Kyung Chun Kim

Bio: Kyung Chun Kim is an academic researcher from Pusan National University. The author has contributed to research in topics: Particle image velocimetry & Organic Rankine cycle. The author has an hindex of 29, co-authored 346 publications receiving 4222 citations. Previous affiliations of Kyung Chun Kim include Shanghai Jiao Tong University & University of Ottawa.

Very large-scale motion in the outer layer

Abstract: Very large-scale motions in the form of long regions of streamwise velocity fluctuation are observed in the outer layer of fully developed turbulent pipe flow over a range of Reynolds numbers. The premultiplied, one-dimensional spectrum of the streamwise velocity measured by hot-film anemometry has a bimodal distribution whose components are associated with large-scale motion and a range of smaller scales corresponding to the main turbulent motion. The characteristic wavelength of the large-scale mode increases through the logarithmic layer, and reaches a maximum value that is approximately 12–14 times the pipe radius, one order of magnitude longer than the largest reported integral length scale, and more than four to five times longer than the length of a turbulent bulge. The wavelength decreases to approximately two pipe radii at the pipe centerline. It is conjectured that the very large-scale motions result from the coherent alignment of large-scale motions in the form of turbulent bulges or packets of...

Potentials of porous materials for energy management in heat exchangers – A comprehensive review

Abstract: Heat exchangers are recognized as popular thermal devices with various and important applications in industrial energy systems. Many techniques were employed in order to manage the energy in these devices. Among these techniques, porous materials with high potentials for the energy management and enhancing the thermal performances in heat exchangers were employed widely. This paper reviews recent developments and utilisation of different types of porous materials in the heat exchangers. Both simulation and experimental works were briefly explained. The gaps in current literatures and designs were investigated and solutions for them were discussed.

3D particle position and 3D velocity field measurement in a microvolume via the defocusing concept

Abstract: This paper reports on a method for detecting three-dimensional particle positions and conducting three-dimensional microflow diagnostics in a microvolume via a three-pinhole defocusing concept. A simple setup and an easy detection method are described. The calibration-based defocusing method is suggested in place of formulae introduced through geometric analyses in previous studies. Depth calibration was performed in a microvolume, and X–Y compensation functions were obtained. By using the calibration functions, three-dimensional particle positions can be calculated at a sub-micron depth resolution. The effects of pinhole masks made with different pattern sizes are also described. The developed method was applied to a microflow in a micro backward-facing step. Time-resolved particle trajectories and three-dimensional volumetric velocity fields at a depth of 50 µm were obtained and are presented here.

Investigation of organic Rankine cycles with zeotropic mixtures as a working fluid: Advantages and issues

Abstract: Global warming has been a major concern, and the amount of CO2 released to the atmosphere keeps increasing due to overuse of the earth's fossil fuel reserves. Overpopulation and lack of comprehensive energy management add to the problem. New and renewable energy sources are still expensive or in the conceptual phase. The organic Rankine cycle (ORC) seems to be a viable option to address these issues by reusing waste and low-grade heat that would otherwise be released into the environment. Many ORC power plants are already in commercial use. Since the introduction of the basic ORC (BORC), there have been many revolutionary ideas to optimize the performance of power generators, but they have not been experimentally tested extensively. This study focuses on zeotropic refrigerant mixtures made of two or three refrigerants instead of a single working fluid. The main advantages of this system are increased exergy efficiency and decreased irreversibility in the evaporator and condenser, where the isothermal phase change of pure refrigerant would not match the temperature profile of the heat source and heat sink. Published experimental studies on this topic are extremely rare. This study discusses almost all the articles on this subject, the proposed mixtures, and the conclusions.

Gold nanoparticles in chemical and biological sensing.

