Transient Analysis of Flat Heat Pipes

2003 ◽  
Author(s):  
Unnikrishnan Vadakkan ◽  
Jayathi Y. Murthy ◽  
Suresh V. Garimella
Keyword(s):  
Heat Pipe ◽  
Numerical Procedure ◽  
Simple Algorithm ◽  
Heat Pipes ◽  
Heat Fluxes ◽  
Temperature Fields ◽  
Interface Temperature ◽  
Finite Volume Scheme ◽  
System Pressure ◽  
Energy And Momentum

A stable numerical procedure is developed to analyze the transient performance of flat heat pipes for large input heat fluxes and high wick conductivity. Computation of flow and heat transfer in a heat pipe is complicated by the strong coupling among the velocity, pressure and temperature fields with phase change at the interface between the vapor and wick. A structured collocated finite volume scheme is used in conjunction with the SIMPLE algorithm to solve the continuity, energy and momentum equations. In addition, system pressurization is computed using overall mass balance. The stability of the standard sequential procedure is improved by accounting for the coupling between the evaporator/condenser mass flow rate and the interface temperature and pressure as well as the system pressure. The improved numerical scheme is applied to a flat two-dimensional heat pipe and shown to perform well. Parametric studies are performed by varying the vapor core thickness of the heat pipe and the heat input at the evaporator. The model predictions are validated by comparing the heat pipe wall temperatures against experimental values.

Sector Rotating Heat Pipe With Interconnected Branches and Reservoir for Turbomachinery Cooling

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Brian Reding ◽  
Yiding Cao
Keyword(s):  
Experimental Study ◽  
Heat Pipe ◽  
Heat Pipes ◽  
High Heat ◽  
Heat Fluxes ◽  
Practical Solution ◽  
Pipe System ◽  
Current Configuration ◽  
Cooling Technique

Heat pipe technology offers a possible cooling technique for structures exposed to high heat fluxes, as in turbomachinery such as compressors and turbines. However, in its current configuration as single heat pipes, implementation of the technology is limited due to the difficulties in manufacturability and costs. Hence, a study to develop a new radially rotating (RR) heat pipe system was undertaken, which integrates multiple RR heat pipes with a common reservoir and interconnected braches for a more effective and practical solution to turbomachinery cooling. Experimental study has shown that the integration of multiple heat pipe branches with a reservoir at the top is feasible.

Thermal Management of a Heat-Pipe Drill: A FEM Analysis

2003 ◽  
Author(s):  
Tien-Chien Jen ◽  
Rajendra Jadhav
Keyword(s):  
Finite Element ◽  
Heat Pipe ◽  
Thermal Management ◽  
Heat Pipes ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Drilling Process ◽  
Generation Process ◽  
Finite Element Software

Thermal management using heat pipes is gaining significant attention in past decades. This is because of the fact that it can be used as an effective heat sink in very intricate and space constrained applications such as in electronics cooling or turbine blade cooling where high heat fluxes are involved. Extensive research has been done in exploring various possible applications for the use of heat pipes as well as understanding and modeling the behavior of heat pipe under those applications. One of the possible applications of heat pipe technology is in machining operations, which involves a very high heat flux being generated during the chip generation process. Present study focuses on the thermal management of using a heat pipe in a drill for a drilling process. To check the feasibility and effectiveness of the heat pipe drill, structural and thermal analyses are performed using Finite Element Analysis. Finite Element Software ANSYS was used for this purpose. It is important for any conceptual design to be made practical and hence a parametric study was carried out to determine the optimum geometry size for the heat pipe for a specific standard drill.

Experimental Investigation of a Flexible Bellows Heat Pipe for Cooling Discrete Heat Sources

1990 ◽  
Vol 112 (3) ◽  
pp. 602-607 ◽  
Author(s):  
B. R. Babin ◽  
G. P. Peterson
Keyword(s):  
Heat Pipe ◽  
Computer Model ◽  
Heat Pipes ◽  
Heat Fluxes ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Operational Characteristics ◽  
And Performance ◽  
Experimental Values ◽  
Operating Temperature Range

A computer model was developed to aid in the design of a flexible bellows heat pipe for cooling small discrete heat sources or arrays of small heat sources. This model was used to evaluate the operational characteristics and performance limitations of these heat pipes and to formulate and optimize a series of conceptual designs. Three flexible bellows heat pipes approximately 40 mm in length and 6 mm in diameter were constructed and tested using three different wick configurations. The test pipes were found to be boiling limited over most of the operating temperature range tested. Heat fluxes in excess of 200 W/cm2 were obtained and thermal resistance values of less than 0.7 °C/W were measured. Although the computer model slightly underestimated the experimentally determined transport limit for one of the wicking configurations, the remaining transport predictions were consistently within 8 percent of the experimental values.

scholarly journals Experimental Set up of Two Closed Loop Pulsating Heat Pipe (CLPHP) with Water base Fluids

