Dynamic Characteristics of the Capillary Pumped Loop for Cooling the Tower-Type Computer

2007 ◽  
Author(s):  
Atsushi Tsujimori ◽  
Masashi Kato ◽  
Maiko Uchida
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Dynamic Characteristics ◽  
Heat Load ◽  
Cooling Water ◽  
Transport Rate ◽  
Working Fluid ◽  
High Heat Flux ◽  
Capillary Pumped Loop ◽  
Heat Loads

Capillary pumped loop has been widely investigated for space thermal control devices. This cooling device with high reliability and thermal controllability is also considered to be suited to cool electronic devices like personal computers. Because the capillary pumped loop is good at absorbing heat from high heat flux region like micro-processors, transporting it and releasing it from the large surface for packaging. In this research, the experimental equipment of the capillary pumped loop was manufactured. The experimental apparatus consists of the evaporator, the condenser, the liquid line, the vapor line and the reservoir. In the experiments heat load is applied to the evaporator by a resistance heater. And heat is released from the condenser to the cooling water which is set to be a constant temperature by the refrigerator. The length and the diameter of the evaporator are 150mm and 27mm respectively and the capillary wick with equivalent diameter of 5μm is embedded in the evaporator. These specifications were designed to give 2500mm heat transport distance and to adapt the natural convection heat transfer to the ambient without a cooling fan. As is proposed in the recent study, the inside of the capillary wick was used as the reservoir to simplify the loop. In our previous study, the heat transport characteristics in steady states were investigated when the heat flux, the cooling water temperature and the evaporator height above the condenser changed, and then the effects of enclosed rate of the working fluid in the reservoir and the inclination angles of the evaporator on heat transport rate were investigated. The computer code was also developed to simulate the heat transport characteristics and evaluate the maximum heat transport rate of the tested capillary pump. In the next step, we focus on the dynamic characteristics. The heat loads of the micro-processors in the computers usually change according to the working conditions of the application software and vary hourly. Thus the active thermal regulation accompanied with the change of heat loads is the important factor for cooling devices in the computers. So in this study the heat transport characteristics in the dynamic conditions of the capillary pumped loop were investigated. In the experiment, the start-up and shut-down mode at a given heat load were tested at first. Then heat load were changed in incremental or decremental steps from 30 to 70W. All results show the good thermal controllability.

Heat Transport Characteristics of the Capillary Pumped Loop for Cooling the Tower-Type Computer

2005 ◽  
Author(s):  
Atsushi Tsujimori ◽  
Masashi Kato ◽  
Hajime Morita ◽  
Maiko Uchida
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Cooling Water ◽  
Heat Rate ◽  
Transport Rate ◽  
Working Fluid ◽  
Equivalent Diameter ◽  
Cooling Device ◽  
Capillary Pumped Loop ◽  
Maximum Heat

In this study the capillary pumped loop was manufactured as a cooling device for the tower-type personal computer and the heat transport characteristics of this cooling device was investigated. The experimental equipment consisted of the evaporator, the condenser, the liquid tube, the vapor tube and the reservoir. The length and the diameter of the evaporator were 150mm and 27mm respectively and had capillary wick in it with equivalent diameter of 5μm. In the experiment, the heat flux to the evaporator and the cooling water temperature were changed. And the effects of enclosed quantity of the working fluid (R134a) in the reservoir and the evaporator height above the condenser on heat transport rate were also investigated. Experimental results shown that this capillary pumped loop was able to transport heat rate of 15 to 95W (heat flux of 995 to 6051 W/m2) with highest temperature of 343K and that the temperature difference in the loop was 16.7 to 43.9 K in the case of 2500mm in its heat transport length and cooling temperature of 293K. And it was derived that the working fluid enclosed rate affected the maximum heat transport rate. The computer code was also developed to evaluate the effect of the refrigerant enclosed rate and the wick thickness on the heat transport rate considering the pressure drop to the circumference direction in the wick.

