• Journal of Energy Engineering
• /
• v.20 no.4
• /
• pp.303-308
• /
• 2011

The present study has been carried out to predict the heat transfer characteristics of reverse heat loss method for a residential refrigerator by using numerical analysis and corresponding experiment. From the measured values of temperature and heat input, one can conclude that, the temperature inside the refrigerator has a nearly linear relationship with heat input. The effect of gasket heat loss was examined with the change of thermal conductivity of gasket region. The appropriate thermal conductivity of gasket region was acquired from the comparison of heat losses with the experimental result and numerical analysis. The result of calculated heat losses had accuracy within 1.8% error with the experimental result. With the selected thermal conductivity of gasket region, the effectiveness of reverse heat loss method was examined with the change of thermal conductivity of vacuum insulation panel.

• Journal of the Society of Naval Architects of Korea
• /
• v.38 no.4
• /
• pp.66-74
• /
• 2001

Plate bending process is indispensible in shipbuilding. The process includes press bending process and heating process. Especially the heating process is carried out exclusively by skillful workers. Many researches have been made to automate the heating process. This study was carried out as a fundamental study to develop a efficient analysis method for triangle heating and focused on clarifying the deformation characteristics of plate by triangle heating and essential elements effect on the deformation. In this paper, we proposed an analysis model for thermal-elastic-plastic analysis and simulated the deformation by triangle heating using ANSYS based on the experimental results of Jang et al.(2001). Also, we showed the deformation characteristics more clearly by comparing the deformation due to triangle heating and line heating in case that the total heat input is same. Finally, we investigated the change characteristics of deformation elements according to the volumetric heat input.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.31 no.4
• /
• pp.5-11
• /
• 2023

This study was conducted to improve energy efficiency and problems such as clumping and fouling in the glue zone that occur in the moisture content range of 40 to 60% when sewage dehydration residue is directly fed into the dryer. The temperature of the hot air is low at 270~300℃, and the paddle-type flotation method and dehydrated residue are applied to the circulated heat storage media to increase the contact area with the hot air, thereby reducing energy recovery and gas emissions. The water content of the dried residue is 2.7. ~7 .5%, the heat of evaporation of moisture was 608.0~690.6 kcal/kg·H₂O, which confirmed an energy saving effect of about 8.8% compared to the heat of evaporation of moisture of 714.5 kcal/kg·H₂O when no heat storage media was used.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.158.1-158.1
• /
• 2010

국내 최초의 생활폐기물고형연료(RDF) 생산플랜트인 원주시 RDF플랜트의 2009년도 운영실적을 정리하여 폐기물 처리단가를 분석하였으며 에너지 생산 효과도 분석하였다. 실적분석에 사용된 자료는 원주 RDF플랜트 위탁운영업체가 운영비를 청구 및 정산하기 위해서 원주시에 상시 측정 및 보고하는 항목으로서, 내용은 트럭으로 플랜트에 반입되는 폐기물 전체량, RDF생산 전체량, 불순물 매립 전체량, 건조 및 탈취용 연료사용 전체량, 전기사용 전체량 등이다. 2009년도 원주시 RDF플랜트에 반입된 폐기물 량은 총 17,504톤이었고, RDF를 총 7,044톤 생산하였으며, 4,120톤의 불연물을 선별하였다. 1년간 사용한 건조 및 탈취용 연료는 총 596,268 리터였으며 연료인 부생유의 가격은 리터 당 평균 864.6원이었다. 사용한 전기량은 총 2,435,397 kWh였고, 이 중에서 성형공정에 사용된 전기량은 총 사용량의 19%였다. 이상의 기록자료들을 분석해 본 결과, 폐기물 1톤을 처리하는데 전기 비용이 14,334원이었고, 연료비가 29,452원이었다. 여기에 폐기물 1톤당 불연물 매립비 6,573원과 위탁인건비를 합하면 폐기물 1톤당 처리비용은 약 116,573원으로 나타났다. 현재 원주시 RDF는 톤당 25,000원에 판매되고 있으므로 이 비용을 감안하면 폐기물 1톤당 처리비용은 105,298원으로 산출되었다. 현재 알려진 유사 규모의 소각로 운영비가 폐기물 1톤당 136,736원인데, 이것은 RDF기술보다 31,438원/톤-폐기물 정도 처리비용이 비싸다. 따라서 100톤 이하 규모의 폐기물처리시설 설치를 할 경우에는 RDF 시설이 경제적으로 타당함을 나타낸다. 원주시 RDF플랜트의 물질수지를 분석해 본 결과, RDF생산 수율은 40.2%였으며 총 투입된 에너지는 8,0587 Gcal였다. 생산된 에너지 총량은 RDF발열량 4,500 kcal/kg으로 했을 때 31,699 Gcal로 나타났다. 투입대비 생산에너지 비율은 25.4%로 계산되었고, 전기의 발전효율을 40%로 감안했을 경우에는 35.3%로 계산되었다. 성형하는데 사용되는 총 에너지는 전체 투입에너지의 4.9%로 나타났고, 비용으로는 폐기물 1톤당 2,723원 이었다.

