scholarly journals CHARACTERIZATION OF HEAT CONDUCTIVITY OF ECCENTRICALLY ROTATING HEAT PIPES USED FOR COOLING OF MOTOR SPINDLES

2021 ◽  
Vol 2021 (3) ◽  
pp. 4698-4705
Author(s):  
B. Denkena ◽  
◽  
B. Bergmann ◽  
K. Kono ◽  
R. Ishiguro ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Pipe ◽  
Heat Exchangers ◽  
Thermal Characteristics ◽  
Heat Pipes ◽  
Simulation Based ◽  
Wick Structure ◽  
Parameter Values

Heat losses within motor spindles lead to undesired effects such as machining inaccuracies and de-creasing lifetime of the motor and bearings. To reduce thermal loads, complex shaft cooling concepts with costly sealing techniques exist. For this reason, a novel, less costly cooling concept has been de-veloped based on heat pipes with high thermal conductivity and fin-shaped heat exchangers. The de-sign and integration of these heat exchanger elements into a motor spindle is carried out using the fi-nite element method. The aim is to optimize the efficiency of the heat pipes and heat exchangers for optimal shaft cooling performance. For a simulation-based development of a prototype spindle, un-known thermal characteristics of the heat transfer elements must be determined. In this paper, the de-termination of the thermal conductivity of the heat pipes is described. The determination of conductivi-ty is done experimentally. First, the developed test rig and the applied procedure for the determination of the conductivity are shown. Subsequently, the experimental results are presented and discussed. Two types of heat pipes were analyzed: Copper heat pipes with sintered wick structure and nickel-plated copper heat pipes with axial grooves. The influences of rotational speed, heat flow rates and the angle between the heat pipe and main axis of rotation were investigated. The results indicate a distinct dependency of the conductivity on the varied parameters. However, changes of parameter values have very different quantitative and qualitative effects on the determined conductivities de-pending on the type of heat pipe.

Experimental Investigation of Graphene Oxide Nanofluids on Thermal Performance of Heat Pipe

2019 ◽  
Author(s):  
Weilin Zhao ◽  
Jun Xu ◽  
Jinkai Li
Keyword(s):  
Thermal Conductivity ◽  
Graphene Oxide ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Heat Pipes ◽  
Air Cooling ◽  
Coating Film ◽  
Water Cooling ◽  
Condenser Section ◽  
Wick Structure

Abstract The graphene oxide-deionized water (GO-DW) and graphene oxide-ethylence glycol (GO-EG) nanofluids were synthesized. The better suspension of nanofluids was achieved. The thermal conductivity of both nanofluids was analyzed. It indicates that GO nanoparticles can strengthen the thermal conductivity of DW base fluids by 22.6%–61.7% and EG base fluids by 15.3%–32.8%. Four copper heat pipes charged with GO-DW and GO-EG nanofluids as well as DW and EG base fluids were experimentally researched, it is discovered that the addition of GO nonoparticles in heat pipe can elevate the condenser wall temperature and reduce the temperature difference. Future analysis finds that, with respect to DW and EG fluids heat pipe, the thermal resistances of GO-DW and GO-EG nanofluids heat pipe are respectively decreased 42.6–52.4% and 31.9%–38.4% for air cooling, and 15.5–16.7% and 11.5%–18.9% for water cooling at condenser section. Besides, the wick structure of GO-DW nanofluids heat pipe was examined by Scanning Electron Microscope, and the effective thermal conductivity of fluid-wick combination was evaluated. The outcomes demonstrate that the evaporator wick surface contains about 0375–1.24μm coating film of GO nanoparticles. Assumed the coating film is 0.75μm, the effective thermal conductivity of fluid-wick combination is respectively enhanced by 66.92 % for GO-DW nonofluids heat pipe and 37.32% for GO-EG nonofluids heat pipe at 70 °C.

