Thermal Resistance Of Heat Sink Research Articles

Analysis and assessment of electrical and thermal performance of five‐phase voltage source inverter under different modulation strategies: Comparative study under balanced and unbalanced load

SummaryThis paper compares four modulation strategies applied to five‐phase voltage source inverters (5PH‐VSI). The modulation strategies under investigation are sine wave pulse width modulation (S‐PWM), fifth‐harmonic injection PWM (FH‐PWM), space vector‐PWM using two large vectors (2V‐SVPWM), and space vector‐PWM using two medium and two large vectors (4V‐SVPWM). The study utilizes simulations to analyze the results based on four performance criteria: low‐order harmonics (LOH), maximum modulation index (MMI), common mode voltage (CMV), and total harmonic distortion (THD) under balanced and unbalanced load. To validate the simulation results for these criteria, an experimental test‐bench is employed, which includes a 5PH‐VSI feeding an R‐L load, and controlled by a low‐cost STM32F4‐DISCOVERY microcontroller board. Additionally, a mathematical approach is used to calculate the total thermal losses (TTL) then simulations are performed using Piecewise Linear Electrical Circuit Simulation (PLECS) software to assess the modulation schemes based on additional thermal performance criteria: conduction losses (CL), switching losses (SL), TTL, the efficiency, and the maximum permissible heat sink thermal resistance (MPHTR) at the steady‐state regime. The results indicate that the 4V‐SVPWM method demonstrates superior efficiency in terms of THD. Furthermore, it showcases the lowest TTL at high switching frequencies, allowing for the best efficiency and minimizing MPHRT, therefore providing the largest margin for the heat sink thermal resistance design. On the other hand, the 2V‐SVPWM offers the highest MMI, but this comes at the cost of high TTL and some LOHs appearing. In addition, it exhibits the highest CMV for unbalanced load. S‐PWM and FH‐PWM offer the advantage of simpler implementation.

Experimental Study on the Effect of In/Out Radial-Finned Heat Sink with PCM under Constant and Intermittent Power Mode in Power LEDs

The findings of the experimental study into optimizing the heat transfer rate of a PCM-based heat sink for high-power LEDs are presented in this work. The study investigated five heat sink types, with and without PCM. The LED case and junction temperatures, LED module temperatures, heat storage and release rate analyses, analyses of three types of cyclic operation modes, luminous flux, and heat sink thermal resistance were all examined independently. The results indicated that the PCM-based LED heat sink had improved thermal performance. The LED junction temperature of the PCM-equipped E-20 heat sink is nine degrees Celsius lower at 10 W than that of the heat sink without PCM. Furthermore, the E-20 heat sink with PCM extends the LED module’s critical lifespan. As a bonus, the E-20 with PCM had a 38.19 percent lower thermal resistance at 10 W than the E-20 without PCM. According to these results, the heat sink E-20 emits 715 lm at 10 W when operated without a phase-change material (PCM). With the same input power, the luminous flux of an E-20 equipped with a heat sink and a phase-change material (PCM) is 750 lm, a gain of 4.7%. Finally, clearly recommend the heat E-20 sink with PCM suitable for high-power LED thermal management system.

Thermal analysis of thermoelectric active cooling including external thermal resistances

Thermoelectric active cooling uses nontraditional thermoelectric materials with high thermal conductivity, high thermoelectric power factor, and relatively low figure of merit (ZT) to transfer large heat flows from a hot object to a cold heat sink. However, prior studies have not considered the influence of external thermal resistances associated with the heat sinks or contacts, making it difficult to design active cooling thermal systems or compare the use of low-ZT and high-ZT materials. Here, we perform a non-dimensionalized analysis of thermoelectric active cooling under forced heat flow boundary conditions, including arbitrary external thermal resistances. We identify the optimal electrical currents to minimize the heat source temperature and find the crossover heat flows at which low-ZT active cooling leads to lower source temperatures than high-ZT and even ZT→+∞ thermoelectric refrigeration. These optimal parameters are insensitive to the thermal resistance between the heat source and thermoelectric materials, but depend strongly on the heat sink thermal resistance. Finally, we map the boundaries where active cooling yields lower source temperatures than thermoelectric refrigeration. For currently considered active cooling materials, active cooling with ZT < 0.1 is advantageous compared to ZT→+∞ refrigeration for dimensionless heat sink thermal conductances larger than 15 and dimensionless source powers between 1 and 100. Thus, our results motivate further investigation of system-level thermoelectric active cooling for applications in electronics thermal management.

