중간 냉각기가 있는 고압 다단 왕복동식 압축기에 관한 열역학적 해석

이억수,김명훈,이승홍,Lee, Euk-Soo,Kim, Myung-Hun,Lee, Sung-Hong 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.9

Simplified thermodynamic analysis of high pressure 4-stage reciprocating compressors with 4 inter-coolers has been investigated to predict a behavior of a compressor system for NGV(natural gas vehicles). A computer program has been developed to predict and estimate the performance of high pressure 4-stage reciprocating compressor system. Thermodynamic properties of compressed natural gas(CNG) were calculated by ideal gas theory and compression cycle was assumed as reversible adiabatic compression and expansion processes, and isobaric intake and discharge processes. Comparison between results predicted by calculation model and measured by experimental tests is presented.

원관 주위의 2차원 전도열전달과 국소 대류열전달

이억수,Lee Euk-Soo 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.1

When a circular tube with uniform heat generation within the wall was placed in a cross flow, heat flows by conduction in the circumferential direction due to the asymmetric nature of the fluid flow around the perimeter of the circular tube The circumferential heat flow affects the wall temperature distribution to such an extent that. in some cases, significantly different results may be obtained for geometrically similar surfaces. In the present investigation, the effect of circumferential wall heat conduction is investigated for forced convection around circular tube in cross flow of air and water Two-dimensional temperature distribution $T_w(r,{\theta})$ is calculated through the numerical analysis. The difference between one-dimensional and two-dimensional solutions is demonstrated on the graph of local heat transfer coefficients. It is observed that the effect of working fluid is very remarkable.

평판의 층류 막응축에서 복합열전달에 대한 근사해

이억수,Lee Euk-Soo 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.5

Liquid film thickness in laminar film condensation for flow over a flat plate generally is so thin that both fluid acceleration and thermal convection within the liquid film can be neglected. An integral solution method is proposed to solve the conjugate problems of laminar film condensation and heat conduction in a solid wall. It is found that approximate solutions of the governing equations involve four physical parameters to describe the conjugate heat transfer problem for laminar film condensation. It is shown that the effects of interfacial shear. mass transfer and local heat transfer are strongly dependent on the thermo-physical properties of the working fluids and the Jacob number.

수평평판의 층류 막응축에서 압력의 영향

이억수(Euk-Soo Lee),이승홍(Sung-Hong Lee) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.12

Laminar film condensation of saturated vapor in forced flow over a flat plate is analysed. The problem is formulated as exact boundary-layer solution and integral approximate solution. From numerical solutions of the governing equations, it is found that the energy transfer by convection and the effect of inertia term in the momentum equation in negligibly small for low pressure but quite important for high pressure. The condensate rate, liquid-vapor interfacial shear stress and local heat transfer are strongly dependent on the reduced pressure Pr and the modified Jacob number Ja/Pr.

원형 실린더 주위의 전도-대류 열전달

이상봉(SANG BONG LEE),이억수(EUK SOO LEE),김시영(SI YEOUNG KIM) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.3

With uniform heat generation within the wall of the cylinder placed in a cross flow, heat flows by conduction in the circumferential direction due to the asymmetric nature of the fluid flow around the perimeter of the cylinder. The circumferential heat flow affects the wall temperature distribution to such an extent that in some cases significantly different results may be obtained for geometrically similar surfaces. In the present investigation, the effects of circumferential wall heat conduction on local convective heat transfer is investigated for the case of forced convection around horizontal cylinder in cross flow of air. Two-dimensional temperature distribution Tw(r, θ) is presented through the numerical analysis. The one-dimensional and two-dimensional solutions are in good agreement with experimental results of local heat transfer coefficients.