Abstract: Detection of chemical and biological agents plays a fundamental role in biomedical, forensic and environmental sciences1–4 as well as in anti bioterrorism applications.5–7 The development of highly sensitive, cost effective, miniature sensors is therefore in high demand which requires advanced technology coupled with fundamental knowledge in chemistry, biology and material sciences.8–13 In general, sensors feature two functional components: a recognition element to provide selective/specific binding with the target analytes and a transducer component for signaling the binding event. An efficient sensor relies heavily on these two essential components for the recognition process in terms of response time, signal to noise (S/N) ratio, selectivity and limits of detection (LOD).14,15 Therefore, designing sensors with higher efficacy depends on the development of novel materials to improve both the recognition and transduction processes. Nanomaterials feature unique physicochemical properties that can be of great utility in creating new recognition and transduction processes for chemical and biological sensors15–27 as well as improving the S/N ratio by miniaturization of the sensor elements.28 Gold nanoparticles (AuNPs) possess distinct physical and chemical attributes that make them excellent scaffolds for the fabrication of novel chemical and biological sensors (Figure 1).29–36 First, AuNPs can be synthesized in a straightforward manner and can be made highly stable. Second, they possess unique optoelectronic properties. Third, they provide high surface-to-volume ratio with excellent biocompatibility using appropriate ligands.30 Fourth, these properties of AuNPs can be readily tuned varying their size, shape and the surrounding chemical environment. For example, the binding event between recognition element and the analyte can alter physicochemical properties of transducer AuNPs, such as plasmon resonance absorption, conductivity, redox behavior, etc. that in turn can generate a detectable response signal. Finally, AuNPs offer a suitable platform for multi-functionalization with a wide range of organic or biological ligands for the selective binding and detection of small molecules and biological targets.30–32,36 Each of these attributes of AuNPs has allowed researchers to develop novel sensing strategies with improved sensitivity, stability and selectivity. In the last decade of research, the advent of AuNP as a sensory element provided us a broad spectrum of innovative approaches for the detection of metal ions, small molecules, proteins, nucleic acids, malignant cells, etc. in a rapid and efficient manner.37 Figure 1 Physical properties of AuNPs and schematic illustration of an AuNP-based detection system. In this current review, we have highlighted the several synthetic routes and properties of AuNPs that make them excellent probes for different sensing strategies. Furthermore, we will discuss various sensing strategies and major advances in the last two decades of research utilizing AuNPs in the detection of variety of target analytes including metal ions, organic molecules, proteins, nucleic acids, and microorganisms.

Reactions in Droplets in Microfluidic Channels

Abstract: Fundamental and applied research in chemistry and biology benefits from opportunities provided by droplet-based microfluidic systems. These systems enable the miniaturization of reactions by compartmentalizing reactions in droplets of femoliter to microliter volumes. Compartmentalization in droplets provides rapid mixing of reagents, control of the timing of reactions on timescales from milliseconds to months, control of interfacial properties, and the ability to synthesize and transport solid reagents and products. Droplet-based microfluidics can help to enhance and accelerate chemical and biochemical screening, protein crystallization, enzymatic kinetics, and assays. Moreover, the control provided by droplets in microfluidic devices can lead to new scientific methods and insights.

Thermometry at the nanoscale

Abstract: Non-invasive precise thermometers working at the nanoscale with high spatial resolution, where the conventional methods are ineffective, have emerged over the last couple of years as a very active field of research. This has been strongly stimulated by the numerous challenging requests arising from nanotechnology and biomedicine. This critical review offers a general overview of recent examples of luminescent and non-luminescent thermometers working at nanometric scale. Luminescent thermometers encompass organic dyes, QDs and Ln3+ions as thermal probes, as well as more complex thermometric systems formed by polymer and organic–inorganic hybrid matrices encapsulating these emitting centres. Non-luminescent thermometers comprise of scanning thermal microscopy, nanolithography thermometry, carbon nanotube thermometry and biomaterials thermometry. Emphasis has been put on ratiometric examples reporting spatial resolution lower than 1 micron, as, for instance, intracellular thermometers based on organic dyes, thermoresponsive polymers, mesoporous silica NPs, QDs, and Ln3+-based up-converting NPs and β-diketonate complexes. Finally, we discuss the challenges and opportunities in the development for highly sensitive ratiometric thermometers operating at the physiological temperature range with submicron spatial resolution.