Heat Sink Temperature Research Articles

Predicting aging of IGBT solder layer using saturation voltage approach with CPO-SVR data modeling

Addressing the criticality of IGBT modules in power electronics and reliability challenges in industrial applications, this study focuses on solving the important problem of solder layer aging failure in IGBT modules. Under defined operating conditions, a specific set of electrical parameters, notably the collector-emitter saturation voltage Vce(sat), serves as a critical indicator for monitoring the degradation of solder layers within IGBT modules. This parameter is indicative of potential solder layer aging failures, which can be identified and studied to predict and mitigate such failures effectively. In order to analyze the aging trend more deeply and accurately, a new nature-inspired meta-heuristic algorithm based on Crested Porcupine Optimizer is introduced. Combining multiple data during the operation of the IGBT module, such as gate voltage, gate current, heatsink temperature, case temperature, collector-emitter current, and Vce(sat), the parameter optimization is carried out by using CPO, and a prediction model based on the optimization of the SVR by CPO is established, which is successfully implemented to predict the accurate prediction of IGBT module solder layer lifetime. The study also validates the effectiveness of the CPO-SVR method on an accelerated aging dataset of IGBT modules provided by NASA Lab. The results of this research contribute to an in-depth understanding and prediction of the aging process of IGBT modules, which in turn improves the reliability and lifetime of the devices.

Conditions for thermally stable color characteristics of trichromatic white light-emitting diodes

We present a method to stabilize color characteristics from a trichromatic white light-emitting diode (LED) consisting of red, green, and blue (RGB) LEDs under varying ambient temperatures. Through colorimetric analyses, it was found that the trichromatic white LED could maintain its chromaticity coordinate by adjusting the light output power (LOP) of green and red LEDs as the temperature varied. Moreover, the correlated color temperature (CCT) could be invariant to the external temperature change by controlling only the LOP of a red LED. Using the developed mathematical model and temperature-dependent spectral data of commercial RGB LED samples, we determined the power ratios between RGB LEDs needed to achieve thermally stable color coordinates or CCT as the heat sink temperature varied from 20 to 100 °C. When operating under thermally stable CCT conditions, the chromaticity coordinate of the trichromatic LED moved along the iso-CCT line with only a minor color deviation as the temperature increased to 100 °C. The presented approach requires adjusting the power of only one LED to achieve thermally stable CCT operation in a trichromatic white LED, which is expected to simplify LED control circuits significantly.

Experimental investigation of the heat transfer characteristics of CO2 at supercritical pressures flowing in heated vertical pipes

Supercritical CO2 shows great potential as a working fluid in power plant cycles due to its moderate critical pressure of 7.38 MPa and critical temperature of 30.98 °C, closely matching typical heat sink temperatures. Understanding the heat transfer characteristics of sCO2 is crucial for designing cycle components. This publication presents a systematic analysis of sCO2 heat transfer in two heated vertical pipes with 4 and 8 mm inner diameters, with both upward and downward flow at pressures of approximately 7.75, 8.00, and 9.50 MPa, and flow inlet temperatures between 5 and 40 °C, based on 196 experiments. The study investigates a range of mass fluxes from 400 to 2000 kg/m2s and heat fluxes from 10 to 195 kW/m2, resulting in a heat to mass flux ratio of 6 to 275 J/kg. The findings reveal enhanced, normal, and deteriorated heat transfer within the experimental dataset. Buoyancy effects are identified as the main cause of deteriorated heat transfer in the investigated parameter range, with flow acceleration showing no significant influence on heat transfer. A new proposed dimensional criterion categorises 36 out of 119 experiments with upward flow in the deteriorated heat transfer regime, accompanied by temperature peaks rising to 47 K. Thermal inflow lengths range from 0 to 480 inner pipe diameters, with some experiments not achieving a thermally fully developed flow over the entire pipe length. Based on a comparison with approximately 8950 experimental data points, two Nusselt correlations are found, capable of reproducing the experimental results with a mean absolute deviation of around 30 %. This publication provides valuable data for validating numerical models and developing correlations to predict the heat transfer of supercritical fluids.