A critical review on renewable battery thermal management system using heat pipes.

The critical review presented here exclusively covers the studies on battery thermal management systems (BTMSs), which utilize heat pipes of different structural designs and operating parameters as a cooling medium. The review paper is divided into five major parts, and each part addresses the role of heat pipes in BTMS categorically. Experimental studies, numerical analyses, combined experimental and numerical investigations, optimum utilization of a phase-change material (PCM) with a heat pipe (HP), oscillating heat pipe (OHP), and micro heat pipes combined with PCM for Li-ion BTMS using heat pipes are presented. The usage of HP's and PCM can keep the temperature of the battery system in the desirable limit for a longer duration compared to other traditional and passive methods. More emphasis is made on how one can achieve a suitable cooling system design and structure, which may tend to enhance the energy density of the batteries, improve thermal performance at maximum and minimum temperature range. Arrangement of battery cells in a pack or module, type of cooling fluid used, heat pipe configuration, type of PCM used, working fluid in a heat pipe, and surrounding environmental conditions are reviewed. According to the study, the battery's effectiveness is significantly influenced by temperature. The usage of flat HPs and heat sink proves to be the best cooling method for keeping the battery working temperature below 50°C and reduces the heat sink thermal resistance by 30%. With an intake temperature of 25°C and a discharge rate of 1 L per minute, an HP that uses water as a coolant is also effective at regulating battery cell temperature and maintaining it below the permissible 55°C range. Using beeswax as a PCM in HPs reduces the temperature of BTMS by up to 26.62°C, while the usage of RT44 in HPs reduces the temperature of BTMS by 33.42°C. The use of fins along with copper spreaders drastically decreases the temperature capability of HPTMS by 11°C. MHPA shows excellent performance in controlling the battery temperature within 40°C. The effective thermal management can be done by incorporating heat pipe alone or by coupling with liquid cooling or metal plate. However, extensive and extended research is required to improve thermal management to safely and effectively use the battery for day-to-day applications.

Enhancement of the cooling performance of a pin fin heat sink based on the chimney effect using aluminum tape

Conventional methods of improving the heat dissipation performance of heat sinks require either modifying existing heat sink geometries or installing additional structures to induce chimney effect. These methods can be problematic to apply if there are limitations of space and cost. In this study, we address the aforementioned problems by developing a novel method of inducing the chimney effect by attaching aluminum tape to a pin fin heat sink. Geometric parameters for optimization were the width and attachment position of the aluminum tape, and changes in the thermal resistance of the pin fin heat sink with a rectangular base were observed according to its orientation angle. First, the widths and attachment positions of the outer and inner aluminum tape strips that minimized the thermal resistance of the heat sink were derived through simulation. The thermal resistance of the heat sink was estimated to be reduced by 10.8% or 7.7%, respectively, only by attaching the outer or the inner aluminum tape strip with optimal width to the top of the pin fin, and it was found to be further reduced by attaching both the outer and inner aluminum tape strips simultaneously. As the next step, the simulation results were verified by experimentally measuring the thermal resistance of actual pin fin heat sinks with and without aluminum tape. It was found that the thermal resistance of the pin fin heat sink was reduced by up to 17.1% by inducing the chimney effect simply through the attachment of both the outer and inner aluminum tape strips with optimal widths to the top of the pin fin. For all heat sink orientation angles tested in the range 0°−180°, the thermal resistance was found to be lower when the aluminum tape was attached than when it was not attached. As a result, the heat dissipation performance could be improved without changing heat sink geometry and by requiring no additional space to install a chimney structure. Our study results show that the safety of heat-generating devices that require heat dissipation can be significantly improved by enhancing the heat dissipation performance of heat sinks if the width and attachment position of the aluminum tape are optimized.

