• Fire Science and Engineering
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• v.27 no.4
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• pp.13-20
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• 2013

Buildings in Korea have been getting higher recently and been being changed environmentally since the Korean fire standard was released in 1968. It should be established to make a appropriate correspondence of fire fighting against the those environmental changes. Most of all, fire water capacity which is basis of fire fighting service is a very significant factor. In this paper, the Korean fire water capacity and fire water duration were compared with China, Japan and the United states. Furthermore, fire water capacity, fire water duration, flow rate were compared by hazard classification, occupant use, number of floor and area with water based fire suppression system. This study has been surveyed to show what are difference, similarity, advantage and disadvantage on fire water capacity in the Korean standard comparing with neighboring countries like China, Japan as well as the United states. This study could be found what level the Korean fire water capacity is. So it suggests about more developed standard on fire water capacity with the result of analysis and comparison.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.489-495
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• 2006

Proton exchange membrane (PEM) should be sufficiently hydrated with a careful consideration of heat and water management. Water management has been a critical operation issue for better understanding the operation and optimizing the performance of a PEM fuel cell. The flooding on cathode side resulting from excess water can limit the fuel cell performance. In this study, the visual cell was designed and fabricated fur the visualization of liquid water droplet dynamics related to cathode flooding in flow channels. The experiment was carried out to observe the formation, growth and removal of water droplets using CCD imaging system. Effects of operating conditions such as cell temperature, air flow rate and air relative humidity on cathode flooding characteristics were mainly investigated. Based on this study, we can get the basic insight into flooding phenomena and its two-phase flow nature. It is expected that data obtained can be effectively used fur the setup and validation of two-phase PEM fuel cell models considering cathode flooding.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.11 s.242
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• pp.1248-1256
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• 2005

This study was undertaken to investigate the flow characteristics of emulsified fuel with the ultrasonic energy-adding system by using the chaotic method. Efffcts of water contents within emulsified fuel, flow rate and tube length with 5m in diameter from an emulsified chamber has been discussed on the strange attractor and power spectral density function. Five probe sensors were set up from 0.5 to 2.5m by length in 0.5m increments in the tube. In particular, the chaotic features of this system have been practically characterized in terms of chaotic statistics such as the power spectral density function and phase space portraits by resorting to the somewhat noble deterministic chaos theory. In the tube, the dominant frequency increased with increasing water contents and flow rate, but decreased a little with an increase in the length from the emulsified chamber.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.532-540
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• 2001

The objectives of this study are to analyze the control variables according to condensation occurrence, to find the range in floor surface temperature and frequency of condensation, and to evaluate the control methods through simulations when the radiant heating system is used for cooling. Through the simulation analysis the control methods such as on/off control, variable flow control and outdoor reset with indoor temperature feedback control are evaluated and compared. The results show that the lowest floor surface temperature is around $23^{\circ}C$, the surface condensation can be prevented by controlling indoor humidity within 20g/kg(DA0, and that outdoor reset with indoor temperature feedback control is more appropriate than on/off control and variable flow control with regard to prevention of the condensation and thermal comfort.

• Journal of Energy Engineering
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• v.22 no.3
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• pp.302-306
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• 2013

A simple method for balancing flow rates in arrays of parallel connected flat plate solar collectors has been developed. The method is based on a computer program which solves for the flow rate through each of the collectors in a reverse return plumbed array. The analysis uses conventional "K-value" techniques and assumes the effects of density variations within the system to to be negligible. It has been found that by appropriately sizing the inlet and outlet manifolds, flow maldistribution can be nearly eliminated without resorting to expensive or complicated balancing techniques.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.12
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• pp.572-578
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• 2014

Heating energy was measured in an apartment housing unit with a district heating system, varying the kind of hot water distributors. Ondol coils passing through a living room raised the temperature of the room where the heating was turned off. Including this characteristic of Ondol heating into the modeling, we performed simulations and showed a verification by comparison with the results of measurements. As a result, a main flow control method, which changes hot water flow rate supplied to a housing unit according to the thermal load, can reduce the supplied flow rate and lower the return temperature, compared with a constant flow method. That can result in decreased heat loss in utility-pipe conduits even though the heating energy supplied is almost the same. An outdoor reset control that raises the temperature of the supplied hot water if the outdoor temperature falls has the effect of a quicker response in heating than the reduced flow rate and return temperature.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.377-379
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• 2007