Application of LED Bulb with Perforated Plus Shape Fin Array in Mines

This paper works on design and developments of cooling system of LED. This work particularly studies on the passive cooling system of a 50W street-light lamp made by multiple LEDs. For analysis purposes, different parameters are considered such as: Density, kinematic viscosity, velocity, junction temperature, heat transfer rate, laminar flow and heat transfer modes. The findings suggest that using plus shape fins with a 1 mm diameter drill can enhance convection heat transfer, resulting in a 21.8% increase in surface area. Additionally, the "Plus" shape of the fins facilitates the formation of an air swirl, contributing to a 30.41% decrease in heat sink temperature. Furthermore, material porosity enhances cooling rates by generating swirls and promoting upward airflow. Ultimately, Plus shape fins emerge as an optimal solution for passive cooling systems, mimicking the efficiency of active cooling systems. The cooling model, proposed along with different shapes and weights of materials having specially designed fins porous materials, is unique so far in our knowledge.

Experimental and numerical investigations of forced convection impingement heat transfer on plate-fin heat sinks using three different electronic cooling fans

An experimental and numerical study was conducted for plate-fin heat sinks subjected to impinging air jets produced by electronic cooling fans. One axial and two different radial fans were used and their distance to the heat sink was varied. The aluminum heat sinks had either plain fins or fins with sinusoidal surface structures, were heated by heat sources either distributed over the entire base plate or concentrated in the center. In total, temperature measurements for 264 settings were performed, and numerical simulations were carried out for 19 selected cases. The results show that the axial fan outperforms the radial fans for the investigated fan distances, that the structured fins lead to lower base plate temperatures and that significant asymmetries in the heat sink temperature distribution can occur in certain cases. The numerical simulations are used to gain a better understanding of the trends observed in the measurements. Particularly, the impact of the velocity profiles at the fan outlets and the influence of certain geometrical details of the fan design on the heat flux distributions and the airflow into the fin channels are explored. The results highlight practical problems that need to be considered when optimizing heat sink-fan combinations.

Modeling and Numerical Investigations of Flowing N-Decane Partial Catalytic Steam Reforming at Supercritical Pressure

Steam reforming is an effective method for improving heat sinks of hypersonic aircraft at high flight Mach numbers. However, unlike the industrial process of producing hydrogen with a high water content, the catalytic steam reforming mechanism for the regeneration cooling process of hydrocarbon fuels with a water content below 30% is still unclear. Catalytic steam reforming (CSR) and catalytic thermal cracking (CTC) reactions occur at low temperatures, with the main products being hydrogen and carbon oxides. Thermal cracking (TC) reactions occur at high temperatures, with the main products being alkanes and alkenes. The above reaction exists simultaneously in the regeneration cooling channel, which is referred to as partial catalytic steam reforming (PCSR). Based on the experimental measurement results, an improved neural network correction method was used to establish a four-step global reaction model for the PCSR of n-decane under low water conditions. The reliability of the four-step model was verified by combining the model with a numerical simulation program and comparing it with the experimental results obtained by electric heating hydrocarbon fuels with a pressure of 3 MPa and a water content of 5/10/15%. The experimental and predicted results using the developed kinetic model are consistent with an error of less than 5% in the decane conversion rate. The average absolute error between the fuel outlet temperature and total heat sink is less than 10%. Using the PCSR model to predict the heat transfer characteristics of mixed fuels with different water contents, the convective heat transfer coefficient is basically the same, and the Nu number is affected by the thermal conductivity coefficient, showing different patterns with changes in the water content.

