• Journal of Navigation and Port Research
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• v.40 no.1
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• pp.7-14
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• 2016

Although the life jacket can provide the buoyance with the drowner, heat loss can make the drowned individual be subject to the hypothermia. In this study, The thermal insulation of two types life jacket including inflatable and foam type were evaluate by both experiments and numerical analysis. To estimate the thermal resistance of the jackets, experiments on the heat flux were conducted by the thermal manikin exposed to cold water. Heat flux loss on the surface of thermal manikin were measured for both foam and inflatable type life jacket. Also, finite element method is applied to a body section in order to understand the level of hypothermia of each life jacket. The segmental of human thigh is represented by a multi-layered section which considers the heat conduction within tissue, bone and fat. As a result, the thermal resistance and hypothermia time of each jackets have been compared based on the finite element analysis. It was found that the insulation ability of suggested life jackets is better than that of conventional type.

• Solar Energy
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• v.19 no.4
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• pp.45-53
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• 1999

This report Introduces a total heat exchanger in a solar air-conditioning system using Lithium Chloride(LiCl) solution. The hot and humid outside air is cooled and dehumidified by LiCl solution that is sprayed on the packed layer of the total heat exchanger. LiCl solution once diluted is concentrated again in a regenerator using solar energy. Three types as the packed materials were used in this experiment and the dehumidification performance was evaluated by the value of $k_xa(kg/h{\cdot}m^3{\cdot}{\Delta}x)$, overall mass transfer coefficient based on a humidity ratio potential difference, the influence of inlet LiCl solution flow rate, air flow rate, packed layer height on $k_xa$ was investigated. It was found that air flow rate, LiCl solution flow rate, packed layer height for all types had a great influnce on the value of $k_xa$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.527-535
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• 2017

Heat management is one of the most critical issues in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) installed inside the fuel cell power pack of a fuel cell battery hybrid UPS. If the heat generated by the chemical reaction in the fuel cell is not rapidly removed, the durability and performance of the fuel cell may be affected, which may shorten its lifetime. Therefore, the objective of this study is to select and propose a proper cooling method for the fuel cells used in the fuel cell power pack of a UPS. In order to find the most appropriate cooling method, the various design factors affecting the cooling performance were studied. The numerical analysis was performed by a commercial program, i.e., COMSOL Multiphysics. Firstly, the surface temperature of the 1 kW class fuel cell stack with the cooling fans placed at the top was compared with the one with the cooling fans placed at the bottom. Various rotation speeds of the cooling fan, viz. 2,500, 3,000, 3,500, and 4,000 RPM, were tested to determine the proper cooling fan speed. In addition, the influence of the inhaled air flow rate was investigated by changing the porous area of the grille, which is the entrance of the air flowing from the outside to the inside of the power pack. As a result, it was found that for the operating conditions of the 1 kW class PEMFC to be acceptable, the cooling fan was required to have a minimum rotating speed of 3500 RPM to maintain the fuel cell surface temperature within an acceptable range. The results of this study can be effectively applied to the development of thermal management technology for the fuel cells inside the fuel cell power pack of a UPS.

• Journal of Powder Materials
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• v.29 no.5
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• pp.411-417
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• 2022

Environmental issues such as global warming due to fossil fuel use are now major worldwide concerns, and interest in renewable and clean energy is growing. Of the various types of renewable energy, green hydrogen energy has recently attracted attention because of its eco-friendly and high-energy density. Electrochemical water splitting is considered a pollution-free means of producing clean hydrogen and oxygen and in large quantities. The development of non-noble electrocatalysts with low cost and high performance in water splitting has also attracted considerable attention. In this study, we successfully synthesized a NiCo₂O₄/NF electrode for an oxygen evolution reaction in alkaline water splitting using a hydrothermal method, which was followed by post-heat treatment. The effects of heat treatment on the electrochemical performance of the electrodes were evaluated under different heat-treatment conditions. The optimized NCO/NF-300 electrode showed an overpotential of 416 mV at a high current density of 50 mA/cm² and a low Tafel slope (49.06 mV dec^-1). It also showed excellent stability (due to the large surface area) and the lowest charge transfer resistance (12.59 Ω). The results suggested that our noble-metal free electrodes have great potential for use in developing alkaline electrolysis systems.

• Journal of Embryo Transfer
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• v.26 no.1
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• pp.37-43
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• 2011

A total 5,946 cows from 24 dairy farms were carried out for the improvement of reproductive performance. Dairy cows in post-parturition 30 day were performed periodic reproductive examination to check for recovery of post-parturition ovary and uterus and for the early diagnosis of reproductive disease. The results obtained from this studies were as follow. The result of 1,126 cows with ovario-uterine disease were 579 slient heat and error of estrus detection (51.4%), 296 ovarian disease (26.3%), 248 uterine disease (22%), mummification and freematin were each 1 head (0.1%), respectively. Hormonal therapeutic effects were follicular cyst 81.5%, luteal cyst 90.7%, endometritis 86.9%, mucometra 90.1%, pyometra 60.9%, respectively. In cows, even if the 1st treatment fails, 2nd, 3rd treatment were performed. Therapeutic effect of 2nd, 3rd were reduced, but the number of cured cows were gradually increased. The cured cows after hormonal treatment were performed service repeatedly and the cumulative conception rate were increased. The cows treated with hormones at first service, the conception rate were follicular cyst 26%, luteal cyst 64.1%, endometritis 38.7%, mucometra 40%, pyometra 20.5%, respectively. The cumulative conception rates were increased by repeated service follicular cyst 57.3%, luteal cyst 84.6%, endometritis 67%, mucometra 75%, pyometra 64.1%, respectively.

