Modeling Size Effects of a Portable Two-Phase Electronics Cooling Loop With Different Refrigerants

2010 ◽  
Author(s):  
Tom Saenen ◽  
Martine Baelmans
Keyword(s):  
Size Effects ◽  
Cooling System ◽  
Electronics Cooling ◽  
Simple Algorithm ◽  
System Model ◽  
Two Phase ◽  
Component Mixture ◽  
Pressure Losses ◽  
Microchannel Cooling ◽  
Cooling Loop

A one dimensional dynamic system model is developed to accurately simulate a two-phase microchannel electronics cooling loop. This model is based on the single component mixture equations for mass, momentum and energy. These equations are solved numerically using a finite volume method in conjunction with the SIMPLE algorithm. To calculate the pressure losses and heat transfer state of the art empirical correlations are used. Furthermore size effects of a typical microchannel cooling system are investigated with the new model. Special attention is given to the accumulator size and its limitations for portable applications. A simple model to investigate the accumulator size effect on the loop is developed and compared to numerical results obtained from the system model. The influence of various loop parameters and possible improvements are also investigated. Finally the effect of using different coolants is studied.

A Novel Electronics Cooling System Using Water Heat Pipes Under Freezing Conditions

2003 ◽  
Author(s):  
Osamu Suzuki ◽  
Atsuo Nishihara
Keyword(s):  
Prediction Model ◽  
Thermal Resistance ◽  
Ambient Temperature ◽  
Cooling System ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
System Model ◽  
Cooling Performance ◽  
Temperature Range ◽  
Metal Block

A novel electronics cooling system that uses water heat pipes under an ambient temperature range from −30°C to 40°C has been developed. The system consists of several water heat pipes, air-cooled fins, and a metal block. The heat pipes are separated into two groups according to the thermal resistance of their fins. One set of heat pipes, which have fins with higher thermal resistance, operates under an ambient temperature range from −30°C to 40°C. The other set, which have lower resistance, operates from 0°C to 40°C. A prediction model based on the frozen-startup limitation of a single heat pipe was first devised and experimentally verified. Then, a prediction model for the whole-system was formulated according to the former model. The whole-system model was used to design a prototype cooling system, and it was confirmed that the prototype has a suitable cooling performance for an environmentally friendly electronics cooling system.

Experimental Validation and Design Simulations of a Passive Two-Phase Cooling System for Datacenters

2020 ◽  
Author(s):  
Jackson B. Marcinichen ◽  
John R. Thome ◽  
Raffaele L. Amalfi ◽  
Filippo Cataldo
Keyword(s):  
Thermal Performance ◽  
Experimental Validation ◽  
Cooling System ◽  
Electronics Cooling ◽  
Operating Conditions ◽  
Two Phase ◽  
Data Set ◽  
Pressure Drops ◽  
Wide Range ◽  
Important Challenge

Abstract Thermosyphon cooling systems represent the future of datacenter cooling, and electronics cooling in general, as they provide high thermal performance, reliability and energy efficiency, as well as capture the heat at high temperatures suitable for many heat reuse applications. On the other hand, the design of passive two-phase thermosyphons is extremely challenging because of the complex physics involved in the boiling and condensation processes; in particular, the most important challenge is to accurately predict the flow rate in the thermosyphon and thus the thermal performance. This paper presents an experimental validation to assess the predictive capabilities of JJ Cooling Innovation’s thermosyphon simulator against one independent data set that includes a wide range of operating conditions and system sizes, i.e. thermosyphon data for server-level cooling gathered at Nokia Bell Labs. Comparison between test data and simulated results show good agreement, confirming that the simulator accurately predicts heat transfer performance and pressure drops in each individual component of a thermosyphon cooling system (cold plate, riser, evaporator, downcomer (with no fitting parameters), and eventually a liquid accumulator) coupled with operational characteristics and flow regimes. In addition, the simulator is able to design a single loop thermosyphon (e.g. for cooling a single server’s processor), as shown in this study, but also able to model more complex cooling architectures, where many thermosyphons at server-level and rack-level have to operate in parallel (e.g. for cooling an entire server rack). This task will be performed as future work.

