• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.1
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• pp.96-103
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• 2014

A liquefied natural gas(LNG) in cryogenic liquid is converted back into gaseous form for distribution to residential and industrial consumers. In this re-gasification process, LNG supplies a plenty of cold thermal energy about $83.7{\times}10^4kJ/kg$. The LNG cold thermal energy is utilized for the re-liquefaction process of cryogenic fluids such as Nitrogen, Hydrogen and Helium, and ice manufacturing process and air-conditioning system in some advanced countries. Therefore, it is also necessary to establish the recovery systems of the LNG cold thermal energy around Incheon, Pyungtaek and Tongyung LNG import terminals in our country. Methane is used as working fluid in this paper, which is the major component of LNG over 85 % by volume, in order to investigate the flow behavior characteristics of LNG with phase change at low heat flux. This paper presents the effects of pipe diameters, pipe inclinations and saturation pressures on the flow boundaries of methane flowing in a cryogenic heat exchanger tube, together with those of nitrogen, propane, R11 and R134a. The outcomes obtained from this theoretical researches are also compared with previous experimental data. It was also found that the effect of pipe inclination on the methane flow boundaries was significant.

• Journal of Bio-Environment Control
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• v.32 no.3
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• pp.181-189
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• 2023

Hydrogen has gained attention as an environmentally friendly energy source among various renewable options, however, its application in agriculture remains limited. This study aims to apply the hydrogen fuel cell triple heat-combining system, originally not designed for greenhouses, to greenhouses in order to save energy and reduce greenhouse gas emissions. This system can produce heating, cooling, and electricity from hydrogen while recovering waste heat. To implement a hydrogen fuel cell triple heat-combining system in a greenhouse, it is crucial to evaluate the greenhouse's heating and cooling load. Accurate analysis of these loads requires considering factors such as greenhouse configuration, existing heating and cooling systems, and specific crop types being cultivated. Consequently, this study aimed to estimate the cooling and heating load using building energy simulation (BES). This study collected and analyzed meteorological data from 2012 to 2021 for semi-enclosed greenhouses cultivating tomatoes in Jeonju City. The covering material and framework were modeled based on the greenhouse design, and crop energy and soil energy were taken into account. To verify the effectiveness of the building energy simulation, we conducted analyses with and without crops, as well as static and dynamic energy analyses. Furthermore, we calculated the average maximum heating capacity of 449,578 kJ·h^-1 and the average cooling capacity of 431,187 kJ·h^-1 from the monthly maximum cooling and heating load analyses.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.481-493
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• 2023

In high-density urban areas, the urban heat island effect increases urban temperatures, leading to negative impacts such as worsened air pollution, increased cooling energy consumption, and increased greenhouse gas emissions. In urban environments where it is difficult to secure additional green spaces, rooftop greening is an efficient greenhouse gas reduction strategy. In this study, we not only analyzed the current status of the urban heat island effect but also utilized high-resolution satellite data and spatial information to estimate the available rooftop greening area within the study area. We evaluated the mitigation effect of the urban heat island phenomenon and carbon sequestration capacity through temperature predictions resulting from rooftop greening. To achieve this, we utilized WorldView-2 satellite data to classify land cover in the urban heat island areas of Busan city. We developed a prediction model for temperature changes before and after rooftop greening using machine learning techniques. To assess the degree of urban heat island mitigation due to changes in rooftop greening areas, we constructed a temperature change prediction model with temperature as the dependent variable using the random forest technique. In this process, we built a multiple regression model to derive high-resolution land surface temperatures for training data using Google Earth Engine, combining Landsat-8 and Sentinel-2 satellite data. Additionally, we evaluated carbon sequestration based on rooftop greening areas using a carbon absorption capacity per plant. The results of this study suggest that the developed satellite-based urban heat island assessment and temperature change prediction technology using Random Forest models can be applied to urban heat island-vulnerable areas with potential for expansion.

• Journal of Bio-Environment Control
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• v.13 no.4
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• pp.217-225
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• 2004

This study was performed to provide the basic knowledge about the mushroom cultivation facilities. Classified current status of cultivation facilities in Gyeongnam province was investigated by questionnaire. The structure of Pleurotus eryngii cultivation facilities can be classified into the simple and permanent frame type. The simple frame structures were mostly single-span type, on the other hand, the permanent frame structures were more multi-span than simple structures. And the scale of cultivation facilities was very different regardless of structural type. But as a whole, the length, width and ridge height were prevailing approximately 20.0 m, $6.6\~7.0m$ and $4.6\~5.0m$ range, respectively. The floor area was about $132\~160\;m^2$, and floor was built with concrete to protect mushrooms from various harmful infection. The roof slope of the simple and permanent type showed about $41.5^{\circ}\;and\;18.6\~28.6^{\circ}$, respectively. The width and layer number of growing bed for mushroom cultivation were around $1.2\~1.6m$, 4 layers in common, respectively. Most of year round cultivation facilities were equipped with cooler, heater, humidifier, and ventilating fan. Hot water boiler was the most commonly used heating system, the next was electric heater and then steam boiler. The industrial air conditioner has been widely used for cooling. And humidity was controlled mostly by ultra-wave or centrifuging humidifier. But some farmers has been using nozzle system for auxiliary purpose. More then $90\%$ of the mushroom house had the independent environment control system. The inside temperature was usually controlled by sensor, but humidity and $CO_2$ concentration was controlled by timer for each growing stage. The capacity of medium bottle was generally 850 cc and 1100cc, some farms used 800 cc, 950 co and 1,250 cc. Most of mushroom producted has been usually shipped to both circulating company and joint market.

• Korean Journal of Agricultural Science
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• v.36 no.1
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• pp.73-85
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• 2009

An investigation was conducted to get the basic data for establishing structural safety and environmental management of tomato greenhouses in Chungnam region. The contents of the investigation consisted of actual state of greenhouse structures and environmental control facilities. Most of greenhouses were arch type single-span plastic houses and they had too low height for growing tomatoes. Frameworks of multi-span greenhouses were suitable, but those of single-span were mostly insufficient. Every greenhouse had thermal curtain movable or covering fixed inside the greenhouse for energy saving, and heating facilities were mostly warm air heater. Irrigation facilities were mostly drip tube and controlled by manual operation or timer. Almost all of the greenhouses didn't install high level of environmental control facilities such as ventilator, air circulation fan, $CO_2$ fertilizer, insect screen, supplemental light, and cooling device.