Analysis of Heat Transfer Factors for a Heat Pipe Absorber Array Connected to a Common Manifold

1986 ◽  
Vol 108 (1) ◽  
pp. 11-16 ◽  
Author(s):  
J. R. Hull
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Efficiency ◽  
Transfer Rate ◽  
Heat Pipes ◽  
Maximum Efficiency ◽  
Pipe Surface ◽  
Transfer Factors ◽  
Collector Efficiency ◽  
Flow Through

Heat transfer factors and thermal efficiency are calculated for a heat pipe absorber array connected to a common manifold. Arrays with less than ten heat pipes are shown to have significantly less efficiency than a conventional flow-through collector. Efficiency is also sensitive to the heat transfer rate per unit temperature difference from the heat pipe fluid to the manifold fluid divided by that from the heat pipe surface to the ambient, with maximum efficiency occurring for ratios greater than 100.

A Novel Quick Qmax Test Method and Experimental Investigation of Heat Pipes

2005 ◽  
Author(s):  
Yao-Chen Chan ◽  
Wei-Keng Lin
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Wall Temperature ◽  
Transfer Rate ◽  
Heat Pipes ◽  
Adiabatic Temperature ◽  
Test Method ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Dry Out

In traditional heat pipe performance test, to keep an adiabatic temperature at a constant value, the evaporator wall temperature would be slowly increased when the thermal power was step input to the evaporator of the heat pipe. The maximum heat transfer rate (Qmax) was then defined that when the evaporator wall temperature rapidly increased at a certain amount of power input to the heat pipe. However, it is not easy to distinguish this sharp increased curve and sometimes result in the wrong Qmax data. In addition, it took too long for waiting the evaporator temperature approach to a steady state, thus this process could not use be for the fully check Qmax of the heat pipe. In this paper, we propose a novel quick test method to predict the maximum heat dissipation of the heat pipes namely Dynamic-Temperature-Tracing (D.T.T). The concept of the D.T.T was when we tracing the evaporator and the adiabatic wall temperature, these two temperature curves should be the same trend before the dry-out phenomena was occurred. Theoretically, when the dry-out start to occur in the heat pipe, the adiabatic temperature profile was no longer kept the same temperature profile as that of the evaporator. Hence, the maximum heat dissipate ability of the heat pipe was then easy to obtained at this measuring adiabatic temperature. The data were also compared with those obtained from the traditional standard method at the same equivalent evaporator length, condenser length and adiabatic temperature. In this experiments, sinter powder and groove heat pipes with diameter 6mm 8mm and 200mm length were selected as the capillary wick structure. Comparing with traditional method results, the errors of maximum heat transfer rate are less than 15%. The results also shown D.T.T. method is much fast and reliable compare with the traditional test method.   This paper was also originally published as part of the Proceedings of the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems.

Development of Thinned Aluminum Flat Heat Pipe Through Inclined Wall and Press Process

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Seok-Hwan Moon ◽  
Su-Hyun Hong ◽  
Hyun-Tak Kim
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Dissipation ◽  
Heat Pipes ◽  
System Level ◽  
Total Thickness ◽  
Capillary Structure ◽  
Flat Heat Pipe

Heat pipes, commonly used for heat dissipation and thermal management in small electronic and communication devices, are regarded as an excellent solution. Heat pipes must be in surface rather than line contact to be applied to the module and system-level heat dissipation package. As such, a round copper heat pipe is transformed into a plate-like shape through a secondary press process. In this study, an extrusion structure is designed to be sloped to solve the difficulty of making it relatively thin compared with the large area of the plate structure. Specifically, substantial partitions separating the working fluid flow space in the plate-type heat pipe are designed to be inclined at 45 deg, and the extruded envelope is developed to obtain the desired total thickness through the secondary press process. The capillary structure is inserted and positioned within the envelope prior to the secondary press process. In this study, an aluminum flat heat pipe (AFHP) with 0.95 mm total thickness, 150 mm total length, and a capillary structure with braided or carbon wire bundles added thereto was designed and manufactured. Performance test results indicated that the heat transfer performance of the AFHP with inclined wall did not show any deterioration characteristic compared with the AFHP with a normal vertical wall. The isothermal characteristics and heat transfer rate of the AFHP with Cu braid wick were superior to those of AFHP with a simple rectangular groove wick. By contrast, when the carbon wire bundle is added in the Cu braid, the isothermal characteristic was enhanced twice, and the heat transfer rate was 15.5 W by improving approximately 42% under the conditions that inclination angle is −90 deg and the evaporator temperature does not exceed 110 °C.

scholarly journals Experimental Study of Al2O3 Nanofluids on the Thermal Efficiency of Curved Heat Pipe at Different Tilt Angle

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
S. Razvarz ◽  
R. Jafari
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Tilt Angle ◽  
Thermal Efficiency ◽  
Volume Concentration ◽  
Pure Water ◽  
Heat Pipes ◽  
Particle Volume

This paper represents an experimental study about the effect of curves related to thermosyphons and heat pipes with different active fluids and inclination angle at the thermal efficiency. The nanofluid utilized in this work is an aqueous soluble of Al2O3 nanoparticles with 35 nm diameter in pure water. The test saturation level of nanoparticles is 0%, 1%, and 3%wt. All the experiments were conducted and repeated at inclination angle of 30°, 60°, and 90° (vertical). The article presents the gravity impacts on the heat transfer characteristics in different angles and the effects of working fluids and tilt angle of heat pipe tube by the addition of nanoparticles and weight fractions on the thermal efficiency of heat pipe at different inclination. According to the experimental results, the heat pipe at the tilt angle of 60° generates the superior results. At a particle volume concentration of 1%, the use of Al2O3/water nanofluid gives significantly higher heat transfer.