• Environmental and Resource Economics Review
• /
• v.20 no.1
• /
• pp.1-31
• /
• 2011

By employing Environmental Input-Output Table 2005, which has 76 intermediate sector and 21 energy sources, this paper analyses the flow of energy demand and $CO_2$ after estimating an induced $CO_2$ emissions from 76 industrial sectors. Index of $CO_2$ intensity($CO_2/GDP$) and other index of $CO_2$ intensity($CO_2/calory$) showed that final demand sector uses more high calory energy source. Intermediate sector used less environmental friendly energy source and emit more $CO_2$ at same calory. Industries those has high induced $CO_2$ emissions are Thermal Power($32.587CO_2-g/Won$), Cement($10.370CO_2-g/Won$), Road Transportation($7.255CO_2-g/Won$), Cokes and Other Coal Products($5.791CO_2-g/Won$), Steam and Hot water supply, Sewage, Sanitary services($4.575CO_2-g/Won$). It is shown that industry such as Iron and Steel which has low $CO_2$ intensity, high backward linkage effect and high forward linkage effect makes high induced $CO_2$ emissions. Environmental load and $CO_2$ emissions in overall economy will decrease when not high $CO_2$ intensity industry but also low $CO_2$ intensity industry makes lower $CO_2$ intensity.

• Journal of Adhesion and Interface
• /
• v.16 no.3
• /
• pp.108-115
• /
• 2015

In the present work, we investigated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/graphene nanocomposites. The electrical, hydrophobic properties and thermal properties of the nanocomposite films having different graphene contents were investigated. The scanning electron microscopy (SEM) morphology showed good dispersion of graphene layers in the PHBV matrix. Based on the X-ray diffraction and differential scanning calorimetry, the addition of graphene increased the crystallinity of PHBV. Thermal stability, hydrophobicity, and electrical conductivity of the nanocomposites were increased with increasing the graphene contents.

• Korean Journal of Soil Science and Fertilizer
• /
• v.42 no.6
• /
• pp.486-491
• /
• 2009

To evaluate the potential value of the major bioenergy crops which are wheat, canola, barley, corn, and sweet potato in Korea, we investigated the production of biomass and calorific value of crops, and also compared input and output factors among bioenergy crops during the cultivation period. There was difference between the biomass values in Agricultural and Forestry statistical yearbook(2006) and the one investigated in this experiment, also there was difference in crops and in species. Among the crops investigated, sweet potato(Jinhongmi, Yulmi) was shown the highest amount of biomass production and corn(Gangdaok) was shown the highest amount of the total biomass which is the total aboveground biomass at harvest. Oilseed canola which is presently a major source of bio-diesel had highest calorific value as $6,673{\sim}6,725cal\;g^{-1}$. Wheat and corn grains which are source of bio-ethanol were in the range of $3,879{\sim}4,317cal\;g^{-1}$. Gangdaok(Corn) produce the highest total calorific value in unit cultivating area among the crops as $8,263kcal\;m^{-2}$. Corn was shown that the input and output factors were the highest level among bioenergy crops during cultivation period. Sweet potato also was shown that output factor was the highest level though its input factors were average level. It is needed to be investigated more crops for collecting the higher potential value of bioenergy production further considering small land area and its effective utilization in Korea.

