Compact Thermosyphon Cooling System For High Heat Flux Servers: Validation Of Thermosyphon Simulation Code Considering New Test Data

2021 ◽  
Author(s):  
Rémy Haynau ◽  
Jackson B. Marcinichen ◽  
Raffaele L. Amalfi ◽  
Filippo Cataldo ◽  
John R. Thome
Keyword(s):  
Flow Rate ◽  
High Performance ◽  
Cooling System ◽  
Heat Removal ◽  
Working Fluid ◽  
High Heat Flux ◽  
Air Cooling ◽  
Simulation Code ◽  
Maximum Heat ◽  
Effective Manner

Abstract Passive, gravity-driven thermosyphons represent a step-change in technology towards the goal of greatly reducing PUE (Power Usage Effectiveness) of datacenters by replacing energy hungry fans of air-cooling approach with a highly-reliable solution able to dissipate the rising heat loads demanded in a cost-effective manner. The European Union has launched a zero carbon-footprint target for datacenters by the timeline of 2030, which would include new standards for implementing green solutions. In the present study, a newly updated version of the general thermosyphon simulation code previously presented at InterPACK 2019 and InterPACK 2020 is considered. To facilitate the industrial transition to thermosyphon cooling technology, with its intrinsic complex flow phenomena, the availability of a general-use, widely validated design tool that handles both air-cooled and liquid-cooled types of thermosyphons is of paramount importance. The solver must be able to analyze and design thermosyphon-based cooling systems with high accuracy and handle the numerous geometric singularities in the working fluid’s flow path, besides that of the secondary coolant. Therefore, a new extensive validation of the thermosyphon simulation solver is performed and presented here versus experimental data gathered for a compact liquid-cooled thermosyphon design, which is being considered for the cooling of high-performance servers. The new experimental database has been gathered to be able to characterize the effect of filling ratio, heat load, secondary coolant temperature and mass flow rate on the cooling performance, using R1234ze(E) as a low GWP (Global Warming Potential) working fluid. This compact design has experimentally demonstrated high performance, maintaining the pseudo chip’s temperature lower than 45°C for evaporator footprint heat fluxes up to 18W/cm2. The comparison shows that the solver is able to accurately predict thermosyphon thermal-hydraulic performance, and based on this prediction, characterize the internal flow rate generated by the thermosyphon, which is key to correctly estimate the maximum heat removal capability.

Novel Design of a Miniature Loop Heat Pipe Evaporator for Electronic Cooling

2007 ◽  
Vol 129 (10) ◽  
pp. 1445-1452 ◽  
Author(s):  
Randeep Singh ◽  
Aliakbar Akbarzadeh ◽  
Chris Dixon ◽  
Masataka Mochizuki
Keyword(s):  
Thermal Resistance ◽  
Electronic Devices ◽  
Working Fluid ◽  
Internal Diameter ◽  
High Heat Flux ◽  
Air Cooling ◽  
Maximum Heat ◽  
Small Thickness ◽  
Flat Evaporator ◽  
Compensation Chamber

Miniature loop heat pipes (mLHPs) are coming up with a promising solution for the thermal management of futuristic electronics systems. In order to implement these devices inside compact electronics, their evaporator has to be developed with small thickness while preserving the unique thermal characteristics and physical concept of the loop scheme. This paper specifically addresses the design and testing of a mLHP with a flat evaporator only 5mm thick for the cooling of high performance microprocessors for electronic devices. A novel concept was used to achieve very small thickness for the mLHP evaporator in which the compensation chamber was positioned on the sides of the wick structure and incorporated in the same plane as the evaporator. This is unlike the conventional design of the flat evaporator for mLHP in which the compensation chamber, as a rule, adds to the overall thickness of the evaporator. The loop was made from copper with water as the heat transfer fluid. For capillary pumping of the working fluid around the loop, a sintered nickel wick with 3–5μm pore radius and 75% porosity was used. In the horizontal orientation, the device was able to transfer heat fluxes of 50W∕cm2 at a distance of up to 150mm by using a transport line with 2mm internal diameter. In the range of applied power, the evaporator was able to achieve steady state without any temperature overshoots or symptoms of capillary structure dryouts. For the evaporator and condenser at the same level and under forced air cooling, the minimum value of 0.62°C∕W for mLHP thermal resistance from evaporator to condenser (Rec) was achieved at a maximum heat load of 50W with the corresponding junction temperature of 98.5°C. The total thermal resistance (Rt) of the mLHP was within 1.5–5.23°C∕W. At low heat loads, the mLHP showed some thermal and hydraulic oscillations in the transport lines, which were predominately due to the flow instabilities imposed by parasitic heat leaks to the compensation chamber. It is concluded form the outcomes of the present investigation that the proposed design of the mLHP evaporator can be effectively used for the thermal control of the compact electronic devices with high heat flux capabilities.

