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  4. Experimental Evaluation and Control of Two-Phase Multi-Microchannel Evaporator Cooling Systems for High Efficiency Data Center
 
doctoral thesis

Experimental Evaluation and Control of Two-Phase Multi-Microchannel Evaporator Cooling Systems for High Efficiency Data Center

Wu, Duan  
2012

Thermal designers of data centers and server manufacturers are showing a greater concern regarding the cooling of the new generation data centers, which consume considerably more electricity and dissipate much more waste heat, a situation that is creating a re- thinking about the most effective cooling systems for the future beyond conventional air cooling of the chips/servers. Potentially, a significantly better solution is to make use of on- chip two-phase cooling, which, besides improving the cooling performance at the chip level while also consuming less energy to drive the cooling process, also adds the capability to reuse the waste heat in a convenient manner, since higher evaporating and condensing temperatures of the two-phase cooling system (from 60-95 °C) are possible with such a new “green” cooling technology. In the present thesis, three such two-phase cooling cycles using micro-evaporation technology were experimentally evaluated with specific attention being paid to (i) controllability of the two-phase cooling system, (ii) energy consumption and (iii) overall exergetic efficiency, with the emphasis on (i). The controllers were evaluated by tracking and disturbance rejection tests, which were shown to be efficient and effective. The average temperatures of the chips were maintained below the upper limit of 85 °C of computer CPU’s for all tests evaluated in steady state and transient conditions. In general, simple SISO and SIMO strategies were sufficient to attain the requirements of control. Regarding energy and exergy analyses, the experimental results showed that all these systems can be thermodynamically improved since only about 6% of the exergy supplied is in fact recovered in the condenser in the present setup. Additionally, a series of tests covering a wide range of operating conditions under steady state regime were done. The main idea was to generate a “map of performance” of the different cooling systems in terms of energy consumption, energy recovery at the condenser and heat exchanger performance. A total of 120 tests were done which considered all combinations of the variables involved. Finally, empirical and semi-empirical correlations for overall thermal conductance and performance of all components and piping of all these systems were developed based on the experimental results obtained, which can be used for simulations and validations of potential codes developed to design and/or evaluate performance of cooling systems. An overall energy balance analysis for each system using the correlations developed showed that 99.17% of the experimental data were bounded within ± 10%.

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Type
doctoral thesis
DOI
10.5075/epfl-thesis-5588
Author(s)
Wu, Duan  
Advisors
Thome, John Richard  
•
Marcinichen, Jackson Braz  
Jury

H.B. Püttgen (président), B. Agostini, D. Favrat, E. Pedone Bandarra Filho

Date Issued

2012

Publisher

EPFL

Publisher place

Lausanne

Public defense year

2012-12-05

Thesis number

5588

Subjects

Data center

•

high performance computers

•

high heat flux

•

two-phase on-chip cooling

•

microevaporator

•

cooling system

•

controller

•

energy recovery

EPFL units
LTCM  
Faculty
STI  
School
IGM  
Doctoral School
EDEY  
Available on Infoscience
December 5, 2012
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/87281
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