scholarly journals Testing algorithm for heat transfer performance of nanofluid-filled heat pipe based on neural network

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 751-760
Author(s):  
Lei Lei
Keyword(s):  
Neural Network ◽  
Heat Transfer ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Volume Fraction ◽  
Heat Pipes ◽  
Transfer Performance ◽  
Analysis Model ◽  
Accurate Analysis ◽  
Testing Algorithm

AbstractTraditional testing algorithm based on pattern matching is impossible to effectively analyze the heat transfer performance of heat pipes filled with different concentrations of nanofluids, so the testing algorithm for heat transfer performance of a nanofluidic heat pipe based on neural network is proposed. Nanofluids are obtained by weighing, preparing, stirring, standing and shaking using dichotomy. Based on this, the heat transfer performance analysis model of the nanofluidic heat pipe based on artificial neural network is constructed, which is applied to the analysis of heat transfer performance of nanofluidic heat pipes to achieve accurate analysis. The experimental results show that the proposed algorithm can effectively analyze the heat transfer performance of heat pipes under different concentrations of nanofluids, and the heat transfer performance of heat pipes is best when the volume fraction of nanofluids is 0.15%.

Theoretical Investigation of Heat Pipes Operating at Low Vapor Pressures

1968 ◽  
Vol 90 (4) ◽  
pp. 547-552 ◽  
Author(s):  
E. K. Levy
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Dimensional Analysis ◽  
Theoretical Investigation ◽  
Heat Pipes ◽  
Vapor Pressures ◽  
One Dimensional ◽  
Evaporator Section ◽  
Heat Transfer Capacity ◽  
Theoretical Results

A one-dimensional analysis of a compressible vapor flowing within the evaporator section of a heat pipe is presented. Comparisons between the theoretical results and existing heat pipe data show that the presence of gasdynamic choking can limit the heat transfer capacity of a heat pipe operating at sufficiently low vapor pressures.

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.

Numerical Analysis of the Phase-Change Heat Transfer Inside a Pulsating Heat Pipe With Overcritical Number of Turns

2020 ◽  
Author(s):  
Alberto Mucci ◽  
Foster Kwame Kholi ◽  
Man Yeong Ha ◽  
Jason Chetwynd-Chatwin ◽  
June Kee Min
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Heat Pipe ◽  
Gas Phase ◽  
Heat Pipes ◽  
Driving Mechanism ◽  
Small Range ◽  
Pulsating Heat Pipe ◽  
Prediction Ability ◽  
Semi Empirical

Abstract The Pulsating Heat Pipe (PHP) is a promising device in the family of heat pipes. With no need for a wick, they exhibit a high heat transfer to weight ratio. Moreover, the wickless design removes limits commonly associated with conventional heat pipes, increasing the maximum power transfer per single heat pipe. These peculiarities make it an ideal candidate for many high power applications. Nonetheless, there is though only partial knowledge on the driving mechanism, which restricts prediction accuracy. Most Pulsating Heat Pipe studies rely on experiments to test configurations, while simulations usually depend on semi-empirical correlations or adaptations of reduced theoretical models. Experiments provide detailed data for a particular geometry in lab fixed conditions, but it offers limited flexibility to test alternative configurations. Semi-empirical models use previous experimental data to create non-dimensional formulations. Though approaching an increased set of conditions, correlations apply with reasonable accuracy only to a small range, outside of which the prediction ability progressively falls. High order numerical analysis such as Computational Fluid Dynamics (CFD) modeling could potentially provide full visualization, but due to the complex flow behavior, previous studies used this method only in simple configurations with a small number of turns. The present research will expand the potential of this modeling technique by presenting the CFD analysis of a complex Pulsating Heat Pipe configuration. The importance of this study lies in the fact that this configuration, with a number of turns greater than a critical parameter, shows a reduced sensitivity to gravity and is therefore particularly important for applications where restrictions on installations make the positioning sub-optimal. The research simulates using a CFD commercial software a two-dimensional Pulsating Heat Pipe with sixteen turns. The heat pipe, with a 2 mm internal diameter, is filled with water at 50% of mass. To visualize the oscillation pattern of liquid and vapor slugs and plugs inside the Pulsating Heat Pipe, the model performs a transient analysis on the device. A Volume of Fluid (VOF) solver for multiphase analysis, coupled with the Lee model for evaporation and condensation mass transfer, calculates the interactions between the liquid and the gas phase inside the tube. The study follows the geometric and operational conditions from previous experiments. The analysis regards a Pulsating Heat Pipe operating in a vertical position with the condenser section placed in the upper sector. During the initial operations, the system flow distribution fluctuates between different flow modes as the fluid slugs and plugs structure forms. After stabilizing the heat transfer results well agree with the tested values. Moreover, the increased resolution allows us to fully visualize the internal operation, retrieving additional information on the temperature and ratio of liquid and gas phase along the heat pipe.

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.

Sign in / Sign up

Export Citation Format

Share Document