Thermal Management Research Studies. Volume 2: Experimental Investigation of Oscillating Heat Pipes for Actuator Cooling PDF Download
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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Book Description
Operation requirements of oscillating heat pipes (OHPs) were proposed. Based on the requirements, OHPs with acetone and nonflammable fluorocarbon fluids, FC-72 and FC-75, as the working fluid were developed. The OHPs had 40 tubing turns formed from a copper tubing with an inner diameter of 1.75 mm and a total length of 18.61 m. The OHPs were formed in the shape of a planer array that was 256-min wide and 446mm high. There were two condensers on both outer sides and one evaporator in the middle of the OHPs. Thermal performance tests were conducted at various operating temperatures and heat rates. The working fluid fill ratio was varied The OHPs with acetone and FC-72 exhibited their highest heat transport performance in excess of 2000 W without dryout. This is the first time that such a performance was demonstrated. The gravitational acceleration did not have noticeable influence on the performance of the OHPs. The thermal performances of the fluorocarbon OHPs were compared with the case of the acetone OHP.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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Book Description
Operation requirements of oscillating heat pipes (OHPs) were proposed. Based on the requirements, OHPs with acetone and nonflammable fluorocarbon fluids, FC-72 and FC-75, as the working fluid were developed. The OHPs had 40 tubing turns formed from a copper tubing with an inner diameter of 1.75 mm and a total length of 18.61 m. The OHPs were formed in the shape of a planer array that was 256-min wide and 446mm high. There were two condensers on both outer sides and one evaporator in the middle of the OHPs. Thermal performance tests were conducted at various operating temperatures and heat rates. The working fluid fill ratio was varied The OHPs with acetone and FC-72 exhibited their highest heat transport performance in excess of 2000 W without dryout. This is the first time that such a performance was demonstrated. The gravitational acceleration did not have noticeable influence on the performance of the OHPs. The thermal performances of the fluorocarbon OHPs were compared with the case of the acetone OHP.
Author: Fritz Laun (Thermal aerospace engineer)
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 21
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Book Description
With ever increasing technological advances in electronics, modern computer components continue to produce higher power densities that present a challenge to thermal management. A radial flat-plate oscillating heat pipe (RFP-OHP) heat spreader is investigated to study the effect of central heating on the heat transport capability in an OHP. The investigated OHP has dimensions of 100 mm x 100 mm x 2.5 mm with central heating using a 30 mm x 30 mm heater. Experimental results show that when heat is added to the center section of one side of the radial flat-plate OHP, and when heat is removed from the whole surface of another side of the heat pipe, the startup power for the oscillating motion increases. In addition, the spacer effect on the heat transport capability including the startup is investigated experimentally. The spacer added between the cooling block and OHP could lower the startup power for oscillatory motion. When compared to a copper slab of the same dimensions in the same test configuration, the temperature difference for the OHP with and without the additional copper spacer was reduced by a maximum of 46 and 25%, respectively, at a power input of 525 W and a heat flux of 58 W/cm2.
Author: Hongbin Ma
Publisher: Springer
ISBN: 1493925040
Category : Science
Languages : en
Pages : 441
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Book Description
This book presents the fundamental fluid flow and heat transfer principles occurring in oscillating heat pipes and also provides updated developments and recent innovations in research and applications of heat pipes. Starting with fundamental presentation of heat pipes, the focus is on oscillating motions and its heat transfer enhancement in a two-phase heat transfer system. The book covers thermodynamic analysis, interfacial phenomenon, thin film evaporation, theoretical models of oscillating motion and heat transfer of single phase and two-phase flows, primary factors affecting oscillating motions and heat transfer, neutron imaging study of oscillating motions in an oscillating heat pipes, and nanofluid’s effect on the heat transfer performance in oscillating heat pipes. The importance of thermally-excited oscillating motion combined with phase change heat transfer to a wide variety of applications is emphasized. This book is an essential resource and learning tool for senior undergraduate, graduate students, practicing engineers, researchers, and scientists working in the area of heat pipes. This book also · Includes detailed descriptions on how an oscillating heat pipe is fabricated, tested, and utilized · Covers fundamentals of oscillating flow and heat transfer in an oscillating heat pipe · Provides general presentation of conventional heat pipes
Author: 邱洛緯
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Author:
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ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Brian V. Borgmeyer
Publisher:
ISBN:
Category : Electronic apparatus and appliances
Languages : en
Pages : 174
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Book Description
As the conventional heat sinks meet their heat transport limit, the pulsating heat pipe as one of advanced phase-change heat transfer devices will present the next generation of electronics cooling. An experimental and theoretical study was conducted regarding the motion of the liquid and vapor slugs within a pulsating heat pipe. A pulsating heat pipe with non-circular channels was investigated to determine the effect of operating parameters such as working fluid, tilted angle, filled liquid ratio, and heat flux level. The mathematical model theoretically solved for the position and velocity of the liquid and vapor slugs using the modified governing equations for a mechanical forced damped system. For comparison, experimental investigations quantified the position and velocity of the liquid-vapor interface through the use of a high speed camera. The mathematical and experimental investigations explored the effect of the various parameters on fluid motion. Experimental data obtained from the high speed camera did not show good relation to the mathematical model developed, however, the effects of each parameter seen in the model related to experimental observations.