Design and Analysis of Microchannels for Heat Dissipation of High-Energy VCSELs Based on Laser 3D Printing

For the problem of high waste heat in the active area of high-power VCSEL arrays and the difficulty of heat dissipation, we took advantage of laser 3D printing technology and combined it with the relevant principles of fluid-structure coupling, three kinds of microchannel heat sink with different structures of pin-fin, honeycomb, and double-layer reflow were designed. The heat dissipation capacity of three kinds of heat sinks to the heat flux density 200 W/cm2 VCSEL array and the influence of the key characteristics of the microchannel on the heat dissipation capacity was studied. The results show that the double-layer reflow microchannel heat sink has the strongest heat dissipation capability, with the minimum thermal resistance value of 0.258 °C/W when the microchannel diameter and the cooling mass flow rate were 0.5 mm and 24 L/h, respectively. The inner wall roughness of the pure copper microchannel prepared by 3D printing technology was 7.08 μm, and the heat sink thermal resistance was reduced by 0.7% compared with the smooth channel wall. The deviation of the microchannel diameter from the design size (500 μm) was −10 μm, and the heat sink thermal resistance was reduced by 0.8% compared to the theoretical value, which shows that the surface roughness and size deviation of the 3D printed microchannel had beneficial effect on enhancing heat dissipation. The actual thermal conductivity of the 3D printed pure copper after heat treatment was 310.4 W/m-K, at which point the thermal resistance was 0.306 °C/W, and the maximum temperature was 35.3 °C, which satisfied the operating temperature range of the chip. This study provides a theoretical basis and implementation method for the fabrication of heat sinks for high-energy VCSEL arrays using laser 3D printing technology.

Melting behavior and migration characteristics of microencapsulated phase change material particles in galinstan flow and application in minichannel heat sink

Mini/microchannel cooling performance can be improved with microencapsulated phase change material (MPCM) slurry as coolant by utilizing latent heat absorption capacity of MPCM. Compared with existing water, using liquid metal (LM) as basefluid can combine the advantages of high apparent heat capacity of MPCM particles and high thermal conductivity of LM. Thus, the prepared MPCM-LM slurry is proposed as coolant for minichannel heat sink. The melting of particles near the bottom enhances heat transfer performance of two-phase MPCM-LM slurry, but migration and aggregation cause the increase of pressure drop. Furthermore, the two-phase model is adopted to investigate the melting behavior and migration characteristics of MPCM particles in galinstan flow and the effect of particle volume percent on minichannel cooling performance. The results show that particles present boundary-to-center melting behavior in MPCM-galinstan slurry, resulting in the larger reduction degree in bulk mean temperature compared to MPCM-water slurry. Different from uniform distribution for small-diameter particles, the large-diameter particles migrate upward, leading to top-aggregation distribution and up-down asymmetry of velocity profile. Finally, the increase of particle volume percent significantly reduces heat capacity thermal resistance of heat sink, and maximum reduction is 59.02% for MPCM-galinstan slurry with φ s = 20% compared to pure galinstan.

A Fault Detection Method of IGBT Bond Wire Fatigue Based on the Reduction of Measured Heatsink Thermal Resistance

Bond wire lift-off is one of the major failure mechanisms in the insulated gate bipolar transistor (IGBT) modules. Detecting the fault of bond wires is important to avoid the open-circuit fault of IGBT to ensure the reliable operation of power converters. In this paper, we propose a novel bond wire fatigue detection method for IGBT, which could be used in normal working conditions. Firstly, we investigated the dependence of bond wire fatigue on heatsink thermal resistance. An aging rate K was proposed to compare the measured thermal resistance with the initial value, which could indicate the bond wire fatigue. Then, this proposed method was verified by simulation and experimental results under different current levels. Finally, a power cycling test was used to show the aging process of the IGBT module, which shows the feasibility of proposed method.

