Experiment of a Novel Capillary-Pumped Loop With a Semi-Arc Porous Evaporator in 1U Simulation Cabinet

2005 ◽  
Author(s):  
Hung-Wen Lin ◽  
Ming-Chieh Wu ◽  
Wei-Keng Lin
Keyword(s):  
Thermal Management ◽  
High Efficiency ◽  
Size Range ◽  
Working Fluid ◽  
Power Electronic ◽  
Capillary Pumped Loop ◽  
Two Phase ◽  
Scale Down ◽  
Two Phase Heat Transfer ◽  
Transfer Device

The CPL is a high efficiency two-phase heat transfer device using the phase change of working fluid to transport heat from evaporator to condenser; it is a cyclic circulation pumped by capillary force. Since CPL does not need any other mechanical force such as pump, it might be used to do the thermal management of high power electronic component on spacecraft. This study presents a novel CPL with a semi-arc porous evaporator in 1U server on the ground with a horizontal position and scale down the whole device to the miniature size (range from mm to cm). This miniature-CPL is made of aluminum with the shape of evaporator and the porous structure using a semi-arc instead of square and cylinder structure. Testing results show that the miniature-CPL could remove heat 45W in steady state and keep the heat source temperature about 73°C.

Mathematical Modeling of Novel Two-Phase Heat Transfer Device for Thermal Management of Light Emitting Diodes

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Karthik S. Remella ◽  
Frank M. Gerner ◽  
Ahmed Shuja
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Management ◽  
Light Emitting Diodes ◽  
Working Fluid ◽  
Two Phase ◽  
Light Emitting ◽  
Phase Mixture ◽  
Two Phase Heat Transfer ◽  
Transfer Device

The paper introduces a novel two-phase heat transfer device (TPHTD) which is employed in the thermal management of light emitting diodes (LEDs). The heat transfer device structurally resembles a conventional loop heat pipe (LHP) without a compensation chamber, but operates very differently from it. The device is comprised of a central evaporator package and a circular coil that acts as a heat exchanger loop. The working fluid leaving the evaporator has a two-phase mixture quality of approximately 0.2. Having introduced the device, the paper delineates a mathematical model for predicting its thermal performance. The primary objective of the model is to provide a fundamental understanding of the operation of the device. A one-dimensional thermal resistance model (TRM) is utilized in modeling the evaporator. The paper presents a detailed discussion on obtaining these resistances from experiments conducted on the device. A correlation for the external heat transfer coefficient of the heat exchanger loop is proposed based on experiments and is found to be in good agreement with literature. The model predicts performance parameters such as board temperature, two-phase mixture quality, and saturation and subcooled temperatures (Tsat and Tsc) of the working fluid for different input thermal powers (Qtot). Based on experimental evidence, it is concluded that the majority of Qtot (∼75%) is utilized in phase change of the working fluid, and the rest reheats the working fluid from a lower subcooled temperature (Tsc) to the saturation temperature (Tsat) of the evaporator.

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.

Optimization Study of a Silicon-Carbide Micro-Capillary Pumped Loop

2003 ◽  
Author(s):  
Laura J. Meyer ◽  
Leslie M. Phinney
Keyword(s):  
Thermal Management ◽  
High Power ◽  
Electronic Devices ◽  
Maximum Size ◽  
Power Electronic ◽  
Power Devices ◽  
Pressure Balance ◽  
Capillary Pumped Loop ◽  
Two Phase ◽  
Bandgap Semiconductors