• Clean Technology
• /
• v.19 no.3
• /
• pp.226-232
• /
• 2013

A 5 kg/hr scale integral dual fluidized-bed gasifier for producing medium heating value syngas from biomass or combustible wastes was manufactured. The effect of operating variables including gasification temperature, rate of feeding, and weight ratio of steam/feed on the behavior of the gasifier was investigated. The contents of $H_2$ and CO in syngas, flow rate of feeding, cold gas efficiency increased with the increased gasification temperature or rate of feeding, but decreased with the increased weight ratio of steam/feed within the experimental range. With wood powder as the feed, the concentrations of $H_2$ and CO in the syngas were as high as 41% and 32%, and the cold gas efficiency and lower heating value of the syngas were as high as 70.1% and $3,428kcal/Nm^3$. With food wastes as the feed, the concentrations of $H_2$ and CO in the syngas were as high as 37% and 23.9%, and the cold gas efficiency and lower heating value of the syngas were as high as 66.7% and $3,670kcal/Nm^3$.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.2
• /
• pp.32-38
• /
• 2020

This study summarizes test methods and evaluation methods for examining the thermal characteristics of Jeju-type ground heat exchangers (GHXs) installed on Jeju Island, and analyzes the ground temperature and thermal characteristics of ground heat exchangers installed in various regions by using thermal response tests (TRT). Jeju Island is composed of volcanic rock layers, and the groundwater flow is well developed. A Jeju-type GHX can be installed up to 30 m from groundwater level after drilling a borehole. The ground heat exchanger has a structure in which several pipes are inserted into the borehole. In order to examine the characteristics of the Jeju-type GHX, tests were conducted on ground heat exchangers installed in four places on Jeju Island (Pyoseon, Jeju, Namwon, and Hallym). As a result of the analysis of the Jeju-type ground heat exchanger, the ground circulating water temperature stabilized according to the heat injection, depending on the installed location, and was formed within one to three hours. The ground heat exchanger capacity in Hallym was highest at 73.4 kW (cooling) and 82.8 kW (heating), and the Jeju-type calculation was lowest at 34.1 kW (cooling) and 23.3 kW (heating).

• Korean Journal of Environmental Agriculture
• /
• v.26 no.1
• /
• pp.1-6
• /
• 2007

In view of energy supply, biogas can be seen as alternative fuel by substituting considerable amount of fossil fuel and may be utilized for heat and power production or for transport fuel production ($CH_4-enriched$ biogas). The aim of this research is to analyse the emission of $NO_x$ and CO from biogas fired combustion engine for electric power production. The result indicate a significant effect of biogas composition ($CH_4-CO_2$ ratio) and biogas flow rate on the air pollutants emission. The emission factors from this study were compared with those of U.S. EPA. Low $CH_4-CO_2$ ratio condition typically shows the lower $NO_x$ and CO emission than higher $CH_4-CO_2$ ratio condition. At normal $CH_4-CO_2$ ratio (7:3) emission factors of $NO_x$ and CO were 1.29 and 30.43 g/MMBtu, respectively. At low $CH_4-CO_2$, ratio (6:4) emission factors of $NO_x$ and CO were 0.646 and 60.86 g/MMBtu, respectively, It should be emphasized that the actual emission may vary considerably from these results due to operating conditions including torque load and engine speed.