The Anti-Gravity Phenomena in EHD Heat Pipe Model

2002 ◽  
Author(s):  
Jiaxiang Yang ◽  
Jiancai Wang ◽  
Chuntian Chen ◽  
Changsheng Yu
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Copper Wire ◽  
Heat Pipes ◽  
Working Fluid ◽  
Dc Voltage ◽  
Pipe Model ◽  
Condensation Section ◽  
Insulating Liquid ◽  
Saturation Vapor

A heat pipe model of electrohydrodynamical (EHD) enhancement heat transfer has been designed and made. The insulating liquid was selected as working fluid and the copper wire whose diameter was 1mm was used as the high voltage electrode. The temperature in the inlet and outlet of both the vaporization section and the condensation section, the saturation vapor pressure inside this model were measured respectively under different applied dc voltage and different tilt angle, that is, the vaporization section was placed higher than the condensation section. The experiment results indicate that the circumfluence between the condensation section and the vaporization section was improved with the increase of the applied dc voltage. Such EHD enhancement heat transfer technology can be practically employed in the heat transfer engineering, and has some reference values for the investigation of heat pipes used in the case of anti-gravity.

scholarly journals The effect of operating parameters on the heat transfer in the heat pipe

2021 ◽  
Vol 2119 (1) ◽  
pp. 012088
Author(s):  
A. A. Litvintceva ◽  
N. I. Volkov ◽  
N. I. Vorogushina ◽  
V. A. Moskovskikh ◽  
V. V. Cheverda
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Heat Pipes ◽  
Working Fluid ◽  
Operating Parameters ◽  
Temperature Stabilization ◽  
Ir Camera ◽  
Fluid Properties

Abstract Heat pipes are a good solution for temperature stabilization, for example, of microelectronics, because these kinds of systems are without any moving parts. Experimental research of the effect of operating parameters on the heat transfer in a cylindrical heat pipe has been conducted. The effect of the working fluid properties and the porous layer thickness on the heat flux and temperature difference in the heat pipe has been investigated. The temperature field of the heat pipe has been investigated using the IR-camera and K-type thermocouples. The data obtained by IR-camera and K-type thermocouples have been compared. It is demonstrated the power transferred from the evaporator to the condenser is a linear function of the temperature difference between them.

scholarly journals An investigation on effect of EDL on heat transfer of micro heat pipe with square and triangular cross section

2020 ◽  
Vol 21 (3) ◽  
pp. 309
Author(s):  
Maryam Fallah Abbasi ◽  
Hossein Shokouhmand ◽  
Morteza Khayat
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Double Layer ◽  
Electric Double Layer ◽  
Heat Pipes ◽  
The Body ◽  
Working Fluid ◽  
Two Phase ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

Electronic industries have always been trying to improve the efficiency of electronic devices with small dimensions through thermal management of this equipment, thus increasing the use of small thermal sinks. In this study micro heat pipes with triangular and square cross sections have been manufactured and tested. One of the main objectives is to obtain an understanding of micro heat pipes and their role in energy transmission with electrical double layer (EDL). Micro heat pipes are highly efficient heat transfer devices, which use the continuous evaporation/condensation of a suitable working fluid for two-phase heat transport in a closed system. Since the latent heat of vaporization is very large, heat pipes transport heat at small temperature difference, with high rates. Because of variety of advantage features these devices have found a number of applications both in space and terrestrial technologies. The theory of operation micro heat pipes with EDL is described and the micro heat pipe has been studied. The temperature distribution have achieved through five thermocouples installed on the body. Water and different solution mixture of water and ethanol have used to investigate effect of the electric double layer heat transfer. It was noticed that the electric double layer of ionized fluid has caused reduction of heat transfer.

