정4각단면 덕트 내에서 비정상 천이유동에 관한 연구

박길문,박선종,최주호,유영태,Park, G.M.,Park, S.J.,Choi, J.H.,Yoo, Y.T. 대한설비공학회 1989 설비공학 논문집 Vol.1 No.3

A system of conservation equations for steady, oscillatory and pulsating duct flows are solved analytically by linearizing non-linear convective terms. Analytical solutions of velocity profiles for these flows are obtained in the form of infinite series. The experimental study for the air flow in a square duct ($40mm{\times}40mm$ and 400 mm long) is carried out to measure velocity profiles and other parameters by using a hot-wire anemometer with data acquisition and processing system. Major characteristics of the flows such as the classification of flow patterns, determination of critical Reynolds number and velocity profiles is accomplished from the experismental results.

曲管에 있어서 熱傳達에 관한 硏究

朴吉文 조선대학교 동력자원연구소 1984 動力資源硏究所誌 Vol.6 No.1

An experimental study of steady and unsteady heat transfer process in helical coiled tubes has been conducted. The heat transfers were studied using a helical coil with a ratio of curvature of 0.053, and distilled water for laminar flow and turbulent flow regimes. The ration of the heat transfer coefficient for the helical coil to that for the straight tube higher in the laminar flow regime than in the turbulent flow regime. The axial temperature distributions show large oscillations with axial distance, which damp out in the fully developed region. The value of resonant frequency agrees with the analytical results of Mori andNakayama.

정4각단면덕트 입구영역에서 층류맥동유동 유동특성에 관한 연구

박길문 대한기계학회 1991 대한기계학회논문집 Vol.15 No.5

본 연구에서는 정4각단면덕트 입구영역에서 층류맥동유동(laminar pulsating flows)의 유동특성을 이론 및 실험적으로 규명하기 위하여, 이론적 방법으로 덕트 입 구영역에서의 층류맥동유동에 대한 운동량방정식을 유도한 후 비선형인 대류항을 선형 화 시켜서 라플라스변환으로 속도분포식의 해를 구하였고, 실험적인 방법으로는 시험 덕트 크기는 횡단면의 가로*세로가 40mm*40mm이고, 길이가 4000mm인 정4각단면덕트 입구영역에서 송풍기에 의한 공기흡입유동으로 층류진동유동을 발생하며 이들 두유동 을 합성시켜 발생한 층류맥동유동에 대하여 열선유속계의 열선신호로부터 얻어진 속도 파형을 고찰하여 덕트내의 맥동유동에 대한 임계레이놀즈수를 결정하고 속도분포를 측 정하였다. 그리고 이론적으로 얻어진 속도분포식과 열선유속계로 측정한 속도분포를 비교검토하여 정확성을 검증하고, 이들 해석결과로 부터 층류맥동유동의 입구길이(en- trance lenght)식을 결정하여 제안하였다.

정사각단면 $180^{\circ}$ 곡관덕트의 입구영역에서 비정상층류유동의 유동특성에 관한 연구

박길문,모양우,조병기,Park, G.M.,Mo, Y.W.,Cho, B.K. 대한의용생체공학회 1996 의공학회지 Vol.17 No.4

The flow characteristics of developing unsteady laminar flow in a square-sectional $180^{\circ}$ curved duct are experimentally investigated by using laser doppler velocimerty (LDV) system with data acquisition and processing system of rotating machinery resolver(RMR) and PHASE software. The major flow characteristics of developing laminar pulsating flows are presented by mean velocity profilel velocity distribution of secondary flow, wall shear stress distributions, entrance lengths according to dimensionless angular frequency($\omega^+$), velocity amplitude ratio($A^1$), and time-averaged Dean number($De_ta$). The velocity profiles and wall shear stress distribution of laminar pulsating flow with dimensionlessangular frequency show the flow characteristics of the quasi-steady laminar flow in a curved duct. The developing region of laminar pulsatile flows in a square-sectional $180^{\circ}$ curved duct is extended to the curved duct angle of approximately $120^{\circ}$ under the present experimental condition.