Development of Cooling System for a Large Area at High Heat Flux by Using Flow Boiling in Narrow Channels

2009 ◽  
Author(s):  
Shinichi Miura ◽  
Yukihiro Inada ◽  
Yasuhisa Shinmoto ◽  
Haruhiko Ohta
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Rate ◽  
Mass Velocity ◽  
Cooling System ◽  
Volumetric Flow Rate ◽  
High Heat ◽  
High Heat Flux ◽  
Gap Size ◽  
Heated Channel

Advance of an electronic technology has caused the increase of heat generation density for semiconductors densely integrated. Thermal management becomes more important, and a cooling system for high heat flux is required. It is extremely effective to such a demand using flow boiling heat transfer because of its high heat removal ability. To develop the cooling system for a large area at high heat flux, the cold plate structure of narrow channels with auxiliary unheated channel for additional liquid supply was devised and confirmed its validity by experiments. A large surface of 150mm in heated length and 30mm in width with grooves of an apex angle of 90 deg, 0.5mm depth and 1mm in pitch was employed. A structure of narrow rectangular heated channel between parallel plates with an unheated auxiliary channel was employed and the heat transfer characteristics were examined by using water for different combinations of gap sizes and volumetric flow rates. Five different liquid distribution modes were tested and their data were compared. The values of CHF larger than 1.9×106W/m2 for gap size of 2mm under mass velocity based on total volumetric flow rate and on the cross section area of main heated channel 720kg/m2s or 1.7×106W/m2 for gap size of 5mm under 290kg/m2s were obtained under total volumetric flow rate 4.5×10−5m3/s regardless of the liquid distribution modes. Under several conditions, the extensions of dry-patches were observed at the upstream location of the main heated channel resulting burnout not at the downstream but at the upstream. High values of CHF larger than 2×106W/m2 were obtained only for gap size of 2mm. The result indicates that higher mass velocity in the main heated channel is more effective for the increase in CHF. It was clarified that there is optimum flow rate distribution to obtain the highest values of CHF. For gap size of 2mm, high heat transfer coefficient as much as 7.4×104W/m2K were obtained at heat flux 1.5×106W/m2 under mass velocity 720kg/m2s based on total volumetric flow rate and on the cross section area of main heated channel. Also to obtain high heat transfer coefficient, it is more useful to supply the cooling liquid from the auxiliary unheated channel for additional liquid supply in the transverse direction perpendicular to the flow in the main heated channel.

Ex-Vessel Loss of Coolant Accident Analysis of ITER Divertor Cooling System Using Modified RELAP/SCADAPSIM/Mod 4.0

2017 ◽  
Vol 3 (4) ◽  
Author(s):  
S. P. Saraswat ◽  
P. Munshi ◽  
A. Khanna ◽  
C. Allison
Keyword(s):  
Heat Flux ◽  
Cooling System ◽  
Heat Removal ◽  
Hydraulic Modeling ◽  
Carbon Fiber Composites ◽  
High Heat Flux ◽  
Vacuum Vessel ◽  
Loss Of Coolant Accident ◽  
Loss Of Coolant ◽  
Accident Scenarios

The initial design of ITER incorporated the use of carbon fiber composites in high heat flux regions and tungsten was used for low heat flux regions. The current design includes tungsten for both these regions. The present work includes thermal hydraulic modeling and analysis of ex-vessel loss of coolant accident (LOCA) for the divertor (DIV) cooling system. The purpose of this study is to show that the new concept of full tungsten divertor is able to withstand in the accident scenarios. The code used in this study is RELAP/SCADAPSIM/MOD 4.0. A parametric study is also carried out with different in-vessel break sizes and ex-vessel break locations. The analysis discusses a number of safety concerns that may result from the accident scenarios. These concerns include vacuum vessel (VV) pressurization, divertor temperature profile, passive decay heat removal capability of structure, and pressurization of tokamak cooling water system. The results show that the pressures and temperatures are kept below design limits prescribed by ITER organization.

