Dynamic Modeling of a Two-Phase On-Chip Cooling System Applied on Parallel High Performance Microprocessors

2013 ◽  
Author(s):  
Nicolas Lamaison ◽  
Jackson B. Marcinichen ◽  
John R. Thome
Keyword(s):  
Heat Flux ◽  
Heat Load ◽  
Cooling System ◽  
Saturation Temperature ◽  
Vapor Quality ◽  
Two Phase ◽  
Chip Temperature ◽  
High Heat Transfer ◽  
On Chip ◽  
Liquid Pump

Transient modeling and control of two-phase on-chip microevaporator cold plates of a liquid pump cooling cycle is studied. The purpose is to cool down multiple micro-processors in parallel and their auxiliary electronics (memories, DC/DC converters, etc.) in series. The cooling system is composed of multiple on-chip microevaporators in parallel, a condenser, a liquid accumulator, a liquid pump and all piping joining these components. In order to achieve high heat transfer and chip temperature uniformity, two-phase flow of HFC134a is considered for the coolant. The dynamics of the system are relevant aspects to be studied since the heat dissipated by the microprocessors is changing continuously. Thus, a new simulation code has been developed here to emulate the operation during transients. Such transient simulations allow us to verify whether critical heat flux (CHF) conditions are reached during heat load disturbances and to track the available heat at the condenser for energy recovery purposes. Presently, a case study with four microprocessors cooled in parallel flow is simulated considering different levels of uniform heat flux (36, 30, 25 and 10 Wcm−2), which showed the robustness of the predictive-corrective solver used. For a desired exit mixing vapor quality of 30%, at an inlet pressure and subcooling of respectively 16 bar (saturation temperature of 57.9 °C) and 2 K, the resulting distribution of the mass flow rates in the microevaporators were 3.6, 4.0, 4.5 and 7.4 kg/h (largest flow rate for lowest heat load) and the total pressure drop over the entire section was 0.6 kPa. The CHF and maximum chip temperature remained below of the critical limits. Preliminary comparisons with experimental tests showed errors in the predictions of mean chip temperature and mixing vapor quality to be within ±10%.

Embedded Two-Phase Cooling of High Flux Electronics via Micro-Enabled Surfaces and Fluid Delivery Systems (FEEDS)

2015 ◽  
Author(s):  
Raphael Mandel ◽  
Serguei Dessiatoun ◽  
Patrick McCluskey ◽  
Michael Ohadi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Saturation Temperature ◽  
Absolute Pressure ◽  
High Flux ◽  
Vapor Quality ◽  
Two Phase ◽  
Fluid Delivery ◽  
Future Work

This work presents the experimental design and testing of a two-phase, embedded manifold-microchannel cooler for cooling of high flux electronics. The ultimate goal of this work is to achieve 0.025 cm2-K/W thermal resistance at 1 kW/cm2 heat flux and evaporator exit vapor qualities at or exceeding 90% at less than 10% absolute pressure drop. While the ultimate goal is to obtain a working two-phase embedded cooler, the system was first tested in single-phase mode to validate system performance via comparison of experimentally measured heat transfer coefficient and pressure drop to the values predicted by CFD simulations. Upon validation, the system was tested in two phase mode using R245fa at 30°C saturation temperature and achieved in excess of 1 kW/cm2 heat flux at 45% vapor quality. Future work will focus on increasing the exit vapor quality as well as use of SiC for the heat transfer surface upon completion of current experiments with Si.

Two-Phase Flow Control of Electronics Cooling With Pseudo-CPUs in Parallel Flow Circuits: Dynamic Modeling and Experimental Evaluation

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Nicolas Lamaison ◽  
Jackson Braz Marcinichen ◽  
John Richard Thome
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Flow Control ◽  
Parallel Flow ◽  
Heat Fluxes ◽  
Vapor Quality ◽  
Two Phase ◽  
Cooling Cycle ◽  
Chip Temperature ◽  
Test Loop

On-chip two-phase cooling of parallel pseudo-CPUs integrated into a liquid pumped cooling cycle is modeled and experimentally verified versus a prototype test loop. The system's dynamic operation is studied since the heat dissipated by microprocessors is continuously changing during their operation and critical heat flux (CHF) conditions in the microevaporator must be avoided by flow control of the pump speed during heat load disturbances. The purpose here is to cool down multiple microprocessors in parallel and their auxiliary electronics (memories, dc/dc converters, etc.) to emulate datacenter servers with multiple CPUs. The dynamic simulation code was benchmarked using the test results obtained in an experimental facility consisting of a liquid pumped cooling cycle assembled in a test loop with two parallel microevaporators, which were evaluated under steady-state and transient conditions of balanced and unbalanced heat fluxes on the two pseudochips. The errors in the model's predictions of mean chip temperature and mixed exit vapor quality at steady state remained within ±10%. Transient comparisons showed that the trends and the time constants were satisfactorily respected. A case study considering four microprocessors cooled in parallel flow was then simulated for different levels of heat flux in the microprocessors (40, 30, 20, and 10 W cm−2), which showed the robustness of the predictive-corrective solver used. For a desired mixed vapor exit quality of 30%, at an inlet pressure and subcooling of 1600 kPa and 3 K, the resulting distribution of mass flow rate in the microevaporators was, respectively, 2.6, 2.9, 4.2, and 6.4 kg h−1 (mass fluxes of 47, 53, 76 and 116 kg m−2 s−1) and yielded approximately uniform chip temperatures (maximum variation of 2.6, 2, 1.7, and 0.7 K). The vapor quality and maximum chip temperature remained below the critical limits during both transient and steady-state regimes.

