Analysis of Using Ferrofluid as an Interface Material in a Field Reversible Thermal Connector

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Ahmed S. Yousif ◽  
Gary L. Solbrekken
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Iron Nanoparticles ◽  
Heat Dissipation ◽  
The Other ◽  
Thermal Interface Material ◽  
Heat Transfer Fluid ◽  
University Of Missouri ◽  
Transfer Path ◽  
Current Design

The electrical functionality of an avionics chassis is limited due to heat dissipation limits. The limits arise due to the fact that components in an avionic computer boxes are packed very compactly, with the components mounted onto plug-in cards, and the harsh environment experienced by the chassis limits how heat can be dissipated from the cards. Convective and radiative heat transfer to the ambient are generally not possible. Therefore, it is necessary to have heat transferred from the components conducted to the edge of the plug-in cards. The heat then needs to conduct from the card edge to a cold block that not only holds the card in place but also removes the generated heat by some heat transfer fluid that is circulated through the cold block. The interface between the plug-in card and the cold block typically has a high thermal resistance since it is necessary for the card to have the capability to be reworkable, meaning that the card can be removed and then returned to the chassis. Reducing the thermal resistance of the interface is the objective of the current study and the topic of this thesis. The current design uses a pressure interface between the card and cold block. The contact pressure is increased through the addition of a wedgelock, which is a field-reversible mechanical connector. To use a wedgelock, the cold block has channels milled on the surface with widths that are larger than the thickness of the plug-in card and the unexpanded wedgelock. The card edge is placed in the channel and placed against one of the channel walls. A wedgelock is then placed between the card and the other channel wall. The wedgelock is then expanded by using either a screw or a lever. As the wedgelock expands, it fills in the remaining channel gap and bears against the other face of the plug-in card. The majority of heat generated by the components on the plug-in card is forced to conduct from the card into the wall of the cold block, effectively a single sided, dry conduction heat transfer path. Having started as a student design competition named RevCon Challenge, work was performed to evaluate the use of new field-reversible thermal connectors. The new design proposed by the University of Missouri utilized oil based iron nanoparticles, commonly known as a ferrofluid, as a thermal interface material. By using a liquid type of interface material, the channel gap can be reduced to a few micrometers, within machining tolerances, and heat can be dissipated off both sides of the card. The addition of nanoparticles improves the effective thermal conductivity of base fluid. The use of iron nanoparticles allows magnets to be used to hold the fluid in place, so the electronic cards may be easily inserted and removed while keeping the ferrofluid in the cold block channel. The ferrofluid-based design which was investigated has shown lower thermal resistance than the current wedgelock design. These results open the door for further development of electronic cards by using higher heat emitting components without compromising the simplicity of attaching/detaching cards from cooling plates.

scholarly journals Measurement of Heat Dissipation and Thermal-Stability of Power Modules on DBC Substrates with Various Ceramics by SiC Micro-Heater Chip System and Ag Sinter Joining

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 745
Author(s):  
Dongjin Kim ◽  
Yasuyuki Yamamoto ◽  
Shijo Nagao ◽  
Naoki Wakasugi ◽  
Chuantong Chen ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Heat Dissipation ◽  
Wide Band ◽  
Middle Layer ◽  
Thermal Interface Material ◽  
Wide Band Gap ◽  
Power Cycle ◽  
Power Cycling ◽  
Power Modules ◽  
Pattern Line

This study introduced the SiC micro-heater chip as a novel thermal evaluation device for next-generation power modules and to evaluate the heat resistant performance of direct bonded copper (DBC) substrate with aluminum nitride (AlN-DBC), aluminum oxide (DBC-Al2O3) and silicon nitride (Si3N4-DBC) ceramics middle layer. The SiC micro-heater chips were structurally sound bonded on the two types of DBC substrates by Ag sinter paste and Au wire was used to interconnect the SiC and DBC substrate. The SiC micro-heater chip power modules were fixed on a water-cooling plate by a thermal interface material (TIM), a steady-state thermal resistance measurement and a power cycling test were successfully conducted. As a result, the thermal resistance of the SiC micro-heater chip power modules on the DBC-Al2O3 substrate at power over 200 W was about twice higher than DBC-Si3N4 and also higher than DBC-AlN. In addition, during the power cycle test, DBC-Al2O3 was stopped after 1000 cycles due to Pt heater pattern line was partially broken induced by the excessive rise in thermal resistance, but DBC-Si3N4 and DBC-AlN specimens were subjected to more than 20,000 cycles and not noticeable physical failure was found in both of the SiC chip and DBC substrates by a x-ray observation. The results indicated that AlN-DBC can be as an optimization substrate for the best heat dissipation/durability in wide band-gap (WBG) power devices. Our results provide an important index for industries demanding higher power and temperature power electronics.

