• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.4
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• pp.32-38
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• 2019

In this study, the effect of hot water supply flow rates on energy consumption for radiant floor heating system in apartment were researched by computer simulation. The parametric study of different hot water supply flow rates was done with regard to energy performance and control characteristics, respectively. Also the effect of different hot water supply flow rates on the hot water supply temperatures is studied. As a result, energy consumption were reduced but the response time is increased by reducing the supply flow rate. And energy consumption can be saved by adjusting the hot water supply temperatures with different supply flow rates.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.5
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• pp.717-723
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• 2008

The purpose of this study is to measure and analyze the indoor thermal conditions of a 8,500GT class chemical carrier which was launched on July 2007. The measurement was operated from 4th June to 4th June 2007, just before handing over to Owner. Followings are the results of this study. (1)The temperature variations of supply air were related to the outdoor temperature variations, but the humidity was stable at $65{\sim}80%$. (2)The temperature variations at the representative position of bridge, restaurant, crew's cabin showed gentle slopes. but that of conference room was very steepy. The humidities of bridge and restaurant were unstable because of outdoor-contact and cooking, respectively. (4)The temperature and humidity of ECR(Engine Control Room) which was designed to supply heating and cooling by PAC(Package Air Conditioner) were directly affected by the operating conditions of PAC. (5)The measured supply air volume from dampers of bridge, crew's cabin and conference room were satisfied with the design supply air volume. (5)For the improvement of the indoor thermal conditions, the temperature of crew's cabin and restaurant and the humidity of conference room, and the temperature and humidity of bridge should be controlled, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.4
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• pp.354-362
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• 2000

Optimal supervisory control strategy for the set points of controlled variables in the central cooling system has been studied by computer simulation. A quadratic linear regression equation for predicting the total cooling system power in terms of the controlled and uncontrolled variables was developed using simulated data collected under different values of controlled and uncontrolled variables. The optimal set temperatures such as supply air temperature, chilled water temperature, and condenser water temperature, are determined such that energy consumption is minimized as uncontrolled variables, load, ambient wet bulb temperature, and sensible heat ratio, are changed. The chilled water loop pump and cooling tower fan speeds are controlled by the PID controller such that the supply air and condenser water set temperatures reach the set points designated by the optimal supervisory controller. The influences of the controlled variables on the total system and component power consumption was determined. It is possible to minimize total energy consumption by selecting the optimal set temperatures through the trade-off among the component powers. The total system power is minimized at lower supply, higher chilled water, and lower condenser water set temperature conditions.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.188-192
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• 2006

This study is conducted to improve efficiency of thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from solar or the others heat sources. However, it has difficulties in storing heat with uniform temperature through the entire tank with respect to vertical direction. This kind of maldistribution of the supplied heat to the storage tank effects on the system performance. In this study is focused on utilization of the thermal stratification to improve thermal comfort for people in the house. To enhance temperature stratification of the tank, a distributor was designed and Installed in the middle of the tank. The distributor is supplies hottest water to the top side of the tank which is very close to inlet of the supply line to the heating load. The hottest water that is accumulated on top side of the tank is firstly supplied to the load with higher temperature. Reminder water takes a little time to warming up until desired supply temperature reached. This kind alternating selection of the supply temperature is improve thermal comfort with moderated system performance.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.146-152
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• 2000

As an improvement in the standard of living and economic growth the demand for air conditioning equipment is increasing rapidly. Nowadays air conditioning equipments are being used for industry large building house and car. Thess equipments was concentrated on improving heat efficiency of economic aspects while they design heat exchanger for cooling and heating,. These air conditioning equipments using heat exchanger cause a discomfort to user due to generating mist at the beginning of operating. Therefore the user demand air of high class and quality. In this experimental study to acquire elementary data for development of heat exchanger which be able to supply air of high quality that is to say possess a restraint effect of mist generation. We estimate an effect on cooling plate kind supply air velocity supply air temperature cooled plate temperature and supply air relative humidity which have an influence on outlet air condition of heat exchanger.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.3
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• pp.46-56
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• 2001