Innovative Realizations of High Heat-Flux Boiling and Condensing Flows for Milli-Meter and Micro-Meter Scale Applications

2014 ◽  
Author(s):  
Michael Kivisalu ◽  
Amitabh Narain ◽  
Patcharapol Gorgitrattanagul ◽  
Ranjeeth Naik
Keyword(s):  
Heat Flux ◽  
Heat Load ◽  
High Heat ◽  
Electronic Cooling ◽  
System Level ◽  
High Heat Flux ◽  
Zero Gravity ◽  
Pressure Drops ◽  
Condensing Flows ◽  
High Heat Load

For shear driven mm-scale flows, the traditional boiler and condenser operations pose serious problems of degraded performance (low heat-flux values, high pressure drops, and device-and-system level instabilities). The innovative devices are introduced for functionality and high heat load capabilities needed for shear dominated electronic cooling situations that arise in milli-meter scale operations, certain gravity-insensitive avionics-cooling and zero-gravity applications.

EMC3-EIRENE simulations of neon impurity seeding effects on heat flux distribution on CFETR

2022 ◽  
Author(s):  
Shuyu Dai ◽  
Defeng Kong ◽  
Vincent Chan ◽  
Liang Wang ◽  
Yuhe Feng ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Load ◽  
Flux Distribution ◽  
Three Dimensional ◽  
Input Power ◽  
Heat Flux Distribution ◽  
Maximum Heat ◽  
Maximum Heat Flux ◽  
Heat Loads ◽  
Injection Location

Abstract The numerical modelling of the heat flux distribution with neon impurity seeding on CFETR has been performed by the three-dimensional (3D) edge transport code EMC3-EIRENE. The maximum heat flux on divertor targets is about 18 MW m-2 without impurity seeding under the input power of 200 MW entering into the scrape-off layer. In order to mitigate the heat loads below 10 MW m-2, neon impurity seeded at different poloidal positions has been investigated to understand the properties of impurity concentration and heat load distributions for a single toroidal injection location. The majority of the studied neon injections gives rise to a toroidally asymmetric profile of heat load deposition on the in- or out-board divertor targets. The heat loads cannot be reduced below 10 MW m-2 along the whole torus for a single toroidal injection location. In order to achieve the heat load mitigation (<10 MW m-2) along the entire torus, modelling of sole and simultaneous multi-toroidal neon injections near the in- and out-board strike points has been stimulated, which indicates that the simultaneous multi-toroidal neon injections show a better heat flux mitigation on both in- and out-board divertor targets. The maximum heat flux can be reduced below 7 MWm-2 on divertor targets for the studied scenarios of the simultaneous multi-toroidal neon injections.

Heat Transport Characteristics in Closed Loop Oscillating Heat Pipes

2005 ◽  
Author(s):  
Shuangfeng Wang ◽  
Shigefumi Nishio
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Closed Loop ◽  
Flow Behavior ◽  
Working Fluid ◽  
Liquid Volume ◽  
High Heat Flux ◽  
Two Phase ◽  
Working Fluids ◽  
Inner Diameter

Heat transport rates of micro scale SEMOS (Self-Exciting Mode Oscillating) heat pipe with inner diameter of 1.5mm, 1.2mm and 0.9mm, were investigated by using R141b, ethanol and water as working fluids. The effects of inner diameter, liquid volume faction, and material properties of the working fluids are examined. It shows that the smaller the inner diameter, the higher the thermal transport density is. For removing high heat flux, the water is the most promising working fluid as it has the largest critical heat transfer rate and the widest operating range among the three kinds of working fluids. A one-dimensional numerical simulation is carried out to describe the heat transport characteristics and the two-phase flow behavior in the closed loop SEMOS heat pipe. The numerical prediction agrees with the experimental results fairly well, when the input heat through was not very high and the flow pattern was slug flow.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.

A Numerical Model of a Reciprocating-Mechanism Driven Heat Loop for Two-Phase High Heat Flux Cooling

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Olubunmi Popoola ◽  
Ayobami Bamgbade ◽  
Yiding Cao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Model ◽  
Performance Optimization ◽  
Numerical Study ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
Transfer Device

An effective design option for a cooling system is to use a two-phase pumped cooling loop to simultaneously satisfy the temperature uniformity and high heat flux requirements. A reciprocating-mechanism driven heat loop (RMDHL) is a novel heat transfer device that could attain a high heat transfer rate through a reciprocating flow of the two-phase working fluid inside the heat transfer device. Although the device has been tested and validated experimentally, analytical or numerical study has not been undertaken to understand its working mechanism and provide guidance for the device design. The objective of this paper is to develop a numerical model for the RMDHL to predict its operational performance under different working conditions. The developed numerical model has been successfully validated by the existing experimental data and will provide a powerful tool for the design and performance optimization of future RMDHLs. The study also reveals that the maximum velocity in the flow occurs near the wall rather than at the center of the pipe, as in the case of unidirectional steady flow. This higher velocity near the wall may help to explain the enhanced heat transfer of an RMDHL.

