scholarly journals Green Cooling of High Performance Microprocessors: Parametric Study Between Flow Boiling and Water Cooling

2011 ◽  
Vol 3 (4) ◽  
Author(s):  
Jonathan A. Olivier ◽  
Jackson B. Marcinichen ◽  
Arnaud Bruch ◽  
John Thome
Keyword(s):  
Ethylene Glycol ◽  
Single Phase ◽  
Flow Boiling ◽  
Hot Spot ◽  
Junction Temperature ◽  
Air Cooling ◽  
Processing Unit ◽  
Exergetic Efficiency ◽  
Two Phase ◽  
Cooling Cycle

Due to the increase in energy prices and spiralling consumption, there is a need to greatly reduce the cost of electricity within data centers, where it makes up to 50% of the total cost of the IT infrastructure. A technological solution to this is using on-chip cooling with a single-phase or evaporating liquid to replace energy intensive air-cooling. The energy carried away by the liquid or vapor can also potentially be used in district heating, as an example. Thus, the important issue here is “what is the most energy efficient heat removal process?” As an answer, this paper presents a direct comparison of single-phase water, a 50% water–ethylene glycol mixture and several two-phase refrigerants, including the new fourth generation refrigerants HFO1234yf and HFO1234ze. Two-phase cooling using HFC134a had an average junction temperature from 9 to 15 °C lower than for single-phase cooling, while the required pumping power for the central processing unit cooling element for single-phase cooling was on the order of 20–130 times higher to achieve the same junction temperature uniformity. Hot-spot simulations also showed that two-phase refrigerant cooling was able to adjust to local hot-spots because of flow boiling’s dependency on the local heat flux, with junction temperatures being 20 to 30 °C lower when compared to water and the 50% water–ethylene glycol mixture, respectively. An exergy analysis was developed considering a cooling cycle composed by a pump, a condenser, and a multimicrochannel cooler. The focus was to show the exergetic efficiency of each component and of the entire cycle when the subject energy recovery is considered. Water and HFC134a were the working fluids evaluated in such analysis. The overall exergetic efficiency was higher when using HFC134a (about 2%), and the exergy destroyed, i.e., irreversibilities, showed that the cooling cycle proposed still have a huge potential to increase the thermodynamic performance.

Thermal Characterization of Interlayer Microfluidic Cooling of Three-Dimensional Integrated Circuits With Nonuniform Heat Flux

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Yoon Jo Kim ◽  
Yogendra K. Joshi ◽  
Andrei G. Fedorov ◽  
Young-Joon Lee ◽  
Sung-Kyu Lim
Keyword(s):  
Integrated Circuits ◽  
Mass Flow Rate ◽  
Thermal Management ◽  
Mass Flow ◽  
Flow Rate ◽  
Single Phase ◽  
Hot Spot ◽  
Three Dimensional ◽  
Two Phase ◽  
Two Phase Cooling

It is now widely recognized that the three-dimensional (3D) system integration is a key enabling technology to achieve the performance needs of future microprocessor integrated circuits (ICs). To provide modular thermal management in 3D-stacked ICs, the interlayer microfluidic cooling scheme is adopted and analyzed in this study focusing on a single cooling layer performance. The effects of cooling mode (single-phase versus phase-change) and stack/layer geometry on thermal management performance are quantitatively analyzed, and implications on the through-silicon-via scaling and electrical interconnect congestion are discussed. Also, the thermal and hydraulic performance of several two-phase refrigerants is discussed in comparison with single-phase cooling. The results show that the large internal pressure and the pumping pressure drop are significant limiting factors, along with significant mass flow rate maldistribution due to the presence of hot-spots. Nevertheless, two-phase cooling using R123 and R245ca refrigerants yields superior performance to single-phase cooling for the hot-spot fluxes approaching ∼300 W/cm2. In general, a hybrid cooling scheme with a dedicated approach to the hot-spot thermal management should greatly improve the two-phase cooling system performance and reliability by enabling a cooling-load-matched thermal design and by suppressing the mass flow rate maldistribution within the cooling layer.

Two-Phase Flow in Microchannels

2001 ◽  
Author(s):  
G. Hetsroni ◽  
A. Mosyak ◽  
Z. Segal
Keyword(s):  
Heat Sink ◽  
High Speed ◽  
Single Phase ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Infrared Radiometry ◽  
Phase Water

Abstract Experimental investigation of a heat sink for electronics cooling is performed. The objective is to keep the operating temperature at a relatively low level of about 323–333K, while reducing the undesired temperature variation in both the streamwise and transverse directions. The experimental study is based on systematic temperature, flow and pressure measurements, infrared radiometry and high-speed digital video imaging. The heat sink has parallel triangular microchannels with a base of 250μm. According to the objectives of the present study, Vertrel XF is chosen as the working fluid. Experiments on flow boiling of Vertrel XF in the microchannel heat sink are performed to study the effect of mass velocity and vapor quality on the heat transfer, as well as to compare the two-phase results to a single-phase water flow.