Thermal Resistance Analysis of Sn-Bi Solder Paste Used as Thermal Interface Material for Power Electronics Applications

2014 ◽  
Vol 136 (1) ◽  
Author(s):  
Rui Zhang ◽  
Jian Cai ◽  
Qian Wang ◽  
Jingwei Li ◽  
Yang Hu ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Power Electronics ◽  
Heat Dissipation ◽  
Laser Flash ◽  
Acoustic Microscopy ◽  
Thermal Interface Material ◽  
Solder Paste ◽  
Good Reliability ◽  
Thermal Interface ◽  
Power Modules

To promote heat dissipation in power electronics, we investigated the thermal conduction performance of Sn-Bi solder paste between two Cu plates. We measured the thermal resistance of Sn-Bi solder paste used as thermal interface material (TIM) by laser flash technique, and a thermal resistance less than 5 mm2 K/W was achieved for the Sn-Bi TIM. The Sn-Bi solder also showed a good reliability in terms of thermal resistance after thermal cycling, indicating that it can be a promising candidate for the TIM used for power electronics applications. In addition, we estimated the contact thermal resistance at the interface between the Sn-Bi solder and the Cu plate with the assistance of scanning acoustic microscopy. The experimental data showed that Sn-Bi solder paste could be a promising adhesive material used to attach power modules especially with a large size on the heat sink.

Effect of Filling Ratio and Tilt Angle on the Performance of a Mini-Loop Thermosyphon

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Trijo Tharayil ◽  
Neha Gitty ◽  
Lazarus Godson Asirvatham ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Wall Temperature ◽  
Tilt Angle ◽  
Heat Dissipation ◽  
Heat Transfer Performance ◽  
Electronics Cooling ◽  
Filling Ratio ◽  
Average Decrease ◽  
Heat Loads

The thermal behavior of a compact mini-loop thermosyphon is experimentally studied at different filling ratios (20%, 30%, 40%, 50%, and 70%) and tilt angles (0 deg, 30 deg, 45 deg, 60 deg, and 90 deg) for the heat loads of 20–300 W using distilled water as the heat pipe fluid. The presence of microfins at the evaporator results in an average decrease of 37.4% and 15.3% in thermal resistance and evaporator wall temperature, respectively, compared with the evaporator with a plain surface. Both filling ratio (FR) and tilt angle influence the heat transfer performance significantly, and the best performance of the mini-loop thermosyphon is obtained at their optimum values. The thermal resistance and thermal efficiency values lie in the ranges of 0.73–0.076 K/W and 65–88.3% for different filling ratios and tilt angles. Similarly, evaporator heat transfer coefficient and evaporator wall temperature show significant variation with changes in filling ratio and tilt angle. A combination of the optimum filling ratio and tilt angle shows a lowest thermal resistance of 0.076 K/W and a highest evaporator wall temperature of 68.6 °C, which are obtained at 300 W. The experimental results recommend the use of mini-loop thermosyphon at an optimum filling ratio for electronics cooling applications, which have a heat dissipation of 20–300 W.

Microchannel Optimization for Heat Dissipation From a Solid Substrate

2008 ◽  
Author(s):  
C. B. Sobhan ◽  
P. S. Anoop ◽  
Kuriyan Arimboor ◽  
Thomas Abraham ◽  
G. P. Peterson
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Thermal Resistance ◽  
Computational Model ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Dissipation ◽  
Three Dimensional ◽  
Solid Substrate ◽  
Nusselt Numbers

A computational model was developed to analyze and optimize the convective heat transfer for water flowing through rectangular microchannels fabricated in a silicon substrate. A baseline case was analyzed by solving the nondimensional governing equations. Using a quasi three-dimensional computational model, the velocity and temperature distributions were obtained and the numerical results were then used to determine the overall dimensionless thermal resistance for the convective heat transfer from the substrate to the fluid. To validate the numerical model, the average Nusselt numbers as determined by the numerical model were compared with experimental results available in the literature, for channels with comparable hydraulic diameters. The procedure for arriving at an optimum geometric configuration and arrangement of microchannels on the substrate, subject to given design constraints, so that the thermal resistance is at a minimum, is described and demonstrated using the computational model.