Investigating the impacts of heat sink design parameters on heat dissipation performance of semiconductor packages

This study investigates the impacts of various heat sink design parameters on the thermal dissipation performance of semiconductor packages using a heat sink as the thermal solution. A multiphase finite volume model was developed for heat transfer simulations to determine the heat sink and junction temperatures of the semiconductor assembly. Additionally, a heat transfer experiment was conducted to measure these temperatures over time. The numerical predictions closely matched the experimental results, with a maximum disparity of 0.26 % for junction temperature and 0.42 % for heat sink temperature, confirming the reliability of the numerical model. The results revealed that pin fin heat sinks demonstrated marginally superior thermal performance, reducing the junction temperature by 0.05 % compared to parallel heat sinks. Increasing the base area from 20x20 mm² to 50x50 mm² resulted in a significant 31.64 % reduction in junction temperature and a corresponding reduction in heat sink temperature from 60.41 °C to 36.42 °C. Extending fin height from 10 mm to 50 mm led to an 18.73 % decrease in junction temperature and a reduction in heat sink temperature from 46.07 °C to 34.56 °C. Enhancing the base thickness from 2 mm to 15 mm achieved a 24.35 % reduction in junction temperature and a decrease in heat sink temperature from 63.2 °C to 44.05 °C. The study concludes that optimizing these design parameters can substantially enhance heat dissipation, improving the reliability and efficiency of semiconductor devices.

The Role of the Working Fluid and Non-Ideal Thermodynamic Effects on Performance of Gas Lubricated Bearings

Abstract Small-scale turbomachinery operating at high rotational speed is a key technology for increasing the power density of energy and propulsion systems. A notable example is the turbine of an organic Rankine cycle turbogenerator for thermal recuperation from prime engines and industrial processes. Such systems typically operate with organic compounds characterized by complex molecular structures, to allow the design of efficient fluid machinery and flexibility in matching the heat source and sink temperature profiles. Gas bearings are considered advantageous compared to traditional oil-lubricated rolling element bearings for supporting the turbine rotor, enabling greater machine compactness and reduced complexity, and to avoid contamination of the working fluid. In certain operating conditions, however, the lubricant of the bearing is in thermodynamic states near the saturated vapor line or in the vicinity of the fluid critical point whereby non-ideal effects are relevant and may affect bearing performance. This work investigates the physics of thin film flows in gas bearings operating with fluids made by complex molecules. The influence of non-ideal thermodynamic effects on gas bearing performance is discussed by analysis of the fluid bulk modulus. Reduced values of the non-dimensional bulk modulus near the critical point or saturated vapor line decrease bearing performance. The main parameter characterizing the influence of molecular complexity on bearing performance is shown to be the acentric factor. For complex fluids with large acentric factors, the impact of non-ideal thermodynamic effects on non-dimensional bearing load capacity and rotor-dynamic characteristics is less pronounced.

Inverse and conventional dual magnetocaloric effects in Ni substituted Y-type Sr2Zn2-xNixFe12O22 hexaferrites

The effects of Ni substitution on magnetic and magnetocaloric effect (MCE) are investigated in polycrystalline Y-type hexaferrites of Sr2Zn2-xNixFe12O22 (x = 0.0, 0.8, and 2.0). With the increasing of temperature, the M-T curves indicate successive magnetic structure transitions exist in Sr2Zn2-xNixFe12O22 (x = 0.0, 0.8, and 2.0), which play significant roles in MCE behaviors. As the Ni2+ doping ratio increases, the shape of −ΔSM−T curves near room temperature evolves gradually from a table-like to a peak-like form. Particularly, a significant contrast between CMCE and IMCE is observed below 100 K, whose behavior can be inherently exploited for heat sink in magnetic refrigeration applications. Among the samples in this series, Sr2Zn1.2Ni0.8Fe12O22 plays the best CMCE and IMCE performances, with the maximum magnetic entropy change (−ΔSMmax) values of 0.78 J/kg K at 354 K and −0.56 J/kg K at 16 K for ΔH=50kOe , respectively. Our work demonstrates that Sr2Zn2-xNixFe12O22 hexaferrites have great potential to be tailored for magnetic refrigeration with special needs such as different operating temperature zones, Ericsson cycle or heat sink at refrigeration.

