal system is formed in subsurface layer and cause heat sink into frozen soil depth. Numerical evolutions for the proposed models correspond to experimental data on the intensity of evaporation and sublimation for the surface and subsurface layers of permafrost, as well as the processes of cooling and freezing in dispersed rocks. This research will be in demand in engineering Cryolithology and Glaciology.

Thermoregulatory Changes in Obese Mexican Young Women Performing Aerobic Exercise

Mexico has the highest rate of obesity worldwide. This pandemic is defined as an abnormal and excessive accumulation of adipose tissue providing an insulating layer that impedes heat loss, thus affecting body homeostasis. To maintain normothermia, obese individuals must increase heat dissipation. Here, we explore the potential role of thermoregulation in obese young Mexican women performing aerobic exercise in order to determine how thermoregulation mechanisms act in such conditions. A group of 60 obese (O), overweight (OW) and normal (N) women, with 20 in each group, performed a 15 min test on the cycle‐ergometer at a 65% heart rate (HR) at room temperature (21.0±0.5) °C and under extreme temperature (38.5±0.5) °C conditions. Body mass index (BMI) and % body fat were calculated. HR, blood pressure (Bp), and core (Tc) and external (Te) temperatures were measured during and after the test. We observed a difference in Tc within subjects and within groups. At room and extreme temperatures, OW and O subjects presented higher Tc compared to N ones by about 30%, adding that the initial Tc of O was higher (15%) compared to the other two groups. N women tended to reach their initial temperature faster than the other groups at room and extreme temperatures. A 45% increment of HR was observed in O compared to OW and N women. From our results we concluded that there exists a direct relation between BMI and the thermoregulatory capacity in the human body, suggesting a failure in homeostasis processes in obese women. This experiment gives us the first insight of an active indicator of a metabolic decompensation in young Mexican women and compelling evidence for a thermogenic handicap in the same population. Further analyses have to be done.Support or Funding InformationSupported partially by UNAM (PAPIIT RA207818) to KPGPThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Investigation of Simultaneous Effects of Surface Roughness, Porosity, and Magnetic Field of Rough Porous Microfin Under a Convective–Radiative Heat Transfer for Improved Microprocessor Cooling of Consumer Electronics

The ever-increasing demand for high-processing compact electronic systems has unequivocally called for improved microprocessor performance. However, increasing microprocessor performance requires increasing power and on-chip power density, both of which are associated with increased heat dissipation. Electronic cooling using fin has been identified as a reliable cooling approach in miniaturized electronic systems. However, an investigation into the thermal behavior of fin would help in the design of miniaturized, effective heatsinks for reliable microprocessor cooling. The aim of this paper is to investigate the simultaneous effects of surface roughness, porosity, and magnetic field on the performance of a porous microfin under a convective-radiative heat transfer mechanism. The developed thermal model considers variable thermal properties according to linear, exponential, and power laws, and is solved using the Chebychev spectral collocation method. A parametric study is carried out using the numerical solutions to establish the influences of porosity, surface roughness, and the magnetic field on the microfin thermal behavior. The results of the simulation establish that thermal efficiency of the microfin is significantly affected by the porosity, magnetic field, geometric ratio, nonlinear thermal conductivity parameter, thermogeometric parameter, and the surface roughness of the microfin. Furthermore, the study establishes that the fin efficiency ratio which is the ratio of efficiency of the rough fin to the efficiency of the smooth fin is found to be greater than unity when the rough and smooth fins of equal geometrical, physical, thermal, and material properties are subjected to the same operating condition.

Improvement of Heat Dissipation Characteristics of Cu Bus-Bar in the Switchboards through Shape Modification and Surface Treatment

In order to improve energy efficiency by increasing heat dissipation performance of bus-bar which distributes the current in high-power switchboard, the heat dissipation effects of the shape modification and surface treatment of Cu bus-bar were studied. The surface temperatures of the conventional plate-type bus-bar, and the improved tunnel-type bus-bar were compared by using electromagnetic and thermal analyses. The optimum thickness of tunnel-type bus-bar and the spacing and array among three bus-bars were calculated; and the surface temperature of tunnel-type bus-bar showed 7.9 °C lower than that of plate-type bus-bar in a 3-phase array condition. In addition, the surface and internal temperatures of the uncoated, CNT (Carbon nanotube)-coated, and BN (Boron nitride)-coated Cu bus-bars were measured with thermal imaging camera and the experiment using a hot plate. It was confirmed that the difference in the internal temperature between uncoated and BN-coated Cu was 19.4 °C. The application of the bus-bar improved from this study might contribute to the increase in power energy efficiency.