Model Predictive Control of a Pumped Two-Phase Cooling System With Microchannel Heat Exchangers

2018 ◽  
Author(s):  
Oyuna Angatkina ◽  
Andrew Alleyne
Keyword(s):  
Heat Flux ◽  
Model Predictive Control ◽  
Predictive Control ◽  
Heat Exchangers ◽  
Cooling System ◽  
High Heat ◽  
High Heat Flux ◽  
Two Phase ◽  
Cooling Systems ◽  
Two Phase Cooling

Two-phase cooling systems provide a viable technology for high–heat flux rejection in electronic systems. They provide high cooling capacity and uniform surface temperature. However, a major restriction of their application is the critical heat flux condition (CHF). This work presents model predictive control (MPC) design for CHF avoidance in two-phase pump driven cooling systems. The system under study includes multiple microchannel heat exchangers in series. The MPC controller performance is compared to the performance of a baseline PI controller. Simulation results show that while both controllers are able to maintain the two-phase cooling system below CHF, MPC has significant reduction in power consumption compared to the baseline controller.

Minimizing the Effects of On-Chip Hotspots Using Multi-Objective Optimization of Flow Distribution in Water-Cooled Parallel Microchannel Heatsinks

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Yaser Hadad ◽  
Vahideh Radmard ◽  
Srikanth Rangarajan ◽  
Mahdi Farahikia ◽  
Gamal Refai-Ahmed ◽  
...  
Keyword(s):  
Flow Distribution ◽  
System Level ◽  
Temperature Uniformity ◽  
Liquid Cooling ◽  
Two Phase ◽  
Chip Area ◽  
Chip Temperature ◽  
Cooling Design ◽  
On Chip ◽  
Novel Concept

Abstract The industry shift to multicore microprocessor architecture will likely cause higher temperature nonuniformity on chip surfaces, exacerbating the problem of chip reliability and lifespan. While advanced cooling technologies like two phase embedded cooling exist, the technological risks of such solutions make conventional cooling technologies more desirable. One such solution is remote cooling with heatsinks with sequential conduction resistance from chip to module. The objective of this work is to numerically demonstrate a novel concept to remotely cool chips with hotspots and maximize chip temperature uniformity using an optimized flow distribution under constrained geometric parameters for the heatsink. The optimally distributed flow conditions presented here are intended to maximize the heat transfer from a nonuniform chip power map by actively directing flow to a hotspot region. The hotspot-targeted parallel microchannel liquid cooling design is evaluated against a baseline uniform flow conventional liquid cooling design for the industry pressure drop limit of approximately 20 kPa. For an average steady-state heat flux of 145 W/cm2 on core areas (hotspots) and 18 W/cm2 on the remaining chip area (background), the chip temperature uniformity is improved by 10%. Moreover, the heatsink design has improved chip temperature uniformity without a need for any additional system level complexity, which also reduces reliability risks.

Two Large-Amplitude/Long-Period Oscillating Boiling Modes in Silicon Microchannels

2003 ◽  
Author(s):  
H. Y. Wu ◽  
Ping Cheng
Keyword(s):  
Heat Flux ◽  
Water Temperature ◽  
Large Amplitude ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
Saturation Temperature ◽  
Phase Flow ◽  
Two Phase ◽  
Long Period

A simultaneous visualization and measurement study has been carried out to investigate flow boiling of water in the 8 parallel silicon microchannels heated from below. It is found that there are two large-amplitude/long-period oscillating boiling modes exist in microchannels depending on the amounts of heat flux and mass flux. When the outlet water temperature is at saturation temperature and the wall temperatures are superheated, while the inlet water temperature is still subcooled, a Liquid/Two-phase Alternating Flow (LTAF) mode appears in the microchannels. This LTAF mode disappears when the inlet temperatures reaches the saturation temperature. As the heat flux is further increased such that the outlet water is superheated while the inlet water temperature is oscillating between subcooled and saturation temperature, a Liquid/Two-phase/Vapor Alternating Flow (LTVAF) mode begins. During these two unstable boiling modes, there are large-amplitude and long-period oscillations of water and wall temperatures with respect to time. Bubbly flow as well as some peculiar two-phase flow pattern are observed during the two-phase flow periods of the two unstable modes in the microchannels.