Wide bandgap semiconductors such as SiC and GaN are materials that are advantageous for high power electronic devices. High power devices generate large amounts of energy that must be removed, and traditional cooling methods are insufficient for maintaining the desired operating temperatures. Thus, thermal management methods for high power electronic devices need to be developed. A SiC micro-capillary pumped loop thermal management system is being evaluated to cool SiC high power devices. Mathematical models incorporating two-phase flow and capillary wicking have been developed to analyze capillary pumped loops or loop heat pipes. This investigation uses a model based on the methodology of Dickey and Peterson (1994). The model takes an energy balance on the condenser and evaporator regions, as well as a pressure balance across the meniscus. A parametric study has been performed on the micro-CPL to determine the best design for a p-i-n diode that is less than 1 cm square and which produces a heat flux at the junction of over 300 W/cm2. The micro-CPL will be limited to a maximum size of 6.5 cm2. The liquid and vapor line lengths, number of grooves, and groove dimensions are varied to determine optimal values. The results and trends of the optimization calculations are discussed.

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.

Experimental Study of Heat Pipe Exchanger for High Power LED Cooling System

2011 ◽  
Vol 295-297 ◽  
pp. 1985-1988
Author(s):  
Yu Jun Gou ◽  
Zhong Liang Liu ◽  
Xiao Hui Zhong
Keyword(s):  
Heat Exchanger ◽  
Heat Pipe ◽  
High Power ◽  
Heat Dissipation ◽  
High Efficiency ◽  
Cooling System ◽  
Two Phase ◽  
High Power Led ◽  
New Type ◽  
Two Phase Heat Transfer

A new cooling concept for high power LED by combining the heat release of high power LED with two-phase heat transfer heat pipes was proposed, and in this study a new type of heat pipe with specific fins structure was developed. Through experimental results, we found the new heat pipe heat exchanger has the features of high efficiency of heat dissipation and compact construction which meets the demand of heat dissipation for high power LED. We also found the heat dissipation performance of the HP heat exchanger changed with the work angle.

Development and Experimental Validation of a Micro/Nano Thermal Ground Plane

2011 ◽  
Author(s):  
H. Peter J. de Bock ◽  
Shakti Chauhan ◽  
Pramod Chamarthy ◽  
Chris Eastman ◽  
Stanton Weaver ◽  
...  
Keyword(s):  
Experimental Validation ◽  
Ground Plane ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
Working Fluid ◽  
Heat Sources ◽  
Two Phase ◽  
Evaporation And Condensation ◽  
Two Phase Heat Transfer ◽  
Thermal Ground Plane

Heat pipes are commonly used in electronics cooling applications to spread heat from a concentrated heat source to a larger heat sink. Heat pipes work on the principles of two-phase heat transfer by evaporation and condensation of a working fluid. The amount of heat that can be transported is limited by the capillary and hydrostatic forces in the wicking structure of the device. Thermal ground planes are two-dimensional high conductivity heat pipes that can serve as thermal ground to which heat can be rejected by a multitude of heat sources. As hydrostatic forces are dependent on gravity, it is commonly known that heat pipe and thermal ground plane performance is orientation dependent. The effect of variation of gravity force on performance is discussed and the development of a miniaturized thermal ground plane for high g operation is described. In addition, experimental results are presented from zero to −10g acceleration. The study shows and discusses that minimal orientation or g-force dependence can be achieved if pore dimensions in the wicking structure can be designed at micro/nano-scale dimensions.

High-Flux Thermal Management With Supercritical Fluids

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Brian M. Fronk ◽  
Alexander S. Rattner
Keyword(s):  
Heat Flux ◽  
Thermal Management ◽  
Heat Sink ◽  
Electronics Cooling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Management Approach ◽  
High Heat Flux ◽  
Two Phase ◽  
Pump Design

A novel thermal management approach is explored, which uses supercritical carbon dioxide (sCO2) as a working fluid to manage extreme heat fluxes in electronics cooling applications. In the pseudocritical region, sCO2 has extremely high volumetric thermal capacity, which can enable operation with low pumping requirements, and without the potential for two-phase critical heat flux (CHF) and flow instabilities. A model of a representative microchannel heat sink is evaluated with single-phase liquid water and FC-72, two-phase boiling R-134a, and sCO2. For a fixed pumping power, sCO2 is found to yield lower heat-sink wall temperatures than liquid coolants. Practical engineering challenges for supercritical thermal management systems are discussed, including the limits of predictive heat transfer models, narrow operating temperature ranges, high working pressures, and pump design criteria. Based on these findings, sCO2 is a promising candidate working fluid for cooling high heat flux electronics, but additional thermal transport research and engineering are needed before practical systems can be realized.