To reduce the chattering errors of reed switch sensors used for automatic remote measurement of water supply system, a reed switch sensor was analyzed and improved. The operation of reed switch sensors can be described as a mechanical contact by approximation of permanent magnet piece to generate an electrical pulse. The reed switch sensors are used in measurement application by detecting the rotational or translational displacement. To apply for flow measurement devices, the reed switch sensors should keep high reliability. They are applied for the electronic digital type of water flow meters. The reed switch sensor is just installed simply on the mechanical type flow meter. A small magnet is attached on a pointer of the water meter counter rotor. Inside the reed sensor, two steel leaf springs make mechanical contact and apart as rotation of flow meter counter. The counting electrical contact pulses can be converted as the water flow amount. The MCU sends the digital flow rate data to the server using the wireless communication network. But it occurs data difference or errors by chattering noise. The reed switch sensor contains chattering error by it self at the force equivalent position. The vibrations such as passing car near to the switch sensor installed location. In order to reduce chattering error, most system uses just software methods for example using filter and also statistical calibration methods. The chattering errors were reduced by changing leaf spring structure using mechanical hysteresis characteristics.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.1
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• pp.61-68
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• 2015

The function of Feed Water Ring is to provide the flow path from Feedwater Nozzle to inside of SG(steam generator). Significant amounts of general FAC on the outside of the Feed Water Ring are not likely due to the low flow velocities in this area. However, on the interior of the Feed Water Ring, there may be areas of local higher flow velocity which could lead to higher FAC rates. These may include the inlet tee from the Feedwater Nozzle into the Feed Water Ring, the areas where the Feed Water Ring changes diameter, and especially the entrance area to the J-Nozzles. In this paper, the results of root cause analysis of through-wall hole observed at domestic WH 51F SG Feed Water Ring and its effect on the integrity and performance of SG are described. And, the maintenance strategy for WH 51F SG Feed Water Ring and the monitoring strategy for Downcomer Feed Water Ring of CE System 80 SG are presented.

• Journal of Korean Society on Water Environment
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• v.20 no.2
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• pp.151-156
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• 2004

A decision support system, Watershed Analysis Risk Management Framework(WARMF), was applied to the Kyungan Stream watershed, a tributary of Lake Paldang, for calculation of total maximum daily loads(TMDL). The WARMF system was developed by Systech Engineering, USA, and has been successfully used in several watersheds, for TMDL studies. The study area was divided into 14 sub-basins, based on digital elevation model(DEM). The integrated watershed and stream model of WARMF was validated by flow and BOD data measured during the year of 1999. There were reasonable agreements between model results and field data, both in water flow and BOD. The validated Kyungan WARMF was extensively utilized to study the quantitative relationship between waste loads and receiving water quality. Based on TMDL guideline at Paldang Lake and Kyungan Stream, the water quality criterion were set to be 3.0mg/L, 3.5mg/L, and 4.0mg/L at the watershed outlet. The allowable waste loads of BOD, both from point and non-point sources, were determined at each water quality criterion. From this study, it was concluded that the WARMF provided several advantages over the conventional application of watershed and stream models for TMDL study, such as time variable simulations, multiple possible soutions, and reduction loads for goal water quality, etc.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.2
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• pp.94-104
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• 1997

Ozone Treatment is getting a common process in a water treatment plant all over the nation. Especially an advanced water treatment using ozone and biofiltration has been a typical method in the regions where using the Nak-Dong River as a drinking water source. The effectiveness of ozone treatment in a continuous flow contact system was investigated with sand filtered water of the Nak-dong River. Pilot tests of the experiments were performed three times of the year like June, August, and October 1995. Most degradable organics of sand filtered water were oxidized in the first and second contact chamber of the system. Ozone treatment was effective for the removal of UV254 absorbance. However, Noticeable removals of $KMnO_4$ demand and TOC(Total Organic Carbon) were occurred when their concentrations exceeded about 5mg/l. The organics causing $KMnO_4$ demand and TOC were degraded into lower molecular matter in an early stage of the ozone contact in the system. Dissolved oxygen concentration was increased after ozone treatment.