A Titanium Based Flat Heat Pipe

2008 ◽  
Author(s):  
Changsong Ding ◽  
Gaurav Soni ◽  
Payam Bozorgi ◽  
Brian Piorek ◽  
Carl D. Meinhart ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Aspect Ratio ◽  
Heat Pipe ◽  
Carrying Capacity ◽  
High Aspect Ratio ◽  
Capillary Flow ◽  
Titanium Substrate ◽  
Heat Pipes ◽  
Working Fluid ◽  
Wick Structure

We are developing innovative heat pipes based on Nano-Structured Titania (NST) with a potential for high heat carrying capacity and high thermal conductivity. These heat pipes have a flat geometry as opposed to a cylindrical geometry found in conventional heat pipes. The flatness will enable a good contact with microprocessor chips and thus reduce the thermal contact resistance. We refer to it as a Thermal Ground Plane (TGP) because of its flat and thin geometry. It will provide the ability to cool the future generations of power intensive microprocessor chips and circuit boards in an efficient way. It also brings the potential to function in high temperature (>150°C) fields because of its high yield strength and compatibility [1]. The TGP is fabricated with Titanium. It adopts the recently developed high aspect ratio Ti processing techniques [2] and laser packaging techniques. The three main components of the TGP are 1) a fine wick structure based on arrays of high aspect ratio Ti pillars and hair like structures of Nano-Structured Titania (NST), 2) A shallow Ti cavity welded onto the wick structure and 3) the working fluid, water, sealed between the cavity and the wick. The heat carrying capacity and the thermal conductivity of a heat pipe are generally determined by the speed of capillary flow of the working fluid through its wick. The TGP wick has the potential to generate high flow rates and to meet the growing challenges faced by electronics cooling community. The TGP wick structure, developed by etching high aspect ratio pillars in a titanium substrate and growing nano scale hairs on the surface of the pillars, is super hydrophilic and capable of wicking water at velocities ∼ 10−2 m/s over distances of several centimeters. The thermal conductivity of the current TGP device was measured to be k = 350 W/m·K. The completed TGP device has the potential of attaining a higher conductivity by improving the wicking material and of carrying higher power density. Washburn equation [3] for dynamics of capillary flow has been employed to explain the results of our experiments. The experiment shows a good agreement with Washburn equation.

Study on the Thermal Characteristics of Heat Pipes with Water-Based MWCNT Nanofluids

2011 ◽  
Vol 110-116 ◽  
pp. 1879-1885
Author(s):  
Hyo Jun Ha ◽  
Ji Hun Park ◽  
Seok Pil Jang
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Volume Fraction ◽  
Thermal Characteristics ◽  
Heat Pipes ◽  
Multiwalled Carbon ◽  
Evaporation Temperature ◽  
Water Based

In this paper, thermal characteristics of miniature heat pipes with grooved wick and water-based multiwalled carbon nanotubes(MWCNT) nanofluids(0.1, 0.2, and 0.5 vol.%) as working fluids are experimentally investigated. The thermal conductivity and thermal resistances are measured and compared with those of DI water. The thermal conductivity of water-based MWCNT nandfluids is enhanced by up to 29% compared with that of DI water. Experiments are performed under the same evaporation temperature condition. The thermal resistance of heat pipe is reduced from 30% to 35.2% as the volume fraction of nanoparticles inceasing from 0.1% to 0.5%. Finally, based on the experimental results, we present the reduction of the thermal resistances of the heat pipes compared with conventional heat pipes cannot be explained by only the thermal conductivity of water-based MWCNT nanofluids.

Steady-State Investigation of Vapor Deposited Micro Heat Pipe Arrays

1995 ◽  
Vol 117 (1) ◽  
pp. 75-81 ◽  
Author(s):  
A. K. Mallik ◽  
G. P. Peterson
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Surface Temperature ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Heat Pipes ◽  
Temperature Gradients ◽  
Bottom Surface ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