Investigation of a Capillary Assisted Thermosyphon (CAT) for Shipboard Electronics Cooling

Volume 4 ◽  
2004 ◽  
Author(s):  
E. H. Larsen ◽  
M. Cerza ◽  
A. N. Smith ◽  
C. Thomas Conroy
Keyword(s):  
Flat Plate ◽  
Heat Input ◽  
Power Dissipation ◽  
Water Flow Rate ◽  
Cooling Water ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Cold Plate ◽  
Capillary Pumped Loop ◽  
Forced Circulation

As microprocessors shrink in size and increase in power dissipation levels, the current need for advanced electronics cooling techniques is paramount since power dissipation levels are rapidly exceeding the capabilities of forced air convection cooling. This paper reports an investigation of using a capillary assisted thermosyphon for the shipboard cooling of electronics components. The capillary assisted thermosyphon differs from the capillary pumped loop or loop heat pipe system in that the basic cooling loop is based on a thermosyphon. The capillary assist comes from the fact that there is a wicking structure in the flat evaporator plate, however, the wicking structure is there to spread the working fluid across the flat plate evaporator in the areas under the heat sources. This differs from a capillary pumped loop in that the wick structure does not produce a capillary pumping head from the liquid return to the vapor outlet side of the evaporator. In fact, the liquid return and vapor outlet are almost at the same pressure. The forced circulation in the thermosyphon is caused by a gravity head between the condenser cold plate and the flat plate evaporator. An experimental facility for conducting research on capillary assisted thermosyphon was developed. In order to simulate the shipboard cooling water encountered at various locations of the ocean, the heat sink temperature of the facility could be varied. A vertical flat plate, CAT evaporator was designed and tested under thermal sink temperatures of 4, 21 and 37°C. The condenser cold plate cooling water flow rate varied from 0.38 to 3 GPM. The heat input varied from 250 to 1500 W evenly spread over the area of the evaporator. The CAT flat plate evaporator performed very well under this range of heat inputs, sink temperatures, and cold plate flow rates. The main result obtained showed that as heat input increased the amount of subcooling between the evaporator vapor outlet line and liquid return line increased. This subcooling did not hinder thermal performance as measured by the internal operating temperature.

Flow Boiling Enhancement in Microchannels With Diffusion Bonded Wire Mesh

2007 ◽  
Author(s):  
Hailei Wang ◽  
Richard Peterson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
High Heat ◽  
Wire Mesh ◽  
Working Fluid ◽  
High Heat Flux ◽  
Vapor Quality ◽  
Heating Wall

Flow boiling and heat transfer enhancement in four parallel microchannels using a dielectric working fluid, HFE 7000, was investigated. Each channel was 1000 μm wide and 510 μm high. A unique channel surface enhancement technique via diffusion bonding a layer of conductive fine wire mesh onto the heating wall was developed. According to the obtained flow boiling curves for both the bare and mesh channels, the amount of wall superheat was significantly reduced for the mesh channel at all stream-wise locations. This indicated that the nucleate boiling in the mesh channel was enhanced due to the increase of nucleation sites the mesh introduced. Both the nucleate boiling dominated and convective evaporation dominated regimes were identified. In addition, the overall trend for the flow boiling heat transfer coefficient, with respect to vapor quality, was increasing until the vapor quality reached approximately 0.4. The critical heat flux (CHF) for the mesh channel was also significantly higher than that of the bare channel in the low vapor quality region. Due to the fact of how the mesh was incorporated into the channels, no pressure drop penalty was identified for the mesh channels. Potential applications for this kind of mesh channel include high heat-flux electronic cooling systems and various energy conversion systems.

