• Nuclear Engineering and Technology
• /
• v.52 no.7
• /
• pp.1396-1408
• /
• 2020

Filtered containment venting system (FCVS) is one of the severe accident mitigation systems designed to release containment pressurization to maintain its integrity. The thermal-hydraulic behaviors in FCVSs are important since they affect the operation characteristics of the FCVS. In this study, a representative FCVS was modeled by RELAP5/Mod3.3 code, and the Station BlackOut (SBO) was chosen as an accident scenario. The thermal-hydraulic behaviors of an FCVS during long-term operation with two venting strategies (open-and-close strategy, open-and-non-close strategy) and the sensitivity analysis of important parameters were investigated. The results show that the FCVS can operate up to 250 h with a periodic open-and-close strategy during an SBO. Under the combined effects of steam condensation and water evaporation, the solution inventory in the FCVS increases during the venting phase and decreases during the intermission phase, showing a periodic pattern. Under this condition, the appropriate initial water level is 3-4 m; however, it should be adjusted according to the environment temperature. The FCVS can accommodate a decay heat power of 150-260 kW and may need to feed water for a higher decay heat power or drain water for a lower decay heat power during the late phase. The FCVS can function within an opening pressure range from 450 kPa to 500 kPa and a closing pressure range between 250 kPa and 350 kPa. When the open-and-non-close strategy is adopted, the solution inventory increases quickly in the early venting phase due to steam condensation and then decreases gradually due to the evaporation of water; drying-up may occur in the late venting phase. Decreasing the venting pipe diameter and increasing the initial water level can mitigate the evaporation of the scrubbing solution. These results are expected to provide useful references for the design and engineering application of FCVSs.

• Journal of Bio-Environment Control
• /
• v.9 no.3
• /
• pp.156-160
• /
• 2000

The Plasma film treated with a high electric voltage was developed to enhance flow down of condensation drops on inside plastic film. Arch type greenhouse framed with iron pipe of 25mm diameter defand 1.5mm thickness were covered with either the developed plasma film or surfactant film(control). Green pepper seedlings raised for 40 days in plug trays were transplanted at a density of 110cm by 30cm in each greenhouse. The mount of condensational water on film surface, generated by 7$0^{\circ}C$ water bath chimney systems and flew down, was collected and measured. The amount of collected water after 150 minutes was 2.56 mL.100c $m^{-2}$ and 0.94mL.100c $m^{-2}$ , respectively, in the plasma film and surfactant film-covered greenhouses. The amount of condensational water drops attached on the cover at 08:20 a.m. at 60 days filter covering was 0.34mL.100c $m^{02}$ and 0.32mL.100c $m^{-2}$ , respectively, in the plasma film- and surfactant film-covered greenhouses. Solar irradiance transmitted into greenhouse was 2.0% higher in the greenhouse covered with the plasma film tan that in the greenhouse covered with the surfactant film. Air temperature in the plasma film-covered greenhouse was higher than the surfactant film-covered greenhouse by 0.5$^{\circ}C$. However, there was no difference in relative humidity between the two greenhouse. Plant height, leaf area, dry weight and early yield showed no significant differences.s.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.2
• /
• pp.5-14
• /
• 2013

Among the various thermal properties, thermal conductivity of soils is one of the most important parameters to design a horizontal ground heat exchanger for ground-coupled heat pump systems. It is well known that the thermal conductivity of soil is strongly influenced by its density and water content because of its particulate structure. This paper evaluates some of the well-known prediction models for the thermal conductivity of particulate media such as soils along with the experimental results. The semi-theoretical models for two-component materials were found inappropriate to estimate the thermal conductivity of dry soils. It comes out that the model developed by Cote and Konrad provides the best overall prediction for unsaturated sands available in the literature. Also, a parametric analysis is conducted to investigate the effect of thermal conductivity, water content and soil type on the horizontal ground heat exchanger design. The results show that a design pipe length for the horizontal ground heat exchanger can be reduced with an increase in soil thermal conductivity. The current research concludes that the dimension of the horizontal ground heat exchanger can be reduced to a certain extent by backfilling materials with a higher thermal conductivity of solid particles.

