• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.8
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• pp.803-809
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• 2012

It is necessary to predict the heating load in order to determine the optimal scheduling control of district heating systems. Heating loads are affected by many complex parameters, and therefore, it is necessary to develop an efficient, flexible, and easy to use prediction method for the heating load. In this study, simple specifications included in a building design document and the estimated temperature and humidity are used to predict the heating load on the next day. To validate the performance of the proposed method, heating load data measured from a benchmark district heating system are compared with the predicted results. The predicted outdoor temperature and humidity show a variation trend that agrees with the measured data. The predicted heating loads show good agreement with the measured hourly, daily, and monthly loads. During the heating period, the monthly load error was estimated to be 4.68%.

• Transactions of Materials Processing
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• v.32 no.3
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• pp.153-159
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• 2023

This paper presents the optimal design of a heating system using radiant heating elements for application in smart farms. Smart farming, an advanced agricultural technology, is based on artificial intelligence and the internet of things and promotes crop production. Temperature and humidity regulation is critical in smart farms, and thus, a heating system is essential. Radiant heating elements are devices that generate heat using electrical energy. Among other applications, radiant heating elements are used for environmental control and heating in smart farm greenhouses. The performance of these elements is directly related to their electrical energy consumption. Therefore, achieving a balance between efficient electrical energy consumption and maximum heating performance in smart farms is crucial for the optimal design of radiant heating elements. In this study, the size, electrical energy supply, heat generation efficiency, and heating performance of radiant heating elements used in these heating systems were investigated. The effects of the size and electrical energy supply of radiant heating elements on the heating performance were experimentally analyzed. As the radiant heating element size increased, the heat generation efficiency improved, but the electrical energy consumption also increased. In addition, increasing the electrical energy supply improved both the heat generation efficiency and heating performance of the radiant heating elements. Based on these results, a method for determining the optimal size and electrical energy supply of radiant heating elements was proposed, and it reduced the electrical energy consumption while maintaining an appropriate heating performance in smart farms. These research findings are expected to contribute to energy conservation and performance improvement in smart farming.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.1
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• pp.82-91
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• 2005

Polymer membrane needs to maintain appropriate moisture. Insufficient moisture causes low conduction of hydrogen ion because of increased contact resistance between electrode and membrane by shrinking membrane, and abundant moisture decreases fuel cell performance as difficulty of diffusion reacting gas. Therefore, water controlling system is very consequential for the polymer membrane fuel cell. If hollow fiber membrane humidification is used between fuel and air lines, it is possible to supply heat to fuel and air by using thermal exchanger. It can supply appropriate humidity depending on operating temperature, and can recover heat from exhaust gas which contains water vapor and air. Because of simple structure of humidification system, this system can be easily applied in the PEMFC and cut down cost.

• Journal of the Korean Solar Energy Society
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• v.37 no.1
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• pp.71-80
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• 2017

A Data center houses a large number of server computers, storage and etc in racks. With the rapid increase of heat generation rates per rack in a data center, energy consumption rates for cooling have been increased year by year. In this study, energy conservation effects of a MOA (multi-stage outdoor air enabled) cooling system in a data center has been investigated when it is applied to 5 different locations, Korea. As results, Energy conservation effects of the MOA cooling system was achieved at about 20% to 30%. Humidifier operation time was 40 to 55 days when supply air temperature was maintained at 13, and humidity condition was kept within the allowed range even though humidifier was off. Furthermore, humidification was not needed when supply air temperature was maintained at $25^{\circ}C$. In selected 5 locations in Korea, the difference of regional climatic conditions affected no more than 5% in cooling energy consumption rates.

• Journal of ILASS-Korea
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• v.8 no.1
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• pp.9-15
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• 2003

The liquid phase LPG injection (LPLI) system is considered as one of the next generation fuel supply systems for LPG, vehicles, since it can accomplish the higher power, higher efficiency, and lower emission characteristics than the existing mixer type fuel supply system. However, during the injection of liquid LPG fuel into the inlet duct of an engine, a large quantity of heat is extracted due to evaporation of fuel. A problem is that the moisture in the air freezes around the outlet of a nozzle, which is called icing Phenomenon. It may cause damage to the outlet nozzle of an injector. The frozen ice deposit detached from the nozzle also may cause a considerable damage to the inlet valve or valve seat. In this work, the experimental investigation of the icing phenomenon was carried out. The results showed that the icing phenomenon and process were mainly affected by humidity of inlet air instead of the air temperature in the inlet duct. Also, it was observed that the icing occurs first in the inlet of a nozzle, and grows considerably at the upper part of the nozzle inlet and the opposite side of the nozzle entrance. An LPG fuel, mainly consisting of butane, has lower latent heat of vaporization than that of propane, which is an advantage in controlling the icing phenomenon.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1059-1065
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• 2005

