2020 Fiscal Year Research-status Report
Making cold from natural rubber: a low-cost and environment friendly refrigeration alternative
| Project/Area Number |
19K04230
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| Research Institution | Tohoku University |
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Principal Investigator |
SEBALD GAEL 東北大学, 高等研究機構等, 客員教授 (10792161)
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| Co-Investigator(Kenkyū-buntansha) |
小宮 敦樹 東北大学, 流体科学研究所, 教授 (60371142)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | solid-state cooling / natural rubber / Refrigeration |
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| Outline of Annual Research Achievements |
Pursuing the objective of developing an environment friendly elastocaloric refrigeration principle, several actions led to important results in FY2020. In this project, we focus especially on active regenerator solution, which consist of stretching natural rubber while cyclically circulating fluid around it. The exact mechanisms of the generation of a net heat flux required deeper investigation.
In FY2019, it was possible to propose a very first preliminary experiment using natural rubber tube, with a system temperature span reaching 2 to 3°C for a 15cm long rubber tube. The power was estimated to be around 50mW for one tube of 5mm initial diameter (2mm when stretched). There are numerous possible operating conditions, and to assist their screening, an analytical model was then developed successfully.
However, the experimental difficulties in controlling thermal boundary conditions on the one hand, and the strong assumptions of the analytical model on the other hand, makes the comparison qualitatively sound, but with strong discrepancies for some operating conditions. Therefore, in FY2020 another modelling technique was developed, based on a 1D solving of the heat diffusion equation. It was revealed especially the importance of the active thermal conductivity resulting from the fluid cyclic displacement, responsible for the decrease of the temperature span of the system.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The 1D model was developed very quickly and its comparison to the analytical model and to the experiments led to a much better understanding of the mechanisms of regenerative refrigeration using caloric materials. Deep discussion with heat transfer experts involved in the project was especially beneficial, and later, several highly promising improvements of the experimental setup were identified and are under construction as of today.
In addition, we identified several new research actions that are especially important: (i) try to parallelize the rubber tube work, (ii) further investigate more deeply what happens in a single tube, both fluid flow, rubber deformation and its elastocaloric effet, and (iii) development of a model at the system level in order to extend analytical model capabilities by adding heat exchanger and heat loss effects. This project results are expected to be presented at the Eurotherm seminar on Caloric Heating and Cooling in July 2021.
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| Strategy for Future Research Activity |
For FY2021, it is planned to focus on
-Deep investigation using one single tube and controlling precisely the fluid flow inside.
-Exploration of other configurations for refrigeration, such as single-stage system.
-Combination of the modelling attempts to reach a fast computing and reliable model.
-Further development the regenerative cooling system. Compared to previous years, it is planned to optimize the instrumentation in order to be able to quantify the mechanical losses and especially the Coefficient of Performance of the elastocaloric cooling using natural rubber.
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