Surface Modifications of Bulk Micromachined Titanium Pillar Arrays: A Wick Material for Thin Flat Heat Pipes

2009 ◽  
Author(s):  
Changsong Ding ◽  
Carl D. Meinhart ◽  
Noel C. MacDonald
Keyword(s):  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Heat Pipes ◽  
Surface Modifications ◽  
Practical Applications ◽  
Plating Method ◽  
Modified Surfaces ◽  
Pillar Arrays ◽  
Extended Surface ◽  
Fundamental Research

Wicking materials with tunable wettability are of great importance for both fundamental research and practical applications such as heat pipes. In this work, we adopt recently developed titanium bulk micromachining[1] techniques to fabricate pillar arrays. Then we modify the micromachined pillars to form micro- & nano-textured (bitextured) titania structures (BTS). Further, we investigated how to plate gold on the modified surfaces to tune the wettability. A wicking material for heat pipe requires super wetting by common fluids such as water. We show theoretical studies and experimental work to investigate the wetting behavior of two different designs/samples. For heat pipe applications the BTS and plating gold not only increases the capillary pressure which enhances liquid pumping from condenser to evaporator, but also increases the heat transfer performance by extended surface and smaller pore sizes[2]. Testing results show that water can completely wet the micromachined Ti pillars (Design A: 5μm in diameter/5μm gap). The BTS helps increase the wetting speed by over 100% for this design. A second design with much larger diameter and gap (Design B: 100μm in diameter/50μm in gap) is also tested to compare with design A for wetting speed. Results show that Design B gives a wetting speed twice of Design A. Plating method is used to decrease pillar gap (from 50μm to 5μm) by growing gold on surfaces. This will help increase thermal conductivity of wicking material which is preferred for the evaporator and condenser regions of heat pipes. Wetting experiment is done on Sample B after plating with gold. Wetting results after Au plating show that wetting velocity decreases but is still significantly large.

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%.

Effect of Increasing Wick Evaporation Area on Heat Transfer Performance for Loop Heat Pipes

2013 ◽  
Vol 711 ◽  
pp. 223-228 ◽  
Author(s):  
Shen Chun Wu ◽  
Jhih Huang Gao ◽  
Zih Yan Huang ◽  
Dawn Wang ◽  
Cho Jeng Huang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Surface Area ◽  
Heat Transfer Performance ◽  
Heat Pipes ◽  
Loop Heat Pipe ◽  
Transfer Performance ◽  
Loop Heat Pipes ◽  
Heat Transfer Capacity

This study investigates the effects of increasing the evaporating area of wick in a loop heat pipe (LHP). This work attempts to improve the performance of the loop heat pipe by increasing the number of grooves and thereby the surface area of the wick. The number of grooves is increased from eight to twelve. Experimental results show that increasing the number of grooves not only increases the surface area of the wick but also enhances LHP performance. When the evaporating surface area increases by 50%, which corresponds to increasing the number of grooves from eight to twelve, the heat transfer capacity increases from 310W to 470W and the thermal resistance is reduced from 0.21°C/W to 0.17°C/W. According to preliminary measurements, increasing the number of grooves in the loop heat pipe is highly promising for improving the heat transfer performance.

An Application and Investigation of Rotating Heat Pipes on Motor Rotor Cooling

2005 ◽  
Author(s):  
Qingjun Cai ◽  
Chung-Lung Chen ◽  
Jimmy Q. Dong
Keyword(s):  
Heat Pipe ◽  
Heat Dissipation ◽  
Heat Transfer Performance ◽  
Heat Pipes ◽  
Temperature Gradients ◽  
Ac Motor ◽  
Thermal Solution ◽  
Improve Heat Transfer ◽  
Fan Cooling ◽  
Rotor Losses

In some industrial AC motor applications, higher heat dissipation results in faster rotor losses than that can be accommodated with conventional shaft-mounted-fan cooling designs. In this paper, one of the heat pipe technologies - rotating heat pipe - is presented as a means of enhancing motor rotor cooling. Novel rotating heat pipes are designed to improve heat transfer performance at various rotational speeds. Preliminary experimental results indicate that this thermal solution can effectively improve motor rotor cooling. Further, the rotating heat pipes with internal wicks can reduce temperature gradients at low rotational speed.

Effect of Al2O3-Water Nanofluid on the Heat Performance of Gravity-Assisted Heat Pipe

2014 ◽  
Vol 692 ◽  
pp. 470-474
Author(s):  
Wei Wu ◽  
Shu Lei Zhao ◽  
Qiang Lin
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Heating Temperature ◽  
Pure Water ◽  
Heat Pipes ◽  
Filling Ratio ◽  
The Difference ◽  
The Heat Transfer Coefficient

The aim of this paper is to investigate the effect of nanofluid on the heat transfer performance of heat pipe and to examine the difference of the thermal conductivity between pure water heat pipes and nanofluid heat pipes. In our experiments, Al2O3-water nanofluid and pure water were used as working fluids respectively in gravity-assisted heat pipes. Effects of filling ratio and heating temperature on the thermal performance of heat pipe were investigated. The thermal resistance of heat pipe was analyzed. Our results showed that nanofluid can significantly increase the heat transfer coefficient and enhance the thermal performance of heat pipe.

