Numerical Study of a New Solar Vacuum Tube Integrating with Phase 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.

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Experimental evaluation of heat transfer performance under natural and forced convection around a phase change material encapsulated in various shapes

Sustainable Energy Technologies and Assessments ◽

10.1016/j.seta.2021.101025 ◽

2021 ◽

Vol 44 ◽

pp. 101025

Author(s):

Xiaolin Wang ◽

Una Djakovic ◽

Huashan Bao ◽

Juan F. Torres

Keyword(s):

Heat Transfer ◽

Phase Change ◽

Phase Change Material ◽

Forced Convection ◽

Experimental Evaluation ◽

Heat Transfer Performance ◽

Transfer Performance ◽

Change Material

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

Volume 8: Heat Transfer and Thermal Engineering ◽

10.1115/imece2019-10697 ◽

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.

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Preparation and Numerical Simulation of Heat Transfer Performance for Methyl Palmitate-Methyl Stearate Binary Eutectic Mixture/Expanded Graphite Composite Phase Change Material

Materials Science Forum ◽

10.4028/www.scientific.net/msf.993.920 ◽

2020 ◽

Vol 993 ◽

pp. 920-926

Author(s):

Bi Chuan Chi ◽

Yan Yao ◽

Su Ping Cui

Keyword(s):

Heat Transfer ◽

Phase Change ◽

Phase Change Material ◽

Phase Change Materials ◽

Heat Transfer Performance ◽

Eutectic Mixture ◽

Fatty Acid Esters ◽

Transfer Performance ◽

Binary Eutectic ◽

Change Material

The binary eutectic mixtures of fatty acid esters are promising phase change materials for energy storage application. However, the low thermal conductivity which is a common problem for organic phase change materials restricts their further and better applications. In order to solve the problem, a novel composite phase change material (CPCM) was prepared in this research by using methyl palmitate-methyl stearate (MP-MS), a typical binary eutectic mixture of fatty acid esters, as phase change material and expanded graphite (EG) as heat transfer enhancer. The heat transfer performance of MP-MS/EG CPCM was numerical simulated by finite element analysis software ABAQUS. Numerical simulation results revealed that EG could notably enhance the heat transfer performance of MP-MS eutectic mixture. The heat transfer rate and phase change reaction rate of MP-MS/EG CPCM were 14 times and 3 times that of MP-MS eutectic mixture, respectively.

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