scholarly journals Recent Advances in High-Flux, Two-Phase Thermal Management

2013 ◽  
Vol 5 (2) ◽  
Author(s):  
Issam Mudawar
Keyword(s):  
Dissipation Rate ◽  
Heat Dissipation ◽  
Future Research ◽  
Air Cooling ◽  
High Flux ◽  
Computer Algorithms ◽  
Two Phase ◽  
Computer Data ◽  
Predictive Tools ◽  
Two Phase Cooling

Recent developments in applications such as computer data centers, electric vehicle power electronics, avionics, radars, and lasers have led to alarming increases in heat dissipation rate, which now far exceeds the capability of air cooling schemes and even the most aggressive single-phase liquid cooling schemes. This trend is responsible for a recent transition to two-phase cooling, which capitalizes upon the coolant's latent heat rather than sensible heat alone to achieve several order-of-magnitude increases in heat transfer coefficient. Three two-phase cooling configurations have surfaced as best contenders for the most demanding applications: mini/microchannel, jet, and spray. This study will explore the implementation of these configurations into practical cooling packages, assess available predictive tools, and identify future research needs for each. It is shown that the design and performance assessment of high-flux, two-phase cooling systems are highly dependent on empirical or semiempirical predictive tools and, to a far lesser extent, theoretical mechanistic models. A major challenge in using such tools is the lack of databases for coolants with drastically different thermophysical properties, and which cover broad ranges of such important parameters as flow passage size, mass velocity, quality, and pressure. Recommendations are therefore made for future research to correct any critical knowledge gaps, including the need for robust computer algorithms. Also discussed is a new class of “hybrid” cooling schemes that capitalize upon the merits of multiple cooling configurations. It is shown that these hybrid schemes not only surpass the basic cooling configurations in heat dissipation rate, but they also provide better surface temperature uniformity.

scholarly journals Recent Advances in High-Flux, Two-Phase Thermal Management

2013 ◽  
Author(s):  
Issam Mudawar
Keyword(s):  
Dissipation Rate ◽  
Heat Dissipation ◽  
Future Research ◽  
Air Cooling ◽  
High Flux ◽  
Computer Algorithms ◽  
Two Phase ◽  
Computer Data ◽  
Predictive Tools ◽  
Two Phase Cooling

Recent developments in applications such as computer data centers, electric vehicle power electronics, avionics, radars and lasers have led to alarming increases in heat dissipation rate, which now far exceeds the capability of air cooling schemes and even the most aggressive single-phase liquid cooling schemes. This trend is responsible for a recent transition to two-phase cooling, which capitalizes upon the coolant’s latent heat rather than sensible heat alone to achieve several order-of-magnitude increases in heat transfer coefficient. Three two-phase cooling configurations have surfaced as top contenders for the most demanding applications: mini/micro-channel, jet and spray. This study will explore the implementation of these configurations into practical cooling packages, assess available predictive tools, and identify future research needs for each. It is shown that the design and performance assessment of high-flux, two-phase cooling systems are highly dependent on empirical or semi-empirical predictive tools and, to a far lesser extent, theoretical mechanistic models. A major challenge in using such tools is the lack of databases for coolants with drastically different thermophysical properties, and which cover broad ranges of such important parameters as flow passage size, mass velocity, quality and pressure. Recommendations are therefore made for future research to correct any critical knowledge gaps, including the need for robust computer algorithms. Also discussed is a new class of ‘hybrid’ cooling schemes that capitalize upon the merits of multiple cooling configurations. It is shown that these hybrid schemes not only surpass the basic cooling configurations in heat dissipation rate, but they also provide better surface temperature uniformity.

Active Flow Instability Control for Transient Two-Phase Electronics Cooling

2010 ◽  
Author(s):  
Tie Jun Zhang ◽  
Yoav Peles ◽  
John T. Wen ◽  
Michael K. Jensen
Keyword(s):  
Active Control ◽  
Flow Instability ◽  
Cooling System ◽  
Flow Instabilities ◽  
Future Research ◽  
Two Phase ◽  
Control Schemes ◽  
Boiling Flow ◽  
Flow Oscillations ◽  
Two Phase Cooling

Because of increasing power densities, refrigeration systems are being explored for two-phase cooling of ultra high power electronic components. Flow instabilities are potential problems in any two-phase refrigeration cooling system especially in transient applications. Oscillatory two-phase flow in a boiling channel can trigger transition to the critical heat flux (CHF). Active control methods can help better dynamic thermal management of electronic systems, even though transient two-phase boiling flow mechanisms are complicated. This paper presents a framework for the transient analysis and active control of pressure-drop flow instabilities under varying imposed heat loads. The first part of the paper is to study the external effects on boiling flow characteristics and the boiling oscillatory flow responses to transient heat load changes. Then based on the theoretical analysis of boiling flow oscillations, a set of active control schemes are developed and studied to suppress flow oscillations and, therefore, to increase the CHF. With the available control devices (i.e., inlet valve and supply pump), different active control schemes are studied to improve the transient two-phase cooling performance. Finally, a discussion is included to address potential future research.

