Thermal Assessment of Cooling System Incorporating Heat Sink and Embedded Heat Pipes for Testing High Power Microelectronics

2005 ◽  
Author(s):  
Victor Adrian Chiriac ◽  
Tien-Yu Tom Lee
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Pipes ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Peak Temperature ◽  
Testing System ◽  
The Impact

A numerical study was conducted to model the transient thermal behavior of a complex testing system including multiple fans, a mixing enclosure, copper inserts and a leaded package dissipating large amounts of power over short time durations. The system is optimized by choosing appropriate heat sink/fan structure for the efficient operation of the device under constant powering. The intent of the study is to provide a better understanding and prediction of a transient powering scenario at high powering levels, while evaluating the impact of alternative cooling fan/heat pipe designs on the thermal performance of the testing system. One design is chosen due to its effective thermal performance and assembly simplicity, with the package embedded in heat sink base with multiple (5) heat pipes. The peak temperature reached by the modified design with 4 cooling fans is ~95°C, with the corresponding Rja thermal resistance ~0.58°C/W. For the transient study (with embedded heat pipes and 4 fans), after one cycle, both peak temperature (at 45 s) and the end temperature (at 49 s) decrease as compared to the previous no heat pipe/single fan case (the end temperature reduces by ~16%). The temperature drop between peak and end for each cycle is ~80.2°C, while the average power per transient cycle is ~31.27W. With this power, the design with 5 perpendicular heat pipes, 4 fans and insert reaches a steady state peak temperature of ~98°C. Applying the superposition principle to the steady state value and 40.1°C fluctuation, the maximum transient temperature after a large number of cycles will not exceed ~138.1°C, satisfying the thermal budget under the current operating conditions. The benefit of the study is related to the possibility to extract the maximum and minimum temperatures for a real test involving a large number of heating-cooling cycles, yet maintaining the initial and peak temperatures within a certain range for the optimal operation of the device. The flow and heat transfer fields are investigated; using a combination of numerical and analytical methods, the thermal performance of the device undergoing large number of periodic thermal cycles is predicted. The comparison between measurement and simulation shows good agreement.

Advanced Cooling With Embedded Heat Pipes for High Power Microelectronics

2009 ◽  
Author(s):  
Victor Adrian Chiriac
Keyword(s):  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Pipes ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Peak Temperature ◽  
Transient Temperature ◽  
Efficient Operation ◽  
The Impact

The transient thermal behavior of a complex testing system including multiple fans, a mixing enclosure, Cu inserts and a leaded package dissipating large amounts of power over short time durations is evaluated via numerical simulations. The system performance is optimized with heat sink/fan structure for device efficient operation under constant powering. The study provides meaningful understanding and prediction of a transient powering scenario at high powering levels, evaluating the impact of alternative cooling fan/heat pipe configurations on the thermal performance of the system. One design is chosen due to its effective thermal performance and assembly simplicity, with the package embedded in heat sink base with multiple (5) heat pipes. The peak temperature reached by the modified design with 4 cooling fans is ∼95°C, with the corresponding Rja thermal resistance ∼0.58°C/W. For the transient study (with embedded heat pipes and 4 fans), after one cycle, both peak temperature (at 45 s) and the end temperature (at 49 s) decrease as compared to the previous no heat pipe/single fan case (especially the end temperature reduces by ∼16%). The temperature drop between peak and end for each cycle is ∼80.2°C, while the average power per transient cycle is ∼31.27W. With this power, the design with 5 perpendicular heat pipes, 4 fans and insert reaches a steady state peak temperature of ∼98°C. Applying the superposition principle, the maximum transient temperature after a large number of operating cycles will not exceed ∼138.1°C, satisfying the thermal budget under the current operating conditions. The benefit of the study is related to the possibility to extract the maximum/minimum temperatures for a real test involving a large number of heating-cooling cycles, yet maintaining the initial and peak temperatures within a certain range for the optimal operation of the device. The flow and heat transfer fields are thoroughly investigated: using a combination of numerical and analytical study, the thermal performance of the device undergoing large number of periodic thermal cycles is predicted. Further comparison between measurement and simulation results reveals good agreement.