Advanced Integrated Cooling Systems for Thermal Management in Data Centers

2009 ◽  
Author(s):  
Yoshiyuki Abe ◽  
Masato Fukagaya ◽  
Takashi Kitagawa ◽  
Haruhiko Ohta ◽  
Yasuhisa Shinmoto ◽  
...  
Keyword(s):  
Thermal Management ◽  
Heat Exchangers ◽  
Single Phase ◽  
Heat Pipes ◽  
Narrow Channel ◽  
Working Fluid ◽  
Two Phase ◽  
Thermal Network ◽  
Flat Type ◽  
Nano Fluids

For a drastic energy conservation in data centers (more than 30%), a new advanced concept of thermal management systems of integrated cooling network in server racks is proposed, and a series of developmental studies toward the realization of the concept have been conducted. The concept consists of the following technological items: - Plug-in thermal network cables, - Narrow channel heat exchangers (single-phase and two-phase), - Thin flat-type heat pipes, - Development of nano-fluids for heat transfer enhancement. In this concept, CPUs in server racks are directly cooled with the aid of advanced 1.5 mm thick flat-type heat pipes or 3 mm thick narrow channel heat exchangers, though CPUs in server racks, at present, are cooled down with massive heat sinks by forced air flow in the racks. In the case of heat pipes, condensation regions are cooled by either single-phase or two-phase narrow channel heat sink instead of air-cooled finned heat sink. These cooling units are accommodated in server racks. In addition, plug-in thermal network cables, in which a working fluid for narrow channel heat exchangers is running, are integrated among server racks, and thermal energy dissipated in server racks are inclusively merged and managed by the thermal network cables. The working fluid heated up by the dissipated heat is recuperated in an outdoor cooling system. An attempt at the applications of silver nano-fluids as a working fluid in heat pipes and thermal network is also conducted in the present study. Silver nano-fluids are thermochemically synthesized by a microwave heating technique, which allows for superior stable suspension characteristics.

Steady State Thermal Behaviour of Ceramic Wick Structure for Application in Two Phase Heat Transfer Devices

2014 ◽  
Vol 1082 ◽  
pp. 302-308
Author(s):  
Lucas Freitas Berti ◽  
Paulo Henrique Dias dos Santos ◽  
Carlos Renato Rambo ◽  
Dachamir Hotza ◽  
Edson Bazzo
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Thermal Behaviour ◽  
Capillary Pumped Loop ◽  
Two Phase ◽  
Evaporator Temperature ◽  
Steady State Condition ◽  
Wick Structure ◽  
Permeability Constants ◽  
Two Phase Heat Transfer

This work reports on results from two phase heat transfer devices assembled with ceramic capillary structure. It is firstly presented the manufacturing of the ceramic wick structures and afterwards the characterization of the morphological-and fluid-dynamical properties of these ceramic wick structures. As closing results, it is presented the thermal behaviour of two different two phase heat transfer devices, i.e. a Capillary Pumped Loop and a Loop Heat Pipe. The properties of the ceramic wick structure are within the desirable range for a correct functioning of these devices, e.g. porosity, pore size and permeability constants ranging from 40 to 60%, from 5 to 30μm and from 10-10 to 10-13m2, respectively. The thermal behaviour tests of the heat transfer devices used power heat load input in range from 10 to 20W and for all devices the evaporator temperature reached steady state condition. Thus, as a result, it can be claimed these ceramic wick structures as successful alternative for assembling capillary evaporator of CPL and LHP.

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