Project 5 Development on Neutron Imaging Application (R3P5)

概要

INTRODUCTION: Enhancement of the spatial and temporal resolutions in neutron radiography (NRG) is very important for multiphase flow visualization. In this work, image denoising for high-speed neutron imaging was evaluated to observe the dynamic phenomena, and the neutron computed tomography (CT) system was im- proved to enhance spatial resolution.

INTRODUCTION: Water management is a key topic of a polymer electrolyte fuel cell (PEFC). It is well known that the water accumulation in the gas diffusion layer (GDL) increases the polarization resistance, where- as the increase in the water content in the proton ex- change membrane (PEM) decreases the proton conduc- tivity in the PEM. The water distribution may change during the PEFC operation because of the water genera- tion. However, the effect of water distribution and the water contents in the GDL and the membrane on the re- sistances has not been fully understood because of the difficulty of measuring water distributions in the PEFC. In this study, neutron radiography and electrochemical impedance spectroscopy (EIS) were employed to clarify the relationship between the water contents and the sources of polarization loss in a PEFC. As a result, the relation between the water contents in the PEM and the ionic conductivity is discussed.

INTRODUCTION: We have synthesized metal oxide nanoparticles by mixing a stream of an aqueous reactant solution with another stream of supercritical water in a flow-type reactor. The mixed reaction solution was grad- ually cooled to room temperature by using a jacket cooler and released from a back pressure regulator. However, the gradual cooling might result in the production of larger nanoparticles with broader size distribution. In this study, we proposed quicker cooling of the reaction solu- tion by mixing cooling water and observed the cooling process by neutron radiography.

INTRODUCTION: Microchannel heat exchanger has several advantages against the conventional fin-tube heat exchanger, thus recently it has been widely used as the heat exchanger of air-conditioning unit. But the structure of microchannel fundamentally causes the flow oscilla- tion especially under non-uniform heat flux condition.
In this series of investigation[1-3], heat and flow char- acteristics has been evaluated by using a single plate mi- crochannel heat exchanger.
In this report, the quantitatively visualization of a dy- namic flow maldistribution by using neutron radiography will be briefly explained.

INTRODUCTION: Recently, heat pumps have been proposed as an effective air conditioning system of heat- ing operation for electric vehicles, because of the inabil- ity to use the engine heat as in the conventional vehicles. However, during the heating operation, frosting occurs on the outdoor heat exchanger of the air conditioning sys- tem. The frost formation causes a serious energy loss on the battery due to the heat transfer performance degrada- tion by increasing the thermal resistance. In addition, the corrugated fin tube heat exchanger which is mainly used as an automotive heat exchanger has a more complicated structure than conventional one, hence it is difficult to capture the frosting situation. In this study, the frost dep- osition on the corrugated fin tube heat exchanger was evaluated by X-ray and neutron cooperative radiography imaging in a pseudo-three-dimensional measurement. Last year, the radiography images were obtained by the image intensifier. In this experiment, the scintillator is used for observing the detail frost distribution on the cor- rugated heat exchanger.

INTRODUCTION: Rice husks are considered an industrial waste product and have been used in rice husk medium, which is a mixture of rice husks and soil at a 3:1 ratio by volume. This inexpensive medium has the advantage of being lightweight, easy to carry, and offers good drainage and resistance to plant root rot. Even if the bottom portion of a potted plant filled with rice husk medium were flooded with water, the capillary rise of the water was less than 8 cm. Therefore, the medium remained dry 8 cm above the waterlogged surface. We investigated the phenomenon of water movement by roots into the arid zone formed in the rice husk medium. This arid region is believed to be a key factor in the development of the plant’s ability to tolerate salt. Neutron imaging is sensitive to water, but not minerals, making it suitable for studying water transfer from the soil to the roots. However, in media with high organic matter, such as the rice husk medium, it is difficult to distinguish between roots and the medium, which leads to inconclusive images. X-ray imaging is not suitable for plant root visualization because of its low sensitivity for biological samples. However, by introducing a contrast agent into the plant roots and increasing the absorption of X-rays compared to rice husk medium, roots in the rice husk medium could be observed. Therefore, this study established a method to locate roots in culture medium with high organic matter using X-ray imaging.

INTRODUCTION: In general, reinforced concrete buildings are fireproof structures because they have cover concrete to resist heat from a fire. However, spalling [1] phenomena may occur to lose their cover concrete when the structures were heated by fire, especially in case of us- ing high strength concrete. In the past research, the expla- nations for this phenomenon have been widely accepted by thermal stress and water vapor pressure, or both. On the other hand, it has been pointed out that the spalling does not occur at the low water content but at the high moisture content. In this study, the effect of moisture content on the spalling phenomena of high-strength concrete was investi- gated by using the neutron imaging technique.

INTRODUCTION: Enhancement of lithium ion con- duction in oxide-based solid electrolyte is one of the fo- cused issues for the development of All Solid-State Bat- teries. We have revealed that LaPO4 dielectric particle dispersion in NASICON-type solid electrolyte LATP (Li1.3Al0.3Ti1.7(PO4)3) improves the conductivity by 3 times [1-3]. The conductivity enhancement is thought to be due to the formation of space charge layer in the vicin- ity of LaPO4 / solid electrolyte interface, in which the defect concentration is higher and thus the lithium diffu- sion occur faster [4]. We have recently measured the tracer diffusion coefficient of lithium ion in pristine and LaPO4 dispersed LATP by means of neutron radiography [5]. Due to large neutron attenuation factor of 6Li, diffu- sion profile has been obtained for LATPs consisting of 7 Li using 6Li as the tracer.
In above experiments, diffusion process has been achieved by simply annealing after applying the tracer. On the other hand, in terms of the battery application, visualization of lithium migration in the solid electrolyte is also significant. In the last year, we have constructed MnO2 / 7Li-LATP / NLi-LATP / Li1.33Ti1.67O4 cells to electrolyze for the neutron imaging. Herein, NLi indicates the natural isotope ratio of 6Li / 7Li. However, the lithium transfer at the interface is relatively difficult to observe the lithium migration in 7Li-LATP. Then, in the present study, we changed the cell configuration as LiMn2O4 / 7 Li-LATP / LiMn2O4 symmetry cell to reduce the sol- id-solid interface.

INTRODUCTION: Electrification of vehicles has been promoted to reduce greenhouse gas. The powertrain of the vehicles is the electric motors which is required to have high performance, more power, and compactness [1]. This leads to the higher emission heat density from the motor package and the effective cooling scheme of the heated stator coil has been important. The stator coil in the motor is cooled by the coolant poured from a noz- zle above. Although there have been some studies of the temperature measurement [2, 3], the coolant profile in- side the coil has not been clarified yet and the pouring conditions are decided empirically. In this study, there- fore, the coolant visualization inside the simplified stator coil structure is carried out by using the neutron radiog- raphy. The coil structure is made of aluminum and com- posed by layered curved rod array.

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