Modeling Strategy in Evaluating Thermal Performance of an RF Module for Wireless Communications

2004 ◽  
Author(s):  
Victor Chiriac ◽  
Tien-Yu Tom Lee
Keyword(s):  
Thermal Performance ◽  
Thermal Characteristics ◽  
Simulation Models ◽  
Operating Conditions ◽  
Peak Temperature ◽  
Load Cells ◽  
Die Temperature ◽  
Rf Module ◽  
Modeling Strategy ◽  
The Impact

A detailed study was performed to evaluate the thermal performance of RF Modules and to identify meaningful correlations between specific design characteristics and the power dissipation needed to satisfy the required thermal budget under various critical operating conditions. The investigation focuses on the thermal characteristics of the RF module die layout and transistor cells, and on the thermal impact of the metallic air bridges connecting the load cells to the collector pads/vias to the overall thermal performance of the RF module. A first-pass modeling predicts higher temperatures than IR measurement, by ~20–30%. The addition of the die layout air bridges connecting the load cells in the detailed simulation models leads to a predicted air bridge temperature of ~9% higher than the IR measurement. Additional modeling reveals that between the open (not encapsulated) and the closed module, the die peak temperature differs by less than 3 °C, most of the heat being dissipated through the substrate and board to the heat stage. Thus, the impact of mold compound is insignificant. For a closed module, the mold compound helps dissipate the heat, so the die temperature is slightly cooler than for the open module (<<3°C). This suggests that the die peak temperature measured in an open module can be adjusted (by subtracting 2–3°C) to represent the die temperature in a closed module.

Circulation Effectiveness of Working Fluid in Inclined Micro Heat Pipes

2015 ◽  
Vol 789-790 ◽  
pp. 422-425
Author(s):  
Fun Liang Chang ◽  
Yew Mun Hung
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Pipes ◽  
Operating Conditions ◽  
Circulation Rate ◽  
Working Fluid ◽  
High Heat Flux ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

Micro heat pipe is a two-phase heat transfer device offering effective high heat-flux removal in electronics cooling. Essentially, micro heat pipe relies on the phase change processes, namely evaporation and condensation, and the circulation of working fluid to function as heat transfer equipment. The vast applications of micro heat pipe in portable appliances necessitate its functionality under different orientations with respect to gravity. Therefore, its thermal performance is strongly related to its orientation. By incorporating solid wall conduction, together with the continuity, momentum, and energy equations of the working fluid, a mathematical model is developed to investigate the heat and fluid flow characteristics of inclined micro heat pipes. We investigate both the favorable and adverse effects of gravity on the circulation rate which is intimately related to the thermal performance of micro heat pipes. The effects of gravity, through the angle of inclination, on the circulation strength and heat transport capacity are analysed. This study serves as a useful analytical tool in the micro heat pipe design and performance analysis, associated with different inclinations and operating conditions.

scholarly journals Researchon Impact of Nanofluids in Heat Pipes

2019 ◽  
Vol 8 (6S3) ◽  
pp. 1162-1165
Keyword(s):  
Heat Pipe ◽  
Heat Pipes ◽  
Operating Conditions ◽  
Working Fluid ◽  
Liquid Form ◽  
Intensity Effect ◽  
Energy Conserving ◽  
Solar Intensity ◽  
Total Capacity ◽  
The Impact

The basic aim of this study is to study the impact of nanofluids such as (Al2O3+Distilled water) in complete liquid form by dispensing aluminium oxide (fluid form) in base fluidand also to investigate the thermal performance of heat pipe solar collector using nanofluids under real operating conditions by theoretically and experimentally.The experimental setup is made with heat pipes and real time temperatures are measured for experimental efficiency. The theoretical investigation is to be done by using Computational Fluid Dynamics (CFD).The main innovation done in this experiment is the nanofluid prepared in complete fluid form without particles suspension to avoid the settling of nanoparticles in thermo syphon setup.For long term applications, we opted this method of preparing the fluid. The operating parameters to be considered are solar intensity, effect of tilt angle and effect of working fluid. Finally, the experimental output is to be compared with the theoretical one (CFD). The efficiency of theoretical was higher than experimental because ofassumptions considered in CFD. The nanofluid filled with 25% of total capacity of heat pipe i.e. 25ml/pipe.Heat pipes are best energy conserving technology for solar energy conversion.