Numerical simulation of heat sinks with different configurations for high power LED thermal management

This study performed a steady-state numerical analysis to understand the temperature in different heat sink configurations for LED applications. Seven heat sink configurations named R, H-6, H-8, H-10, C, C3, and C3E3 were considered. Parameters like input power, number of fins, heat sink configuration were varied, and their influence on LED temperature distribution, heat sink thermal resistance and thermal interface material temperature were studied. The results showed that the temperature distribution of the H-6 heat sink decreased by 46.30% compared with the Cheat sink for an input power of 16 W. The result of the H-6 heat sink shows that the heat sink thermal resistance was decreased by 73.91% compared with the Cheat sink at 16 W. The lowest interface material temperature of 54.11 °C was achieved by the H-6 heat sink when the input power was used 16 W. The H-6 heat sink exhibited better performance due to more surface area with several fins than other heat sinks.

Experimental investigation of carbon nanotube coated heat sink for LED thermal management

In this paper, brushing technique was used to coat carbon nanotubes (CNT) on 6063 aluminium alloy in order to investigate the heat transfer performance for Light Emitting Diode (LED) application. The two different thickness such as 0.5 mm and 1 mm coating of CNT was applied an aluminium plate. Performance parameters, like LED case and junction temperatures and heat sink thermal resistance were studied. The results showed that the LED case temperature for 0.5 mm thick CNT coated heat sink decreased by 16.25 % when compared to alumimum plate at 400 mA. For the 400 mA, the 0.5 mm CNT coated heat sink has junction temperature 89 °C while the junction temperature of 1 mm CNT coated heat sink is 111 °C, reduced by 19.81 %. Heat sink thermal resistance for 0.5 mm thick CNT coated heat sink was reduced by 37.72 % compared with that of the 1 mm thick CNT heat sink at 300 mA. The CNT coating thickness of 0.5 mm was identified to produce efficient heat dissipation.

Thermoelectric heat transfer intensifiers

The work of thermoelectric heat transfer intensifier is analyzed in the paper. Criteria for the efficiency of such intensifiers are given. The advantage of using a thermoelectric cooler is evaluated depending on the temperature difference on the heat sink when applied without a thermoelectric module. It is shown that in many cases a thermoelectric cooler cannot intensify heat transfer. In case a thermoelectric cooler is used to reduce the object temperature, it is also necessary to reduce the heat sink thermal resistance. Keywords: thermoelectric cooler, heat exchange, intensifier, efficiency.

Heat Transfer Analysis of Plate Fin Heat Sink with Dimples and Protrusions: Investigation of New Designs

Numerous works have been carried out in the design and analysis of Heat Sink, however hardly any work have been reported with studies on dimples and protrusions being added to the heat sink geometries. This paper aims to find the worthiness for addition of dimples and protrusions to the common plate fin heat sink geometries for heat transfer enhancement. Analysis was carried out in forced convention environment for 9 different velocities computationally for 12 heat sink geometries at constant heat flux boundary condition applied to base of heat sink. Decrease in base temperature and thermal resistance of heat sink was considered as the performance factors. Further these computational results were validated experimentally. The results obtained from computational analysis were in good agreement with experimental results. The research outcome show that addition of dimples has proved its worthiness at slightly higher velocity regime with thermal performance being increased for a dimpled heat sink as compared to non-dimpled heat sink. Therefore, currently developed dimpled heat sinks can be a potential model that can be used in forced convection environment for better thermal performance and economy.

Enhanced thermal performance of phase change material-integrated fin-type heat sinks for high power electronics cooling

We report the enhanced cooling performance of the phase change material (PCM)-integrated fin-type heat sink compared to conventional fin-type heat sink in high power electronics with two localized hot spots. The PCM-integrated fin-type heat sink is fabricated by embedding the phase change composite to the base plate of the heat sink. As an effort to effectively utilize thermal capacitive effects of PCM, the phase change composites with paraffin infiltrated to copper foams are deployed within circular hole arrays in the base plate, which is subsequently covered by a graphite sheet, to achieve excellent heat spreading characteristics. Considering the cooling environments of commercial high power electronics (insulated-gate bipolar transistor (IGBT)), thermal performance of the PCM-integrated and the conventional fin-type heat sinks is experimentally and numerically investigated upon the heating powers of 400∼800 W. While the PCM-integrated fin-type heat sinks have similar heat sink thermal resistance with the conventional fin-type heat sinks, the PCM-integrated fin-type heat sinks exhibit an effective time delay up to ∼27.3% of the hot-spot temperature rise until 80 ℃ of the heat sinks in reduced cooling conditions, showing the potential as an effective thermal managing platform of the PCM-integrated heat sinks in convection-limited cooling environments.