Performance Assessment of Single and Multiple Jet Impingement Configurations in a Refrigeration-Based Compact Heat Sink for Electronics Cooling

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Pablo A. de Oliveira ◽  
Jader R. Barbosa
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Cooling System ◽  
Electronics Cooling ◽  
Jet Impingement ◽  
Small Scale ◽  
Two Phase ◽  
R 134A ◽  
Steady State Heat Transfer ◽  
Vapor Compression Cooling

The performance of a novel impinging two-phase jet heat sink operating with single and multiple jets is presented and the influence of the following parameters is quantified: (i) thermal load applied on the heat sink and (ii) geometrical arrangement of the orifices (jets). The heat sink is part of a vapor compression cooling system equipped with an R-134a small-scale oil-free linear motor compressor. The evaporator and the expansion device are integrated into a single cooling unit. The expansion device can be a single orifice or an array of orifices responsible for the generation of two-phase jet(s) impinging on a surface where a concentrated heat load is applied. The analysis is based on the thermodynamic performance and steady-state heat transfer parameters associated with the impinging jet(s) for single and multiple orifice tests. The two-phase jet heat sink was capable of dissipating cooling loads of up to 160 W and 200 W from a 6.36 cm2 surface for single and multiple orifice configurations, respectively. For these cases, the temperature of the impingement surface was kept below 40 °C and the average heat transfer coefficient reached values between 14,000 and 16,000 W/(m2 K).

Role of a Liquid Accumulator in a Passive Two-Phase Liquid Cooling System for Electronics: Experimental Analysis

2017 ◽  
Author(s):  
Nicolas Lamaison ◽  
Raffaele L. Amalfi ◽  
Jackson B. Marcinichen ◽  
John R. Thome ◽  
Todd Salamon
Keyword(s):  
Cooling System ◽  
Flow Boiling ◽  
Relative Size ◽  
Electronics Cooling ◽  
Filling Ratio ◽  
Liquid Cooling ◽  
Two Phase ◽  
Wide Range ◽  
Phase Liquid ◽  
Liquid Cooling System

Gravity-driven two-phase liquid cooling systems using flow boiling within micro-scale evaporators are becoming a game-changing solution for electronics cooling. The optimization of the system’s filling ratio can however become a challenging problem for a system operating over a wide range of cooling capacities and temperature ranges. The benefits of a liquid accumulator to overcome this difficulty are evaluated in the present paper. An experimental thermosyphon cooling system was built to cool multiple electronic components up to a power dissipation of 1800 W. A double-ended cylinder with a volume of 150 cm3 is evaluated as the liquid accumulator for two different system volumes (associated to two different condensers). Results demonstrated that the liquid accumulator provided robust thermal performance as a function of filling ratio for the entire range of heat loads tested. In addition, the present liquid accumulator was more effective for a small volume system, 599 cm3, than for a large volume system, 1169 cm3, in which the relative size of the liquid accumulator increased from 12.8 % to 25% of the total system’s volume.

Development of an R245fa for Electronics Cooling System for High Heat Flux Applications

2009 ◽  
Author(s):  
Farhad Saffaraval ◽  
Amir Jokar
Keyword(s):  
Heat Flux ◽  
Heat Exchanger ◽  
Cooling System ◽  
Electronics Cooling ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
Microchannel Heat Exchanger ◽  
Mass Flow Rates

The objective of this study is to experimentally explore thermodynamic performance of R245fa, as a low-pressure and environmentally-friendly refrigerant, in a microchannel heat exchanger. This heat exchanger is used in an electronics cooling application with high-power density. Due to the large amount of latent heat that is released during evaporation process, the two-phase microchannel coolers are able to remove much more energy compared to single-phase cooling systems. In this study, R245fa is used as the working fluid in a refrigeration pump loop that mainly includes an evaporator, a condenser, a refrigerant pump, and a pressure regulator valve. The goal is to obtain optimal mass flow rates and system pressures while the temperatures in evaporator and condenser are kept constant for specific conditions. The results obtained from this study are then compared to the results previously obtained for water as the working fluid in a similar cooling system. It is expected the evaporative cooling through the microchannel heat exchanger be a viable and effective solution, especially for higher heat flux applications.

Role of a Liquid Accumulator in a Passive Two-Phase Liquid Cooling System for Electronics: Experimental Analysis

2018 ◽  
Vol 140 (1) ◽  
Author(s):  
Nicolas Lamaison ◽  
Raffaele L. Amalfi ◽  
Todd Salamon ◽  
Jackson B. Marcinichen ◽  
John R. Thome
Keyword(s):  
Cooling System ◽  
Flow Boiling ◽  
Relative Size ◽  
Electronics Cooling ◽  
Liquid Cooling ◽  
Two Phase ◽  
Wide Range ◽  
Gravity Driven ◽  
Phase Liquid ◽  
Liquid Cooling System