Thermal Performance Evaluation of New Power QFN (Quad Flat No Lead) Packages for Automotive Applications

2004 ◽  
Author(s):  
Victor Chiriac ◽  
Tien-Yu Tom Lee
Keyword(s):  
Steady State ◽  
Thermal Performance ◽  
Numerical Study ◽  
Peak Temperature ◽  
Junction Temperature ◽  
Automotive Applications ◽  
Isothermal Boundary ◽  
Die Attach ◽  
Transient Thermal ◽  
The Impact

An extensive 3-D conjugate numerical study is conducted to assess the thermal performance of the novel Power Quad Flat No Lead (PQFN) packages for automotive applications. Several PQFN packages are investigated, ranging from smaller die/flag size to larger ones, single or multiple heat sources, operating under various powering and boundary conditions. The steady state and transient thermal performance are compared to those of the classical packages, and the impact of the thicker lead frame and die attach material on the overall thermal behavior is also evaluated. Under one steady state (1W) operating scenario, the PQFN package reaches a peak temperature of ~106.3°C, while under 37W@40ms of transient powering, the peak temperature reached by the corner FET is ~260.8°C. With an isothermal boundary (85°C) attached to the board backside, the junction temperature does not change, as the PCB has no significant thermal impact. However, when the isothermal boundary is attached to package bottom, it leads to a drop in by almost 20% after 40 ms. Additional transient cases are evaluated, with an emphasis on the superior thermal performance of this new class of power packages for automotive applications.

An Investigation of the Effect of interrupted fin arrangements on the Thermal Performance of a Heat Sink under a Free Convection Condition

2019 ◽  
Vol 7 (1) ◽  
pp. 43-53
Author(s):  
Abbas Jassem Jubear ◽  
Ali Hameed Abd
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Convection ◽  
Thermal Performance ◽  
Heat Sink ◽  
Numerical Study ◽  
Ansys Fluent ◽  
Fluent Software ◽  
Steady State Heat ◽  
Steady State Heat Transfer

The heat sink with vertically rectangular interrupted fins was investigated numerically in a natural convection field, with steady-state heat transfer. A numerical study has been conducted using ANSYS Fluent software (R16.1) in order to develop a 3-D numerical model.  The dimensions of the fins are (305 mm length, 100 mm width, 17 mm height, and 9.5 mm space between fins. The number of fins used on the surface is eight. In this study, the heat input was used as follows: 20, 40, 60, 80, 100, and 120 watts. This study focused on interrupted rectangular fins with a different arrangement and angle of the fins. Results show that the addition of interruption in fins in various arrangements will improve the thermal performance of the heat sink, and through the results, a better interruption rate as an equation can be obtained.

Steady-State Investigation of Vapor Deposited Micro Heat Pipe Arrays

1995 ◽  
Vol 117 (1) ◽  
pp. 75-81 ◽  
Author(s):  
A. K. Mallik ◽  
G. P. Peterson
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Surface Temperature ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Heat Pipes ◽  
Temperature Gradients ◽  
Bottom Surface ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

An experimental investigation of vapor deposited micro heat pipe arrays was conducted using arrays of 34 and 66 micro heat pipes occupying 0.75 and 1.45 percent of the cross-sectional area, respectively. The performance of wafers containing the arrays was compared with that of a plain silicon wafer. All of the wafers had 8 × 8 mm thermofoil heaters located on the bottom surface to simulate the active devices in an actual application. The temperature distributions across the wafers were obtained using a Hughes Probeye TVS Infrared Thermal Imaging System and a standard VHS video recorder. For wafers containing arrays of 34 vapor deposited micro heat pipes, the steady-state experimental data indicated a reduction in the maximum surface temperature and temperature gradients of 24.4 and 27.4 percent, respectively, coupled with an improvement in the effective thermal conductivity of 41.7 percent. For wafers containing arrays of 66 vapor deposited micro heat pipes, the corresponding reductions in the surface temperature and temperature gradients were 29.0 and 41.7 percent, respectively, and the effective thermal conductivity increased 47.1 percent, for input heat fluxes of 4.70 W/cm2. The experimental results were compared with the results of a previously developed numerical model, which was shown to predict the temperature distribution with a high degree of accuracy, for wafers both with and without the heat pipe arrays.

