Experimental Investigation of Micro/Nano Heat Pipe Wick Structures

2008 ◽  
Author(s):  
H. Peter J. de Bock ◽  
Kripa Varanasi ◽  
Pramod Chamarthy ◽  
Tao Deng ◽  
Ambarish Kulkarni ◽  
...  
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
High Performance ◽  
Heat Pipes ◽  
High Heat ◽  
Two Phase ◽  
Wick Structure ◽  
Two Phase Heat Transfer ◽  
Heat Transport Capability ◽  
Transfer Device

The performance of electronic devices is limited by the capability to remove heat from these devices. A heat pipe is a device to facilitate heat transport that has seen increased usage to address this challenge. A heat pipe is a two-phase heat transfer device capable of transporting heat with minimal temperature gradient. An important component of a heat pipe is the wick structure, which transports the condensate from the condenser to the evaporator. The requirements for high heat transport capability and high resilience to external accelerations leads to the necessity of a design trade off in the wick geometry. This makes the wick performance a critical parameter in the design of heat pipes. The present study investigates experimental methods of testing capillary performance of wick structures ranging from micro- to nano-scales. These techniques will facilitate a pathway to the development of nano-engineered wick structures for high performance heat pipes.

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.

A High Performance Semi-Passive Cooling System: The Pulse Thermal Loop

Volume 3 ◽  
2004 ◽  
Author(s):  
Mark M. Weislogel ◽  
Michael A. Bacich
Keyword(s):  
Heat Transport ◽  
High Performance ◽  
Driving Forces ◽  
Cooling System ◽  
Heat Pipes ◽  
Thermal Control ◽  
High Heat ◽  
Transport Systems ◽  
Passive Cooling ◽  
Cooling Systems

Over the past decade, the search for and development of high performance thermal transport systems for a variety of cooling and thermal control applications have intensified. One approach employs a new semi-passive oscillatory heat transport system called the Pulse Thermal Loop (PTL). The PTL, which has only recently begun to be characterized, exploits large pressure differentials from coupled evaporators to force (pulse) fluid through the system. Driving pressures of over 1.8MPa (260psid) have been demonstrated. Other passive cooling systems, such as heat pipes and Loop Heat Pipes, are limited by capillary driving forces, typically less than 70kPa (10psid). Large driving forces can be achieved by a mechanically pumped loop, however, at the expense of increased power consumption, increased total mass, and increased system cost and complexity. The PTL can be configured in either active or semi-passive modes, it can be readily designed for large ∼ O(100kW) or small ∼ O(10W) heat loads, and it has a variety of unique performance characteristics. For low surface tension dielectric fluids such as R-134a, the PTL system has over a 10-fold heat carrying capacity in comparison to high performance heat pipes. Data accumulated thus far demonstrate that the PTL can meet many of the requirements of advanced terrestrial and spacecraft cooling systems: a system that is robust, ‘semi-passive,’ high flux, and offers high heat transport thermal control while remaining flexible in design, potentially lightweight, and cost competitive.

Experimental Model to Optimize the Design of Cylindrical Heat Pipes for Solar Collector Application

2013 ◽  
Vol 393 ◽  
pp. 735-740
Author(s):  
Fairosidi Idrus ◽  
Nazri Mohamad ◽  
Ramlan Zailani ◽  
Wisnoe Wirachman ◽  
Mohd Zulkifly Abdullah
Keyword(s):  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Pipes ◽  
Design Parameters ◽  
Working Fluid ◽  
Pipe Material ◽  
Efficient Design ◽  
Wick Structure ◽  
To Come ◽  
Transfer Device

A heat pipe is a heat-transfer device that use the principles of thermal conductivity and phase change to transfer heat between two ends at almost constant temperature. The thermal peformance of cylindrical heat pipes depends on design parameters such as dimensions of the heat pipe, material, wick structure and the working fluid. An experimental strategy was designed to study the effect of these parameters on the thermal performance of cylindrical heat pipes. The experimental design was conceived by employing the Taguchi method. The final aim of the experiments is to come up with design parameters that will yield optimum thermal performance. This paper presents an efficient design of experiment and the associated experimental setup and procedures to be carried out in order to optimize the design of cylindrical heat pipes.