Experimental Investigations of Different Loudspeakers Applied as Synthetic Jet Actuators

The paper presents the preliminary results of the experimental investigation of four various loudspeakers used for driving the synthetic jet actuator. The parameters, characteristic synthetic jet velocity, pressure inside the cavity, device sound pressure level (SPL), and the heat sink thermal resistance, were presented for various input power and driving frequency. The resonance frequency was determined based on electrical impedance. The highest synthetic jet momentum velocity was achieved at diaphragm resonance frequency. The maximum sound pressure level was observed, also at resonant frequency. For the same real power delivered to the actuator and for its resonance frequency, the heat sink thermal resistance had the lowest value for the specific loudspeaker. In turn, the synthetic jet velocity reached maximum for this actuator. For all actuators tested, the sound pressure level was dependent on momentum velocity.

Utilization of thermoelectric technology in converting waste heat into electrical power required by an impressed current cathodic protection system

Supplying an energy source for impressed current cathodic protection is considered as the main challenge for pipelines corrosion protection in remote areas. The purpose of this study is to construct and evaluate the performance of an impressed current cathodic protection system using waste heat to replace the external electrical power supply. The system consists of four thermoelectric modules producing the electrical power from the hot combusted gas stream. Mathematical modeling and Buckingham Pi theorem were applied to obtain five dimensionless parameters and several models to estimate the system performance. According to the experimental results, the generated voltage, electrical current, and temperature difference have been increased rapidly during the experiment up to 201 mV, 44 mA, and 20 K, respectively. Moreover, mathematical modeling and Buckingham Pi theorem were also utilized to obtain three equations, two nonlinear and one dimensionless equation, to calculate the generated electrical voltage with the maximum error of 1.22%, 9.11%, and 10%, respectively. The results indicate that the temperature difference (between inlet gas and environment) and the figure of merit have a direct effect, and heat sink thermal resistance has an inverse effect on the generated electrical voltage.

Multidisciplinary optimization of liquid cooled heat sinks with compound jet/channel structures arranged in a multipass configuration

• Microchannel layouts are optimized for turbulent condition. • The physics filed is solved by a simplified reduced-order model. • Average temperature minimization and 60% volume constraint benefit the optimization. • An integrated optimization strategy is developed and compared with SIMP. • Hybrid strategy based design reduce the heat sink thermal resistance up to 14.04%. In this paper, we present the multidisciplinary optimization of microchannel layout in a multipass heat sink by topology optimization. Unlike previous approaches that have focused on designing microchannels in laminar region, the current work focuses on manipulating fin geometries of heat sinks in turbulence region, which allows more complex and higher velocity flow and therefore results in better heat sink performance. To save the computational cost in topology optimization, a simplified Darcy-flow based model is utilized to cope with turbulence calculation, of which the permeability parameter is carefully calibrated in order to make the output physical fields ideally be close to those from full Navier Stokes-based model. As an iterative process, topology optimization gradually evolves channel layout from simple to complex. The selection of objective function and the setting of fluid volume constraints are studied in the optimization process. Besides the SIMP-based optimization, an integrated optimization strategy is developed, which comprises two different topology optimizers: a moving morphable components based optimizer (MMC) for the initial topology prediction and a density based optimizer (SIMP) for subsequent topology elaboration. Detailed 3D computational fluid dynamics (CFD) analysis is then implemented to examine the thermohydraulic characteristics of the optimized heat sinks and a specially designed experimental set up is built to validate the 3D simulation results. The numerical predictions about the trend of the pressure drop and unit thermal resistance change with the coolant inlet flow are in good agreement with the experimental results. Compared with SIMP-based optimization, the design based on hybrid optimization strategy has lower unit thermal resistance at the same inlet flow rate without large pressure drop increasing.