An experimental investigation of vapor deposited micro heat pipe arrays was conducted using arrays of 34 and 66 micro heat pipes occupying 0.75 and 1.45 percent of the cross-sectional area, respectively. The performance of wafers containing the arrays was compared with that of a plain silicon wafer. All of the wafers had 8 × 8 mm thermofoil heaters located on the bottom surface to simulate the active devices in an actual application. The temperature distributions across the wafers were obtained using a Hughes Probeye TVS Infrared Thermal Imaging System and a standard VHS video recorder. For wafers containing arrays of 34 vapor deposited micro heat pipes, the steady-state experimental data indicated a reduction in the maximum surface temperature and temperature gradients of 24.4 and 27.4 percent, respectively, coupled with an improvement in the effective thermal conductivity of 41.7 percent. For wafers containing arrays of 66 vapor deposited micro heat pipes, the corresponding reductions in the surface temperature and temperature gradients were 29.0 and 41.7 percent, respectively, and the effective thermal conductivity increased 47.1 percent, for input heat fluxes of 4.70 W/cm2. The experimental results were compared with the results of a previously developed numerical model, which was shown to predict the temperature distribution with a high degree of accuracy, for wafers both with and without the heat pipe arrays.

Novel Fluorescent Visualization Method to Characterize Transport Properties in Micro/Nano Heat Pipe Wick Structures

2009 ◽  
Author(s):  
Pramod Chamarthy ◽  
H. Peter J. de Bock ◽  
Boris Russ ◽  
Shakti Chauhan ◽  
Brian Rush ◽  
...  
Keyword(s):  
Heat Pipe ◽  
High Performance ◽  
Gravitational Force ◽  
Driving Forces ◽  
Electronics Cooling ◽  
Heat Pipes ◽  
High Permeability ◽  
Permeability Characteristics ◽  
Wick Structure ◽  
Initial Results

Heat pipes have been gaining a lot of popularity in electronics cooling applications due to their ease of operation, reliability, and high effective thermal conductivity. An important component of a heat pipe is the wick structure, which transports the condensate from condenser to evaporator. The design of wick structures is complicated by competing requirements to create high capillary driving forces and maintain high permeability. While generating large pore sizes will help achieve high permeability, it will significantly reduce the wick’s capillary performance. This study presents a novel experimental method to simultaneously measure capillary and permeability characteristics of the wick structures using fluorescent visualization. This technique will be used to study the effects of pore size and gravitational force on the flow-related properties of the wick structures. Initial results are presented on wick samples visually characterized from zero to nine g acceleration on a centrifuge. These results will provide a tool to understand the physics involved in transport through porous structures and help in the design of high performance heat pipes.

Material Characterization of Additively Manufactured Part via Multi-Level Stochastic Upscaling Method

2015 ◽  
Author(s):  
Recep M. Gorguluarslan ◽  
Sang-In Park ◽  
David W. Rosen ◽  
Seung-Kyum Choi
Keyword(s):  
Material Characterization ◽  
Modeling Framework ◽  
Upscaling Technique ◽  
Simulation Based ◽  
Scale Models ◽  
Multiple Levels ◽  
Multiscale Modeling Framework ◽  
Input Uncertainties

An integrated multiscale modeling framework that incorporates a simulation-based upscaling technique is developed and implemented for the material characterization of additively manufactured cellular structures in this paper. The proposed upscaling procedure enables the determination of homogenized parameters at multiple levels by matching the probabilistic performances between fine and coarse scale models. Polynomial chaos expansion is employed in upscaling procedure to handle the computational burden caused by the input uncertainties. Efficient uncertainty quantification is achieved at the mesocale level by utilizing the developed upscaling technique. The homogenized parameters of mesostructures are utilized again at the macroscale level in the upscaling procedure to accurately obtain the overall material properties of the target cellular structure. Actual experimental results of additively manufactured parts are integrated into the developed procedure to demonstrate the efficacy of the method.