Cooling of High Powered GPUs Using Liquid Nitrogen Cold Plates Made With Additive Manufacturing

2021 ◽  
Author(s):  
Alec Nordlund ◽  
Rachel McAfee ◽  
Rebecca Ledsham ◽  
Joshua Gess
Keyword(s):  
Additive Manufacturing ◽  
Liquid Nitrogen ◽  
Data Center ◽  
Power Efficiency ◽  
Thermal Design ◽  
Cryogenic Cooling ◽  
Air Cooling ◽  
Two Phase ◽  
Computational Performance ◽  
Two Phase Cooling

Abstract Processor energy density is exceeding the capabilities of conventional air-cooling technology, but two-phase cooling has the potential to manage these resulting heat fluxes at reliable temperatures and higher electrical efficiency. When two-phase cooling is used in tandem with overclocking, data center footprints are reduced as individual chip processing power can be set at limits well beyond the manufacturer’s Thermal Design Power (TDP) or nominal operating condition. This study examines how Liquid Nitrogen (LN2) can be used with Additive Manufacturing (AM) and overclocking to increase the computational performance of a commercially available GPU. The power consumption and frequency relationship were established for both the cryogenically cooled solution and a comparative air-cooled solution. The cryogenic solution saw up to a 17.4% increase in compute efficiency and an 18.1% improvement in compute speed with comparable power efficiency at an equivalent performance level to the air-cooled solution. This study considers the computational performance and efficiency gains that can be acquired through cryogenic cooling on an individual graphics card, which can be replicated on a larger scale in data center applications.

Blading Heat Transfer Considerations in a Reheat-Gas-Turbine Combined Cycle

1981 ◽  
Author(s):  
P. E. Jenkins ◽  
I. G. Rice
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Steam Injection ◽  
Combined Cycle ◽  
Future Research ◽  
Air Cooling ◽  
Two Phase ◽  
Cooling Fluid ◽  
Cycle System ◽  
Transfer Equations

A brief presentation of the basic heat transfer equations for blade cooling is presented. Various cooling schemes have been developed over the past twenty years utilizing air as the cooling fluid. The mathematical models have subsequently predicted cooling schemes for the air cooling with little consideration for two phase fluids. This paper is written to describe the research needs for utilizing steam as a cooling fluid in a reheat-gas-turbine combined cycle system. The basic heat transfer equations are derived and discussed with regard to implementing the steam blanket cooling mechanism. The steam injection and dispersion problem is discussed, along with the need for future research in using steam as a viable cooling technique.

An Assessment of Effects of Nanofluids on Heat Transfer Performance of Two-Phase Cooling Systems

2021 ◽  
Author(s):  
Alexander V. Korobko ◽  
Sana Fateh
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Data Centers ◽  
Heat Transfer Performance ◽  
Future Research ◽  
Transfer Performance ◽  
Two Phase ◽  
Cooling Systems ◽  
The Impact ◽  
Two Phase Cooling

Abstract The recent increase in complexity of computations and the expansion of edge computing have led to the emergence of high power density data centers with an urgent demand for more advanced thermal management systems. Two-phase passive cooling systems such as thermosyphons and heat pipes have been widely used in industry to maintain the temperature of the servers below the threshold of failure and carry away a large quantity of heat from a small area. Such systems are economically viable and sustainable since they have no moving parts and consume lower power. However, an upgrade to these cooling systems is imminent due to the ever-increasing power densities of the data centers and more challenging thermal management issues faced by the industry. Nanofluids have emerged recently as a new class of cooling liquids claiming to enhance the heat transfer performance in single and two-phase cooling systems. As per several studies presented in this paper, the thermal performance of thermosyphons is shown to be enhanced by employing nanofluids. In this paper, a comprehensive review is presented on the effect of nanofluids in improving the Critical Heat Flux (CHF) and Heat Transfer Coefficient (HTC) in two-phase cooling systems. The boiling phenomenon and working principles of thermosyphons will be discussed to understand the underlying mechanisms affecting heat transfer in the evaporator region, where the heat is absorbed from the source. The impact of nanoparticle features, concentration, and deposition pattern on HTC enhancement will also be studied. Additionally, estimates of the heat dissipation improvement by using nanofluids along with the bottlenecks and challenges faced in applying such fluids practically are reviewed as well. In conclusion, recommendations are made for future research needed to overcome the risks and commercialize the nanofluids in two-phase cooling systems for providing significant improvement in heat transfer performance as compared to conventional working fluids.

