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基礎講座 電気泳動(Electrophoresis)

An introduction to heat transfer

Nanofluids are potential heat transfer fluids with enhanced thermophysical properties and heat transfer performance can be applied in many devices for better performances (i.e. energy, heat transfer and other performances). In this paper, a comprehensive literature on the applications and challenges of nanofluids have been compiled and reviewed. Latest up to date literatures on the applications and challenges in terms of PhD and Master thesis, journal articles, conference proceedings, reports and web materials have been reviewed and reported. Recent researches have indicated that substitution of conventional coolants by nanofluids appears promising. Specific application of nanofluids in engine cooling, solar water heating, cooling of electronics, cooling of transformer oil, improving diesel generator efficiency, cooling of heat exchanging devices, improving heat transfer efficiency of chillers, domestic refrigerator-freezers, cooling in machining, in nuclear reactor and defense and space have been reviewed and presented. Authors also critically analyzed some of the applications and identified research gaps for further research. Moreover, challenges and future directions of applications of nanofluids have been reviewed and presented in this paper. Based on results available in the literatures, it has been found nanofluids have a much higher and strongly temperature-dependent thermal conductivity at very low particle concentrations than conventional fluids. This can be considered as one of the key parameters for enhanced performances for many of the applications of nanofluids. Because of its superior thermal performances, latest up to date literatures on this property have been summarized and presented in this paper as well. However, few barriers and challenges that have been identified in this review must be addressed carefully before it can be fully implemented in the industrial applications.

/pdf/a-review-on-applications-and-challenges-of-nanofluids-ibdekzmmqr.pdf

A review on applications and challenges of nanofluids

Bacteria primarily exist in robust, surface-associated communities known as biofilms, ubiquitous in both natural and anthropogenic environments. Mature biofilms resist a wide range of antimicrobial treatments and pose persistent pathogenic threats. Treatment of adherent biofilm is difficult, costly, and, in medical systems such as catheters or implants, frequently impossible. At the same time, strategies for biofilm prevention based on surface chemistry treatments or surface microstructure have been found to only transiently affect initial attachment. Here we report that Slippery Liquid-Infused Porous Surfaces (SLIPS) prevent 99.6% of Pseudomonas aeruginosa biofilm attachment over a 7-d period, as well as Staphylococcus aureus (97.2%) and Escherichia coli (96%), under both static and physiologically realistic flow conditions. In contrast, both polytetrafluoroethylene and a range of nanostructured superhydrophobic surfaces accumulate biofilm within hours. SLIPS show approximately 35 times the reduction of attached biofilm versus best case scenario, state-of-the-art PEGylated surface, and over a far longer timeframe. We screen for and exclude as a factor cytotoxicity of the SLIPS liquid, a fluorinated oil immobilized on a structured substrate. The inability of biofilm to firmly attach to the surface and its effective removal under mild flow conditions (about 1 cm/s) are a result of the unique, nonadhesive, “slippery” character of the smooth liquid interface, which does not degrade over the experimental timeframe. We show that SLIPS-based antibiofilm surfaces are stable in submerged, extreme pH, salinity, and UV environments. They are low-cost, passive, simple to manufacture, and can be formed on arbitrary surfaces. We anticipate that our findings will enable a broad range of antibiofilm solutions in the clinical, industrial, and consumer spaces.

https://www.pnas.org/content/pnas/109/33/13182.full.pdf

Liquid-infused structured surfaces with exceptional anti-biofouling performance

The feasibility of useing a flexible, printed indium-tin-oxide (ITO) sensor to detect hazardous and noxious substances was investigated. The resistivities of this printed ITO (P-ITO) film and that of a commercial sputtered ITO (S-ITO) film were 35.9 and 1.5 × 10 −4 Ω·cm, respectively. The corresponding grain sizes, a determined via X-ray diffractometry, were 31.7 and 102.6 nm. This difference in grain size between the two films led to a remarkable difference in the respective carrier scattering mechanisms. To evaluate the chemical sensing property of both ITO films, we tested their NH3 sensing abilities; the printed film exhibited a higher sensitivity and better electrical properties.

Electrical and Chemical Sensing Properties of a Printed Indium-Tin-Oxide Film for the Detection of Hazardous and Noxious Substances

The present invention relates to a method to treat surfaces of metal substrates for improving efficiency of an offshore equipment. The method comprises: (a) a step of forming a porous oxide film on a surface of an aluminum substrate; and (b) a step of coating a corrosion inhibitor on the surface of the aluminum substrate formed with the oxide film. According to the present invention, the method to treat the surfaces of the aluminum substrate has superior anti-fouling and anti-corrosion effects of the metal substrate compared to a conventional surface treatment method of coating only the corrosion inhibitor, by forming the porous oxide film on the surface of the aluminum substrate by a surface treatment, to allow a portion of the corrosion inhibitor to be absorbed to the porous oxide film.

Method for treating surface of metal substrates for improving efficiency of offshore equipment

In this study, reliability evaluation in conceptual design stage is performed to develop the dehydration package of offshore plant equipment. Dehydration package is commonly used in the gas treatment system but has still being developed. Since the technology for the dehydration package relies on almost 100 % in overseas companies, it is necessary to acquire the design/engineering technology for dehydration package. The design must also consider reliability and safety with the special characteristic of ocean environment and the danger of gas process. Therefore, the concept of adsorption dehydration package and design philosophy for development of dehydration package is derived through reliability evaluation in conceptual design stage in this study. After defining the equipment for dehydration package by IDEF0, reliability evaluation of conceptual design for the dehydration package is performed using fault tree analysis (FTA), based on the result of hazard identification (HAZID) analysis. In the future, this result will be applied in detail design.

Reliability evaluation of conceptual design for the dehydration package

A bubble-powered micro pump is provided to form a triple structure to obtain large flux with low power, observe bubble movement in a chamber to control bubbles in the optimum condition to obtain desired flux, and remove a mechanical driving part to secure long-term reliability A first silicon wafer layer is a mark layer, having a groove formed on a top side to interpose a micro heater(21) A second silicon wafer layer is accumulated on the first silicon wafer layer, having a passage(31) in a direction of crossing the micro heater A glass wafer layer has a power supply path connected with both ends of the micro heater to receive power through grounding, a fluid inlet(42) and a fluid exhaust port(43) connected with both ends of the passage

Bubble-powered micro pump

Proteinaceous bubbles of 185 nm average diameter were synthesized by a sonochemical treatment of bovine serum albumin (BSA) in an aqueous solution and the nanoparticles (TiO2) solution was made by ultrasonic irradiation. To study the macroscopic flow behavior associated with the changes in the state of the microparticles, a flow test of these solutions in microchannels was done. Also, the size distributions of the proteinaceous bubbles in solution before and after the flow test were measured by a light scattering method. Test results show that the air-filled proteinaceous bubbles in solution adjust their size to reduce the shear stress encountered in the flow through the microchannel. On the other hand, the mass flow rate of the solution with nanoparticle suspensions becomes smaller than that of deionized water in a microchannel of dimension 100×100 μm2.

Jung-Yeul Jung

Papers

Electrical and Chemical Sensing Properties of a Printed Indium-Tin-Oxide Film for the Detection of Hazardous and Noxious Substances

Method for treating surface of metal substrates for improving efficiency of offshore equipment

Reliability evaluation of conceptual design for the dehydration package

Bubble-powered micro pump

Proteinaceous bubble and nanoparticle flows in microchannels