Multilayer Wick Structure of Loop Heat Pipe

2007 ◽  
Author(s):  
Qingjun Cai ◽  
Chung-Lung Chen ◽  
Julie F. Asfia
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Loop Heat Pipe ◽  
Two Phase ◽  
Transfer Resistance ◽  
Heat Leakage ◽  
Wick Structure ◽  
Operating Temperatures ◽  
Compensation Chamber ◽  
Two Phase Heat Transfer

Loop heat pipe (LHP) is known as a two-phase heat transfer device that utilizes the evaporation and condensation of an operating fluid to transfer heat. At the LHP low operating temperatures, heat leakage induced by saturated temperature differences between the evaporator and compensation chamber is more serious than at high operating temperatures, due to inherent thermophysical properties of the operating liquid. The serious heat leakage at the low operating temperature not only causes high liquid subcooling requirement but also leads to high total temperature difference and degraded heat transfer performance. In this paper, research efforts are placed on reducing the heat leakage by introducing a multilayer wick structure into the LHP. Based on the previous research results of LHP non-metallic wick structures, the multilayer wick LHP combines advantages of both metallic and non-metallic wick structures, retains good heat conduction from the evaporator case to the liquid/vapor interface and inhibits the reverse heat transfer from the interface to compensation chamber. By demonstrating the concept on a methanol LHP, experimental results exhibit a significant enhancement in reducing heat leakage and the total heat transfer resistance.

Electronics Thermal Management Using Advanced Hybrid Two-Phase Loop Technology

2007 ◽  
Author(s):  
Chanwoo Park ◽  
Aparna Vallury ◽  
Jon Zuo ◽  
Jeffrey Perez ◽  
Paul Rogers
Keyword(s):  
Thermal Management ◽  
High Performance ◽  
Cooling System ◽  
Active Flow Control ◽  
Heat Pipes ◽  
High Heat ◽  
Heat Fluxes ◽  
Significant Advance ◽  
Two Phase ◽  
Phase Loop

The paper discusses an advanced Hybrid Two-Phase Loop (HTPL) technology for electronics thermal management. The HTPL combined active mechanical pumping with passive capillary pumping realizing a reliable yet high performance cooling system. The evaporator developed for the HTPL used 3-dimensional metallic wick structures to enhance boiling heat transfer by passive capillary separation of liquid and vapor phases. Through the testing using various prototype hybrid loops, it was demonstrated that the hybrid loops were capable of removing high heat fluxes from multiple heat sources with large surface areas up to 135cm2 and 10kW heat load. Because of the passive capillary phase separation, the hybrid loop operation didn’t require any active flow control of the liquid in the evaporator, even at highly transient and asymmetrical heat inputs between the evaporators. These results represent the significant advance over state-of-the-art heat pipes, loop heat pipes and evaporative spray cooling devices in terms of performance, robustness and simplicity.

Visualization of Two-Phase Flow in 3D Printed Polycarbonate Pulsating Heat Pipe With Aluminum Substrate

2018 ◽  
Author(s):  
Takahiro Arai ◽  
Masahiro Kawaji ◽  
Yasushi Koito
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Two Phase Flow ◽  
Aluminum Plate ◽  
Working Fluid ◽  
Phase Flow ◽  
Pulsating Heat Pipe ◽  
Two Phase ◽  
Flow Channels ◽  
Heat Transport Capability

A pulsating heat pipe (PHP) is a passive device with a good heat transport capability compared to other heat pipes. This paper describes an experimental investigation of a PHP with a serpentine channel fabricated by using a 3-D printer. The configuration of the flow channels in the PHP was close to that of commercially available PHPs made entirely of aluminum. To improve the heat transport capability and enable flow visualization, an aluminum plate was used on one side as the heat-transfer surface, on which transparent flow channels were fabricated by a 3-D printer and a polycarbonate filament. The interface between the aluminum plate and polycarbonate flow channel was cemented with a heat-resistant glue to ensure long term sealing. HFE-7000 was used as a working fluid. Oscillating two-phase flow in the PHP was observed with a high-speed digital video camera and transient surface temperatures at evaporator, insulator and condenser sections were measured by fine diameter thermocouples. The two-phase flow and thermal characteristics of the PHP at different heater power levels are presented.