Study on Alternative Cooling Methods Beyond Next Generation Microprocessors

2003 ◽  
Author(s):  
Albert Chan ◽  
Jie Wei
Keyword(s):  
Heat Dissipation ◽  
Low Cost ◽  
Ambient Pressure ◽  
Operating Conditions ◽  
Heat Sinks ◽  
Air Cooling ◽  
Liquid Cooling ◽  
Two Phase ◽  
Field Service ◽  
Cooling Methods

Feasibility study on alternative cooling methods to air-cooling with heat sinks is provided in this paper. The study focuses on cooling of 64-bit microprocessor at 80nm technology node with projected heat dissipation of 200W. An example was presented to illustrate limitation of air-cooling for the 200W microprocessor using an all-Cu heat sink with tall fins. Three alternatives to air-cooling were studied in this work: liquid cooling, two-phase convective flow cooling and refrigeration cooling. Thermodynamic analysis was used to estimate operating conditions and fluid flow rates for each alternative. The information provides a preliminary basis for assessing capabilities and weaknesses among alternatives. Liquid and two-phase cooling simply transfer heat from high to low temperature. In contrast, refrigeration cooling operates as a heat pump, moving heat from low to high temperature. Refrigeration cooling offers capability to cool microprocessor (LSI) chip to temperatures below ambient or freezing. The drawback is more heat must be removed from the system. Liquid cooling operates at close to ambient pressure, while two-phase and refrigeration cooling operate at higher pressures. Challenges to implementation of all three alternatives include availability of low cost, miniature components (pumps or compressors, heat exchanger and condenser), designing for redundancy (or reliability) and ease of installation and field service. In terms of component availability and cost, liquid cooling is preferred choice, followed by two-phase and refrigeration cooling.

Effects of Varying Geometrical Parameters on Boiling From Microfabricated Enhanced Structures

2003 ◽  
Vol 125 (1) ◽  
pp. 103-109 ◽  
Author(s):  
C. Ramaswamy ◽  
Y. Joshi ◽  
W. Nakayama ◽  
W. B. Johnson
Keyword(s):  
Heat Dissipation ◽  
Layer Structure ◽  
Single Layer ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Small Range ◽  
Two Phase ◽  
Wall Superheat

The current study involves two-phase cooling from enhanced structures whose dimensions have been changed systematically using microfabrication techniques. The aim is to optimize the dimensions to maximize the heat transfer. The enhanced structure used in this study consists of a stacked network of interconnecting channels making it highly porous. The effect of varying the pore size, pitch and height on the boiling performance was studied, with fluorocarbon FC-72 as the working fluid. While most of the previous studies on the mechanism of enhanced nucleate boiling have focused on a small range of wall superheats (0–4 K), the present study covers a wider range (as high as 30 K). A larger pore and smaller pitch resulted in higher heat dissipation at all heat fluxes. The effect of stacking multiple layers showed a proportional increase in heat dissipation (with additional layers) in a certain range of wall superheat values only. In the wall superheat range 8–13 K, no appreciable difference was observed between a single layer structure and a three layer structure. A fin effect combined with change in the boiling phenomenon within the sub-surface layers is proposed to explain this effect.

scholarly journals Numerical Study of a Cooling System Using Phase Change of a Refrigerant in a Thermosyphon

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3634
Author(s):  
Grzegorz Czerwiński ◽  
Jerzy Wołoszyn
Keyword(s):  
Mass Transfer ◽  
Phase Change ◽  
Heat Dissipation ◽  
Cooling System ◽  
Numerical Study ◽  
Relaxation Parameter ◽  
Phase Changes ◽  
Transfer Time ◽  
Two Phase ◽  
Time Relaxation

With the increasing trend toward the miniaturization of electronic devices, the issue of heat dissipation becomes essential. The use of phase changes in a two-phase closed thermosyphon (TPCT) enables a significant reduction in the heat generated even at high temperatures. In this paper, we propose a modification of the evaporation–condensation model implemented in ANSYS Fluent. The modification was to manipulate the value of the mass transfer time relaxation parameter for evaporation and condensation. The developed model in the form of a UDF script allowed the introduction of additional source equations, and the obtained solution is compared with the results available in the literature. The variable value of the mass transfer time relaxation parameter during condensation rc depending on the density of the liquid and vapour phase was taken into account in the calculations. However, compared to previous numerical studies, more accurate modelling of the phase change phenomenon of the medium in the thermosyphon was possible by adopting a mass transfer time relaxation parameter during evaporation re = 1. The assumption of ten-fold higher values resulted in overestimated temperature values in all sections of the thermosyphon. Hence, the coefficient re should be selected individually depending on the case under study. A too large value may cause difficulties in obtaining the convergence of solutions, which, in the case of numerical grids with many elements (especially three-dimensional), significantly increases the computation time.

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