Effects of Surface Coating of Nanoparticles on Thermal Performance of Open Loop Pulsating Heat Pipes

2012 ◽  
Author(s):  
Mehdi Taslimifar ◽  
Maziar Mohammadi ◽  
Ali Adibnia ◽  
Hossein Afshin ◽  
Mohammad Hassan Saidi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Surface Coating ◽  
Heat Pipes ◽  
Open Loop ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Performance Of Heat Transfer

Homogenous dispersing of nanoparticles in a base fluid is an excellent way to increase the thermal performance of heat transfer devices especially Heat Pipes (HPs). As a wickless, cheap and efficient heat pipe, Pulsating Heat Pipes (PHPs) are important candidates for thermal application considerations. In the present research an Open Loop Pulsating Heat Pipe (OLPHP) is fabricated and tested experimentally. The effects of working fluid namely, water, Silica Coated ferrofluid (SC ferrofluid), and ferrofluid without surface coating of nanoparticles (ferrofluid), charging ratio, heat input, and application of magnetic field on the overall thermal performance of the OLPHPs are investigated. Experimental results show that ferrofluid has better heat transport capability relative to SC ferrofluid. Furthermore, application of magnetic field improves the heat transfer performance of OLPHPs charged with both ferrofluids.

Circulation Effectiveness of Working Fluid in Inclined Micro Heat Pipes

2015 ◽  
Vol 789-790 ◽  
pp. 422-425
Author(s):  
Fun Liang Chang ◽  
Yew Mun Hung
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Pipes ◽  
Operating Conditions ◽  
Circulation Rate ◽  
Working Fluid ◽  
High Heat Flux ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

Micro heat pipe is a two-phase heat transfer device offering effective high heat-flux removal in electronics cooling. Essentially, micro heat pipe relies on the phase change processes, namely evaporation and condensation, and the circulation of working fluid to function as heat transfer equipment. The vast applications of micro heat pipe in portable appliances necessitate its functionality under different orientations with respect to gravity. Therefore, its thermal performance is strongly related to its orientation. By incorporating solid wall conduction, together with the continuity, momentum, and energy equations of the working fluid, a mathematical model is developed to investigate the heat and fluid flow characteristics of inclined micro heat pipes. We investigate both the favorable and adverse effects of gravity on the circulation rate which is intimately related to the thermal performance of micro heat pipes. The effects of gravity, through the angle of inclination, on the circulation strength and heat transport capacity are analysed. This study serves as a useful analytical tool in the micro heat pipe design and performance analysis, associated with different inclinations and operating conditions.

Use of an Inorganic Aqueous Solution to Prevent Non-Condensable Gas Formation in Aluminum Heat Pipes

2013 ◽  
Author(s):  
Michael Stubblebine ◽  
Sean Reilly ◽  
Qi Yao ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Aqueous Solution ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Solid Metal ◽  
Aluminum Surface ◽  
Working Fluid ◽  
Water Based ◽  
Inorganic Aqueous Solution ◽  
Over Time

Heat pipes are used in many applications as an effective means for transferring heat from a source to a sink. The basic heat pipe typically consists of a solid metal casing within which a working fluid is sealed inside at a given pressure. The latent heat transfer via the heat pipe’s working fluid allows it to carry a larger amount of heat energy than would normally be possible with an identically dimensioned solid metal rod. Water is often used as a working fluid due to its high heat of vaporization and suitable operating range for electronics cooling. For many applications, especially space, aluminum is desired as a casing material for its high thermal conductivity, low weight, and low cost. However, water is incompatible for use with aluminum heat pipes because it forms a non-condensable gas (NCG), hydrogen, when they contact. In this work, an inorganic aqueous solution (IAS), which has thermophysical properties similar to water, has been used as the working fluid with an aluminum alloy 5052-H2 casing. The prepared thermosiphon underwent long-term lifetime testing and the results indicate no tube failure or significant NCG formation for the duration of the 9 week study. Furthermore, the data indicate that the IAS fluid not only inhibited NCG production but also led to a reduction in heat pipe thermal resistance over time. It is believed that the chemicals in IAS react with the aluminum surface to create a compact oxide layer and electrochemical reaction which prevents hydrogen generation. A secondary, hydrophilic surface coating is also generated by the fluid on top of the first oxide (passivation) layer. This hydrophilic layer is believed to be responsible for the heat transfer enhancement which was observed during testing and the reduction in ΔT (defined as Tevap−Tcond) over time. Aluminum heat pipes used currently in practice utilize ammonia, or other non-water based working fluids, which have inferior latent heats of vaporization compared to water or an aqueous-based fluid such as IAS. The use of aluminum heat pipe casings in combination with a water-based fluid such as IAS has the potential to provide a significant increase in heat transport capability per device unit mass over traditional ammonia charged aluminum heat pipes.

