scholarly journals Investigation of the Use of an Inorganic Aqueous Solution in Copper-Made Phase-Change Heat Transfer Devices

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Qi Yao ◽  
Jacob Supowit ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Aqueous Solution ◽  
Phase Change ◽  
Heat Transfer Performance ◽  
Capillary Rise ◽  
Copper Surface ◽  
Working Fluid ◽  
Transfer Performance ◽  
Phase Change Heat Transfer ◽  
Inorganic Aqueous Solution

A novel inorganic aqueous solution (IAS) is shown to have a better heat transfer performance than water when used as the working fluid in copper-made phase-change heat transfer devices. First, the physical properties of IAS are measured and compared to those of water. Another, a chemical analysis is performed, and the chemical reactions involved between IAS and the copper surface are listed and categorized by their contributions to the heat transfer performance. In addition, a capillary rise test is performed to show how each chemical contributes to the improvement of the surface wettability. Last, using IAS in copper-made phase-change heat transfer devices is discussed, and the main focus is how IAS improves the heat transfer performance by a smaller thermal resistance and a larger critical heat flux. The conclusion is validated by thermo-siphon tests at different inclination angles.

Using an Inorganic Aqueous Solution (IAS) in Copper and Aluminum Phase Change Heat Transfer Devices

2013 ◽  
Author(s):  
Qi Yao ◽  
Mike Stubblebine ◽  
Sean Reilly ◽  
Ladan Amouzegar ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Aqueous Solution ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Transfer Performance ◽  
Reactive Material ◽  
Boiling Process ◽  
Phase Change Heat Transfer ◽  
Aluminum Surfaces ◽  
Inorganic Aqueous Solution

A novel Inorganic Aqueous Solution (IAS) is shown to have a better thermal performance than water when used as the working fluid in copper or aluminum made heat transfer devices. The effect of each chemical in the IAS and how it benefits heat transfer performance for different materials is explained. It was found that the IAS fluid reacts with copper and coats the surface with a layer of hydrophilic products during the initial boiling process. The surface roughness and wettability were increased which led to an enhanced heat transfer performance. The IAS passivates aluminum surfaces and makes water compatible for use with aluminum heat transfer devices. In addition, IAS has potential to improve the heat transfer performance by 50% lower the superheat when used with non-reactive material heat transfer devices.

A Novel Inorganic Aqueous Solution and its Effect on Liquid Spreading and Freeze/Thaw Processes

2013 ◽  
Author(s):  
Jacob Supowit ◽  
Sean Reilly ◽  
Ladan Amouzegar ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Aqueous Solution ◽  
Phase Change ◽  
Melting Process ◽  
Melting Rate ◽  
Working Fluid ◽  
Freeze Thaw ◽  
Liquid Spreading ◽  
Phase Change Heat Transfer ◽  
Inorganic Aqueous Solution

Frozen startup of phase change heat transfer devices is a complex problem that can have a large impact on heat transfer systems. A patented novel working fluid developed at UCLA comprised of an inorganic aqueous solution (IAS) was investigated for potential effects on the freeze/thaw capabilities in phase change heat transfer devices by examining the melting process of droplets. Preliminary visual tests were conducted to gain insight into any physical processes that surface augmentation created by this fluid may have on the freezing and melting process. These tests demonstrated significant differences in liquid spreading, the melting process, and the melting rate of droplets on surfaces pre-treated with IAS. Contact angle measurements exhibited enhanced wetting properties. SEM images of frozen droplets showed that liquid freezes in the small capillary wick formed by the initial evaporation of IAS. Video of melting droplets showed a significant increase in melting rate when the surface was first treated with IAS due to superior liquid spreading.

scholarly journals Numerical Study of a New Solar Vacuum Tube Integrating with Phase Change Material

2019 ◽  
Vol 11 (24) ◽  
pp. 6960
Author(s):  
Juan Shi ◽  
Hua Xue ◽  
Zhenqian Chen ◽  
Li Sun
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Heat Transfer Performance ◽  
Melting Time ◽  
Transfer Performance ◽  
Vacuum Tube ◽  
Fin Thickness ◽  
Phase Change Heat Transfer ◽  
Fin Spacing ◽  
Change Material

In this work, a new solar vacuum tube (SVT) integrating with phase change material is introduced and numerically investigated. The mathematical model and the numerical solution of phase change heat transfer is introduced. The heat transfer of the solar energy collection system during the energy storage process is simulated. Solid-liquid phase change characteristics of the SVT with paraffin inside is analyzed. Optimization analysis of fin structure parameters (fin thickness and fin spacing) in the vacuum tube is conducted. The results showed that the metal fin has a great effect on the phase change heat transfer of paraffin in SVTs. The closer the paraffin is to the fins, the more uniform the paraffin temperature is and the sooner the paraffin melts. As the fin thickness increases and the spacing between the fins decreases, the melting time of the paraffin decreases. Meanwhile, the effect of fin spacing on the overall heat transfer performance of the phase change energy storage tube is larger than the effect of the fin thickness. When the fin thickness is 2 mm, the melting time of paraffin with a fin spacing of 80 mm is 21,000 s, which is almost three times of that with a fin spacing of 10 mm (7400 s). Therefore, decreasing fin spacing is an effective way of enhancing phase change heat transfer. When the total fin volume is constant, a SVT with small fin space and small fin thickness performs better in heat transfer performance.