Feasibility Assessment of Air-Cooling System As an Ultimate Heat Sink of the ATOM System

2018 ◽  
Author(s):  
Doyoung Shin ◽  
Gwang Hyeok Seo ◽  
Min Wook Na ◽  
Sung Joong Kim ◽  
Yonghee Kim ◽  
...  
Keyword(s):  
Flow Rate ◽  
Heat Sink ◽  
Cooling System ◽  
Air Cooling ◽  
Primary Coolant ◽  
Final Heat ◽  
Feasibility Assessment ◽  
Environment Temperature ◽  
Air Cooling System ◽  
Atom System

Nowadays Small Modular Reactors (SMRs) have been receiving considerable attentions worldwide for potential advantages of an excellent flexibility for siting, low capital investment, and advanced safety. In Korea, a new research project has launched for the development of a conceptual design of a further advanced SMR which aims for a naturally-safe and autonomous operation, so called Autonomous Transportable On-demand reactor Module (ATOM). Major design objectives of the ATOM system are focused on the soluble boron-free (SBF) primary coolant system which enables the SMR to operate automatically in a load following mode. For the secondary system, the SCO2 power conversion cycle with air-cooling system as a final heat sink is being considered. The air-cooling system is expected to show flexible response even to extreme environmental conditions, such as a desert where utilization of cooling water is limited. The objective of this study is a feasibility assessment for applying the air-cooling system as a final heat sink of the ATOM by means of experimental work. As a 1st phase of the ATOM development, we first conducted the experiments using a typically considered primary coolant, water-steam, to verify that air flow has enough cooling capability to remove developed heat which the coolant carries. An Integrated Condensation Loop with Air-cooling System (ICLASS) experimental facility with three pressure boundaries (Steam, coolant, and air) was established. The cooling capability of the air-cooling system was evaluated by varying steam mass flow rate, coolant flow rate, and air environment temperature as experiment variables. Overall heat transfer rate by condensation was compared with numerical simulations of a 1D thermal-hydraulics analysis code, using the MARS model of the ICLASS facility.

scholarly journals Influence of the ambient temperature on the cooling efficiency of the high performance cooling device with thermosiphon effect

2018 ◽  
Vol 180 ◽  
pp. 02073
Author(s):  
Patrik Nemec ◽  
Milan Malcho
Keyword(s):  
Ambient Temperature ◽  
High Performance ◽  
Convection Heat Transfer ◽  
Heat Removal ◽  
Measuring Method ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Cooling Efficiency ◽  
Cooling Device

This work deal with experimental measurement and calculation cooling efficiency of the cooling device working with a heat pipe technology. The referred device in the article is cooling device capable transfer high heat fluxes from electric elements to the surrounding. The work contain description, working principle and construction of cooling device. The main factor affected the dissipation of high heat flux from electronic elements through the cooling device to the surrounding is condenser construction, its capacity and option of heat removal. Experimental part describe the measuring method cooling efficiency of the cooling device depending on ambient temperature in range -20 to 40°C and at heat load of electronic components 750 W. Measured results are compared with results calculation based on physical phenomena of boiling, condensation and natural convection heat transfer.