2019 ◽  
Vol 8 (12S) ◽  
pp. 715-719
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Dissipation ◽  
Heat Pipes ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Water Mixture ◽  
Working Fluids ◽  
Pure Fluids ◽  
Acetone Water

Heat pipes are deliberated to be effective heat dissipation devices compared to other types of heat sinks due to their high effective thermal conductivity. Because of the flexibility in the design and layout of heat pipe turns along the heat source, pulsating heat pipes have gained popularity. One of the parameters that have the mainimpact on the presentation of CLPHP is the thermo physical properties of the working fluid. The properties of the working fluid affect the temperature difference between the evaporator and the condenser which in turn affect the thermal resistance of the CLPHP. In this connection, the influence of different working fluids is experimentally investigated on a two loop CLPHP, varying the evaporator heat flux. Pure fluids, viz., water, acetone, benzene and binary mixture, viz., Acetone-water and Benzene-water are utilized on working fluids. The heat input considered at the evaporator is 32W, 48W and 60W. The filling ratio is kept as 50 %. The results show that among the working fluids considered for the study, acetone exhibits least thermal resistance among the pure fluids at all heat fluxes considered in the analysis, while Acetone-water mixture has exhibited least thermal resistance among the water based mixtures.

Transient Multidimensional Analysis of Nonconventional Heat Pipes With Uniform and Nonuniform Heat Distributions

1991 ◽  
Vol 113 (4) ◽  
pp. 995-1002 ◽  
Author(s):  
Y. Cao ◽  
A. Faghri
Keyword(s):  
Heat Pipe ◽  
Three Dimensional ◽  
Leading Edge ◽  
Heat Pipes ◽  
High Heat ◽  
Heat Fluxes ◽  
Multidimensional Analysis ◽  
Vapor Flow ◽  
Operating Limits ◽  
Good Agreement

A numerical analysis of transient heat pipe performance including nonconventional heat pipes with nonuniform heat distributions is presented. A body-fitted grid system was applied to a three-dimensional wall and wick model, which was coupled with a transient compressible quasi-one-dimensional vapor flow model. The numerical results were first compared with experimental data from cylindrical heat pipes with good agreement. Numerical calculations were then made for a leading edge heat pipe with localized high heat fluxes. Performance characteristics different from conventional heat pipes are illustrated and some operating limits concerning heat pipe design are discussed.

Effects of Working Fluid, Fill Ratio and Orientation on Looped and Unlooped Pulsating Heat Pipes

2005 ◽  
Author(s):  
Kathryn Nikkanen ◽  
Christian G. Lu ◽  
Masahiro Kawaji
Keyword(s):  
Heat Pipe ◽  
Rectangular Channel ◽  
Heat Pipes ◽  
High Heat ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Fill Ratio ◽  
Triangular Channel ◽  
Horizontal Orientation

Improved miniaturization and a trend towards increasingly dense and compact architectures have led to unmanageably high heat fluxes in electronic components. In order to keep temperatures at operational levels more advanced cooling solutions are being required that go beyond the solid heat sink and forced convection. Pulsating heat pipes made out of multi port extrusion tubing are a proposed solution. Typically, gas-liquid slug flow occurs in the serpentine channel imbedded in the pulsating heat pipe. Vapour is produced in the heated section and condensed in the cooled section located at opposite ends of the heat pipe. In this work, experiments were conducted on four Multi-Port Extruded (MPE) aluminum tubing heat pipes with different internal structures: rectangular channel looped, rectangular channel unlooped, triangular channel looped, and triangular channel unlooped. The effect of changing the working fluid (ethanol or de-ionized water), fill ratio, and orientation were measured and compared for the different heat pipes. It was found that most of the heat pipes performed better with ethanol than de-ionized water. Only the looped rectangular channel heat pipe performed satisfactorily with de-ionized water, which is attributed both to the larger channel size and the looped architecture. The unlooped heat pipes performed best at the lowest fill ratios (10%) while the looped heat pipes showed their best performances between 30 and 50% with marked decrease at the lower and higher fill ratios. Both looped heat pipes performed poorly in horizontal orientation as compared to vertical, however, the unlooped heat pipes performed quite well in both orientations. This may be more the effect of the fill ratio on horizontal performance as literature suggests that horizontal orientation requires a lower fill ratio to perform satisfactorily.