Non-isolated load sharing direct current system operation with use of the auctioneering diodes

The paper presents the background and results of numerical simulation and experimental research of a system using auctioneering diodes used to distribute the electrical power between two power converters connected with intermediate circuits in parallel, direct connection. Presented non-isolated power distribution system which utilizes blocking diodes placed in DC branches are used in the selected ship's electrical systems, however, they create problems related to control and handling ground faults. Another issue occurring during the operation of this type of systems is increased heat dissipation while diodes switching. Selected problems related to the operation of experimental system have been identified by means of simulation studies and experiments carried out in a 11 kVA laboratory system and the theoretical basis along with results are provided in the article.

Electrical and Thermal Characterization of 3D Printed Thermoplastic Parts with Embedded Wires for High Current-Carrying Applications.

Fabrication of parts exhibiting multi-functionality has recently been complemented by hybrid polymer extrusion additive manufacturing in combination with wire embedding technology. While much mechanical characterization has been performed on parts produced with fused deposition modeling, limited characterization has been performed when combined electrical and thermal loads are applied to 3D printed multi-material parts. As such, this work describes the design, fabrication, and testing of 3D printed thermoplastic coupons containing embedded copper wires that carried current. An automated fabrication process was used employing a hybrid additive manufacturing machine that dispensed polycarbonate thermoplastic and embedded bare copper wires. Testing included AC and DC hipot testing as well as thermal testing on as-fabricated and heat treated coupons to determine the effect of porosity in the substrate. The heat-treated parts contained reduced amounts of porosity, as corroborated through scanning electron microscopy, which led to 50 % increased breakdown strength and 30 to 40 % increased heat dissipation capabilities. The results of this research are describing a set of design protocol that can be used as a guideline for 3D printed embedded electronics to predict the electrical and thermal behavior.

Effect of perspired moisture and material properties on evaporative cooling and thermal protection of the clothed human body exposed to radiant heat

Perspired moisture plays a crucial role in the thermal physiology and protection of the human body wearing thermal protective clothing. Until now, the role of continuous sweating on heat transfer, when simultaneously considering internal and external heat sources, has not been well-investigated. To bridge this gap, a sweating torso manikin with 12 thermal protective fabric systems and a radiant heat panel were applied to mimic firefighting. The results demonstrated how the effect of radiant heat on heat dissipation interacted with amount of perspired moisture and material properties. A dual effect of perspired moisture was demonstrated. For hydrophilic materials, sweating induced evaporative cooling but also increased radiant heat gain. For hydrophilic station uniforms, the increment of radiant heat gain due to perspired moisture was about 11% of the increase of heat dissipation. On the other hand, perspired moisture can increase evaporative cooling and decrease radiant heat gain for hydrophobic materials. In addition to fabric thermal resistance ( Rct) and evaporative resistance ( Ret), material hydrophilicity and hydrophobicity, emissivity and thickness are important when assessing metabolic heat dissipation and radiant heat gain with profuse sweating under radiant heat. The results provide experimental evidence that Rct and Ret, the general indicators of the clothing thermo-physiological effect, have limitations in characterizing thermal comfort and heat strain during active liquid sweating in radiant heat. This paper offers a more complete insight into clothing thermal characteristics and human thermal behaviors under radiant heat, contributing to the accurate evaluation of thermal stress for occupational and general individuals.

Cooling Effect Efficiency Prediction of Aluminum Dimples Block using DOE Technique

The main aim of the present work is to study the effect of heat enhancement method on the cooling process of a spherical dimple profile. It was prominently known that introducing dimples configuration causes an enhancement in heat transfer over a surface. In this project, an experimental investigation was carried out to examine the cooling effect of the spherical dimple profile during steady laminar flow in a wind tunnel. Seventeen different sets of parameters related to dimple diameter (mm), dimple orientation (angle) and air stream velocity (m/s) were studied. The Box-Behnken of Response Surface Methodology (RSM) was used as design of experiments (DoE) tool to evaluate these parameters on cooling time. This work deals with the analysis of variance (ANOVA) in order to establish the significant effect of input parameters. The result reveals that an increase in dimple diameter and air stream velocity increase heat dissipation. The shortest cooling time of 7 minutes can be achieved when the dimple diameter is 12 mm; the dimple orientation is 60° and air flow velocity at 18 m/s. The mathematical model has been rendered where the model has been experimentally validated with the average error of 6%.