Fundamental Heat Transfer Experiments of Heat Pipes for Turbine Cooling

1998 ◽  
Vol 120 (3) ◽  
pp. 580-587 ◽  
Author(s):  
S. Yamawaki ◽  
T. Yoshida ◽  
M. Taki ◽  
F. Mimura
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Cooling System ◽  
Infrared Image ◽  
Heat Pipes ◽  
Performance Criteria ◽  
Working Fluid ◽  
Steel Shell ◽  
Turbine Cooling ◽  
Start Up

Fundamental heat transfer experiments were carried out for three kinds of heat pipes that may be applied to turbine cooling in future aero-engines. In the turbine cooling system with a heat pipe, heat transfer rate and start-up time of the heat pipe are the most important performance criteria to evaluate and compare with conventional cooling methods. Three heat pipes are considered, called heat pipe A, B, and C, respectively. All heat pipes have a stainless steel shell and nickel sintered powder metal wick. Sodium (Na) was the working fluid for heat pipes A and B; heat pipe C used eutectic sodium-potassium (NaK). Heat pipes B and C included noncondensible gas for rapid start-up. There were fins on the cooling section of heat pipes. In the experiments, and infrared image furnace supplied heat to the heat pipe simulating turbine blade surface conditions. In the results, heat pipe B demonstrated the highest heat flux of 17 to 20 W/cm2. The start-up time was about 6 minutes for heat pipe B and about 16 minutes for heat pipe A. Thus, adding noncondensible gas effectively reduced start-up time. Although NaK is a liquid phase at room temperature, the startup time of heat pipe C (about 7 to 8 minutes) was not shorter than the heat pipe B. The effect of a gravitational force on heat pipe performance was also estimated by inclining the heat pipe at an angle of 90 deg. There was no significant gravitational dependence on heat transport for heat pipes including noncondensible gas.

scholarly journals Fundamental Heat Transfer Experiments of Heat Pipes for Turbine Cooling

1997 ◽  
Author(s):  
Shigemichi Yamawaki ◽  
Toyoaki Yoshida ◽  
Masanobu Taki ◽  
Fujio Mimura
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Cooling System ◽  
Infrared Image ◽  
Heat Pipes ◽  
Performance Criteria ◽  
Working Fluid ◽  
Steel Shell ◽  
Turbine Cooling ◽  
Start Up

Fundamental heat transfer experiments were carried out for three kinds of heat pipes which may be applied to turbine cooling in future aero-engines. In the turbine cooling system with a heat pipe, heat transfer rate and start-up time of the heat pipe are the most important performance criteria to evaluate and compare with conventional cooling methods. Three heat pipes are considered, called heat pipe A, B and C, respectively. All heat pipes have a stainless steel shell and nickel sintered powder metal wick. Sodium(Na) was the working fluid for heat pipes A and B; heat pipe C used eutectic sodium-potassium(NaK). Heat pipes B and C included non-condensible gas for rapid start-up. There were fins on the cooling section of heat pipes. In the experiments, an infrared image furnace supplied heat to the heat pipe simulating turbine blade surface conditions. In the results, heat pipe B demonstrated the highest heat flux of 17 to 20 W/cm2. The start-up time was about 6 minutes for heat pipe B and about 16 minutes for heat pipe A. Thus adding non-condensible gas effectively reduced start-up time. Although NaK is a liquid phase at room temperature, the start-up time of heat pipe C (about 7 to 8 minutes) was not shorter than the heat pipe B. The effect of a gravitational force on heat pipe performance was also estimated by inclining the heat pipe at an angle of 90 degrees. There was no significant gravitational dependence on heat transport for heat pipes including non-condensible gas.