New Thermal Management Systems for Data Centers

2012 ◽  
Vol 4 (3) ◽  
Author(s):  
Mayumi Ouchi ◽  
Yoshiyuki Abe ◽  
Masato Fukagaya ◽  
Takashi Kitagawa ◽  
Haruhiko Ohta ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Single Phase ◽  
Data Centers ◽  
Cooling System ◽  
Heat Pipes ◽  
Air Cooling ◽  
Liquid Cooling ◽  
Two Phase ◽  
Cooling Jacket ◽  
Cooling Methods

Energy consumption in data centers has seen a drastic increase in recent years. In data centers, server racks are cooled down in an indirect way by air-conditioning systems installed to cool the entire server room. This air cooling method is inefficient as information technology (IT) equipment is insufficiently cooled down, whereas the room is overcooled. The development of countermeasures for heat generated by IT equipment is one of the urgent tasks to be accomplished. We, therefore, proposed new liquid cooling systems in which IT equipment is cooled down directly and exhaust heat is not radiated into the server room. Three cooling methods have been developed simultaneously. Two of them involve direct cooling; a cooling jacket is directly attached to the heat source (or CPU in this case) and a single-phase heat exchanger or a two-phase heat exchanger is used as the cooling jacket. The other method involves indirect cooling; heat generated by CPU is transported to the outside of the chassis through flat heat pipes and the condensation sections of the heat pipes are cooled down by coolant with liquid manifold. Verification tests have been conducted by using commercial server racks to which these cooling methods are applied while investigating five R&D components that constitute our liquid cooling systems: the single-phase heat exchanger, the two-phase heat exchanger, high performance flat heat pipes, nanofluid technology, and the plug-in connector. As a result, a 44–53% reduction in energy consumption of cooling facilities with the single-phase cooling system and a 42–50% reduction with the flat heat pipe cooling system were realized compared with conventional air cooling system.

Heat Transfer in Annular Channel With Continuous Flow Twisting

2010 ◽  
Author(s):  
S. E. Tarasevich ◽  
A. B. Yakovlev
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Flow Boiling ◽  
Annular Channel ◽  
Equivalent Diameter ◽  
Phase Flow ◽  
Two Phase ◽  
Channel Diameter ◽  
Subcooled Flow Boiling ◽  
Annular Channels

In paper the experimental results on a heat transfer in annular channels with continuous twisting at length at one- and two-phase flows are observed. For a flow twisting the wire was spirally coiled on the central body of the annular channel (diameter of a wire is equal to annular gap altitude). Results of experimental data of a heat transfer of authors and various researchers at a single phase flow in annular channels with a continuous twisting are analyzed. Sampling of diagnostic variables (equivalent diameter and velocity) is spent and generalizing associations for heat transfer calculation on the concave and convex surfaces in a single-phase phase are offered. Also the technique of definition of temperature of the subcooled flow boiling beginning on surfaces of annular channels with a twisting is offered. Features of boiling, origination of heat transfer crisis and results of visualization of a two-phase flow structure in annular channels with twisting are described.

Thermal Performance and Key Challenges for Future CPU Cooling Technologies

2005 ◽  
Author(s):  
Ioan Sauciuc ◽  
Ravi Prasher ◽  
Je-Young Chang ◽  
Hakan Erturk ◽  
Gregory Chrysler ◽  
...  
Keyword(s):  
Power Density ◽  
Thermal Performance ◽  
Hot Spot ◽  
Average Power ◽  
Building Blocks ◽  
Thermal Design ◽  
Air Cooling ◽  
Back Side ◽  
Two Phase ◽  
Density Factor

Over the past few years, thermal design for cooling microprocessors has become increasingly challenging mainly because of an increase in both average power density and local power density, commonly referred to as “hot spots”. The current air cooling technologies present diminishing returns, thus it is strategically important for the microelectronics industry to establish the research and development focus for future non air-cooling technologies. This paper presents the thermal performance capability for enabling and package based cooling technologies using a range of “reasonable” boundary conditions. In the enabling area a few key main building blocks are considered: air cooling, high conductivity materials, liquid cooling (single and two-phase), thermoelectric modules integrated with heat pipes/vapor chambers, refrigeration based devices and the thermal interface materials performance. For package based technologies we present only the microchannel building block (cold plate in contact with the back-side of the die). It will be shown that as the hot spot density factor increases, package based cooling technologies should be considered for more significant cooling improvements. In addition to thermal performance, a summary of the key technical challenges are presented in the paper.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.

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.

