• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.5
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• pp.805-816
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• 2015

In the present study, external restraints imposed normal to the plate during the cooling stage were determined to be effective for reduction of the angular distortion of butt-welded or fillet-welded plate. A welding analysis model under external force during the cooling stage was idealized as a prismatic member subjected to pure bending. The external restraint was represented by vertical force on both sides of the work piece and bending stress forms in the transverse direction. The additional bending stress distribution across the plate thickness was reflected in the improved inherent strain model, and a set of inherent strain charts with different levels of bending stress were newly calculated. From an elastic linear FE analysis using the inherent strain values taken from the chart and comparing them with those from a 3D thermal elasto-plastic FE analysis, welding deformation can be calculated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.12-15
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• 2011

The most widely used kerosene-LOx liquid-propellant rocket engines in these days have a similar engine schematic to those of the past because of the development cost and the reliability. The efficiency of engines could be increased by the factors such as a cooling method, engine cycles, shape of cooling channels, additional coolant and so on. In this article, it is described that some design ideas for performance enhancement by exchange kerosene with LOx of a coolant.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.5
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• pp.98-104
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• 2022

When processing parts, the cutting oil can improve the cooling performance of the workpiece and tool to increase the precision of the workpiece or extend the life of the tool and facilitate chip extraction. Since such cutting oil has a harmful effect on the environment and the human body due to additives such as sulfur, research on a minimum lubrication supply method using an eco-friendly oil is recently underway. The minimum lubrication supply method minimizes the amount of cutting oil used during processing and processes it, which can reduce the amount of cutting oil used, but has a problem in that cooling performance efficiency is poor. Therefore, this study conducted a study on mist cooling of lubricants to reduce the amount of cutting oil used and maximize the cooling effect of processing heat generated during tapping processing. Spray pressure, processing speed, direction, and lubricant spray amount, which are considered to have an effect on cooling performance, were set as process conditions, and the effect on temperature was analyzed by performing an experiment using the box benquin method among experiments were analyzed. Through the experimental analysis results, the optimal conditions for mist and processing that maximize the cooling effect were derived, and the validity of the results derived through additional experiments was verified. In the case of processing by applying the mist lubrication method verified through this study, it is considered that high-precision processing is possible by improving the cooling effect.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1190-1198
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• 2012

A hot forming of large thick Al plate using a grid-type hybrid die is a process to make a shell plate for the production of a spherical LNG tank. This process is characterized by using a grid-typed die with an additional air cooling system for reducing the cooling time of the heated plate after hot forming. The process consists of the plate's feeding, heating, forming and cooling in detail and each of them is continuously performed along the rail. This paper was designed to propose the analytical and experimental methods for determining the convection and interfacial heat transfer coefficients required in hot forming analysis of Al plate. These values in the analysis are to reproduce numerically the cooling performance of grid-typed die and cooling device. Interfacial heat transfer was obtained from the heat transfer experiments for different pressures and inverse analysis method. To verify the efficiency of the coefficient values obtained from above methods, FE analysis and experiment of the hot spherical-forming process were conducted for a small-scaled model. The convection coefficient was also calculated from flow analysis of air released by cooling device within grid-typed die using ANSYS-CFX.

• Structural Engineering and Mechanics
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• v.70 no.4
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• pp.479-497
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• 2019

In the current code design, the use of a uniform internal pressure coefficient of cooling towers as internal suction cannot reflect the 3D characteristics of flow field inside the tower body with different ventilation rate of shutters. Moreover, extreme weather such as heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind. In this study, the world's tallest cooling tower under construction, which stands 210m, is taken as the research object. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed iteratively using continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind speed and rainfall intensity on the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower body is analyzed. The combination of wind velocity and rainfall intensity that is most unfavorable to the cooling tower in terms of distribution of internal pressure coefficient is identified. On this basis, the wind/rain loads, distribution of aerodynamic force and working mechanism of internal pressures of the cooling tower under the most unfavorable working condition are compared between the four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the amount of raindrops captured by the internal surface of the tower decreases as the wind velocity increases, and increases along with the rainfall intensity and ventilation rate of the shutters. The maximum value of rain-induced pressure coefficient is 0.013. The research findings lay the basis for determining the precise values of internal surface loads of cooling tower under extreme weather conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.1
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• pp.8-15
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• 2011

