• Journal of the Korean Wood Science and Technology
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• v.35 no.3
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• pp.22-28
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• 2007

Using woodceramics made from sawdust board of pine thinning logs, changes in surface temperature were investigated, by the heating rate and keeping time at maximum temperature. The heating rate of $2^{\circ}C/min$ and keeping time at maximum temperature 1 hour, were the highest in surface temperature. Also, it was found that woodcermics maintained heat for a long time because the descending velocity of their surface temperature was slower than that of the heater.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.2
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• pp.39-50
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• 2000

Thermodynamic cycle analysis is presented to estimate the maximum liquefaction rate of hydrogen for various systems using a Gifford-McMahon(GM) cryocooler. Since the present authors` previous experiments showed that the gaseous hydrogen was liquefied approximately at the rate of 5.1 mg/s from the direct contact with a commercial two-stage GM refrigerator, this study has been proposed to predict how much the liquefaction rate can be increased in different configurations using the GM cooler and with improved heat exchangers. The optimal operating conditions have been analytically sought with real properties of normal hydrogen for the Linde-Hampson(L-H) system precooled by single-stage GM, the direct-contact system with two-stage GM, the L-H system precooled by two-stage GM, and the direct-contact system with helium GM-JT (Joule-Thomson). The maximum liquefaction rate has been predicted to be only about 7 times greater than the previous experiment, even though the highly effective heat exchangers may be employed. It is concluded that the liquefaction rate is limited mainly because of the cooling capacity of the commercially available GM cryocoolers and a practical scale of hydrogen liquefaction is possible only if the GM cooler has a greater capacity at 70-100 K.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.3
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• pp.85-93
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• 1994

The engine performance and combustion characteristics of diesel oil and fish oil blended with diesel oils were investigated at various blending rate of fish oil in a diesel engine. The maximum pressure showed no significant difference among test fuels at low load, but it was higher as the blending rate of fish oil increases at high load. Increasing the blending rate of fish oil, the rate of heat release and burned fraction were higher than those of diesel oil. The ignition delay became longer than that of diesel oil as the blending rate of fish oil increases, and its differences were larger at different loads. The combustion duration and density of smoke were shorter and lower as the blending rate of fish oil increases. The rate of fuel consumption showed no significant difference between diesel oil and fish blended with diesel oils.

• Fire Science and Engineering
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• v.32 no.1
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• pp.16-23
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• 2018

In a closed-compartment with various configurations, the correlation that can predict the maximum heat release rate (HRR) with the changes in internal volume and fire growth rate was investigated numerically. The volume of the compartment was controlled by varying the length ratio based on the bottom surface shape of the ISO 9705 fire room, where the ceiling height was fixed to 2.4 m. As a main result, the effect of a change in ceiling height on the maximum HRR was examined by a comparison with a previous study that considered the change in ceiling height. In addition, a more generalized correlation equation was proposed that could predict the maximum HRR in closed-compartments regardless of the changes in ceiling height. This correlation had an average error of 7% and a maximum error of 19% for various fire growth rates when compared with the numerical results. Finally, the applicability of the proposed correlation to representative fire compartments applied to the domestic performance-based design (PBD) was examined. These results are expected to provide useful information on predicting the maximum HRR caused by flashover in closed-compartments as well as the input information required in a fire simulation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.5
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• pp.414-420
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• 2004

The heat transfer and pressure drop characteristics associated with the gas cooling of the supercritical carbon dioxide in a horizontal tube have been investigated experimentally. This problem is of particular interest in the design of a gas cooler of cooling systems using $CO_2$refrigerant. The test section is consisted of 6 series of 455 mm in length, 4.15 mm ID copper tube, respectively. The effects of the inlet temperature, pressure and mass flow rate on the heat transfer and pressure drop of $CO_2$in a horizontal tube is studied in detail. The heat transfer coefficient of $CO_2$is varied by temperature, inlet pressure, and mass flow rate of $CO_2$. This has maximum value at near the pseudocritical temperature. The pressure drop is changed by inlet pressure and mass flow rate of $CO_2$. The results have been compared with those of previous work. The heat transfer correlation at the supercritical gas cooling process is also suggested.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.18-23
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• 2005