In this study, an nutrient solution control system have been designed and implemented, which controls the density of nutrient and the nutrient supply automatically using embedded real time operating system and fuzzy control algorithm. The factors which affect the growth of crop consist of solar radiation, external temperature, and external humidity. Also, nutrient temperature, electric conductivity(ED, and pH are monitored. According to the surveyed results, a fuzzy control algorithm for nutrient control is developed in order to control the density of nutrient and the nutrient supply. The exclusive embedded controller which consists of an embedded real time operating system, a korean LCD, and a graphic is developed for common users.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.3
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• pp.224-229
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• 2012

The importance of ventilation system is being emphasized by interest of indoor air quality. Especially, heat recovery ventilation system has attracted attention as most effective ventilation plan. Because it can reduce hazardous construction materials, indoor air pollutions, and also can reduce air conditioning energy cost. In heat recovery ventilator, the element core is the most important part. The element core is composed of liner and spacer. And liner and spacer are stacked alternately. On the Liner, heat and humidity transfer are made between supply and exhaust air. And spacer plays a role as a tunnel of exhaust and supply. In this study, we investigated and analyzed the efficiency of a heat recovery ventilator, when the spacer's properties are changed. As a result, difference spacer's properties affect an efficiency of heat recovery ventilator.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.1
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• pp.68-77
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• 1998

The purpose of this paper is to establish a method estimating the daily urban water demand using statistical analysis that is used for developing the efficient management and operation of the water supply facilities, and accurary of the model is verified by error rate and F-value. The data used in this study were the daily urban water use, the weather conditions such as temperature, precipitation, relative humidity, etc, and the day of The week. The case study was taken placed for the city of Namwon in Korea. The raw data used in this study were rearranged either by month or by season for analysis purpose, and the statistical analysis was applied to the data to obtain the regression model As a result of this study, the linear regression model was developed to estimate the daily urban water use with weather condition. The regression constant and coefficients of the model were determined for each month of a year. The accuracy of the model was within 3% of average error and within 11% of maximum error. The resulting model was found to he useful to the practical operation and management of the water supply facilities.

• Journal of Bio-Environment Control
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• v.7 no.3
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• pp.268-274
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• 1998

The mass flow of water in the stem of melon measured by Sap Flow Gauge was compared with the actual flow calculated by the difference between supply and drainage nutrient water to investigate the possibility and accuracy of estimation of melon's transpiration in rockwool culture. The Sap Flow Gauge which was made with copper-constantan theromocouple and nichrome fiber by our research team, was attached to the 3rd node of melon. The outdoor temperature, room temperature, solar radiation and relative humidity were continually measured. The amount of supply and drainage nutrient water were simultaneously measured for calculation of practical consumption of nutrient water to compare with mass flow of sap. The measuring errors of Sap Flow Gauge were 0.3 to 31.8%, which were small at solar radiation of 20MJ.m$^{2}$.d$^{-1}$ . The mass flow of water was lower for the measured value by Sap Flow Gauge than the actual value at higher solar intensity, however it was higher at lower solar intensity The variation of error rate of each Sap Flow Gauge was 0.1 to 13.0%. The measuring error with Sap Flow Gauge was negatively related with solar intensity and temperature. Therefore, to measure more exactly the mass flow of sap for estimation of melon's transpiration, the compensation factor must be calculated.

• Journal of Korea Multimedia Society
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• v.22 no.11
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• pp.1324-1337
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• 2019

This study set out to investigate an energy harvesting device to ensure stable energy supply to batteries and data collection devices and a monitoring system for acer pictum sap to check collected data. Acer pictum sap farmers have written down weather information and yield of acer pictum sap manually for data storage. Since the job is done manually, there are many missing values in their data. In addition, it is not easy to manage batteries due to the characteristics of the areas where acer pictum sap is collected. The present study thus decided to build an energy harvesting device based on new renewable energy to ensure stable energy supply by taking into consideration power load, daily power consumption, and number of days with no sunshine for various devices. For a monitoring system, the investigator proposed a JSP-based web page to monitor temperature, humidity, volume of collected water, and battery state in real time. The proposed energy harvesting device was applied to reduce missing values in data. It promoted stable energy supply to the batteries and data collection devices, reducing the percentage of missing values in data from 30.55% to 0%.