• Journal of Adhesion and Interface
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• v.23 no.3
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• pp.80-86
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• 2022

In this study, water-based acrylic tackifier with different contents of 1-dodecanethiol(n-DM), a chain transfer agent(CTA), were synthesized to improve the performance and adhesive properties of water-based acrylic pressure sensitive adhesive(PSA). In order to investigate the change in physical properties according to the amount of water-based acrylic tackifier added, 10/20/30 phr of water-based acrylic tackifier was added to the water-borne acrylic emulsion to measure the physical properties. The molecular weight and glass transition temperature(T_g) of the synthesized water-based acrylic tackifier tended to decrease as the content of n-DM increased. When a water-based acrylic tackifier was added to the water-borne acrylic emulsion, the peel strength and heat-resistance were increased. Also, when the water-based acrylic tackifiers were added at 10 phr or 20 phr, the best value was shown.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.10
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• pp.530-537
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• 2017

Scales generated inside pipes cause negative effects on heat transfer performance, pressure loss and flow rate due to increased thermal resistance and reduced flow cross-sectional area. If these scales are not prevented or eliminated, thermal-fluid performance of the facilities can be deteriorated, or in extreme cases, accidents such as explosion due to overheating can occur. There are two ways to remove the scales, physically and chemically. Removing the scales physically needs specific machines which are expensive, and removing them chemically may provoke corrosion or shorten the age of the facilities. In this study, an eco-friendly pipe scale cleaner using natural organic acid is developed by applying the concept of a limestone cave generation. The manufactured scale cleaner is applied to remove the scales in industrial, water heating and urinal pipes. The results show that this cleaner removes scales more effectively and safely compared to existing scale treatments. Scale removal efficiencies of this work is 1.2~10.7 times for industrial pipes and 1.8~15.5 times for boiler water heating pipes higher than those of conventional cleaners.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.18-25
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• 2016

Enhanced tubes are used widely in the evaporators of large tonnage compression-type refrigerators. The evaporators consist of tube bundles, and the refrigerant properties are dependent on the locations in the tube bundles. In particular, the saturation temperatures of low pressure refrigerants (R-11, R-123) are strongly dependent on the locations due to the saturation temperature-pressure curve characteristics. Therefore, for the proper design of evaporators, local property predictions of the refrigerants are necessary. In this study, a computer program that simulates the flooded refrigerant evaporators was developed. The program incorporated theoretical models to predict the refrigerant shell-side boiling heat transfer coefficients and pressure drops across the tube bundle. The program adopted an incremental iterative procedure to perform row-by-row calculations over the specified incremental tube lengths for each water-side pass. The program was used to simulate the flooded refrigerant evaporator of the "T" company operating with R-123, which yielded satisfactory results. The program was extended to predict the performance of the flooded refrigerant evaporator operating with R-11, R-123, and R-134a. The effects of bundle aspect ratio are investigated.

• Journal of Bio-Environment Control
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• v.5 no.1
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• pp.57-64
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• 1996

To use effectively the solar energy in greenhouse heating, a high performance solar collector should be developed. And then the size of the solar collector and thermal storage tank should be determined through the calculation of heating load. The solar collector must be set in the optimum tilt angle and direction to take daily solar radiation maximally, and the flow rate of heat transfer fluid through the solar collector should be kept in the optimum range. In this research, the performance tests of a capillary tube solar collector were performed to determine the optimum water flow rate and the results summarized as follows. 1. The regressive equations for efficiency estimations of the capillary tube solar collector in the open loop were modeled in the water flow rate of 700-l,000 $\ell$/hr. 2. The optimum water flow rate of the solar collector was estimated by the second order polynomial regression and the maximum efficiency was 80% at the water flow rate of 850 $\ell$/hr. 3. The solar thermal storage system consisted of a capillary tube solar collector and a water storage tank was tested at the water flow rate of 850 $\ell$/hr in the closed loop, and obtained the solar thermal storage efficiency of 55.2%. 4. As the capillary tube solar collector engaged in this experiment was made of non-corrosive polyolefin tubes, its weight was as light as 1/30 of the flat plate solar collector made of copper tubes. Therefore it was considered to be suitable for the greenhouse heating system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.7
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• pp.625-631
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• 2015

In this study, a numerical analysis on the discharging performance of a thermal storage tank completely filled with packing modules is investigated. The enthalpy-porosity method is adopted to analyze phase change phenomenon. Using this method, the melting process of a packing module in the thermal storage tank was studied as the HTF (heat transfer fluid) flows down from the top of the tank at the discharging mode. There are some design factors such as the module arrangement and the number of modules, but this study focuses on the effects of varying the flow rate of the HTF on the outlet temperature of the HTF, molten fraction, and thermal storage density. As the flow rate increases, the outlet temperature of the HTF gets higher and the total melting time of the PCM decreases. Additionally, the thermal storage density is increased so that it reaches about 93% for the desired value.