Transient Analysis of Nonuniform Heat Input Propagation Through a Heat Sink Base

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Srivathsan Sudhakar ◽  
Justin A. Weibel
Keyword(s):  
Heat Source ◽  
Heat Input ◽  
Heat Sink ◽  
Three Dimensional ◽  
Temperature Response ◽  
Flow Distribution ◽  
Temporal Variations ◽  
Step Response ◽  
Dimensional System ◽  
Two Phase

For thermal management architectures wherein the heat sink is embedded close to a dynamic heat source, nonuniformities may propagate through the heat sink base to the coolant. Available transient models predict the effective heat spreading resistance to calculate chip temperature rise, or simplify to a representative axisymmetric geometry. The coolant-side temperature response is seldom considered, despite the potential influence on flow distribution and stability in two-phase microchannel heat sinks. This study solves three-dimensional transient heat conduction in a Cartesian chip-on-substrate geometry to predict spatial and temporal variations of temperature on the coolant side. The solution for the unit step response of the three-dimensional system is extended to any arbitrary temporal heat input using Duhamel's method. For time-periodic heat inputs, the steady-periodic solution is calculated using the method of complex temperature. As an example case, the solution of the coolant-side temperature response in the presence of different transient heat inputs from multiple heat sources is demonstrated. To represent a case where the thermal spreading from a heat source is localized, the problem is simplified to a single heat source at the center of the domain. Metrics are developed to quantify the degree of spatial and temporal nonuniformity in the coolant-side temperature profiles. These nonuniformities are mapped as a function of nondimensional geometric parameters and boundary conditions. Several case studies are presented to demonstrate the utility of such maps.

Transient Analysis of Non-Uniform Heat Input Propagation Through a Heat Sink Base

2016 ◽  
Author(s):  
Srivathsan Sudhakar ◽  
Justin A. Weibel
Keyword(s):  
Heat Sink ◽  
Temperature Response ◽  
Flow Distribution ◽  
Temporal Variations ◽  
Heat Sinks ◽  
Two Phase ◽  
Periodic Models ◽  
Temperature Solution ◽  
Periodic Heat ◽  
Complex Temperature

For thermal management architectures wherein the heat sink is embedded close to a dynamic heat source, non-uniformities may propagate through the heat sink base to the coolant. Available transient models predict the effective heat spreading resistance to calculate chip temperature rise, or simplify to a representative axisymmetric geometry. The coolant-side temperature response is seldom considered, despite the potential influence on flow distribution and stability in two-phase microchannel heat sinks. This study uses multi-dimensional transient and steady-periodic models to predict spatial and temporal variations of temperature within the heat sink base. The response to arbitrary transient heat inputs is obtained using Duhamel’s method. For time-periodic heat inputs, the steady-periodic solution is calculated using the method of complex temperature. Solution of the coolant-side temperature response in the presence of multiple different transient heat inputs is demonstrated. The degree of spatial and temporal non-uniformity in the coolant-side temperature profiles are mapped as a function of nondimensional geometric parameters and boundary conditions. Several case studies are presented to demonstrate the utility of such maps.

Mixed Convection of Impinging Air Cooling Over Heat Sink in Telecom System Application

2004 ◽  
Vol 126 (4) ◽  
pp. 519-523 ◽  
Author(s):  
Siddharth Bhopte ◽  
Musa S. Alshuqairi ◽  
Dereje Agonafer ◽  
Gamal Refai-Ahmed
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Mixed Convection ◽  
Heat Sink ◽  
Three Dimensional ◽  
Source Surface ◽  
Air Cooling ◽  
Transfer Rates ◽  
Nusselt Numbers ◽  
Air Jet

The current numerical investigation will examine the effect of an impinging mixed convection air jet on the heat transfer rate of a parallel flat plate heat sink. A three-dimensional numerical model was developed to evaluate the effects of the nozzle diameter d, nozzle-to-target vertical placement H/d, Rayleigh number, and the jet Reynolds number on the heat transfer rates from a discrete heat source. Simulations were performed for a Prandtl number of 0.7 and for Reynolds numbers ranging from 100 to 5000. The governing equations were solved in the dimensionless form using a commercial finite-volume package. Average Nusselt numbers were obtained, at H/d=3 and two jet diameters, for the bare heat source, for the heat source with a base heat sink, and for the heat source with the finned heat sink. The heat transfer rates from the bare heat source surface have been compared with the ones obtained with the heat sink in order to determine the overall performance of the heat sink in an impingement configuration.