Boron Nitride‐Based Paint with High Heat Dissipation Performance

In order to increase heat dissipation efficiency of the heat sink, heat dissipating paint using hexagonal boron nitride (hBN) as a thermal conductive additive is designed and evaluated. The adhesion strength of the heat dissipating paint onto the aluminum (Al) plate is confirmed by the cross‐cut adhesion test method (ISO 2409). The ratio of detachment of the coating film from the Al plate is observed to be 5% or less and, from the resultants, it is found that the adhesion strength of the hBN‐based heat dissipation paint is excellent. The heat dissipation performance of the heat dissipating paint is determined by the temperature difference between the paint coated Al plate and the unpainted Al plate when the heat generated from the heat source is transferred to the around through the Al plate. The hBN‐based heat dissipating paint has the effect of lowering the temperature of the Al plate by 6 °C or more, and the heat dissipation performance of the paint tends to gradually increase with time. When the thickness of the coating film is reduced by about 20%, the heat dissipation performance is improved by more than 50%. As a result, the hBN‐based heat dissipating paint is able to achieve heat dissipation performance of more than 10 °C.

Design of origami fin for heat dissipation enhancement

Recent years have seen the emerging of application of origami in many areas. The extended surface enabled by origami structures apparently has great potential to be employed as fin for heat dissipation where surface area is a major consideration. However, the application of origami in heat transfer and the influence of its geometrical parameters to heat dissipation enhancement have not yet been sufficiently appreciated. Here we propose a fin design of origami shape for free convection, forced convection and radiation heat dissipations. It is found that origami fin can effective increase heat dissipation for all heat transfer scenarios. Origami fin design strategy has also been discussed. This study will provide valuable rationales in harnessing fin of origami shape for heat dissipation.

Central cholinergic activation induces greater thermoregulatory and cardiovascular responses in spontaneously hypertensive than in normotensive rats

There is evidence that central cholinergic stimulation increases heat dissipation in normotensive rats besides causing changes on the cardiovascular system via modulation of baroreceptors activity. However, the contribution of the central cholinergic system on thermoregulatory responses and its relationship with cardiovascular adjustments in spontaneously hypertensive rats (SHRs), an animal model of reduced baroreceptor sensitivity and thermoregulatory deficit, has not been completely clarified. Therefore, the aim of this study was to verify the involvement of the central cholinergic system in cardiovascular and thermoregulatory adjustments in SHRs. Male Wistar rats (n = 17) and SHRs (n = 17) were implanted with an intracerebroventricular cannula for injections of 2 µL of physostigmine (phy) or saline solution. Tail temperature (Ttail), internal body temperature (Tint), systolic arterial pressure (SAP), heart rate (HR) and metabolic rate were registered during 60 min while the animals remained at rest after randomly receiving the injections. The variability of the SAP and the HR was estimated by the fast Fourier transform. Phy treatment began a succession of cardiovascular and thermoregulatory responses that resulted in increased SAP, reduced HR and increased Ttail in both Wistar and SHRs groups. The magnitude of these effects seems to be more intense in SHRs, since the improvement of heat dissipation reflected in Tint. Taken together, these results provide evidence that hypertensive rats present greater cardiovascular and thermoregulatory responses than normotensive rats after central cholinergic stimulation.

Carbon fiber waste incorporation in blast furnace slag geopolymer-composites

This work evaluates the properties of geopolymer-composites based on blast furnace slag with additions of a carbon fiber waste coming from the aircraft industry. Two parameters were considered: slag/waste ratio (100/0, 80/20 and 60/40) and nature of activating solution (8 M NaOH and sodium silicate). Open porosity and compressive strength were analysed. Geopolymers were also subjected to a sulphuric attack and thermal resistance test (compressive strength after 105, 300, 500 and 700 °C was assessed). Porosities increased and compressive strengths decreased as the slag was replaced by the carbon fiber waste. A positive effect of the carbon fiber waste on the acid attack was observed mainly due to the created porosity which could generate space to calcium-sulphate products precipitation. CFW incorporation improved the thermal resistance since higher porosity could provide channel to increase heat dissipation.