A Multilevel Upscaling Method for Material Characterization of Additively Manufactured Part Under Uncertainties

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Recep M. Gorguluarslan ◽  
Sang-In Park ◽  
David W. Rosen ◽  
Seung-Kyum Choi
Keyword(s):  
Material Characterization ◽  
Modeling Framework ◽  
Upscaling Technique ◽  
Simulation Based ◽  
Scale Models ◽  
Multiple Levels ◽  
Multiscale Modeling Framework ◽  
Input Uncertainties

An integrated multiscale modeling framework that incorporates a simulation-based upscaling technique is developed and implemented for the material characterization of additively manufactured cellular structures in this paper. The proposed upscaling procedure enables the determination of homogenized parameters at multiple levels by matching the probabilistic performance between fine and coarse scale models. Polynomial chaos expansion (PCE) is employed in the upscaling procedure to handle the computational burden caused by the input uncertainties. Efficient uncertainty quantification is achieved at the mesoscale level by utilizing the developed upscaling technique. The homogenized parameters of mesostructures are utilized again at the macroscale level in the upscaling procedure to accurately obtain the overall material properties of the target cellular structure. Actual experimental results of additively manufactured parts are integrated into the developed procedure to demonstrate the efficacy of the method.

Evaporation, Condensation, and Flow in an Idealized Micro Heat Pipe

2002 ◽  
Author(s):  
Jin Zhang ◽  
Harris Wong
Keyword(s):  
Thermal Conductivity ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Three Dimensional ◽  
Heat Pipes ◽  
Rigorous Analysis ◽  
Evaporation And Condensation ◽  
Micro Heat Pipe ◽  
Complicated Geometry ◽  
Micro Heat Pipes

Micro heat pipes have been used in cooling micro electronic components. However their effective thermal conductivity is low compared with that of conventional heat pipes. Due to the complexity of the coupled heat and mass transport, and to the complicated three-dimensional bubble geometry inside micro heat pipes, there is a lack of rigorous analysis. As a result, the relatively low effective thermal conductivity remains unexplained. We have conceptualized an idealized micro heat pipe that eliminates the complicated geometry, but retains the essential physics. Given the simplified geometry, many effects can be studied, such as thermocapillary flow, and evaporation and condensation physics. In this talk, we will present the flow field induced by evaporation.

Thermal Characteristics of a Cylindrical Heat Pipe using Multi-Layer Screen Mesh Wick

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
R. Sankar Rao ◽  
S. Bhanu Prakash
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Characteristics ◽  
Wire Mesh ◽  
Working Fluid ◽  
Wick Structure ◽  
Screen Mesh

Heat pipe is the most widely used heat exchanging device in removal of heat from any given system at a faster rate. The thermal characteristics of heat pipe with single and multi-layered screen mesh wicks have been observed with two working fluids water and acetone. Heat pipe of length 250 mm and 12.7 mm outer diameter, made of copper material is used in all the trials of with and without wick structure. A 100 mesh stainless steel screen wire mesh is chosen as wick structure. Experiments were conducted at different heat loads and various inclinations with 100% fill ratio in evaporator. The performance is measured based on total thermal resistance and overall heat transfer coefficient. The heat pipe is found effective at 60o inclination with acetone as a working fluid and with four layered screen mesh wick. Uncertainty in thermal resistance and heat transfer coefficient is calculated for a heat input of 10W at 0 and 60 inclinations.

Design Shell for Parametric Design at Embodiment Stage

2003 ◽  
Author(s):  
Adwait Vaidya ◽  
Jami Shah
Keyword(s):  
Parametric Design ◽  
Problem Definition ◽  
Design Stage ◽  
Embodiment Design ◽  
System Requirements ◽  
Parameter Values ◽  
Domain Independent

The embodiment design stage involves determination of geometric sizes, key parameter values, and matching of component variables to system requirements. This embodiment design stage can be parametrically represented as an iterative design-redesign problem. This paper presents a domain independent characterization of such problems; the characterization includes problem definition, design relations/procedures, and measures of goodness. The paper also discusses representation issues and solution techniques for design-redesign problems. Design tasks are differentiated as domain independent or problem specific and the scope of each design task with respect to the characterization is delineated. A Design Shell implemented on the basis of this characterization is described. This shell can be configured for evaluating designs in any domain. A case study illustrates the use of this Design Shell in characterizing a specific design problem and exploring its design space.

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