• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.7
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• pp.380-394
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• 2015

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.6
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• pp.256-268
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• 2016

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2015. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering were carried out in the areas of flow, heat and mass transfer, cooling and heating, and air-conditioning, the renewable energy system and the flow inside building rooms. Research issues dealing with air-conditioning machines and fire and exhausting smoke were reduced. CFD seems to be spreading to more research areas. (2) Research works on heat transfer area were carried out in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the economic analysis of GHG emission, micro channel heat exchanger, effect of rib angle on thermal performance, the airside performance of fin-and-tube heat exchangers, theoretical analysis of a rotary heat exchanger, heat exchanger in a cryogenic environment, the performance of a cross-flow-type, indirect evaporative cooler made of paper/plastic film. In the area of pool boiling and condensing, the bubble jet loop heat pipe was studied. In the area of industrial heat exchangers, researches were performed on fin-tube heat exchanger, KSTAR PFC and vacuum vessel at baking phase, the performance of small-sized dehumidification rotor, design of gas-injection port of an asymmetric scroll compressor, effect of slot discharge-angle change on exhaust efficiency of range hood system with air curtain. (3) In the field of refrigeration, various studies were carried in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, a cold-climate heat pump system, $CO_2$ cascade systems, ejector cycles and a PCM-based continuous heating system were investigated. In the alternative refrigeration/energy system category, a polymer adsorption heat pump, an alcohol absorption heat pump and a desiccant-based hybrid refrigeration system were investigated. In the system control category, turbo-refrigerator capacity controls and an absorption chiller fault diagnostics were investigated. (4) In building mechanical system research fields, eighteen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the user and location awareness technology applied dimming lighting control system, the lighting performance evaluation for light-shelves, the improvement evaluation of air quality through analysis of ventilation efficiency and the evaluation of airtightness of sliding and LS window systems. The subjects of building energy were worked on the energy saving estimation of existing buildings, the developing model to predict heating energy usage in domestic city area and the performance evaluation of cooling applied with economizer control. The studies were also performed related to the experimental measurement of weight variation and thermal conductivity in polyurethane foam, the development of flame spread prevention system for sandwich panels, the utilization of heat from waste-incineration facility in large-scale horticultural facilities.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.6
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• pp.292-298
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• 2012

In this study, Cu-2.5at.%Ni-1at.%Si alloys were fabricated by horizontal continuous casting system to improve the electrical conductivity and mechanical properties of Cu-Ni-Si alloy. Withdrawing speed was changed with 50, 100, 150 and 200 mm/min for the optimum manufacturing condition. Microstructure was observed using OM, FE-SEM and TEM. Electrical conductivity was measured by 4-point probe method and mechanical properties were tested. A horizontal continuous cast thin slab had sound macro and micro structures with partly crystallized structures. Electrical resistivity decreased with increasing annealing temperature from 250 to $850^{\circ}C$, with increasing annealing temperature The maximum hardness and tensile strength were Hv 130, 610 MPa at $550^{\circ}C$, respectively. With changing withdrawing speed from 50 to 150 mm/min, hardness, tensile strength, yield strength and elongation were Hv 60-65, 210-230 MPa, 65-75 MPa and 40-50%, respectively.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.427-431
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• 2001

In this research, porous materials were made from mine's waste slime. As a temperature changes, a phase changes, a porosity, and a mechanical strength of porous materials were observed and measured. The process of pore-formation was observed by SEM according to the change of heat-treatment temperature and time. It fumed out that the foaming reaction of mine's waste slime was resulted from liquid phase by decomposition of the sanidine and the muscovite-3T. When heat- treated at over 120$0^{\circ}C$, it appeared high porosity. And, to activate the foaming reaction, an alkaline oxide concerned with liquid formation was added and its effects were examined.

