| 研究課題/領域番号 |
19K04230
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| 研究機関 | 東北大学 |
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研究代表者 |
SEBALD GAEL 東北大学, 高等研究機構等, 客員教授 (10792161)
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| 研究分担者 |
小宮 敦樹 東北大学, 流体科学研究所, 教授 (60371142)
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| 研究期間 (年度) |
2019-04-01 – 2022-03-31
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| キーワード | solid-state cooling / natural rubber / Refrigeration |
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| 研究実績の概要 |
The main objective of the project is to develop refrigeration technology based on elastocaloric material (natural rubber) and regenerative heat transfer mechanism. Cyclic stretching of the rubber induces cyclic temperature variation. A heat transfer fluid (water) moves synchronously around the rubber, leading to a net heat flux along one direction. The elucidation of the mechanism of the heat flux generation is the main key question addressed by the project. The first year of the project was therefore devoted to (i) the completion of an experimental bench and (ii) the validation of the analytical model, as an attempt to better understand the refrigeration mechanism of regenerative elastocaloric system.
The preliminary experimental bench consisted of actuators able to stretch cyclically natural rubber tube and pumping oscillatory fluid inside. Especially, the thermal boundary conditions are difficult to control properly, and the pumping system was optimized. Also, temperature is now recorded both by thermocouples inserted inside the fluid, and IR camera measuring the external rubber temperature. The first results show that a temperature spatial gradient along the rubber is achieved, around 2 to 3 °C over 15 cm, when the temperature variations of the rubber is about 2°C. This corresponds to a regenerative coefficient above 1. The analytical model was completed and adapted to be able to simulate axisymmetric situation, as well as Poiseuille flow of the fluid. The simulations appear to be in good qualitative agreement with the first experimental results.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
The experimental setup was developed and optimized more quickly than earlier planed and produced results as early as October 2019. Especially the effect of the amplitude of the displacement of the heat transfer fluid, as well as the effect of the frequency were experimentally measured using a rubber tube of external diameter of 5mm inside which water was cyclically flowing. In addition, the optimization of the thermal boundary condition was made possible by 3D printing of ABS holding parts ensuring a very low heat conduction (porous parts), and solved most of the previously encountered issues. In parallel the analytical model was successfully completed in terms of more realistic conditions (flow type and geometry). The agreement between simulation and experiment was found better than firstly expected. As a consequence, the results were gathered in a publication that was sent to a special issue of the Journal of Applied Physics in October 2019, and was accepted in January 2020. It presents the analytical model, which is the first model of this kind for regenerative solid-state cooling. It was distinguished also by the American Institute of Physics as an editor’s pick, and a scientific highlight (Scilight) offering a good visibility to the article.
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| 今後の研究の推進方策 |
The analytical highlighted several unclear features about the exact mechanisms of heat flux generation. Especially, it is related to a complex interaction between fluid motion speed and its time variations of temperature. The nature of the flow and its effect on the cooling capability will be more deeply investigated. It is planned to implement an optical visualization of the inner flow, to determine the flow pattern. As detailed in the research plan, it is expected that a non-axial flow is better for the performance, and the experimental validation is important.
Also, the analytical model shows high limitations due to the necessary assumptions. Before developing Computational Fluid Dynamics simulations, it is developed a numerical model using a mean temperature solving scheme. It can waive several assumptions from the analytical approach, and the comparison between both models and experiments is expected to bring several answers to the main questioning of the project. Finally, from an experimental point of view, it is planned that the thermal boundary condition is updated by using passive temperature control system.
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