Dependence of Heat Transfer Coefficient on Porous Structure in Porous Media

2008 ◽  
Author(s):  
Akira Matsui ◽  
Kazuhisa Yuki ◽  
Hidetoshi Hashizume
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Porous Media ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Performance ◽  
Heat Removal ◽  
High Heat ◽  
Metal Foams ◽  
High Heat Flux

Detailed heat transfer characteristics of particle-sintered porous media and metal foams are evaluated to specify the important structural parameters suitable for high heat removal. The porous media used in this experiment are particle-sintered porous media made of bronze and SUS316L, and metal foams made of copper and nickel. Cooling water flows into the porous medium opposite to heat flux input loaded by a plasma arcjet. The result indicates that the bronze-particle porous medium of 100μm in pore size shows the highest performance and achieves heat transfer coefficient of 0.035MW/m2K at inlet heat flux 4.6MW/m2. Compared with the heat transfer performance of copper fiber-sintered porous media, the bronze particlesintered ones give lower heat transfer coefficient. However, the stable cooling conditions that the heat transfer coefficient does not depend on the flow velocity, were confirmed even at heat flux of 4.6MW/m2 in case of the bronze particle-sintered media, while not in the case of the copper-fiber sintered media. This signifies the possibility that the bronze-particle sintered media enable much higher heat flux removal of over 10MW/m2, which could be caused by higher permeability of the particle-sintered pore structures. Porous media with high permeability provide high performance of vapor evacuation, which leads to more stable heat removal even under extremely high heat flux. On the other hand, the heat transfer coefficient of the metal foams becomes lower because of the lower capillary and fin effects caused by too high porosity and low effective thermal conductivity. It is concluded that the pore structure having high performance of vapor evacuation as well as the high capillary and high fin effects is appropriate for extremely high heat flux removal of over 10MW/m2.

Performance Evaluation of DRACS System for FHTR and Time Assessment of Operation Procedure

2013 ◽  
Author(s):  
Junya Nakata ◽  
Mikihiro Wakui ◽  
Michitsugu Mori ◽  
Hiroto Sakashita ◽  
Charles Forsberg
Keyword(s):  
Performance Evaluation ◽  
High Temperature ◽  
Cooling System ◽  
Heat Removal ◽  
Severe Accident ◽  
Air Cooling ◽  
Fluoride Salt ◽  
Nuclear Power Reactor ◽  
Decay Heat ◽  
Operation Procedure

The Fluoride-salt-cooled High-temperature Reactor (FHR) is a new concept of nuclear power reactor being investigated mainly in U.S. and China. The coolant is a liquid salt with a melting point of about 460°C and a boiling point of over 1400°C. As the baseline decay heat removal system, a passive Direct Reactor Air Cooling System (DRACS) is utilized. Though DRACS system has been developed in Sodium Fast reactors (SFR), there are some differences between both. For example, the system in FHR must decrease heat removal when temperatures are low to avoid freezing of the salt and blocking the flow of liquid. Therefore, considering its characteristics, a numerical investigation of DRACS system is needed to evaluate whether FHR has proper ability to remove decay heat and to be robust for a long-time cooling operation after even a severe accident. Furthermore, in addition to its performance evaluation, it is required to make up the operation plan of FHR considering features of this system. It is highly important, with the view of avoiding severe accident, to determine by when the system should be started up. In both countries mentioned above, Fluoride-salt-cooled High-temperature Test Reactor (FHTR) is currently in progress to build. Reviewing its design and system is a crucial step needed to develop the FHR technology. In this research, a performance of DRACS system under some thermal-hydraulic basic events was evaluated by numerical simulation. This paper also suggested the adequate operation procedure suitable for FHTR to avoid a severe accident.

scholarly journals Enhancement of Thermal Efficiency of Heat Exchanger using Titanium – Oxide nanofluid

2019 ◽  
Vol 8 (9) ◽  
pp. 871-875
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flow Rate ◽  
Removal Rate ◽  
Heat Removal ◽  
Working Fluid ◽  
Viscous Property ◽  
Volume Percentage ◽  
Conducting Property ◽  
Thermal Conducting