Cooling load reduction was analysed of a ventilation system adopting a regenerative evaporative cooler. The regenerative evaporative cooler is a kind of indirect evaporative cooler which cools the air down to its inlet dewpoint temperature in principle without change in the humidity ratio. The regenerative evaporative cooler was found able to cool the ventilation air to $18{\sim}21^{\circ}C$ when the outdoor condition ranges $25{\sim}35^{\circ}C$ and 0.01~0.02 kg/kg. When the outdoor humidity ratio is lower than 0.018 kg/kg, the regenerative evaporative cooler was found to provide cooling performance enough to compensate the ventilation load completely and to supply additional cooling as well. Energy simulation during the summer was carried out for a typical office building with the ventilation system using the regenerative evaporative cooler. The results showed that the seasonal cooling load can be reduced by about 40% by applying the regenerative evaporative cooler as a ventilation conditioner. The reduction was found to increase as the outdoor temperature increases and the outdoor humidity ratio decreases.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.42-48
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• 2013

The global warming of the Korean Peninsula proceeds most rapidly in the world and its abnormal climate is more deepening. In the result of the surged electricity consumption by intense heat of summer and severe cold of winter, electricity supply and demand status is in hard situation. Currently, the supply of natural gas is increased because natural gas has the lowest greenhouse-gas emissions among the existed fossil fuel. Natural gas cooling has a lot of advantage such as decreasing electricity peak, reducing construction expenses in additional power plant, operating natural gas storage facilities efficiently, and playing a role as distributed generations. Therefore, this study analyzes the economic feasibilities of gas cooling as an alternative for electric power load management.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.133-139
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• 2009

An analysis has been performed on the specific impulse for a liquid rocket engine of gas generator cycle. The present analysis method has been validated through the comparison of the optimal specific impulse for the 300t thrust conceptual engine against the published data. The engine specific impulse can be increased by applying film coolant decreasing the fuel pump head for regenerative cooling despite the decrease of specific impulse of the combustion chamber when the film coolant participates combustion more than the critical amount. The improved condition shows that higher combustion chamber pressure is achieved with less fuel pump head rise by additional film cooling.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.17-22
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• 2014

Recently, the quick heating performance is an important issue in the car because engine power becomes so high. So car makers have been adapted the additional heating devices as like PTC(Positive Temperature Coefficient) heater. And the quick cooling performance is also important issue because its result is used in the IQS(Initial Quality Study). In this paper, control of the HVAC(Heating, Ventilation and Air Conditioning) intake door has been studied for the quick heating and cooling performance. Heating performance is improved $4.0^{\circ}C$ at $-20^{\circ}C$ ambient temperature after 20 minutes. And cooling performance is improved $1.5^{\circ}C$ at $35^{\circ}C$ ambient temperature after 10 minutes. In addition, intake door control system brings on the cost reduction because the flab door can be eliminated. This intake door control system has been adapted to the new developing cars.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.3
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• pp.303-308
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• 2015

Compressed air has many uses on board ship, ranging from diesel engine starting to the cleaning of machinery during maintenance. In an effort to enhance the performance of the marine compressed air system, this work studied a way to reduce condensation from the air compressor via experiments. Especially more condensation is produced when the temperature at compressor outlets and the humidity of the air are higher. so in the research, drain production change has been observed by additionally installing the cooling fan on the suction portion of the air to air compressor and this is the method for reducing the compressed air drain that has passed through the compressor. For the result, it was verified that when the cooling fan was used, less drain was made where per hour it was 500.9ml of drain and the measured result after installing the cooling fan was that less drain was made. Other additional and various researches are needed including experiments like silica gel passing through the suction portion afterwards.