Transient Analysis of a Cylindrical Heat Pipe Considering Different Wick Structures

2016 ◽  
Author(s):  
Mehdi Famouri ◽  
M. Mahdi Abdollahzadeh ◽  
Ahmed Abdulshaheed ◽  
GuangHan Huang ◽  
Gerardo Carbajal ◽  
...  
Keyword(s):  
Heat Pipe ◽  
Experimental Studies ◽  
Simple Algorithm ◽  
Heat Pipes ◽  
Working Fluid ◽  
Time Step ◽  
Base Scheme ◽  
The Stability ◽  
Stability And Accuracy ◽  
Energy Equations

Heat pipes have been shown to be one of the most efficient passive cooling devices for electronic cooling. Only a handful of studies were capable of solving transient performances of heat pipes based on realistic assumptions. A segregated finite volume base scheme using SIMPLE algorithm is used along with system pressurization and overall mass balance to solve mass transfer at the interface, continuity, momentum and energy equations. The fluid flow and heat transfer are solved throughout the wick and vapor core and no assumptions are made at the locations where evaporation and condensations occur. Water is the working fluid and variable densities are used for both liquid and vapor phases to account for continuity at the interface as well as inside of wick and vapor core. The wick is modeled as a non-homogeneous porous media and the effective thermal conductivities and viscous properties are calculated for each type of structure separately using the available relations from the literature. In this study, an axisymmetric two-dimensional solver for cylindrical heat pipe is developed using FLUENT package with the help of User Defined Functions (UDFs) and User Defined Scalar (UDS). The model is tested for grid and time step independency and the results show the stability and accuracy of the proposed method. The numerical results of the present study were in good agreement with the data from previous numerical and experimental studies available in the literature. Additionally, two different wick structures were studied to determine its effect on the thermal performance of heat pipes.

An Analytical Model for Prediction of Tool Temperature Fields during Continuous and Interrupted Cutting

1994 ◽  
Vol 116 (2) ◽  
pp. 135-143 ◽  
Author(s):  
R. Radulescu ◽  
S. G. Kapoor
Keyword(s):  
Analytical Model ◽  
Metal Cutting ◽  
Cutting Speed ◽  
Time History ◽  
Heat Fluxes ◽  
Temperature Fields ◽  
Heat Transfer Analysis ◽  
Interface Temperature ◽  
Tool Temperature ◽  
Interrupted Cutting

An analytical model for prediction of tool temperature fields in metal cutting processes is developed. The model can be applied to any continuous or interrupted three-dimensional cutting process. To accurately represent the heating and cooling cycles encountered during interrupted cutting, the analysis predicts time dependent heat fluxes into the cutting tool. A time history of this heat flux is obtained by performing an energy balance on the chip formation zone. The variation with time of the tool temperature fields is determined from a heat transfer analysis with prescribed heat generation rate. The analysis requires the cutting forces as inputs. The model tool-chip interface temperatures agree well with the experimental tests reported in the literature, for all cutting conditions and work materials investigated. The results indicate that the tool-chip interface temperature increases with cutting speed during both continuous and interrupted cutting.

Computational Modeling of Vapor Chambers With Nanostructured Wicks

2009 ◽  
Author(s):  
E. Bozorg-Grayeli ◽  
C. Fang ◽  
A. Rogacs ◽  
K. Goodson
Keyword(s):  
Finite Difference ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Heat Fluxes ◽  
Heat Output ◽  
Simulation Tool ◽  
Vapor Chamber ◽  
Future Studies ◽  
Variable Porosity ◽  
Spatially Varying

As the power and heat output of modern CPUs climb ever higher and the interest in compact, passively cooled devices grows, there is an urgent need for thinner and more effective vapor chamber technologies. Nanostructured wick technologies based on oxide and organic nanowires have been proposed as a method of improving heat pipe performance in such applications. This work performs finite difference simulations of a 2D heat pipe accounting for variable porosity in the wick. For heat fluxes of 10 and 100 W/cm2, we find that temperature difference between the evaporator and condenser regions decreases by 10%, which is promising for spreading thermal energy. We find that spatially varying porosity yields improvements in spreading heat throughout the entire wick region. Finally, we observe that boiling is depressed in the evaporator region. These results verify the benefits of nanostructured wicks. This simulation tool provides the groundwork for future studies of 3D flat package heat pipes.

Heat Pipes for Cooling High Flux/High Power Semiconductor Chips

1993 ◽  
Vol 115 (1) ◽  
pp. 112-117 ◽  
Author(s):  
M. T. North ◽  
C. T. Avedisian
Keyword(s):  
Heat Pipe ◽  
High Power ◽  
Cooling Water ◽  
Base Plate ◽  
Heat Pipes ◽  
Heat Fluxes ◽  
Total Power ◽  
Condenser Section ◽  
Power Semiconductor ◽  
Surface Temperatures

Results of an experimental study are reported which demonstrate the ability of heat pipes to simultaneously dissipate high heat fluxes and high total power at low surface temperatures. The application is to cooling high power density (and high total power) semiconductor chip modules. The two designs studied incorporate air or liquid cooling in the condenser sections. The air-cooled design consisted of a manifold base plate with a series of holes drilled in it each of which was lined with sintered copper powder which served as the wick. An array of wick lined tubes was attached normal to the plate and served as the condenser section. The other heat pipe was disk shaped and also had a sintered wick structure. Cooling water channels were placed over the entire periphery of the housing except in the region of heat input. Reported steady heat fluxes are up to 31 W/cm2 corresponding to total power dissipation of up to 1400 W for the water cooled heat pipe and up to 47 W/cm2 (900 W total power) for the air cooled heat pipe with surface temperatures under 100°C.

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