Study of impact of nano fluids on performance of microchannel heat exchangers using CFD

Addressing the critical issue of heat generation in electronic devices due to miniaturization and higher power density is essential. As electronic components become more compact, they generate more heat flux, necessitating efficient thermal management solutions. Traditional methods and fluids, such as water, struggle to meet the demand for efficient heat dissipation. To address this challenge, the utilization of nanofluids presents a promising solution. The objective of this study is to use CFD methods to examine how a nanofluid can improve heat transmission and lower the maximum temperature in a microchannel heatsink. This article presents the study of microchannel heatsinks with two distinct channel counts (five and eight). A constant flow, incompressible, laminar model was used to verify the findings. The working fluids used in the study were water in various concentrations, water-based nanofluids of Fe3O4-water and MWCNTs. CFD simulations revealed that a MWCNT-water nanofluid at 0.2 % concentration significantly improved cooling performance compared to water, demonstrating the potential of nanofluids for efficient thermal management in electronic devices.

High-power 940 nm DFB laser diode with large optical cavity.

High-power laser diodes with a stable wavelength and narrow linewidth are crucial for many applications. In this study, we introduce a first-order distributed feedback (DFB) grating into an asymmetric large-cavity laser diode operating around 940 nm. This design maintains high output power and offers a wide temperature locking range. The nearly sinusoidal shape first-order grating is fabricated by ultraviolet (UV) nanoimprint lithography, inductively coupled plasma (ICP) dry etching, and wet polishing. At a heat sink temperature of 25°C, the DFB laser diode, with a 200 µm stripe width and 4 mm cavity length, achieves a maximum output power of 24.8 W and a full width at half maximum (FWHM) of 0.4 nm under continuous-wave (CW) conditions. The maximum slope efficiency is calculated to be 1.04 W/A. At an output power of 10.7 W, the device reaches a peak wall-plug efficiency of 56%. Under quasi-continuous operation at 20 A, the laser output spectrum remains locked to the DFB grating over a temperature range from -10°C to 110°C, with a temperature coefficient of 0.062 nm/°C.

Experimental study on the flat loop heat pipe with minichannel wick under low heat flux

Stable operating under low heat flux condition is crucial for loop heat pipe. To investigate the performance of the flat loop heat pipe under low heat flux, a visual structure of evaporator with longitudinal replenishment characterized by minichannel wick is proposed and fabricated. The minichannel wick increases the permeable area and reduces flow resistance to enhance the heat transfer capacity. However, under low heat flux condition, excessive liquid permeation into the vapor line and the local reverse vapor flow may deplete the liquid storage in the compensation chamber, resulting in a wick temperature increase of 4.7 °C under extreme condition. Lowering the heat sink temperature does not necessarily lead to a lower stable wick temperature in specific cases but rather poses operational challenges and further raises the stable wick temperature by 9 °C. By visualizing the flow structure, it is found that arduous vapor–liquid prestart distribution leads to prolonged circulation establishment time and higher wick temperature, resulting in a higher stable wick temperature. As the heat flux increases, the effect of prestart distribution on the stable wick temperature weakens as the redistribution capability improves.