원형관로내 층류 맥동유동의 속도와 압력 분포에 관한 연구

박길문,유영태,위광환,이충주,정지철 조선대학교 생산기술연구소 1996 生産技術硏究 Vol.18 No.2

In this study basic equations for the pulsatile laminar flow in a circular rigid pipe containing a slightly compressible fluid are derived and analytical solutions for the distributions of wave propagation factor K, cross-sectional mean velocity u_(m) and pressure P are schematically developed and confirmed experimentally. The pulsatile flow with 0 ≤ f ≤ 48Hz and 0 ≤ Re ≤ 2500 generated by summing the oscillatory flow made by ball valve into steady one. The wave form of pulsatile flow is described as a longitudinal wave and particle velocities measured experimentally are group velocities of the wave packet which are always smaller than phase velocities which are approximate to the sonic velocity C when the radial dispersion and wall friction are negligible. Therefore wave number is approximated to k = ω/c for high angular velocity region. The axial pressures and centerline velocities were measured by strain-gage type pressure transducers and Pito-static tubes, respectively. The cross-sectional mean velocities calculated from centerline velocities with the parabolic distributions of the laminar flow and confirmed by using the ultrasonic flowmeter. We knew that axial distributions of oscillatory velocity and pressure coincide with thoeretical and depend on the Reynolds number and angular velocity.

4각덕트의 입구영역에서 난류진동유동의 유동특성에 관한 연구

박길문,조병기,고영하 조선대학교 동력자원연구소 1996 動力資源硏究所誌 Vol.18 No.1

The flow characteristics of developing turbulent oscillatory flow are investigated experimentally in the entrance region of a square duct (40 ㎜ X 40 ㎜ and 4,000 ㎜). Experimental results of mean velocity profiles, turbulence intensity and entrance length are measured by using a hot-wire anemometer system together with data acquisition and processing systems. For turbulent oscillatory flow, the turbulent components in the velocity waveforms increase as the dimensionless transverse position approaches the wall. Velocity distribution are not change fully developed region. Inflow and outflow are nearly symmetrical form in the fully developed region such as x/D_h≥40. Turbulence intensity increases as the dimensionless transverse position increases from the center to the wall of the duct, and is slightly smaller in the accelerating phase than in the decelerating phase for the developing turbulent oscillatory flows. The entrance length of the turbulent oscillatory flow is about 40 times as large as the hydraulic diameter in the present experimental conditions.

정사각단면 곡관덕트에 연결된 직관덕트에서 층류유동의 속도분포

박길문,이행남,이홍구,손현철 대한기계학회 2004 大韓機械學會論文集B Vol.28 No.9

직관덕트내에서 정상유동, 진동유동과 맥동유동의 임계레이놀즈수에 관한 연구

박길문,봉태근 한국마린엔지니어링학회 1998 한국마린엔지니어링학회지 Vol.22 No.1

The critical reynolds number in a square-sectional straight duct is investigated experimentally. The experimental study for the air flow in a square-sectional straight duct is carried out to calssify critical Reynolds number on steady flow and unsteady flow. To calssify the critical Reynolds number we obtained velocity waveform by using a hot-wireanemometer and data acquisition system with photocorder.

기체 방사성 물질 제거를 위한 첨착 활성탄 필터 시스템 성능에 관한 연구

김대욱,손현철,이명석,이석범,박길문 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.1

This paper presents an application of impregnated activated carbon and impregnated activated carbon filters. They are used for the removal of gaseous radioactive materials at radioactive material handling facilities such as nuclear power plants and research facilities. High adsorption efficiencies as well as stability are required for them to remove hazardous radioactive gases such as activated free iodine released during normal operation or accident condition. This research was initiated to enhance the independence of nuclear industry and raise the level of nuclear technology to that of the leading nuclear nations. By attaining the capability of design and development of HVAC system, national technological competitiveness can be achieved. Also, the ground for technology export will be hardened. Therefore, it is well timed to initiate the project to develope those filter systems domestically utilizing all the relevant technologies available.

정4각 덕트 입구영역에서 층류정상 유동특성에 관한 연구

박길문,고영하 대한기계학회 1990 대한기계학회논문집 Vol.14 No.4

본 연구에서는 정4각 단면덕트의 입구영역에서 층류 정상유동의 유동특성을 이론적 및 실험적인 방법으로 속도파형과 속도분포를 얻어서 유동이 발달되고 있는 유 동특성과 입구길이를 규정하였다. 이론적인 방법으로는 덕트입구영역에서 공기유동 에 대한 운동량방정식을 유도한 후, 운동량방정식 중의 비선형인 대류항을 선형화시켜 서 Laplace변환으로 속도 분포식의 해를 구하였고, 실험적인 방법으로는 시험덕트의 크기가 40*40*4,000nm(가로*세로*높이)인 정 4각단면덕트에 송풍기로 공기를 흡입 하여 정상유동을 얻었고, 열선유속계에 의하여 속도파형과 속도분포 등의 측정한 결과 를 이론식과 비교검토하였다.