The present study concerns the numerical simulation of a supply airflow control in a variable air volume (VAY) system. A stratified thermal model (multi-zone model) is suggested to predict a local thermal response of an air-conditioned space. The effects of various thermal parameters such as the cooling system capacity, the thermal mass of an air-conditioned space, the time delay of thermal effect, and the building envelope heat transmission are investigated. Further, the influence of control parameters such as the supply air temperature, the PI control factor and the thermostat location on a VAV system is quantitatively delineated. The results obtained show that the previous homogeneous lumped thermal model (single zone model) may overestimate the time taken to the set point temperature. It is also found that there exist the appropriate ranges of the control parameters for the optimal airflow control of the VAV system.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2004.05a
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• pp.123-128
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• 2004

Semiconductor Wet Station has a very important place in semiconductor process. It is important that to discharge chemical with fit concentration and temperature using chemical supply system for clean process. The chemical supply system which is used currently is not only difficult to make a fit mixing rate of chemical which is need in clean process, but also difficult to make fit concentration and temperature. Moreover, it has high stability but it is inefficient spatially because its volume is great. We propose In-line System to improve system with implement analysis of fluid and thermal transfer on chemical supply system and understand problem of system.

• KIEAE Journal
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• v.8 no.5
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• pp.49-54
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• 2008

The experimental of temperature, humidity and velocity was taken from the underground pit which utilized the system of ground heat source quite similar to the cool-pit system. Also, through CFD analysis, one could review the effectiveness of analysis of future alternatives. Furthermore, the temperature range of mock up cool-pit system was analyzed by inputting the weather data of annual average soil temperature provided by KMA(Korea Meteorological Administration) into the fluid simulation of anticipated heat distribution. Firstly, the difference between the temperature of air exhaust of the pit or the temperature of air supply of the compressor room and the experimental data for the month of May from the CFD analysis came out to be $0.6^{\circ}C$ and $0.9^{\circ}C$ respectively with tolerance of 3.1% and 4.7%. Secondly, the difference between the temperature of air exhaust of the Pit or the temperature of air supply of the compressor room and the experimental data for the month of July from the CFD analysis came out to be $0.8^{\circ}C$ and $1.1^{\circ}C$ respectively with tolerance of 3.3% and 4.5%. Thirdly, for the month of May, the difference between the experimental data taken for the air exhaust of the Pit or the air supply of the compressor room and soil temperature provided by KMA for monthly and yearly average temperature of Jeonju region came out be $1.9^{\circ}C$ and $1.8^{\circ}C$ respectively with tolerance of 10.7% and 9.8%. Fourthly, for the month of July, the difference between the experimental data taken for the air exhaust of the Pit or the air supply of the compressor room and soil temperature provided by KMA for monthly and yearly average temperature of Jeonju region came out be $1.1^{\circ}C$ and $1.4^{\circ}C$ respectively with tolerance of 4.5% and 5.8%. The result of above experiments allowed us to establish CFD model set up as a verification tool that is based on experimental data collected within the Pit area. Also, one could confirm the possibility to apply weather data of soil temperature provided by KMA in order to anticipate proper value for CFD analysis.

• Journal of Biosystems Engineering
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• v.28 no.1
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• pp.11-18
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• 2003

This study was carried cut to get basic data of troubles in starting and supply of farm diesel engines in cold winter. The results of the study are summarized as follows: 1. As the result of farm survey. the proportions of farms which had starting problems or troubles in fuel supply in cold winter for the last 5 years were 38% for the farms with power-tillers and 32% for the farms with tractors. Most of the farms which had starting problems or troubles in fuel supply in cold winter used light oil for summer. spring or fall rather than for winter. 2. As the result of fuel supply test, fuel supply was stopped at -6$^{\circ}C$ and -18$^{\circ}C$ for summer light oil and winter light oil. respectively 3. The lowest temperatures of winter light oil for starting engine were -7.5$^{\circ}C$ for power-tiller. -12.5$^{\circ}C$ for tractor of 38ps, and -17.5$^{\circ}C$ for tractor of 45ps. which were 5~7.5$^{\circ}C$ lower than that of summer light oil. 4. The performance of engine starting and the trouble of fuel supply system at lower temperature were significantly improved by using winter hight oil rather than summer light oil.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.577-580
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• 1999

High power density on-board power supply is implemented by using flat transformer. In the high frequency switching converters, large leakage inductance increases the switching stress and duty cycle loss, which sometimes limits maximum switching frequency. The flat transformer is designed by using special core structure, which has very low profile and low temperature rise since the thermal loading is spread evenly over a larger area. 100W, 3.3V output on board supply is built and tested and 50.7W/$\textrm{inch}^{3}$ power density is achieved.