Continuous wave operation of broad area and ridge waveguide laser diodes at 626 nm

AbstractThe authors present continuous wave (CW) high‐power broad area and ridge waveguide lasers with laser emission at 626 nm at room temperature. For this, the authors employ GaAs‐based diode lasers in the AlGaInP system for laser emission at 626 nm at room temperature. The laser structure is grown on three‐inch wafers by metal organic vapour phase epitaxy. Broad area and ridge waveguide lasers are fabricated. Pulsed broad area laser characterisation on bar level shows laser operation at 20 C heat sink temperature. The authors measured peak lasing wavelengths as short as 625 nm and total maximum output power of both facets up to 1.4 W at an injection current of 2 A. Both, broad area and ridge waveguide lasers show laser operation and CW excitation at room temperature. The ridge waveguide lasers emit output powers of over 90 mW at 626 nm at a maximum injection current of 200 mA with a nearly diffraction‐limited beam profile.

Experimental and numerical investigations on the intermittent heat transfer performance of phase change material (PCM)-based heat sink with triply periodic minimal surfaces (TPMS)

The excessive heat generated during the operation of electronic components leads to significant temperature increases, posing a significant risk to their service life. For the problem of efficient thermal management of electronic devices in confined spaces experiencing high heat flow, a scheme using triply periodic minimal surfaces and a phase change material-based active–passive cooling heat sink is proposed to control the temperature of electronic equipment. The apparent heat capacity method is employed to simulate the intermittent process of the phase change material-based heat sink. The optimization based on Box-Behnken Design and Nondominated Sorting Genetic Algorithm II is analyzed to obtain an improved triply periodic minimal surface structure. The effect of thermal performance (including base temperature, liquid fraction, and Grashof number) of an intermittent heat sink based on an improved structure is discussed. Visualization and temperature testing platforms are established. Through visualization experiments, the internal temperature and liquid fraction distribution of the heat sink are obtained, and the simulation results are in good agreement with the test results. The results show that the base temperature, liquid fraction, and Grashof number achieve a steady periodic variation during the intermittent process. Specifically, the base temperature remains stable in the range of 314 K to 340 K, the liquid fraction stabilizes between 0.8 and 1.0, and the Grashof number stabilizes between 100 and 1000. At the heating power of 30 W or below, the base temperature of the heat sink exhibits a steady periodic variation. At the heating power of 40 W, the maximum base temperature of the heat sink exceeds 370 K.

High-power distributed feedback laser diode arrays with narrow spectral width over a wide temperature range

High-power semiconductor lasers with stabilized wavelengths are recognized as exemplary pumping sources for solid-state lasers. This study introduces distributed feedback (DFB) laser diode arrays designed to maintain an extensive temperature locking range. We report experimentally on high-power 808 nm DFB laser diode arrays. The first-order sinusoidal grating was fabricated using nanoimprint lithography, succeeded by inductively coupled plasma (ICP) dry etching and subsequent wet polishing. These 808 nm DFB laser diode arrays have demonstrated a measured output power of 134 W under a pulsed current of 150 A, with the heat sink temperature maintained at 25°C. The slope efficiency was determined to be 1.1 W/A. At a current of 150 A, the laser operated with a narrow spectral width over a wide temperature range, extending from −30 to 90°C, with a temperature drift coefficient of 0.0595 nm/K.

Experimental study on startup characteristics of instant heat pump water heater with non-azeotropic natural blend

The effects of starting mode and outlet temperature of heat sink (OTHS) on the starting performances of direct-heated heat pump water heater using natural blend were investigated experimentally. The results indicated that both starting mode and OTHS had notable impact on starting time of transient performance parameters. Both warm start and lower OTHS helps to quickly obtain hot water at the target temperature, mainly because the system startup time in the warm start was 16.73 % shorter than that in the cold start and the system gained the shortest startup time (1015 s) in low temperature condition. The transient heat sink outlet temperature had a rapid temperature rise section and a slow temperature rise section (STRS), and the STRS consumed 56.58 %–66.67 % of the system starting time, so the improvement of STRS is the key to realize the fast startup. The effects of startup mode on the trends of transient performance parameters were memorably different, but the OTHS had no apparent effect on their trends. The transient refrigerant pressures and transient refrigerant temperatures had the fluctuations. The transient suction pressures had the minimum values (0.3925–0.5575 MPa), and both cold start mode and higher OTHS resulted in a decrease in the minimum value.