Investigation of the Effects of Simultaneous Internal Flow Boiling and External Condensation on the Heat Transfer Performance

2019 ◽  
Author(s):  
M. M. Kabir ◽  
Sangsoo Lee
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Single Phase ◽  
Heat Transfer Performance ◽  
Flow Boiling ◽  
Internal Flow ◽  
Transfer Performance ◽  
Test Rig ◽  
Phase Change Heat Transfer

Abstract Recent leaps in heat dissipation make it difficult for typical heat exchangers to meet the requirements of the advanced applications even with the maximally obtainable heat transfer performance associated with a single-phase process. Especially high heat flux applications such as thermal management in microelectronics, advanced material processing, and nuclear fusion reactors require extreme heat transfer methods to overcome the current limits. In this study, a heat exchanger adopting simultaneously two-opposite, phase-change heat transfer processes (internal flow boiling and external condensation) was proposed and analytically investigated. The phase-change heat transfer analyses were conducted for internal flow boiling and external condensation at a test section and the heat transfer performances were compared with that of a system with an internal single-phase, liquid flow process. It is found that the proposed heat exchanger configuration with an internal flow boiling can substantially enhance the heat transfer performances and provide better methods to manage the temperature difference comparing to those with an internal single-phase heat transfer due to its significant increase in a heat transfer coefficients and constant temperatures during phase-change processes. Additionally, this study also explains the design for a test rig to evaluate and validate the results in detail. The test rig consists of an internal flow boiling loop with a test section, an external condensation loop, sensors, auxiliary monitoring parts, and controlling and data acquisition systems. Thermodynamic cycle, pressure drop, and heat transfer analyses were conducted to determine the conditions and the specifications of components and sensors for the test rig.

scholarly journals Investigation of the Use of an Inorganic Aqueous Solution in Aluminum-Made Phase-Change Heat Transfer Devices

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Qi Yao ◽  
Michael J. Stubblebine ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Aqueous Solution ◽  
Natural Convection ◽  
Phase Change ◽  
Aluminum Surface ◽  
Back Flow ◽  
Convection Cooling ◽  
Phase Change Heat Transfer ◽  
Aluminum Passivation ◽  
Inorganic Aqueous Solution

An inorganic aqueous solution, known as IAS, has shown its compatibility with aluminum phase-change heat transfer devices. When using IAS in aluminum devices, aluminum prefers to react with the two oxidizers, permanganate and chromate, rather than water to generate a thin and compact layer of aluminum oxide, which protects the aluminum surface and prevents further reactions. In addition, an electrochemical theory of aluminum passivation is introduced, and the existence of an electrochemical cycle is demonstrated by an aluminum thermosiphon test. The electrochemistry cycle, built up by liquid back flow and tube wall, allows the oxidizers to passivate the aluminum surface inside the device without being directly in contact with it. However, failure was detected while using IAS in thermosiphons with air natural convection cooling. The importance of a continuous liquid back flow to aluminum passivation in phase-change heat transfer devices is pointed out, and a vertical thermosiphon test with natural convection cooling is used to demonstrate that a discontinuous liquid back flow is the main reason of the failures.

The Start-Up Performance of Pulsating Heat Pipe With Communicating Pipe at Different Inclination Angles

2019 ◽  
Author(s):  
Fu-Min Shang ◽  
Shi-Long Fan ◽  
Jian-Hong Liu
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Transfer Performance ◽  
Pulsating Heat Pipe ◽  
High Heat Transfer ◽  
Start Up ◽  
Inclination Angles

Abstract The pulsating heat pipe (PHP) is a passive cooling device, which has the advantages of simple structure, high heat transfer performance and low production cost. The complex vapor-liquid phase change occurs in the in the initial stage of PHP. In this work, we explore the start-up performance of PHP at different inclination angles and the experiment shows that start-up performance is respectively different when the angles are 0°, 45°, 90°, 135° and 180°. Since the gravitational auxiliary function, the working fluid in the communicating pipe which takes longer time to vaporize change phase earlier than that in PHP’s loop when the angles are 0° and 45°. Nevertheless, when the angle is 90°, the phase change of working fluid in communicating pipe and in the loop occurs at the same time. Meanwhile, the oscillating mode affects the stability of the starting and heat transfer performance of the PHP.

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