• Fire Science and Engineering
• /
• v.34 no.4
• /
• pp.69-77
• /
• 2020

With the recent enlargement and complication of buildings, damage caused by the incidents of fires breaking out are escalating. Consequently, the use of sprinkler facilities is increasing among water-based fire extinguishing systems. Piping materials used in fire prevention systems include carbon steel (for general or pressure pipeline), CPVC, copper, and stainless-steel. Among these, the steel and CPVC pipes, which are commonly employed in fire prevention, were considered for testing the reliability of the water-based systems. This analysis was performed using the PIPENET software to perform hydraulic calculations in order to examine the flow and pressure at the terminal head when the corrosion coefficient was applied; this coefficient was applied considering the aging of pipes. Assuming a uniform pipe diameter in the steel pipes, the rated flow in the pump installed on the first floor of the basement was reduced by over 10% after 20 years had passed (C value of 90); moreover, the reduction in pressure and flow at its terminal head exceeded 30% and 16.5%, respectively. The results indicate that it is difficult to ensure the reliability of these fire prevention facilities. Furthermore, according to our estimation, considering 30 years had passed (C value of 80), the rated flow of the pump was reduced by over 15%, and the corresponding reduction in pressure and flow at its terminal head exceeded 42% and 24%, respectively.

• The Journal of Engineering Geology
• /
• v.26 no.2
• /
• pp.251-260
• /
• 2016

Groundwater flow due to hydraulic gradients across a geologic barrier surrounding a dam reservoir can cause swamps or wetlands to form on the downstream side of the dam, thereby restricting land use. The difference in head between the reservoir level and the downstream groundwater level creates a hydraulic gradient, allowing water to flow through the geologic barrier. We constructed a drainage system at the Daecheong dam to study the effects on groundwater levels and soil moisture contents. The drainage system consisted of a buried screened pipe spanning a depth of 1-1.5 m below a land surface. Groundwater levels were monitored at several monitoring wells before and after the drainage system was installed. Most well sites recorded a decline in groundwater level on the order of 1 m. The high-elevated site (monitoring well W1) close to the reservoir showed a significant decline in groundwater level of more than 2 m, likely due to rapid discharge by the drainage system. Soil moisture contents were also analyzed and found to have decreased after the installation of the drainage system, even considering standard deviations in the soil moisture contents. We conclude that the drainage system effectively lowered groundwater levels on the downstream side of the dam. Furthermore, we emphasize that water seepage analyses are critical to embankment dam design and construction, especially in areas where downstream land use is of interest.

• Journal of Bio-Environment Control
• /
• v.21 no.3
• /
• pp.163-169
• /
• 2012

We have conducted three experiments to develop a fertilizer-dissolving apparatus used in fertigation or hydroponics cultivation in order to decrease the fertilizer dissolving time and labor input via automation. All of the experiments were conducted twice. In the first experiment, four selected treatments were tested to dissolve fertilizers rapidly. The first treatment was to dissolve fertilizer by spraying water with a submerged water pump, placed in the nutrient solution tank. The water was sprayed onto fertilizer, which is dissolved and filtered through the hemp cloth mounted on the upper part of the nutrient solution tank (Spray). The second treatment was to install a propeller on the bottom of the nutrient solution tank (Propeller). The third treatment was to produce a water stream with a submerged water pump, located at the bottom of the tank (Submerged). Finally, the fourth treatment was to produce an air stream through air pipes with an air compressor located at the bottom of the tank (Airflow). The Spray treatment was found to take the shortest time to dissolve fertilizer, yet it was inconvenient to implement and manage after installation. The Airflow treatment was thought to be the best method in terms of the time to dissolve, labor input, and automation. In the second experiment, Airflow treatment was investigated in more detail. In order to determine the optimal number of air pipe arms and their specification, different versions of 6- and 8-arm air pipe systems were evaluated. The apparatus with 6 arms (Arm-6) that was made of light density polyethylene was determined to be the best system, evaluated on its time to dissolve fertilizer, easiness to use regardless of the lid size of the tank, and easiness to produce and install. In the third experiment, the Submerged and Arm-6 treatments were compared for their dissolving time and economics. Arm-6 treatment decreased the dissolving time by 8 times and proved to be very economic. In addition, dissolving characteristics were investigated for $KNO_3$, $Ca(NO_3)_2{\cdot}4H_2O$, and Fe-EDTA.