Improvement of heat removal rate in heat exchanger using passive techniques is considered to be one of the most challenging task for engineers and scientist. In this study efficiency of the heat exchangers has been studied with TiO2 / water based nanofluid. The thermal properties, physical properties and heat removal efficiency of heat exchanger with nano-fluid as working fluid was investigated. Nanoparticle concentration of about 0.1 and 0.3 vol% was used. It was detected that the thermal conducting property and viscous property of the nanofluid increased proportionally with volume percentage. With the increased heat, the thermal conducting property increased while the viscous property of the nanofluid decreased. The heat removal rate on both shell outlet and tube outlet was estimated for different mass flow rate. The experiment results showed that with increased volume percentage and flow rate, the heat transfer performance improved. A maximum enhancement of 34% was observed at 0.3 vol% and 6l/min. Though there is increase in heat transfer rate the pressure dropped and pumping requirement increase with volume concentration and flow rate.

scholarly journals A Numerical Analysis of the Air-Cooling System of a Spark Ignition Aeronautical Engine

2020 ◽  
Vol 197 ◽  
pp. 06003
Author(s):  
Maria Faruoli ◽  
Annarita Viggiano ◽  
Paolo Caso ◽  
Vinicio Magi
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cooling System ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Air Cooling ◽  
Air Mass ◽  
Air Cooling System

It is well known that spark ignition internal combustion engines for aeronautical applications operate within a specific temperature range to avoid structural damages, detonations and loss of efficiency of the combustion process. An accurate assessment of the cooling system performance is a crucial aspect in order to guarantee broad operating conditions of the engine. In this framework, the use of a Conjugate Heat Transfer method is a proper choice, since it allows to estimate both the heat fluxes between the engine walls and the cooling air and the temperature distribution along the outer wall surfaces of the engine, and to perform parametric analyses by varying the engine operating conditions. In this work, the air-cooling system of a 4-cylinder spark ignition engine, designed by CMD Engine Company for aeronautical applications, is analysed in order to evaluate the amount of the air mass flow rate to guarantee the heat transfer under full load operating conditions. A preliminary validation of the model is performed by comparing the results with available experimental data. A parametric study is also performed to assess the influence of the controlling parameters on the cooling system efficiency. This study is carried out by varying the inlet air mass flow rate from 1.0 kg/s to 1.5 kg/s and the temperature of the inner wall surfaces of the engine combustion chambers from 390 K to 430 K.

ARCTIC: A Rotary Compressor Thermally Insulated µCooler

2005 ◽  
Author(s):  
Joshua D. Heppner ◽  
David C. Walther ◽  
Albert P. Pisano
Keyword(s):  
Hot Spots ◽  
Cooling System ◽  
Heat Removal ◽  
Coefficient Of Performance ◽  
The Arctic ◽  
Working Fluid ◽  
Rotary Compressor ◽  
Speed Increase ◽  
Rotary Engine ◽  
Compressor Design

Microscale cooling to date relies largely on passive on-chip cooling in order to move heat from hot spots to alternate sites. Such passive cooling devices include capillary pump loops (CPL), heat pipes, and thermosiphons. Recent developments for active cooling systems include thermal electric coolers (TECs) for heat removal. This paper focuses on the design of an active microscale closed loop cooling system that uses a Rankine vapor compression cycle cooling system. In this design, a rotary compressor will generate the high pressure required for efficient cooling and will circulate the working fluid to move heat away from chip level hot spots to the ambient. The rotary compressor will leverage technology gained from the Rotary Engine Power System (REPS) program at the UC Berkeley, most specifically the 367 mm3 displacement platform. The advantage of a Wankel (Maillard) compressor is that it provides six compression strokes per revolution rather than a single compression stroke common to other popular compressors such as the rolling piston. The current Wankel compressor design will achieve a theoretical compression ratio of 8:1. The ARCTIC (A Rotary Compressor Thermally Insulated μCooler) system will be a microscale hybrid system consisting of some microfabricated (or MEMS) components including microchannels, in plane MEMS valves, and potentially MEMS temperature, pressure and flow sensors integrated with mesoscale, traditionally machined steel components, including the compressor itself. The system is designed to remove between 25-35 W of heat at 1000 rpm using R-134a but the system is easily scaleable through a speed increase or decrease of the compressor. Further, the current compressor design has a theoretical coefficient of performance (C.O.P.) of approximately 2, a significant improvement over comparable TECs with C.O.P.s of approximately .05-.1. Finally, a thermal circuit analysis determines that the time constant to achieve refrigeration temperature in 12 seconds is possible.

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