A Review of Two-Phase Forced Cooling in Three-Dimensional Stacked Electronics: Technology Integration

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Craig Green ◽  
Peter Kottke ◽  
Xuefei Han ◽  
Casey Woodrum ◽  
Thomas Sarvey ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Sink ◽  
Three Dimensional ◽  
High Heat ◽  
Heat Fluxes ◽  
Thermal Design ◽  
High Heat Flux ◽  
Two Phase ◽  
Forced Cooling ◽  
Fluidic Routing

Three-dimensional (3D) stacked electronics present significant advantages from an electrical design perspective, ranging from shorter interconnect lengths to enabling heterogeneous integration. However, multitier stacking exacerbates an already difficult thermal problem. Localized hotspots within individual tiers can provide an additional challenge when the high heat flux region is buried within the stack. Numerous investigations have been launched in the previous decade seeking to develop cooling solutions that can be integrated within the 3D stack, allowing the cooling to scale with the number of tiers in the system. Two-phase cooling is of particular interest, because the associated reduced flow rates may allow reduction in pumping power, and the saturated temperature condition of the coolant may offer enhanced device temperature uniformity. This paper presents a review of the advances in two-phase forced cooling in the past decade, with a focus on the challenges of integrating the technology in high heat flux 3D systems. A holistic approach is applied, considering not only the thermal performance of standalone cooling strategies but also coolant selection, fluidic routing, packaging, and system reliability. Finally, a cohesive approach to thermal design of an evaporative cooling based heat sink developed by the authors is presented, taking into account all of the integration considerations discussed previously. The thermal design seeks to achieve the dissipation of very large (in excess of 500 W/cm2) background heat fluxes over a large 1 cm × 1 cm chip area, as well as extreme (in excess of 2 kW/cm2) hotspot heat fluxes over small 200 μm × 200 μm areas, employing a hybrid design strategy that combines a micropin–fin heat sink for background cooling as well as localized, ultrathin microgaps for hotspot cooling.

Modeling of Two-Phase Evaporative Heat Transfer in Three-Dimensional Multicavity High Performance Microprocessor Chip Stacks

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Yassir Madhour ◽  
Brian P. d'Entremont ◽  
Jackson Braz Marcinichen ◽  
Bruno Michel ◽  
John Richard Thome
Keyword(s):  
Integrated Circuit ◽  
Hot Spots ◽  
High Performance ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Simulation Method ◽  
Heat Fluxes ◽  
Signal Delay ◽  
Two Phase ◽  
Signal Delay Time

Three-dimensional (3D) stacking of integrated-circuit (IC) dies increases system density and package functionality by vertically integrating two or more dies with area-array through-silicon-vias (TSVs). This reduces the length of global interconnects and the signal delay time and allows improvements in energy efficiency. However, the accumulation of heat fluxes and thermal interface resistances is a major limitation of vertically integrated packages. Scalable cooling solutions, such as two-phase interlayer cooling, will be required to extend 3D stacks beyond the most modest numbers of dies. This paper introduces a realistic 3D chip stack along with a simulation method for the heat spreading and flow distribution among the channels of the evaporators. The model includes the significant sensitivity of each channel's friction factor to vapor quality, and hence mass flow to heat flux, which characterizes parallel two-phase flows. Simulation cases explore various placements of hot spots within the stack and effects which are unique to two-phase interlayer cooling. The results show that the effect of hot spots on individual dies can be mitigated by strong interlayer heat conduction if the relative position of the hot spots is selected carefully to result in a heat load and flow which are well balanced laterally.

Three-Dimensional Simulation of Thermoelectric Devices With Compact Numerical Models

2003 ◽  
Author(s):  
Eric Prather ◽  
Bhalchandra Puranik
Keyword(s):  
Heat Source ◽  
Heat Sink ◽  
Numerical Models ◽  
Three Dimensional ◽  
Electronics Cooling ◽  
Step Function ◽  
Compact Model ◽  
Zone Model ◽  
Detailed Model ◽  
Source Power

Thermoelectric cooling modules (TECs) are widely used within electronic equipment for both temperature reduction and control of individual components. The techniques presented in this paper demonstrate that it is possible to construct a simple three-zone model, that represents the transient and 3D properties of a typical TEC, and can be easily built within existing CFD software packages for a known electric current or voltage input. A comparison of compact model results, detailed model results, and experimental results is presented for a typical electronics cooling setup, including a heat source (from which heat is absorbed by the TEC), TEC device, and air-cooled heat sink. Variables examined include heat source power dissipation, TEC current, and heat sink airflow. Finally, the response of the setup to a step function in current is examined to investigate the transient performance of the compact model.