An investigation into gravity independent oscillating heat pipes

2012 ◽  
Author(s):  
◽  
Aaron A. Hathaway
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Heat Pipes ◽  
Experimental Results ◽  
Transfer Performance ◽  
Channel Diameter ◽  
Inverted Position ◽  
Oscillating Motion

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] A number of oscillating heat pipes (OHPs) with unbalanced structures were investigated in an effort to develop methods enabling OHPs to be gravity independent. The unbalanced structures investigated herein include the effects of uneven turn and check valves. Two 2-D and two 3-D tubular uneven-turn OHPs, four miniature uneven-turn OHPs, and one OHP with check-valves were investigated. At the same time, the theoretical analysis of the maximum channel diameter was conducted in order to find the primary factor affecting the channel size in an OHP. A model was developed that attempts to determine the maximum channel diameter by considering the contact angle effect. It is found that the contact angle significantly affects the maximum channel diameter of an OHP. In order to verify that the uneven-turn structure can generate the oscillating motion in an OHP, a heat pipe with 3 turns in the condenser and 6 turns in the evaporator was first tested. The heat pipe with uneven turns can generate and maintain oscillating motion. When the turn number increases with 16 turns in the condenser and 20 turns in the evaporator, the heat transfer performance can be further increased. An experimental investigation of a new 3-D OHP with uneven turn design was conducted in order to further develop a gravity independent OHP. Experimental results show that the uneven turn OHP developed herein can start the oscillating motion in the negative vertical position (the evaporator being above the condenser) and demonstrate that the uneven turn OHPs can significantly reduce the effect of gravity on the heat transport capability in an OHP. Three miniature OHPs (18-turn acetone OHP, 18-turn water OHP, and 20-turn acetone OHP) were developed and tested to determine whether the uneven-turn OHPs can function in a high-g environment. Experimental results demonstrate that these miniaturized uneven turn designs are extremely capable in high gravity environments and will operate effectively in any orientation. An OHP with check valves has been successfully developed and tested to determine the check valve effect on the oscillating motion and heat transfer performance in an OHP. Experimental results show that the OHP with check valves can function well in both the inverted and vertical positions with little variation between the two positions in performance once startup occurred, while the control OHP without check valves which had the same channel layout was not able to achieve startup in the inverted position. This shows that the check valves allowed the OHP to operate in the inverted position first achieving startup and then maintain oscillating motion.

scholarly journals Heterodimer Formation of the Homodimeric ABC Transporter OpuA

2021 ◽  
Vol 22 (11) ◽  
pp. 5912
Author(s):  
Patricia Alvarez-Sieiro ◽  
Hendrik R. Sikkema ◽  
Bert Poolman
Keyword(s):  
Abc Transporter ◽  
Conformational Dynamics ◽  
Host Organism ◽  
Affinity Tag ◽  
Practical Applications ◽  
Fundamental Research ◽  
Protein Multimerization ◽  
Biochemical Analyses

Many proteins have a multimeric structure and are composed of two or more identical subunits. While this can be advantageous for the host organism, it can be a challenge when targeting specific residues in biochemical analyses. In vitro splitting and re-dimerization to circumvent this problem is a tedious process that requires stable proteins. We present an in vivo approach to transform homodimeric proteins into apparent heterodimers, which then can be purified using two-step affinity-tag purification. This opens the door to both practical applications such as smFRET to probe the conformational dynamics of homooligomeric proteins and fundamental research into the mechanism of protein multimerization, which is largely unexplored for membrane proteins. We show that expression conditions are key for the formation of heterodimers and that the order of the differential purification and reconstitution of the protein into nanodiscs is important for a functional ABC-transporter complex.

The Heat Transport Capacity of Micro Heat Pipes

1998 ◽  
Vol 120 (4) ◽  
pp. 1064-1071 ◽  
Author(s):  
J. M. Ha ◽  
G. P. Peterson
Keyword(s):  
Experimental Data ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heat Pipes ◽  
Original Model ◽  
Semiempirical Model ◽  
Transport Capacity ◽  
Predictive Tool ◽  
Maximum Heat ◽  
Micro Heat Pipes

The original analytical model for predicting the maximum heat transport capacity in micro heat pipes, as developed by Cotter, has been re-evaluated in light of the currently available experimental data. As is the case for most models, the original model assumed a fixed evaporator region and while it yields trends that are consistent with the experimental results, it significantly overpredicts the maximum heat transport capacity. In an effort to provide a more accurate predictive tool, a semi-empirical correlation has been developed. This modified model incorporates the effects of the temporal intrusion of the evaporating region into the adiabatic section of the heat pipe, which occurs as the heat pipe approaches dryout conditions. In so doing, the current model provides a more realistic picture of the actual physical situation. In addition to incorporating these effects, Cotter’s original expression for the liquid flow shape factor has been modified. These modifications are then incorporated into the original model and the results compared with the available experimental data. The results of this comparison indicate that the new semiempirical model significantly improves the correlation between the experimental and predicted results and more accurately represents the actual physical behavior of these devices.

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