Experimental evaluation of a compact two-phase cooling system for high heat flux electronic packages

2019 ◽  
Vol 163 ◽  
pp. 114338 ◽  
Author(s):  
Fengze Hou ◽  
Wenbo Wang ◽  
Hengyun Zhang ◽  
Cheng Chen ◽  
Chuan Chen ◽  
...  
Keyword(s):  
Heat Flux ◽  
Experimental Evaluation ◽  
Cooling System ◽  
High Heat ◽  
High Heat Flux ◽  
Electronic Packages ◽  
Two Phase ◽  
Two Phase Cooling

Visualization of the Heat Transfer Enhancement During Condensation in a Microfin Tube

2006 ◽  
Author(s):  
Alberto Cavallini ◽  
Davide Del Col ◽  
Luca Doretti ◽  
Simone Mancin ◽  
Luisa Rossetto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Saturation Temperature ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Vapor Quality ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Plain Tube ◽  
The Heat Transfer Coefficient

Microfins tubes are largely used in refrigeration industry for in-tube refrigerant condensation, because of the heat transfer enhancement when compared to equivalent smooth tubes under the same operating conditions. But not much evidence about the effect of microfins on the condensation flow patterns is available in the open literature. There is agreement in the open literature that the mechanisms of heat transfer are intimately linked with the prevailing two-phase flow regime. The present authors have recently measured the heat transfer coefficient during condensation of R410A in a microfin tube. The heat transfer enhancement in this tube can be experimentally evaluated by comparing those coefficients to the ones measured by Cavallini et al. (2001) in a plain tube, at the same operating conditions. The same operative conditions (saturation temperature, vapor quality and mass flux), occurring during the heat transfer measurements, were reproduced in a different section for visualization of flow patterns during condensation of R410A. The flow visualization has been carried out both in the plain tube and in the microfin tube. The objective of the present paper is to present the heat transfer enhancement during condensation of R410A and to show the flow visualized at the same operating condition for both the smooth and the microfin tube, aiming to link the heat transfer enhancement to the flow pattern variation.

Effects of Orientation on Critical Heat Flux From Chip Arrays During Flow Boiling

1992 ◽  
Vol 114 (3) ◽  
pp. 290-299 ◽  
Author(s):  
C. O. Gersey ◽  
I. Mudawar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Single Phase ◽  
Cooling System ◽  
Flow Boiling ◽  
Flow Channel ◽  
Two Phase ◽  
Channel Orientation ◽  
Two Phase Cooling ◽  
Layer Development

Boiling experiments were performed with FC-72 on a series of nine in-line simulated microelectronic chips in a flow channel to ascertain the effects of channel orientation on critical heat flux (CHF). The simulated chips, measuring 10 mm × 10 mm, were flush-mounted to one wall of a 20 mm × 5 mm flow channel. The channel was rotated in increments of 45 degrees through 360 degrees such that the chips were subjected to coolant in upflow, downflow, or horizontal flow with the chips on the top or bottom walls of the channel with respect to gravity. Flow velocity was varied between 13 and 400 cm/s for subcoolings of 3, 14, 25, and 36°C and an inlet pressure of 1.36 bar. While changes in angle of orientation produced insignificant variations in the single-phase heat transfer coefficient, these changes had considerable effects on the boiling pattern in the flow channel and on CHF for velocities below 200 cm/s,’ with some chips reaching CHF at fluxes as low as 18 percent of those corresponding to vertical upflow. Increased subcooling was found to slightly dampen this adverse effect of orientation. The highest CHF values were measured with near vertical upflow and/or upward-facing chips, while the lowest values were measured with near vertical downflow and/or downward-facing chips. These variations in CHF were attributed to differences in flow boiling regime and vapor layer development on the surfaces of the chips between the different orientations. The results of the present study reveal that, while some flexibility is available in the packaging of multi-chip modules in a two-phase cooling system, some orientations should always be avoided.

Breakdown of a Locally Heated Liquid Film Shear-Driven in a Minichannel

2006 ◽  
Author(s):  
D. V. Zaitsev ◽  
O. A. Kabov
Keyword(s):  
Heat Flux ◽  
Liquid Film ◽  
High Speed ◽  
Cooling System ◽  
Flow Regimes ◽  
High Heat ◽  
Liquid Films ◽  
High Heat Flux ◽  
Film Breakdown ◽  
High Heat Transfer

The paper focuses upon shear-driven liquid film evaporative cooling of high-speed computer chips. Thin liquid films may provide very high heat transfer rates, however development of cooling system based on thin film technology requires significant advances in fundamental research. The paper presents new experimental data on flow and breakdown of a liquid film driven by the action of a forced gas flow in a horizontal minichannel (2 mm high), heated from a 22×6.55 mm heater. A map of isothermal flow regimes is plotted and the lengths of smooth region and region of 2D/3D wave occurrence are measured. The scenario of liquid film breakdown under heating is found to differ widely for different flow regimes. It is revealed that the critical heat flux at which film breakdown occurs for a shear-driven liquid film can be several times higher than that for a gravitationally-driven liquid film. This fact makes shear-driven liquid films very promising in high heat flux cooling applications.

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