Reciprocating-Mechanism Driven Heat Loops and Their Applications

2003 ◽  
Author(s):  
Yiding Cao ◽  
Mingcong Gao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Electronics Cooling ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
Condenser Section ◽  
Evaporator Section ◽  
Two Phase Heat Transfer ◽  
Transfer Device

This paper introduces a novel heat transfer mechanism that facilitates two-phase heat transfer while eliminating the so-called cavitation problem commonly encountered by a conventional pump. The heat transfer device is coined as the reciprocating-mechanism driven heat loop (RMDHL), which includes a hollow loop having an interior flow passage, an amount of working fluid filled within the loop, and a reciprocating driver. The hollow loop has an evaporator section, a condenser section, and a liquid reservoir. The reciprocating driver is integrated with the liquid reservoir and facilitates a reciprocating flow of the working fluid within the loop, so that liquid is supplied from the condenser section to the evaporator section under a substantially saturated condition and the so-called cavitation problem associated with a conventional pump is avoided. The reciprocating driver could be a solenoid-operated reciprocating driver for electronics cooling applications and a bellows-type reciprocating driver for high-temperature applications. Experimental study has been undertaken for a solenoid-operated heat loop in connection with high heat flux thermal management applications. Experimental results show that the heat loop worked very effectively and a heat flux as high as 300 W/cm2 in the evaporator section could be handled. The applications of the bellows-type reciprocating heat loop for gas turbine nozzle guide vanes and the leading edges of hypersonic vehicles are also illustrated. The new heat transfer device is expected to advance the current two-phase heat transfer device and open up a new frontier for further research and development.

Effect of Fluid Loading on the Performance of Wicked Heat Pipes

Volume 3 ◽  
2004 ◽  
Author(s):  
R. Kempers ◽  
A. Robinson ◽  
C. Ching ◽  
D. Ewing
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Pipes ◽  
Working Fluid ◽  
Fluid Loading ◽  
Maximum Heat ◽  
Horizontal Orientation ◽  
Maximum Heat Flux ◽  
Dry Out

A study was performed to experimentally characterize the effect of fluid loading on the heat transport performance of wicked heat pipes. In particular, experiments were performed to characterize the performance of heat pipes with insufficient fluid to saturate the wick and excess fluid for a variety of orientations. It was found that excess working fluid in the heat pipe increased the thermal resistance of the heat pipe, but increased maximum heat flux through the pipe in a horizontal orientation. The thermal performance of the heat pipe was reduced when the amount of working fluid was less than required to saturate the wick, but the maximum heat flux through the heat pipe was significantly reduced at all orientations. It was also found in this case the performance of this heat pipe deteriorated once dry-out occurred.

Nucleate Boiling of Dielectric Liquids on Hydrophobic Patterned Surfaces

2014 ◽  
Author(s):  
Nihal E. Joshua ◽  
Denesh K. Ajakumar ◽  
Huseyin Bostanci
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nucleate Boiling ◽  
High Heat ◽  
Copper Surface ◽  
Dielectric Liquid ◽  
Working Fluid ◽  
Patterned Surfaces ◽  
High Heat Flux ◽  
Dielectric Liquids

This study experimentally investigated the effect of hydrophobic patterned surfaces in nucleate boiling heat transfer. A dielectric liquid, HFE-7100, was used as the working fluid in the saturated boiling tests. Dielectric liquids are known to have highly-wetting characteristics. They tend to fill surface cavities that would normally trap vapor/gas, and serve as active nucleation sites during boiling. With the lack of these vapor filled cavities, boiling of a dielectric liquid leads to high incipience superheats and accompanying temperature overshoots. Heater samples in this study were prepared by applying a thin Teflon (AF400, Dupont) coating on 1-cm2 smooth copper surfaces following common photolithography techniques. Matching size thick film resistors, attached onto the copper samples, generated heat and simulated high heat flux electronic devices. Tests investigated the heater samples featuring circular pattern sizes between 40–100 μm, and corresponding pitch sizes between 80–200 μm. Additionally, a plain, smooth copper surface was tested to obtain reference data. Based on data, hydrophobic patterned surfaces effectively eliminated the temperature overshoot at boiling incipience, and considerably improved nucleate boiling performance in terms of heat transfer coefficient and critical heat flux over the reference surface. Hydrophobic patterned surfaces therefore demonstrated a practical surface modification method for heat transfer enhancement in immersion cooling applications.

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