Author: Christopher Smoot
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 62
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Book Description
A new disc oscillating heat pipe has been developed and tested for use in high heat flux applications with a localized heat source. The results show that the heat pipe offers a significant improvement in performance over a copper disc when charged with water or acetone. Despite the improvement, the heat pipe displayed some unexpected behavior. The heat pipe required far more power input to achieve startup than expected, given the heat pipe's small size, and the heat pipe demonstrated much smaller temperature oscillation amplitude than expected. To investigate this behavior, two additional oscillating heat pipes were constructed to test the effect of heat conduction through the adiabatic section of the heat pipe. The results clearly demonstrated that the presence of heat conduction through the adiabatic section of a heat pipe required far more power to startup, between 25 and 275 W additional power depending on the working fluid, condenser temperature, and orientation. The presence of heat conduction through the adiabatic section also demonstrated reduced oscillation amplitude. It was also found that the presence of heat conduction through the adiabatic section of an oscillating heat pipe resulted in better performance than a heat pipe without conduction through the adiabatic section.
Author: Uzoma Cornelius Mmeje
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Pulsating heat pipes (PHPs) have been studied since the 1990s and are potential replacements for copper thermal buses or standard heat pipes. Currently there is not a well-defined process for PHP design for a particular heat load or application. This is partially because of the number of variables that affect the performance of a PHP. PHP's that operate using cryogenic fluids have been studied even less than those that operate at near room temperature and higher. In this work we endeavor to expand the understanding of the performance and behavior of cryogenic PHPs including conductance and maximum heat load capacity (load at dry out) with respect to operating temperature, fill ratio and working fluid properties. This study focuses on exploring the operating regions not previously explored in cryogenic pulsating heat pipes at UW Madison. An experimental device (pulsating heat pipe) has been built, consisting of a single evaporator and a single condenser separated by an adiabatic length. The main purpose of this study is to characterize the effective conductivity of the device for a range of condenser temperatures and increase the heat load until dry-out is achieved. This test procedure was conducted for a range of fill ratios. The data were analyzed to obtain optimal parameters that can be used in the design of a pulsating heat pipe using Nitrogen as a working fluid. The second purpose of this experimental study was to explore dry-out phenomena. Because the PHP is a cryogenic device it is non-optical, so the flow pattern cannot be visually observed, but some information about near dry-out behavior can be obtained from the temperature fluctuations observed in the condenser, evaporator, and adiabatic sections. Additional experiments with Argon and a mixture (Air) as the working fluid were run. The results of these studies and the Nitrogen results are compared with respect to conductance and dry-out behavior.
Author: Shibin Liang
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages :
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Book Description
A mathematical model describing the oscillation characteristics of slug flow in a capillary tube is presented. The model considers the vapor bubble as the gas spring for the oscillating motions in a capillary tube including effects of capillary force, gas spring constant, dimensions, gravitational force, and initial pressure distribution of the working fluid. Numerical results indicate that the isentropic bulk modulus generates stronger oscillations than the isothermal bulk modulus. While it demonstrates that the capillary tube diameter, bubble size, and unit cell numbers determine the oscillation, the capillary force, gravitational force, and initial pressure distribution of the working fluid significantly affect the frequency and amplitude of oscillating motion in the capillary tube. An experimental study of a five-turn closed loop oscillating heat pipe has been conducted. The oscillating heat pipes charged with HPLC grade water, acetone and ethanol have been tested respectively. In a vertical orientation, the oscillating motion of the slug flow in the oscillating heat pipe has been observed.
Author: Aaron A. Hathaway
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 45
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Book Description
An experimental investigation on oscillating heat pipes with uneven turns was conducted in order to determine the effect of short turns on the heat transport capability. The shorter turns do not go through both the evaporating and condensing sections; the short turns were placed only in the evaporating section. The design of the OHP consists of 14 long turns which run from the evaporator to the condenser and 6 short turns were placed only on the evaporating section. An extensive experimental investigation on the effects of the input power, tilted angle, condensing temperature, and charging ratio was conducted. Experimental results show that for all test conditions, the OHP functions very well and it can transport an input power up to 1200 W and can reach a thermal resistance of 0.028. From the experimental results of tilted angle effect, it can be found that the heat pipe is almost independent of the tilted angle. Most importantly, it is shown that with a number of short turns placed on the evaporating section, the OHP can operate efficiently without the assistance of the gravitational force. In other words, the heat pipe developed herein can operate at a condition of the heating section on the top and the cooling section on the bottom with a distance of 18.5 cm from the center of the evaporator section the center of the condensing section. In addition, the results show that the heat transfer performance depends on the operating temperature and charging ratio. When the operating temperature increases, the heat transfer performance of the OHP investigated herein significantly increase. WC/o.