Understanding the Impact of Flow Bypass on the Thermal Performance of Air Cooled Heat Sinks

2014 ◽  
Author(s):  
Krishna Kota ◽  
Mohamed M. Awad
Keyword(s):  
Energy Conservation ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Sinks ◽  
Laminar Regime ◽  
Flow Energy ◽  
Factor Α ◽  
The Impact ◽  
Fundamental Mass

In this effort, theoretical modeling was employed to understand the impact of flow bypass on the thermal performance of air cooled heat sinks. Fundamental mass and flow energy conservation equations across a longitudinal fin heat sink configuration and the bypass region were applied and a generic parameter, referred as the Flow Bypass Factor (α), was identified from the theoretical solution that mathematically captures the effect of flow bypass as a quantifiable parameter on the junction-to-ambient thermal resistance of the heat sink. From the results obtained, it was found that, at least in the laminar regime, the impact of flow bypass on performance can be neglected for cases when the bypass gap is typically less than 5% of the fin height, and is almost linear at high relative bypass gaps (i.e., usually for bypass gaps that are more than 10–15% of the fin height). It was also found that the heat sink thermal resistance is more sensitive to small bypass gaps and the effect of flow bypass decreases with increasing bypass gap.

scholarly journals Integration of a Pulsating Heat Pipe in a Flat Plate Heat Sink

2014 ◽  
Author(s):  
Mitchell P. Hoesing ◽  
Gregory J. Michna
Keyword(s):  
Thermal Resistance ◽  
Flat Plate ◽  
Heat Pipe ◽  
Heat Sink ◽  
New Technologies ◽  
Operating Conditions ◽  
Working Fluid ◽  
High Heat Flux ◽  
Pulsating Heat Pipe ◽  
Plate Heat

The ongoing development of faster and smaller electronic components has led to a need for new technologies to effectively dissipate waste thermal energy. The pulsating heat pipe (PHP) shows potential to meet this need, due to its high heat flux capacity, simplicity, and low cost. A 20-turn flat plate PHP was integrated into an aluminum flat plate heat sink with a simulated electronic load. The PHP heat sink used water as the working fluid and had 20 parallel channels with dimensions 2 mm × 2 mm × 119 mm. Experiments were run under various operating conditions, and thermal resistance of the PHP was calculated. The performance enhancement provided by the PHP was assessed by comparing the thermal resistance of the heat sink with no working fluid to that of it charged with water. Uncharged, the PHP was found to have a resistance of 1.97 K/W. Charged to a fill ratio of approximately 75% and oriented vertically, the PHP achieved a resistance of .49 K/W and .53 K/W when the condenser temperature was set to 20°C and 30°C, respectively. When the PHP was tilted to 45° above horizontal the PHP had a resistance of .76 K/W and .59 K/W when the condenser was set 20°C and 30°C, respectively. The PHP greatly improves the heat transfer properties of the heat sink compared to the aluminum plate alone. Additional considerations regarding flat plate PHP design are also presented.

Development and Application of a Thin Flat Heat Pipe Design Optimization Tool for Small Satellite Systems

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Steven A. Isaacs ◽  
Caelan Lapointe ◽  
Peter E. Hamlington
Keyword(s):  
Computational Modeling ◽  
Cost Function ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Operating Conditions ◽  
Small Scale ◽  
Small Satellite ◽  
Modeling And Optimization ◽  
Satellite Systems ◽  
Flat Heat Pipe

Abstract With easier access to space and the growing integration of power-dense components, small-scale thermal management solutions are increasingly in demand for small satellite systems. Due to the strict mass and volume requirements commanded by such power-dense small spacecraft, heat pipes with thin and flat architectures provide nearly ideal solutions for the efficient transfer and dissipation of heat. Unlike traditional heat pipes, however, the performance of thin heat pipes is heavily dependent on details of the internal heat pipe structure, including the vapor core geometry and structural mechanical characteristics. In this study, the development and testing of a new computational modeling and optimization tool are presented for the design of thin flat heat pipes. The computational model is described in detail and includes parameters that define properties of the liquid wick, vapor core, and structural case. The model is coupled to a gradient-based optimization procedure that minimizes a multi-objective cost function for a range of operating conditions. The cost function is expressed as the weighted sum of the total temperature drop, the liquid/vapor pressure ratio, the total mass of the heat pipe, and the structural deflection of the heat pipe during operation. The combined computational modeling and optimization tool is then used to design a copper-methanol flat heat pipe for a small satellite mission, where the optimization is performed with respect to both cold and hot orbital conditions. Validation of the optimized heat pipe is performed using computational fluid dynamics (CFD) simulations of the initial and final designs.

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