Self-Cooling Cavity Burs for Surgical Drills

2007 ◽  
Vol 1 (4) ◽  
pp. 293-296 ◽  
Author(s):  
Calvin C. Silverstein
Keyword(s):  
Heat Pipe ◽  
Heat Transport ◽  
Brain Tissue ◽  
Conceptual Design ◽  
Heat Sink ◽  
Thermal Damage ◽  
Heat Pipes ◽  
Cutting Edge ◽  
Cooling Cavity ◽  
Heat Transport Capability

In a self-cooled drill, an especially designed bur is used to transport heat generated at the cutting edge into the handpiece, where it is dissipated into an air heat sink. The bur contains a sealed cavity partially filled with water, which transports heat via the principle of rotating heat pipe technology. The heat transport capability of burs fitted out as rotating heat pipes was established. A conceptual design for a representative bur was prepared, based on surgical drill sculpting criteria. It appears that a self-cooled surgical drill for sculpting can limit bone temperatures below levels for the initiation of thermal damage in bone, nerve, and brain tissue, without the need to employ an externally applied coolant.

Analytical Modeling of a Loop Heat Pipe at Positive Elevation

2004 ◽  
Author(s):  
Po-Ya Abel Chuang ◽  
John M. Cimbala ◽  
Jack S. Brenizer ◽  
C. Thomas Conroy
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Experimental Results ◽  
State Model ◽  
Loop Heat Pipe ◽  
Operating Characteristics ◽  
Two Phase ◽  
Steady State Model ◽  
Two Phase Heat Transfer ◽  
Transfer Device

A two-phase heat transfer device, a loop heat pipe (LHP), is studied analytically. It is noted that a LHP behaves differently when it is operated against gravity (adverse elevation) or at gravity assisted (positive elevation) conditions. Steady-state modeling of LHP operating characteristics at adverse or zero elevation was broadly studied in the past. This paper presents a steady-state model of a LHP when it is operated at positive elevation based on experimental results. The effects of elevation on the trend of steady-state operating temperature (SSOT) are then studied using the newly developed steady-state model. Experimental results agree with the model predictions at adverse (88.9mm), zero, and positive (88.9mm) elevations. This steady-state model is the only model known to have the capability to predict the operating characteristics at positive elevation. The model will help to design the LHPs utilized in terrestrial applications.

Comparison of Experiments and 1-D Steady-State Model of a Loop Heat Pipe

2002 ◽  
Author(s):  
Po-Ya Abel Chuang ◽  
John M. Cimbala ◽  
Jack S. Brenizer ◽  
C. Thomas Conroy ◽  
A. A. El-Ganayni ◽  
...  
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
State Model ◽  
Loop Heat Pipe ◽  
Two Phase ◽  
Comparison Of Experiments ◽  
Steady State Model ◽  
Model Predictions ◽  
Two Phase Heat Transfer ◽  
Transfer Device

A modern, effective, two-phase heat transfer device, a loop heat pipe (LHP), was studied analytically and experimentally. A 1-D steady-state model was developed based on energy balance equations. The mathematical modeling procedures of each component are explained in detail, including a model of the secondary wick in the evaporator. Other models neglect the existence of the secondary wick because the detailed designs of the secondary wick are often proprietary. Three sets of experiments were performed at different elevations. Results of experimental data are compared with 1-D steady-state model predictions. The comparisons show that the model predictions of steady state operating temperatures for both zero elevation and adverse elevation are within 2 percent. It has been clearly demonstrated that the 1-D steady-state model is a useful tool for future LHP study.

Performance Improvement in Pulsating Heat Pipes Using a Self-Rewetting Fluid

2009 ◽  
Author(s):  
K. Fumoto ◽  
M. Kawaji
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heated Surface ◽  
Heat Pipes ◽  
Input Power ◽  
Water Mixture ◽  
Pulsating Heat Pipe ◽  
Maximum Heat ◽  
Heat Transport Capability

New experimental results have been obtained on the enhancement of heat transport by a pulsating heat pipe (PHP) using a self-rewetting fluid. Self-rewetting fluids have a property that the surface tension increases with temperature unlike other common liquids. The increasing surface tension at a higher temperature could cause the liquid to be drawn towards a heated surface if a dry spot appears, and improving boiling heat transfer. In the present experiments, 1-butanol was added to water at a concentration of less than 1 wt% to make the self-rewetting fluid. A pulsating heat pipe made from an extruded multi-port tube was partially filled with the butanol-water mixture and tested for its heat transport capability at different input power levels. The experiments showed that the maximum heat transport capability was enhanced by a factor of four when the maximum heater temperature was limited to 120 °C. Thus, the use of a self-rewetting fluid in a PHP has been shown to be highly effective in improving the heat transport capability of pulsating heat pipes.

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