Experimental Investigation on Flow and Thermal Characteristics of a Micro Phase-Change Cooling System With a Microgroove Evaporator

2006 ◽  
Author(s):  
Xuegong Hu ◽  
Dawei Tang
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Dissipation ◽  
Cooling System ◽  
Thermal Sensitivity ◽  
Thermal Characteristics ◽  
Cooling Capacity ◽  
Input Power ◽  
Maximum Heat ◽  
Transportation Capacity

In this paper, a natural convection micro cooling system with a capillary microgroove evaporator is proposed. An experimental study on the characteristics of thermal resistance, pressure drop and heat transfer of the cooling system was carried out. Experimental results indicate that the liquid fill ratio has a significant influence on thermal resistance and heat transfer in the cooling system. Increasing system’s cooling capacity at higher input power depends on decreasing the thermal resistance between the outer surfaces of the condenser and ambient environment. Compared with a flat miniature heat pipe (FMHP) and a current fan-cooled radiator for CPU chip of Pentium IV, the present micro cooling system has a stronger heat dissipation capacity. Its best cooling performance at a surface temperature of heat source below 373K reaches 1.68×106W/m2 and the maximum heat transportation capacity is 131.8W. The novel kind of cooling system is suitable for remote cooling of those electronic parts with micro size, high power and thermal sensitivity.

Performance Comparison of Rectangular and Air-Foil Shapes Offset Strip Flow Paths Micro Heat Exchangers

2007 ◽  
Author(s):  
Chien-Yuh Yang ◽  
Chun-Ta Yeh ◽  
Ting-Yu Lin
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Performance Comparison ◽  
The Other ◽  
Transfer Performance ◽  
Test Results ◽  
Flow Paths

Six micro heat exchangers with rectangle, airfoil and shuttle type strips was designed and fabricated in the present work. Two major parameters were considered for heat transfer performance comparison. One is the effect of strip type and the other is the strip arrangement. From the test results, we may notice that for both rectangle and airfoil strips heat exchangers, those with shorter strips performed lower thermal resistance than those with longer strips. Furthermore, the heat exchangers with more strips have better heat transfer performance. However, the space between strips is limited by the fabrication techniques.

scholarly journals JATROPHA OIL WITH IRON NANOPARTICLES APPLICATION IN DRILLING PROCESSES

2019 ◽  
Vol 59 (3) ◽  
pp. 299-304
Author(s):  
Veikko Shalimba ◽  
Vít Sopko
Keyword(s):  
Heat Transfer ◽  
High Performance ◽  
Iron Nanoparticles ◽  
Volume Fraction ◽  
Volume Ratio ◽  
Heat Transfer Fluid ◽  
Nanoparticle Volume Fraction ◽  
Jatropha Oil ◽  
Heat Transfer Fluids ◽  
Performance Of Heat Transfer

A performance of heat transfer fluids has a substantial influence on the size, weight and cost of heat transfer systems, therefore, a high-performance heat transfer fluid is very important in many industries. Over the last decades, nanofluids have been developed. According to many researchers and publications on nanofluids, it is evident that nanofluids have a high thermal conductivity. The aim of this experimental study was to investigate the change of the workpiece temperature during drilling using Jatropha oil with iron nanoparticles and water with iron nanoparticles as lubricating and cooling fluids. These experiments were carried out with samples of nanofluid with different nanoparticles volume ratio, such as samples JN1, JN5 and JN10 of iron nanoparticles in the base Jatropha oil with a nanoparticle volume fraction of 1 %, 5% and 10% respectively and samples WN1, WN5 and WN10 of iron nanoparticles in the base water with a nanoparticle volume fraction of 1 %, 5% and 10% respectively.

scholarly journals Numerical Investigation on Forced Hybrid Nanofluid Flow and Heat Transfer Inside a Three-Dimensional Annulus Equipped with Hot and Cold Rods: Using Symmetry Simulation