Steady State Modeling of a Rotating Heat Pipe With a Composite Wick Structure

Volume 3 ◽  
2004 ◽  
Author(s):  
T. A. Jankowski ◽  
J. A. Waynert ◽  
F. C. Prenger ◽  
A. Razani
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Working Fluid ◽  
Round Cross Section ◽  
State Heat ◽  
Pipe Model ◽  
Axis Of Rotation ◽  
Wick Structure ◽  
Steady State Heat

A steady state heat pipe model, capable of calculating temperature and pressure distributions in the working fluid of a rotating heat pipe, is described here. The model can predict the performance of rotating heat pipes with a round cross-section, containing an annular gap composite wick structure. In addition to straight heat pipes, with a longitudinal axis that may or may not coincide with the axis of rotation, the model also allows for simulation of bent heat pipes. Using this model, results are generated for a bent heat pipe proposed for use in cooling rotating machinery. For the bent heat pipe, the condenser and adiabatic sections coincide with the axis of rotation, while the evaporator consists of an off-axis eccentrically rotating component, and a bend that allows for portion of the evaporator to be nearly perpendicular to the axis of rotation. The presence of the composite wick allows for heat pipe operation in both the rotating and stationary operating modes. Model results for the stationary operating mode compare favorably to the steady state heat pipe analysis code HTPIPE [1]. These comparisons for the stationary operating limit are significant, since HTPIPE has been benchmarked against experimental heat pipe data for nearly 30 years. As the rotational speed is increased, the rotation induced forces are used to drive the liquid flow to the evaporator. At high rotation rates, the liquid recedes from the wick, and forms a thin layer against the inside wall of the heat pipe. The results show that when a stable liquid layer is formed against the wall of the pipe, the shear stress opposes the rotation induced forces acting on the liquid, and limits the magnitude of the pressure and temperature rises in the working fluid (from the values predicted using a hydrostatic approximation).

Model for Heat Pipe Position Optimization of Transformers Cooled by Heat Pipes

2011 ◽  
Vol 347-353 ◽  
pp. 3765-3771
Author(s):  
Xi Zhang ◽  
Jun Bao Yang ◽  
Min Deng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Equilibrium ◽  
Heat Pipes ◽  
Newton Iteration ◽  
Evaporation And Condensation ◽  
Section Area ◽  
Condensation Section ◽  
Set Up

In the view of heat pipe position optimization of transformers cooled by heat pipes, using the thermal equilibrium equation and the empirical formula of heat transfer coefficient of the evaporation and condensation section, applying Newton Iteration, computing the optimal condensation section area, the optimal computation of heat pipes’ position is implemented and the model of heat pipe position optimization of transformers cooled by heat pipes is set up.

scholarly journals Experimental investigations and optimization of process parameters of meshed-wick heat pipe

2020 ◽  
Vol 184 ◽  
pp. 01026 ◽  
Author(s):  
B.Ch Nookaraju ◽  
B. Hemanth Sai ◽  
K.V.N.S Himakar ◽  
N. Limba Reddy ◽  
N Sateesh
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Heat Pipe ◽  
Heat Pipes ◽  
Working Fluid ◽  
Outer Diameter ◽  
Cylindrical Shape ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Screen Mesh

Heat pipes are used to transfer heat, which are hollow cylindrical shape device filled with small amount of working fluid, which can change its phase. The rate of heat transfer in heat pipes compared to normal heat exchanging devices is more. Depending on the applications of heat transfer various heat pipes are being designed. Methanol fluid is used with 50% fill ratio. It is made of copper with outer diameter of 15.88mm and inner diameter of 14.88mm. It consists of a screen mesh made of copper powder inside it with thickness of 0.5mm. Due to heat input methanol changes its phase from liquid to vapor. The vapor loses its heat and changes its phase back to liquid in the condenser. At the condenser section the vapour gives up it heat and changes its phase from vapour to liquid. The screen mesh assists the flow of condensed working fluid through capillary action. Optimized the results by “Taguchi method” using “Minitab software”. The Thermal analysis was done with the optimum conditions, which were obtained as a result from the optimization method by Ansys Fluent software. Then finally compared the thermal parameters obtained from experiments with the Thermal analysis result. It is found the maximum heat transfer rate is optimized using meshed wick heat pipe conditions.

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