Performance investigation of radial heat sink with pin fins placed normally on circular base edge

This study analyzed the dissipation performance of a heat sink having pin fins placed normally to circular base edge, for a LED bulb heat sink having concentric hollow cylinder and circular base. A numerical approach was employed to analyze the influence of the Rayleigh number, the number of fins, orientation angle, and base radius on the heat sink thermal resistance, and its prediction accuracy was verified via experiments. The influences of the length and number of fins on the heat sink thermal resistance were analyzed, and the thermal resistance was found to be low when the fin length was 3.8 mm and the number of fins was 36. A parametric study was conducted to analyze the heat sink thermal resistance in consideration of the design parameters of the radial heat sink. Moreover, a correlation equation for predicting the thermal resistance of the heat sink was derived, and the thermal resistance of the heat sink could be accurately predicted within 17.3 % error.

Reduction of Device Operating Temperatures with Graphene-Filled Thermal Interface Materials

The majority of research into few layer graphene (FLG) thermal interface materials (TIM) concerns the direct quantification of innate composite properties with much less direct analysis of these materials in realistic applications. In this study, equilibrium temperatures of engineered device substitutes fixed to passive heat sink solutions with varying FLG concentration TIMs are experimentally measured at varying heat dissipation rates. A custom, precisely-controlled heat source’s temperature is continually measured to determine equilibrium temperature at a particular heat dissipation. It is found that altering the used FLG TIM concentrations from 0 vol.% to as little as 7.3 vol.% resulted in a decrease of combined TIM and passively-cooled heat sink thermal resistance from 4.23∘C/W to 2.93∘C/W, amounting to a reduction in operating temperature of ≈108∘C down to ≈85∘C at a heat dissipation rate of 20 W. The results confirm FLG TIMs’ promising use in the application of device heat dissipation in a novel, controllable experimental technique.

Experimental investigation on heat transfer enhancement of air-cooled heat sink using multiple synthetic jets

The heat transfer enhancement of air-cooled heat sink using multiple synthetic jets is investigated experimentally. A heat sink is located inside synthetic jet actuator cavity in order to reduce space occupied by the cooling device. It has been observed that heat sink located inside the synthetic jet actuator cavity dissipates heat in a manner similar to the heat sink cooled by impinging synthetic jet. The thermal resistance of the heat sink depends on the synthetic jet Reynolds number and dimensionless stroke length. The paper presents experimental results of synthetic jet Reynolds number, dimensionless stroke length as well as the heat sink thermal resistance and coefficient of performance. The value of the heat sink thermal resistance of 0.22 K/W was measured during operation of synthetic jest cooling while the thermal resistance of the heat sink without loudspeaker was found to be 1.4 K/W. A correlation of thermal resistance as a function of Reynolds number and dimensionless stroke length based on the experimental results is presented and discussed.

Thermal analysis and parametric optimization of plate fin heat sinks under forced air convection

Heat dissipation is becoming more and more challenging with the preface of new electronic components having staggering heat generation levels. Present day solutions should have optimized outcomes with reference to the heat sink scenarios. The experimental and theoretical results for plate type heat sink based on mathematical models have been presented in the first part of the paper. Then the parametric optimization (topology optimization) of plate type heat sink using Levenberg-Marquardt technique employed in the COMSOL Multiphysics? software is discussed. Thermal resistance of heat sink is taken as objective function against the variable length in a predefined range. Single as well as multi-parametric optimization of plate type heat sink is reported in the context of pressure drop and air velocity (Reynolds number) inside the tunnel. The results reported are compared with the numerical modeled data and experimental investigation establish the conformity of results for applied usage. Mutual reimbursements of greater heat dissipation with minimum flow rates are confidently achievable through balanced, heat sink geometry as evident by the presented simulation outcome. About 12% enhancement in pressure drop and up to 51% improvement in thermal resistance is reported for the optimized plate fin heat sink as per data manifested.