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조금남(Keumnam Cho),김용찬(Yongchan Kim),홍희기(Hiki Hong),김상노(Sang No Kim),김인택(In Taek. Kim),전호철(Ho Cheol Jeon) 대한설비공학회 2006 대한설비공학회 학술발표대회논문집 Vol.2006 No.6
Efficient load management on natural gas is strongly required to allow stable and reasonable energy use. The present study investigated domestic and international cases for demand management of natural gas. The directions of load management were discussed. The reasonable evaluation methods of demand management were analyzed and specific evaluation items were suggested.
마이크로핀관 증발기내 전열 성능에 미치는 냉동기유의 영향
조금남,태상진,Cho, Keumnam,Tae, S.J. 대한설비공학회 1999 설비공학 논문집 Vol.11 No.1
The present study experimentally investigated the effect of refrigeration lubricant on the heat transfer performance in the straight sections and U-bend of a microfin tube evaporator by using R-22/mineral oil and R-407C/POE oil. The apparatus consisted of test section with U-bend, preheater, condenser, oil injection and sampling devices, magnetic pump, mass flow meter etc. The experimental parameters were oil concentration of 0 to 5 wt%, inlet quality of 0.1 to 0.5, mass flux of 219 and $400kg/m^2s$ and heat flux of 10 and $20kW/m^2$. The effects of parameters on the heat transfer coefficients were large in the order of inlet quality, mass flux and heat flux as oil concentration got increased. As oil concentration was increased, heat transfer coefficients were continuously decreased for R-22 and increased by 3% up to the concentration of 1% and then decreased for R-407C under the condition of large inlet quality, and small mass flux and heat flux. But, the heat transfer coefficients were increased up to the concentration of 3% and then decreased for both R-22 and R-407C refrigerants under the opposite conditions. The variation of enhancement factors for R-407C was under 50% of that for R-22 and the variation with respect to the positions in the test section was small. The pressure drops were increased for both R-22 and R-407C refrigerants as oil concentration was increased. The pressure drops for R-407C were smaller by the maximum of 18% than those for R-22.
R-134a를 사용한 자동차용 스크롤 압축기의 스크롤 형상변화가 성능에 미치는 영향
이건호,김학수,조금남,유정열,Lee, Geonho,Kim, Haksoo,Cho, Keumnam,Yoo, Jungyul 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.11
The present study investigated the effects of geometric parameters considered on the performance of an automotive scroll compressor by assuming ideal, semi-real and real gases for R-134a. The geometric parameters were center thickness of scroll, height of scroll and the size of discharge port. Fourth-order Runge-Kutta method was applied to solve the thermodynamic equations, leaking rate equation and the equation of motion of discharge valve for ideal, semi-real, and real gases. The volumetric and adiabatic efficiencies for semi-real and real gases differed little, but those for ideal gas differed by 18% and 25% compared with those for real gas at 2,000rpm. The volumetric efficiency changed little as the design angle of scroll (${\gamma}$) changed, but the adiabatic efficiency at ${\gamma}$ of $34^{\circ}$ was higher by 2.4% than that of $147^{\circ}$ for 2,000rpm. The volumetric and adiabatic efficiencies at scroll height of 29.8mm were higher by 1.7% and 2.8% than those of 65.8mm. The volumetric efficiency changed little as the size of discharge port changed, but the adiabatic efficiency increased a little as the size of discharge port decreased.
조홍기(Honggi Cho),조금남(Keumnam Cho),김정훈(Jeung-Hoon Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The objective of the present study was to calculate the pressure drop of two-phase flow in a heat exchanger with flat tubes. The heat exchanger had 15 flat tubes and both inlet and outlet headers with the inner diameter of 19.4㎜, respectively. Each flat tube had 8 rectangular channels with the hydraulic diameter of 1.0㎜. It was found that two-phase pressure drop through the flat tube showed the largest value among the other pressure loss components. Pressure drops through the tube end projection that blocked the refrigerant flow in the headers were relatively larger than those of the sudden expansion and sudden contraction. Based on the Yang and Webb correlation, pressure drop through the flat tube was larger by 43% to 72% than those of the other correlations.