The experimental investigation was carried out to evaluate the performance of air-to-air heat exchanger with rotating porous plates newly developed in this study. The rotating porous plates are mounted with an equal interval of 18 mm inside the heat exchanger where the hot and cold airs enter at opposite ends. When flowing in opposite directions by the separating plate installed in the center of the rotating porous plates, the airs give and receive the heat each other. The material of the porous plate is cooper and its thickness is 1.0 mm. Air flow rate is varied from 10 to 120 m3/h. From the experiment of air-to-air heat exchanger with the rotating porous plates, the heat exchange performance increased with the increase in RPM of the porous rotating discs at the conditions of the same air flow rate. The sensible heat exchange efficiency was maximum 60 to 70 percent, and enthalpy exchange efficiency 50 to 60 percent.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.4
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• pp.184-191
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• 2002

This study concerns the performance of the condensing heat transfer performance of two-phase closed thermosyphons with plain copper tube and tubes having 50, 60, 70, 80, 90 internal micro grooves. Distilled water, methanol, ethanol have been used as the working fluid. The numbers of grooves and operating temperature have been investigated as the experimental parameters. Condensing heat transfer coefficients and heat flux are obtained from experimental data for each case of specific parameter. The experimental results are assessed and compared with existing correlations. The results show that working fluids, numbers of grooves are very important factors for the operation of thermosyphons. The working fluid with high latent heat such as water has a good heat transfer rate compared to methanol and ethanol. The relatively high rate of heat transfer is achieved when the thermosyphon with internal micro grooves is used compared to that with plain tube. Condensing heat transfer coefficient of grooved thermosyphon is 1.5∼2 times higher in methanol and 1.3∼l.5 times higher in ethanol compared to plain tube. The best condensation heat transfer performance is obtained for 60 grooves, and the maximum value of this case is 2.5 times higher than that of the plain tube.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.180-188
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• 1997

The theoretical analysis and experiment with simulator were performed to obtain the temperature distributions in radiant heating panel and heat supply from hot water to heating space for the purpose of the development of comfortable living space from a point of view of the improvement of air quality and the enhancement of system efficiency. The relations of various parameters, such as pipe pitch, room temperature as well as flow rate and temperature of hot water and so on, with the rate of heat supplied, mean temperature and maximum temperature difference at panel surface were discussed. The effects of these parameters were also verified on the thermal performance of heating panel using the relations which could be used for the optimal design and operation of the radiant heating panel.

• Journal of the Korean Solar Energy Society
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• v.31 no.6
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• pp.49-56
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• 2011

In this study a novel cogeneration system driven by low-temperature sources at a temperature level below $190^{\circ}C$ is investigated by first and second laws of thermodynamics. The system consists of Organic Rankine Cycle(ORC) and an additional heat generation as a parallel circuit. Seven working fluids of R143a, R22, R134a, R152a, $iC_4H_{10}$(isobutane), $C_4H_{10}$(butane), and R123a are considered in this work. Maximum mass flow rate of a working fluid relative to that of the source fluid and optimum turbine inlet pressure are considered to extract maximum power from the source. Results show that due to a combined heat and power generation, both the efficiencies by first and second laws can be significantly increased in comparison to a power generation, however, the second law efficiency is more resonable in the investigation of cogeneration systems. Results also show that the working fluid for the maximum system efficiency depends on the source temperature.

• Journal of the Korean Society of Safety
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• v.3 no.1
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• pp.37-45
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• 1988

This research investigated the condition for plant design on reclamation of waste plastic by heat decomposition. The results were summarized as follows 1. The highest of oil product by heat decomposition is about 54.7％. 2. The optimum reaction temperature is about 300­40$0^{\circ}C$. 3. The optimum reaction time is 2­3 hours. 4. When the flow rate of 8­16 cm/sec in column reactor the yield is maximum. 5. Waste plastics yielded of carbon black product by heat decomposition at the optimum condition is about 23.5%. 6. Calorific values 0：1 were 9820 Kcal/kg.