Gravity-driven two-phase liquid cooling systems using flow boiling within microscale evaporators are becoming a game-changing solution for electronics cooling. The optimization of the system's filling ratio (FR) can however become a challenging problem for a system operating over a wide range of cooling capacities and temperature ranges. The benefits of a liquid accumulator (LA) to overcome this difficulty are evaluated in the present paper. An experimental thermosyphon cooling system was built to cool multiple electronic components up to a power dissipation of 1800 W. A double-ended cylinder with a volume of 150 cm3 is evaluated as the LA for two different system volumes (associated with two different condensers). Results demonstrated that the LA provided robust thermal performance as a function of FR for the entire range of heat loads tested. In addition, the present LA was more effective for a small volume system, 599 cm3, than for a large volume system, 1169 cm3, in which the relative size of the LA increased from 12.8% to 25% of the total system's volume.

Pumpless Loop for Narrow Channel and Micro-Channel Boiling

2003 ◽  
Vol 125 (3) ◽  
pp. 431-441 ◽  
Author(s):  
Swaraj Mukherjee ◽  
Issam Mudawar
Keyword(s):  
Cooling System ◽  
Narrow Channel ◽  
Separation Distance ◽  
System Response ◽  
Two Phase ◽  
Small Surface ◽  
Two Fluids ◽  
Pass Through ◽  
Cooling Loop ◽  
Narrow Gaps

A compact cooling system is examined which capitalizes upon fluid density differences between two vertical, parallel, interconnected tubes to achieve a pumpless cooling loop. A heat-dissipating device is incorporated into a boiler at the bottom of the hot tube. The large density differences between the two tubes produces a substantial nonequilibrium in hydrostatic pressure, drawing liquid downwards through the cold tube as a two-phase mixture is released upwards in the hot tube. Cooling with this pumpless loop is fundamentally different from, and far superior to, pool boiling thermosyphons because of the former’s ability to separate the path of replenishment liquid from that of the released vapor. Experiments were performed to explore the effects of boiler gap (separation distance between the boiling surface and opposite insulating wall) on cooling performance and critical heat flux (CHF) for water and FC-72. The gap, which is the primary measure of boiler miniaturization, was varied from 0.051 to 21.46 mm. For large gaps, CHF showed insignificant dependence on the gap for both fluids. However, small gaps produced CHF variations that were both drastic and which followed opposite trends for the two fluids. Decreasing the gap below 3.56 mm produced a substantial rise in CHF for FC-72. For water, CHF was fairly insensitive down to 0.51 mm, below which it began to decrease sharply. These trends are shown to be closely related to the small surface tension and contact angle of FC-72 producing very small bubbles which can easily pass through narrow gaps in FC-72, while much larger bubbles in water obstruct liquid replenishment in narrow gaps. A numerical model is constructed to determine how the gap influences the various components of pressure drop, velocities, coolant flow rate, and hence system response to heat input.

Passive Thermosyphon Cooling System for High Heat Flux Servers

2015 ◽  
Author(s):  
Sylwia Szczukiewicz ◽  
Nicolas Lamaison ◽  
Jackson B. Marcinichen ◽  
John R. Thome ◽  
Peter J. Beucher
Keyword(s):  
Heat Flux ◽  
Cooling System ◽  
Cost Savings ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Net Benefit ◽  
Operation Performance ◽  
Two Phase ◽  
Cooling Loop

The main aim of the current paper is to demonstrate the capability of a two-phase closed thermosyphon loop system to cool down a contemporary datacenter rack, passively cooling the entire rack including its numerous servers. The effects on the performance of the entire cooling loop with respect to the server orientation, micro-evaporator design, riser and downcomer diameters, working fluid, and approach temperature difference at the condenser have been modeled and simulated. The influence of the thermosyphon height (here from 5 to 20 cm with a horizontally or vertically oriented server) on the driving force that guarantees the system operation whilst simultaneously fulfilling the critical heat flux (CHF) criterion also has been examined. In summary, the thermosyphon height was found to be the most significant design parameter. For the conditions simulated, in terms of CHF, the 10 cm-high thermosyphon was the most advantageous system design with a minimum safety factor of 1.6 relative to the imposed heat flux of 80 W cm−2. Additionally, a case study including an overhead water-cooled heat exchanger to extract heat from the thermosyphon loop has been developed and then the entire rack cooling system evaluated in terms of cost savings, payback period, and net benefit per year. This approximate study provides a general understanding of how the datacenter cooling infrastructure directly impacts the operating budget as well as influencing the thermal/hydraulic operation, performance, and reliability of the datacenter. Finally, the study shows that the passive two-phase closed loop thermosyphon cooling system is a potentially economically sound technology to cool high heat flux servers of datacenters.

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