Symmetry ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1873
Author(s):  
Aysan Shahsavar Goldanlou ◽  
Mohammad Badri ◽  
Behzad Heidarshenas ◽  
Ahmed Kadhim Hussein ◽  
Sara Rostami ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Ethylene Glycol ◽  
Base Fluid ◽  
Thermal Characteristics ◽  
Reynolds Numbers ◽  
The Other ◽  
Heat Transfer Fluid ◽  
Hybrid Nanofluid ◽  
Cu Nanoparticles ◽  
Flow And Heat Transfer

A 3D computational fluid dynamics method is used in the current study to investigate the hybrid nanofluid (HNF) flow and heat transfer in an annulus with hot and cold rods. The chief goal of the current study is to examine the influences of dissimilar Reynolds numbers, emissivity coefficients, and dissimilar volume fractions of nanoparticles on hydraulic and thermal characteristics of the studied annulus. In this way, the geometry is modeled using a symmetry scheme. The heat transfer fluid is a water, ethylene–glycol, or water/ethylene–glycol mixture-based Cu-Al2O3 HNF, which is a Newtonian NF. According to the findings for the model at Re = 3000 and ϕ1 = 0.05, all studied cases with different base fluids have similar behavior. ϕ1 and ϕ2 are the volume concentration of Al2O3 and Cu nanoparticles, respectively. For all studied cases, the total average Nusselt number (Nuave) reduces firstly by an increment of the volume concentrations of Cu nanoparticles until ϕ2 = 0.01 or 0.02 and then, the total Nuave rises by an increment of the volume concentrations of Cu nanoparticles. Additionally, for the case with water as the base fluid, the total Nuave at ϕ2 = 0.05 is higher than the values at ϕ2 = 0.00. On the other hand, for the other cases, the total Nuave at ϕ2 = 0.05 is lower than the values at ϕ2 = 0.00. For all studied cases, the case with water as the base fluid has the maximum Nuave. Plus, for the model at Re = 4000 and ϕ1 = 0.05, all studied cases with different base fluids have similar behavior. For all studied cases, the total Nuave reduces firstly by an increment of the volume concentrations of Cu nanoparticles until ϕ2 = 0.01 and then, the total Nuave rises by an increment of the volume concentrations of Cu nanoparticles. The Nuave augments are found by an increment of Reynolds numbers. Higher emissivity values should lead to higher radiation heat transfer, but the portion of radiative heat transfer in the studied annulus is low and therefore, has no observable increment in HNF flow and heat transfer.

Maximum Resolution of a Probe-Based, Steady-State Thermal Interface Material Characterization Instrument

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Ronald J. Warzoha ◽  
Andrew N. Smith ◽  
Maurice Harris
Keyword(s):  
Steady State ◽  
Thermal Resistance ◽  
High Performance ◽  
Heat Dissipation ◽  
Thermal Contact ◽  
Thermal Interface Material ◽  
Interfacial Thermal Resistance ◽  
Uniform Heat Flux ◽  
Thermal Probe ◽  
Thermal Interface

Thermal interface materials (TIMs) constitute a critical component for heat dissipation in electronic packaging systems. However, the extent to which a conventional steady-state thermal characterization apparatus can resolve the interfacial thermal resistance across current high-performance interfaces (RT < 1 mm2⋅K/W) is not clear. In this work, we quantify the minimum value of RT that can be measured with this instrument. We find that in order to increase the resolution of the measurement, the thermal resistance through the instrument's reference bars must be minimized relative to RT. This is practically achieved by reducing reference bar length. However, we purport that the minimization of reference bar length is limited by the effects of thermal probe intrusion along the primary measurement pathway. Using numerical simulations, we find that the characteristics of the probes and surrounding filler material can significantly impact the measurement of temperature along each reference bar. Moreover, we find that probes must be spaced 15 diameters apart to maintain a uniform heat flux at the interface, which limits the number of thermal probes that can be used for a given reference bar length. Within practical constraints, the minimum thermal resistance that can be measured with an ideal instrument is found to be 3 mm2⋅K/W. To verify these results, the thermal resistance across an indium heat spring material with an expected thermal contact resistance of ∼1 mm2⋅K/W is experimentally measured and found to differ by more than 100% when compared to manufacturer-reported values.

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