조수기용 증기분사 열교환기에 대한 모델링

홍철현(Cheol-Hyun Hong),이억수(Euk-Soo Lee) 한국마린엔지니어링학회 2008 한국마린엔지니어링학회지 Vol.32 No.6

원관 주위의 전도 열전달과 공기의 대류 열전달

이승홍,이억수 釜山大學校生産技術硏究所 1997 生産技術硏究所論文集 Vol.52 No.-

가열되는 원관에 대하여 수직방향에서 공기가 유동할 경우, 원관의 주위 온도를 측정, 분석함으로서, 원관 주위의 강제 대류 열전달에 대한 원주(θ)방향으로 전도 열전달의 영향을 연구하였다. 실린더의 내벽에서 일정한 열유속을 반경(r)방향으로 공급하면, 대류에 의한 원형 실린더 주위의 비대칭적인 온도분포 때문에, 열은 전도에 의해서 원관을 통하여 원주(θ)방향으로 전도 열전달이 존재하고, 실린더 주위로 대류에 의한 대류 열전달이 동시에 일어난다. 기하학적으로 유사한 표면과 경계조건에 대해서, 전도 열전달율은 원관의 열전도계수와 두께에 의존하고 그리고 고체 원관의 벽면을 통하여 발생하는 전도 열전달이 대류 열전달에 미치는 영향은 유체의 열전도계수와 반경의 크기에도 영향을 받는다. 복합 무차원 계수 가 원주방향의 전도 열전달의 대류 열전달에 관한 영향을 나타내는 계수로 사용되었다. 국소 열전달율과 국소 대류 열전달계수에 대한 원주방향의 전도 열전달의 영향은 복합 무차원계수 K*가 작을 경우에 매우 큰 영향을 주고 있음이 발견되었다. The influence of circumferential wall heat conduction on convection heat transfer is investigated for the case of forced convection around a circular tube in cross flow of air by measurements of surface temperature of circular tubes. Keeping uniform heat generation from the inner surface of the cylinder in radial direction, heat is transferred by wall conduction in the circumferential (θ) direction due to the asymmetric nature of the temperature distribution of the cylinder and by convection around the perimeter of the cylinder simultaneously. The wall heat conduction rate depends on conductivity of the tube and size of the tube thickness and the effect of wall conduction on convection heat transfer also depends on conductivity of the fluid and size of the tube radius for geometrically similar surfaces and cross flow conditions. A non-dimensional conjugation parameter has been used to express the effect of the circumferential wall heat conduction. The significant effects of wall conduction on the local convective heat transfer rate and local convective heat transfer coefficients around a circular tube is found when value of the conjugation parameter k* becomes smaller.

원관 주위의 대류 열전달에 대한 원둘레 방향의 열전도의 영향

이승홍,이억수,정은행 釜山大學校生産技術硏究所 1997 生産技術硏究所論文集 Vol.53 No.-

원관축의 수직방향으로 유체가 유동하는 경우에, 가열되는 수평 원관 주위에서 원둘레 (θ)방향으로 비대칭적으로 균일하지 않게 온도가 분포하기 때문에 원둘레 방향으로의 전도 열전달이 존재하고 비균일 대류 열전달 현상이 생긴다. 본 연구에서는 공기와 물을 작동유체로 하고 직교 유동내에 있는 수평 원관의 열전달 실험에서 국소 대류 열전달에 대한 원둘레 방향 열전도의 영향에 대하여 연구하였다. 에너지 방정식에서 유도된 무차원 수가 반경방향에 대한 원둘레 방향의 열전도의 영향을 나타내는 무차원 수로 사용되었다. 4가지 모델을 직접 전기저항 가열방식으로 가열하고, 원관 표면의 온도를 직접 측정하여 2차원 온도분포의 경계조건으로 사용하여 원관의 단면 내부에서 2차원 온도분포 T(r,θ) 를 보여준다. With uniform heat generation in a horizontal cylindrical heater placed in a cross flow boundary condition, heat flow that is conducted along the wall of the heater creates a non-isothermal surface temperature and heat flux distribution. In the present investigation, the effects of circumferential wall heat conduction on convection heat transfer is investigated for the case of forced convection around horizontal cylinder in cross flow of air and water. Non-dimensional conjugation parameter which can be deduced from the governing energy differential equation should be used to express the effect of circumferential wall conduction heat transfer. Two-dimensional temperature solutions T(r,θ) distribution is presented. The influence of circumferential wall heat conduction is demonstrated on graph of local Nusselt number.