Heat Sink Equivalent Thermal Test Method and Its Application in Low-Orbit Satellites

Heat Sink Equivalent Thermal Test Method and Its Application in Low-Orbit Satellites

State of the art of heat pumps for heating above 150 °C

In current aim to catch long-term energy and climate policies, the role of the heating sector cannot be overstated. Heating, accounting for 50% of final global energy consumption, stands as a huge target for transformation. In this context, heat pumps are emerging as a potential decarbonization tool that promises to significantly reduce emissions through the use of renewable or waste energy, as they can utilize waste heat to elevate temperature to higher levels more efficiently compared to any other existing technology. Despite their potential, heat pumps are currently only used to a limited extent for industrial high-temperature heating, which makes it necessary to investigate viable options for improving their effectiveness in this area. This paper offers an insightful exploration into the current state of the art in high-temperature heat pumps (HTHPs) with heat sink temperatures above 150 °C. Our primary focus centers on the examination of vapour-compression systems, examining factors such as heating capacity, efficiency, and environmental considerations. Additionally, we provide valuable recommendations and guidelines for the future exploitation of industrial HTHPs.

Characterization testing of the Northrop Grumman MiniCoolerPlus (MCP)

Northrop Grumman Space Park (NGSP) introduced the Mini Cooler Plus (MCP) to their family of pulse tube cryocoolers in 2019 [1] and presented the details of its TRL6 qualification testing in 2022 [2]. The thermal mechanical unit (TMU) of the MCP is an extension of space-qualified pulse tube coolers, all of which are designed to provide a long life (ten-plus years) of delivering low-mass, high-cooling capacity for hyperspectral and infrared imaging payloads in tactical airborne and space applications. The cooler is of modular split configuration allowing flexibility in the compressor (wave generator) and cold head placements to meet the available envelope of packaging constraints. The cold head assembly can be oriented at any position relative to the compressor assembly, and the transfer line (length and shape) can be customized to individual applications. The TMU (thermo-mechanical unit) weighs less than 3kg and can lift 1.5 W at 45 K or 11 W at 110K with 150 W electrical input at 300 K reject. The thermal performance has been characterized as a function of input voltage and as a function of cold tip load and temperature at variety of heat sink temperatures of -20C, 0C, +20C and +40C. Functional testing of the MCP was performed to higher input powers and MCP performance data versus operating conditions were collected. An analytical expression for cold tip load (Qc), impedance (Z) and power factor (PF) as a function of reject temperature (Trej), cold tip temperature (Tc), frequency (f), and input power (Pac) were generated. These tests were repeated with third party control electronics. All results will be presented here.

Experimental study on dynamic power generation of three ORC-based cycle configurations under different heat source/sink conditions

Organic Rankine cycle (ORC) is used for geothermal power generation, and other two derived cycle configurations, parallel double-stage organic Rankine cycle (PDORC) and organic Rankine flash cycle (ORFC), have been proposed to improve the geothermal power generation performance. However, no experimental comparison have been done before. An experimental device that can switch between three cycles was designed and constructed to compare the power generation performance of three cycles. The operational performance of the three cycles at different heat source and heat sink temperatures are analyzed in this paper. The results show that under the heat source temperature of 90 °C and heat sink temperature of 15 °C, the output power of ORFC is 876.59 W, which is higher than that of the PDORC and ORFC. Moreover, the exergetic efficiency is greater than other two cycles due to the smallest irreversible loss of ORFC. The exergetic efficiencies of the ORC, PDORC and ORFC are 31.87 %, 31.32 % and 34.79 %, respectively. The increase of heat sink temperature is beneficial for the isentropic efficiency of the expander, but not conducive to power generation performance and energy utilization. PDORC and ORFC promote the effective utilization of heat source, outputting more power but with a lower efficiency.