Numerical Modeling of Two-Phase Flow in a Bipolar Plate of a PEM Electrolyzer Cell

2008 ◽  
Author(s):  
Jianhu Nie ◽  
Yitung Chen ◽  
Robert F. Boehm
Keyword(s):  
Distribution System ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Bipolar Plate ◽  
Electrolysis Cell ◽  
Low Velocity ◽  
Two Phase ◽  
Bubble Generation ◽  
Oxygen Bubble

Optimization of electrolysis cell for producing hydrogen is dependent of a set of complex physical and chemical processes simultaneously occurring within the electrolysis cell. Similar to fuel cells, it has been demonstrated that these processes are strongly dependent on the fluid dynamics inside the electrolysis & fuel cell. Bipolar plates are important components of PEM electrolysis cells because they are the first stage of the flow distribution system. Numerical simulations were performed for three-dimensional two-phase water/oxygen flow in the anode side of a bipolar plate with a diagonal flow design. The water flowrate was maintained as constant of 260 ml/min, while the oxygen bubble generation rate was assumed to change from 0–0.014 g/s. Numerical results reveal that a minimum of the peak values of mainstream velocity component in the channels develops in the middle of the plate. Pressure drop and volume fraction of oxygen at the exit become higher as the oxygen bubble generation flowrate increases. The irregular velocity profile (locally low velocity magnitude near the exit port section) is not observed when the oxygen bubble flowrate is relatively low.

scholarly journals Numerically Investigating the Effects of Cross-Links in Scaled Microchannel Heat Sinks

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Minh Dang ◽  
Ibrahim Hassan ◽  
Sung In Kim
Keyword(s):  
Pressure Drop ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Heat Sinks ◽  
Straight Channel ◽  
Two Phase ◽  
Microchannel Heat Sinks ◽  
Cross Links ◽  
Channel Configuration

Thermal management as a method of heightening performance in miniaturized electronic devices using microchannel heat sinks has recently become of interest to researchers and the industry. One of the current challenges is to design heat sinks with uniform flow distribution. A number of experimental studies have been conducted to seek appropriate designs for microchannel heat sinks. However, pursuing this goal experimentally can be an expensive endeavor. The present work investigates the effect of cross-links on adiabatic two-phase flow in an array of parallel channels. It is carried out using the three-dimensional mixture model from the computational fluid dynamics software, FLUENT 6.3. A straight channel and two cross-linked channel models were simulated. The cross-links were located at 1/3 and 2/3 of the channel length, and their widths were one and two times larger than the channel width. All test models had 45 parallel rectangular channels, with a hydraulic diameter of 1.59 mm. The results showed that the trend of flow distribution agrees with experimental results. A new design, with cross-links incorporated, was proposed and the results showed a significant improvement of up to 55% on flow distribution compared with the standard straight channel configuration without a penalty in the pressure drop. Further discussion about the effect of cross-links on flow distribution, flow structure, and pressure drop was also documented.

Three Dimensional Velocity Measurements in an Automotive-Size Evaporator Using Particle Image Velocimetry

Volume 3 ◽  
2004 ◽  
Author(s):  
Steven P. O’Halloran ◽  
B. Terry Beck ◽  
Mohammad H. Hosni ◽  
Steven J. Eckels
Keyword(s):  
Particle Image Velocimetry ◽  
Single Phase ◽  
Particle Image ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Stereoscopic Particle Image Velocimetry ◽  
Experimental Results ◽  
Two Phase ◽  
Volume Fractions ◽  
Image Velocimetry

The flow distribution inside of an evaporator is important to fully understand in order to optimize the design of the evaporator. A stereoscopic particle image velocimetry (PIV) system was used to measure single-phase water flow in a Plexiglas model of an automotive-sized evaporator. The evaporator is a “U-shape” type. Flow enters the inlet header and travels through a series of 26 parallel rectangular tubes. The tubes have a width of 15.5-mm, a flow gap (thickness) of 0.9-mm, and a length of 231-mm. The flow then enters the upper header and flows through another series of 26 parallel tubes to the outlet header. PIV measurements were only made within the headers due to the small size of the tubes, however detailed results were observed. In addition to the single-phase experimental results, computational fluid dynamics (CFD) simulations were conducted using the commercially available software Fluent, and the results compare well to the experimental results. Further work was conducted by injecting nitrogen into the flow to obtain two-phase flow under adiabatic conditions. Due to high vapor volume fractions, PIV could not be used for flow measurement, but a volume collection method was used to measure the flow of water through each tube. Significantly different flow distributions were observed at different inlet volume fractions of nitrogen and further investigation is underway.

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