Phase-Change Heat Transfer of Ethanol-Water Mixtures: Towards Development of a Distributed Hydrogen Generator

2013 ◽  
Author(s):  
Manoj Kumar Moharana ◽  
Rohan M. Nemade ◽  
Sameer Khandekar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Flow Boiling ◽  
Phase Region ◽  
Design Flow ◽  
Two Phase ◽  
Vapor Region

Hydrogen fuel from renewable bio-ethanol is a potentially strong contender as an energy carrier. Its distributed production by steam reforming of ethanol on microscale platforms is an efficient upcoming method. Such systems require (a) a pre-heater for liquid to vapor conversion of ethanol water mixtures (b) a gas-phase catalytic reactor. We focus on the fundamental experimental heat transfer studies (pool and flow boiling of ethanol-water mixtures) required for the primary pre-heater boiler design. Flow boiling results (in a 256 μm square channel) clearly show the influence of mixture composition. Heat transfer coefficient remains almost constant in the single-phase region and rapidly increases as the two-phase region starts. On further increasing the wall superheat, heat transfer starts to decrease. At higher applied heat flux, the channel is subjected to axial back conduction from the single-phase vapor region to the two-phase liquid-vapor region, thus raising local wall temperatures. Simultaneously, to gain understanding of phase-change mechanisms in binary mixtures and to generate data for the modeling of flow boiling process, pool-boiling of ethanol-water mixtures has also been initiated. After benchmarking the setup against pure fluids, variation of heat transfer coefficient, bubble growth, contact angles, are compared at different operating conditions. Results show strong degradation in heat transfer in mixtures, which increases with operating temperature.

Thermofluid Characteristics of Two-Phase Microgap Coolers

2007 ◽  
Author(s):  
Dae W. Kim ◽  
Emil Rahim ◽  
Avram Bar-Cohen ◽  
Bongtae Han
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Pressure Drop ◽  
Single Phase ◽  
Flow Boiling ◽  
Phase Flow ◽  
Dissolved Gas ◽  
Single Phase Flow ◽  
Two Phase ◽  
Phase Water

The thermofluid characteristics of a chip-scale microgap cooler, including single-phase flow of water and FC-72 and flow boiling of FC-72, are explored. Heat transfer and pressure drop results for single phase water are used to validate a detailed numerical model and, together with the convective FC-72 data, establish a baseline for microgap cooler performance. Experimental results for single phase water and FC-72 flowing in 120 μm, 260 μm and 600 μm microgap coolers, 31mm wide by 34mm long, at velocities of 0.1 – 2 m/s are reported. “Pseudo-boiling” driven by dissolved gas and flow boiling of FC-72 are found to provide significant enhancement in heat transfer relative to theoretical single phase values.

Experimental study of transition flow from single phase to two phase flow boiling in nanofluids

2017 ◽  
Vol 231 ◽  
pp. 11-19 ◽  
Author(s):  
Ehsan Abedini ◽  
Taleb Zarei ◽  
Masoud Afrand ◽  
Somchai Wongwises
Keyword(s):  
Experimental Study ◽  
Single Phase ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Phase Flow ◽  
Transition Flow ◽  
Two Phase

Liquid Cooling Network Systems for Energy Conservation in Data Centers

2011 ◽  
Author(s):  
Mayumi Ouchi ◽  
Yoshiyuki Abe ◽  
Masato Fukagaya ◽  
Haruhiko Ohta ◽  
Yasuhisa Shinmoto ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Data Center ◽  
Single Phase ◽  
Cooling System ◽  
Heat Pipes ◽  
Air Cooling ◽  
Liquid Cooling ◽  
Two Phase ◽  
Cooling Systems ◽  
Cooling Methods

Energy consumption in data center has been drastically increasing in recent years. In data center, server racks are cooled down by air conditioning for the whole room in a roundabout way. This air cooling method is inefficient in cooling and it causes hotspot problem that IT equipments are not cooled down enough, but the room is overcooled. On the other hand, countermeasure against the heat of the IT equipments is also one of the big issues. We therefore proposed new liquid cooling systems which IT equipments themselves are cooled down and exhaust heat is not radiated into the server room. For our liquid cooling systems, three kinds of cooling methods have been developed simultaneously. Two of them are direct cooling methods that the cooling jacket is directly attached to heat source, or CPU in this case. Single-phase heat exchanger or two-phase heat exchanger is used as cooling jackets. The other is indirect cooling methods that the heat generated from CPU is transported to the outside of the chassis through flat heat pipes, and condensation sections of the heat pipes are cooled down by liquid. Verification tests have been conducted by use of real server racks equipped with these cooling techniques while pushing ahead with five R&D subjects which constitute our liquid cooling system, which single-phase heat exchanger, two-phase heat exchanger, high performance flat heat pipes, nanofluids technology, and plug-in connector. As a result, the energy saving effect of 50∼60% comparing with conventional air cooling system was provided in direct cooling technique with single-phase heat exchanger.

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