• Journal of Korea Water Resources Association
• /
• v.45 no.1
• /
• pp.101-111
• /
• 2012

In this paper, the feedback loop mechanisms among the operational indices and exogenous variables of a sewerage system that are inherent in the operation and maintenance of a sewerage system were identified using the System Dynamics (SD) modeling methodology. The identified feedback loops were used to develop a SD computer simulation model that can be used to predict future operational conditions of a sewerage system and identified the efficient ways of operation. The data of Busan metropolitan city sewerage system was applied to verify the developed SD model and predict future operational conditions of the system. As a result, it was predicted that sewage treatment efficiency, volume of sewage treatment and cost recovery rate will be gradually increased, whereas service rate which was already very close to the target will remain almost the same as the current value. Furthermore, sensitivity analysis concerning some operational indices was performed in order to discover the policy leverage. As a result, it was found that the exogenous variables related to the pipe maintenance had a great effect on facility using rate, volume of sewage treatment as well as sewage treatment efficiency.

• Journal of the Korean Wood Science and Technology
• /
• v.2 no.2
• /
• pp.32-34
• /
• 1974

The important results which have been obtained in the investigation can be recapitulated as follows. 1. As demonstrated by the experimental results and analyses concerning their effects in the on-ground type mushroom house, the constructions in relation to the side wall and ceiling of the experimental house showed a sufficient heat insulation on effect to protect insides of the house from outside climatic conditions. 2. As the effect on the solar type experimental mushroom house which was constructed in a half basement has been shown by the experimental results and analyses, it has been proved to be effective for making use of solar heat. However there were found two problems to be improved for putting solar house to practical use in the farm mushroom growing: (1) the construction of the roof and ceiling should be the same as for the on ground type house, and (2) the solar heat generating system should be reconstructed properly. 3. Among several ventilation systems which have been studied in the experiments, the underground earthen pipe and ceiling ventilation, and vertical side wall and ceiling ventilation systems have been proved to be most effective for natural ventilation. 4. The experimental results have shown that ventilation systems such as the vertical side wall and underground ventilation systems are suitable to put to practical use as natural ventilation systems for farm mushroom house. These ventilation systems can remarkably improve the temperature of fresh air which is introduced into the house by heat transfers within the ventilation passages, so as to approach to the desired temperature of the house without any cooling or heating operation. For example, if it is assuming that X is the outside temperature and Y is the amount of temperature adjustment made by the influence of the ventilation system, the relationships that exist between X and Y can be expressed by the following regression lines. Underground iron pipe ventilation system. Y=0.9X-12.8 Underground earthen pipe ventilation system. Y=0.96X-15.11 Vertical side wall ventilation system. Y=0.94X-17.57 5. The experimental results have 8hown that the relationships existing between the admitted and expelled air and the $CO_2$ concentration can be described with experimental regression lines or an exponent equation as follows: 5.1 If it is assumed that X is an air speed cm/sec. and Y is an expelled air speed in cm/sec. in a natural ventilation system, since the Y is a function of the X, the relationships that exist between X and Y can be expressed by the regression lines shown below: 5.2 If it IS assumed that X is an admitted volume of air in $m^3$/hr. and Y is an expelled volume of air in $m^3$/hr. in a natural ventilation system, since the Y is a function of the X, the relationships that exist between X and Y can be expressed by the regression lines shown below. 5.3 If it is assumed that expelled air speed in emisec. and replacement air speed in cm/sec. at the bed surface in a natural ventilation system are shown as X and Y. respectively, since the Y is a function of the X. the relationships that exist between X and Y can be expressed by the following regression line: GE(100%)-CV (50%) ventilation system. Y=-0.54X+0.84 5.4 If it is assumed that the replacement air speed in cm/sec. at the bed surface is shown as X, and $CO_2$ concentration which is expressed by multiplying 1000 times the actual value of $CO_2$ % is shown as Y, in a natural ventilation system, since the Y is a function of the X, the relationships that exist between X and Y can be expressed by the following regression line: GE(100%)-CV(50%) ventilation system. Y=114.53-6.42X 5.5 If it is assumed that the expelled volume of air is shown as X and the $CO_2$ concencration which is expressed by multiplying 1000 times the actual of $CO_2$% is shown as Y in a natural ventilation system, since the Y is a function of the X, the relationships that exist between X and Y can be expressed by the following exponent equation: GE(100%)-CV(50%) ventilation system. Y=$127.18{\times}1.0093^{-x}$ 5.6 The experimental results have shown that the ratios of the cross sectional area of the GE and CV vent to the total cubic capacity of the house, required for providing an adequate amount of air in a natural ventilation system, can be estimated as follows: GE(admitting vent of the underground ventilation) 0.3-0.5% (controllable) CV(expelling vent of the ceiling ventilation) 0.8-1.0% (controllable) 6. Among several heating devices which were studied in the experiments, the hot-water boilor which wasmodified to be fitted both as hot-water boiler and as a pressureless steam-water was found most suitable for farm mushroom growing.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.6
• /
• pp.521-537
• /
• 2012