• Corrosion Science and Technology
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• v.11 no.5
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• pp.196-204
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• 2012

Corrosion failure of petrochemical facilities is one of the difficulties in maintenance, since operating conditions of crude oil production, storage, and refinement are very aggressive. UNS N08810, which has been used for crude oil transportation pipes and storage tanks in petrochemical industries, shows good resistance to general corrosion and localized corrosion in several environments. Among its environments, UNS N08810 showed better corrosion resistance in fuel gas containing sulfuric acid and phosphoric acid and sulfur. However, ductility and toughness at high temperature over about $500^{\circ}C$ were greatly reduced due to microstructural change. In general, welding process is the representative method to join the parts in industrial components. Because the alloy by welding can be sensitized and corroded, the manufacturing process should be controlled. In this work, UNS N08810 was used and heat treatment conditions including solution and stabilization treatments were controlled. Oxalic acid etch test by ASTM A262 Practice A was done to evaluate the qualitative sensitization in room temperature. Huey test by ASTM A262 Practice C was done to evaluate the intergranular corrosion rate in boiling 65% $HNO_3$ solution. Also, the microstructure by thermal history was analyzed. Experimental alloy showed high intergranular corrosion rate and its corrosion mechanism was elucidated.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.44-56
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• 1998

Separate heat pipe exchanger is considered as the high thermal transportation equipment, because evaporator and condenser are separately positioned in the long distance. Its characteristics are that the working fluid is circulated naturally by the position height of two exchangers. But the operating characteristics are restricted by the temperature of hot and cold fluid, flow pattern and diameter of vapor line, etc. in this study, the vapor pressure and the minimum height of two exchangers are studied about the factors restricting the operating characteristics.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.2
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• pp.49-56
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• 2020

Magnesium alloy is a metal with high specific strength and light weight, and is attracting attention as a next generation metal for environmentally friendly automobiles and transportation equipment. However, magnesium alloys have a problem of degrading formability due to the basal texture developed during processing, and their application is limited. Although active researches on the control of textures have been conducted in order to minimize this problem, there is a lack of research on the formation of microstructures and textures according to elemental differences. In this study, AZ61 and AZ80 magnesium alloys were selected to investigate the effects of aluminum addition on the microstructure development of magnesium alloys. This research has proven that the increase of the rolling rate results in the decrease of the average grain size of the two alloys, the increase of the hardness, and the increase of the fraction of twins. As shown on this research below, the basal texture developed strongly as the rolling ratio increased. On the other hand, this research also has proven that the two alloys exhibited different texture strength and distribution tendencies, which could be due to the effects of aluminum addition on work hardening, grain size, and twin behavior.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.1
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• pp.23-29
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• 2013

In recent years, development of energy conversion systems using hydrogen as an energy source has been accelerated globally. Even though hydrogen is an environment-friendly energy source, safety and effectiveness issues in storage, transportation, and usage of hydrogen should be clearly resolved in every application. Therefore, sensors for detecting hydrogen leakage, especially for fuel cell electric vehicles, should be designed to have much higher resolution and accuracy in comparison with conventional gas sensors. In this study, we conducted to determine the design parameters for the semiconductor hydrogen sensor with optimized sensing conditions under the thermal distribution characteristic and thermal transfer characteristic. The heat generation study on power supply voltage was studied for correlation analysis of thermal energy according to the power supply voltage variation from 1.0 voltage to 10.0 voltage every 0.5 voltage. And we studied for the temperature coefficient of resistance with hydrogen sensor.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.4
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• pp.313-321
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• 2008

Dynamics of the proton exchange membrane fuel cell is specially important when the system is frequently working on transient conditions. Even though the dynamics of proton exchange membrane fuel cell for residential power generation is less critical than that of PEMFC for transportation application, the system dynamics of PEMFC for RPG can be very important for daily start-up and stop. In particular, thermal management of the PEMFC for RPG is very important because the heat generation from electrochemical reaction is delivered to the home for hot water usages. Additionally, the thermal management is also very important for heat balance of the system and temperature control of the fuel cell. The objective of this study is to develop a dynamic system model for the study of PEMFC performance over various BOP options. Basic simulation results will be presented.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.6
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• pp.608-614
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• 2023

The fast filling process of high-pressure hydrogen has an important impact on the filling efficiency and safety. In this paper, a specific study is carried out on the thermophysical phenomena during the fast filling process. Starting from the gas state equation of hydrogen, the change law of the hydrogen storage temperature is obtained, and then the temperature rise prediction is constructed. The model can clarify the relationship between the filling parameters and the temperature rise during the fast filling process, thereby revealing the flow and heat transfer laws of the fast charging process. To improve the theoretical research basis for the evaluation of vehicle-mounted hydrogen fast charging capacity, temperature prediction and optimization of hydrogenation methods.