Research and Analysis of Cooling System for Diesel Locomotive

With the continuous development of diesel locomotives in the direction of single power, the heat dissipation ofthe locomotive cooling system is getting bigger and bigger, and its performance directly affects the economy andreliability of the locomotive. Due to the limitation of locomotive axle load and structural space size, there is a greattechnical problem between the cooling system design and the arrangement of the cooling device and the overalllayout of the locomotive. The increase in the number of radiators, making the number of cooling system processesare correspondingly increased, resulting in locomotive cooling system water resistance and water system pressure aregreatly improved. The traditional cooling system form and the radiator structure are diffi cult to meet the developmentrequirements of high power locomotive. Based on the conventional cooling system design method, a multi-processradiator is proposed. The multi-process cooling system has the advantages of high cooling effi ciency, simple structure,small auxiliary power consumption of the pump and high reliability of the cooling system components. In this paper,the cooling system and its function, the existing cooling technology and the multi-process radiator are studied andanalyzed, and the three-process radiator and the single-process radiator are tested and compared. In this paper, a newmulti-process radiator structure scheme is proposed for the design requirements of CKD9 diesel locomotive coolingsystem. The program eff ectively uses the radiator cooling water and cooling air temperature diff erence, to achieve thepurpose of increasing heat dissipation.

Comparative Analysis of Free Natural Convection Heat Transfer on Rectangular and Triangular Fins with and without Perforation

The importance of heat transfer by free natural convection can be found in many engineering application such as energy transfer in buildings, solar collectors, nuclear reactors and electronic packaging. In this research work, we carried out the investigation and comparative analysis of heat transfer by natural convection on rectangular and triangular fins with and without circular perforation. A total of six (6) specimens were used. Other materials that were used in this research work include four digital thermometers, one heating element, four thermocouple K-type and a power source. The fins used in this research work were welded to a cylindrical pipe which served as the heat sink. The heat supplied was maintained at 2500C and the temperature drop through the fin was recorded for duration of 30minutes with intervals of 5minutes. It was observed that the temperature dropped more rapidly with the triangular fins than the rectangular fin. Also, the rate of heat dissipation increase with a corresponding increase in the number of perforation.

Comparative Analysis of Free Natural Convection Heat Transfer on Rectangular and Triangular Fins with and without Perforation

The importance of heat transfer by free natural convection can be found in many engineering application such as energy transfer in buildings, solar collectors, nuclear reactors and electronic packaging. In this research work, we carried out the investigation and comparative analysis of heat transfer by natural convection on rectangular and triangular fins with and without circular perforation. A total of six (6) specimens were used. Other materials that were used in this research work include four digital thermometers, one heating element, four thermocouple K-type and a power source. The fins used in this research work were welded to a cylindrical pipe which served as the heat sink. The heat supplied was maintained at 2500C and the temperature drop through the fin was recorded for duration of 30minutes with intervals of 5minutes. It was observed that the temperature dropped more rapidly with the triangular fins than the rectangular fin. Also, the rate of heat dissipation increase with a corresponding increase in the number of perforation.

A review on microscale polymerase chain reaction based methods in molecular diagnosis, and future prospects for the fabrication of fully integrated portable biomedical devices.

Since the advent of microfabrication technology and soft lithography, the lab-on-a-chip concept has emerged as a state-of-the-art miniaturized tool for conducting the multiple functions associated with micro total analyses of nucleic acids, in series, in a seamless manner with a miniscule volume of sample. The enhanced surface-to-volume ratio inside a microchannel enables fast reactions owing to increased heat dissipation, allowing rapid amplification. For this reason, PCR has been one of the first applications to be miniaturized in a portable format. However, the nature of the basic working principle for microscale PCR, such as the complicated temperature controls and use of a thermal cycler, has hindered its total integration with other components into a micro total analyses systems (μTAS). This review (with 179 references) surveys the diverse forms of PCR microdevices constructed on the basis of different working principles and evaluates their performances. The first two main sections cover the state-of-the-art in chamber-type PCR microdevices and in continuous-flow PCR microdevices. Methods are then discussed that lead to microdevices with upstream sample purification and downstream detection schemes, with a particular focus on rapid on-site detection of foodborne pathogens. Next, the potential for miniaturizing and automating heaters and pumps is examined. The review concludes with sections on aspects of complete functional integration in conjunction with nanomaterial based sensing, a discussion on future prospects, and with conclusions. Graphical abstract In recent years, thermocycler-based PCR systems have been miniaturized to palm-sized, disposable polymer platforms. In addition, operational accessories such as heaters and mechanical pumps have been simplified to realize semi-automatted stand-alone portable biomedical diagnostic microdevices that are directly applicable in the field. This review summarizes the progress made and the current state of this field.