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2011. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of fluid machinery and fluid flow, thermodynamic cycle, and new and renewable energy. Various topics were presented in the field of fluid machinery and fluid flow. Research issues mainly focused on the rankine cycle in the field of thermodynamic cycle. In the new and renewable energy area, researches were presented on geothermal energy, fuel cell, biogas, reformer, solar water heating system, and metane hydration. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer, nanofluids and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer above liquid helium surface in a cryostat, methane hydrate formation, heat and mass transfer in a liquid desiccant dehumidifier, thermoelectric air-cooling system, heat transfer in multiple slot impinging jet, and heat transfer enhancement by protrusion-in-dimples. In the area of pool boiling and condensing heat transfer, researches on pool boiling of water in low-fin and turbo-B surfaces, pool boiling of R245a, convective boiling two-phase flow in trapezoidal microchannels, condensing of FC-72 on pin-finned surfaces, and natural circulation vertical evaporator were actively performed. In the area of nanofluids, thermal characteristics of heat pipes using water-based MWCNT nanofluids and the thermal conductivity and viscosity were measured. In the area of industrial heat exchangers, researches on fin-tube heat exchangers for waste gas heat recovery and Chevron type plate heat exchanger were implemented. (3) Refrigeration systems with alternative refrigerants such as $CO_2$, hydrocarbons, and mixed refrigerants were studied. Heating performance improvement of heat pump systems were tried applying supplementary components such as a refrigerant heater or a solar collector. The effects of frost growth were studied on the operation characteristic of refrigeration systems and the energy performance of various defrost methods were evaluated. The current situation of the domestic cold storage facilities was analyzed and the future demand was predicted. (4) In building mechanical system fields, a variety of studies were conducted to achieve effective consumption of heat and maximize efficiency of heat in buildings. Various researches were performed to maximize performance of mechanical devices and optimize the operation of HVAC systems. (5) In the fields of architectural environment and energy, diverse purposes of studies were conducted such as indoor environment, building energy, and renewable energy. In particular, renewable energy and building energy-related researches have mainly been studied as reflecting the global interests. In addition, various researches have been performed for reducing cooling load in a building using spot exhaust air, natural ventilation and energy efficiency systems.

• Journal of Korean Society of Environmental Engineers
• /
• v.33 no.3
• /
• pp.191-195
• /
• 2011

The measurement and prediction of bacterial transport of bacteria in aquatic systems is of fundamental importance to a variety of fields such as groundwater bioremediation ascending urinary tract infection. The motility of pathogenic bacteria is, however, often missing when considering pathogen translocation prediction. Previously, it was reported that flagellated E. coli can translate upstream under low shear flow conditions. The upstream swimming of flagellated microorganisms depends on hydrodynamic interaction between cell body and surrounding fluid flow. In this study, we used a breathable microfluidic device to image swimming E. coli at a glass surface under low shear flow condition. The tendency of upstream swimming motion was expressed in terms of 'A' value in parabolic equation ($y=Ax^2+Bx+C$). It was observed that high shear flow rate increased the 'A' value as the shear force acting on bacterium increased. Shorter bacterium turned more tightly into the flow as they swim faster and experience less drag force. The result obtained in this study might be relevant in studying the fate and transport of bacterium under low shear flow environment such as irrigation pipe, water distribution system, and urethral catheter.