Bent Duct 내부 유동의 손실 측정

노우진(U Jin Roh),임주현(Ju Hyun Im),송성진(Seung Jin Song) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.5

Bent duct 는 손실을 가중시키고, 효율을 저하시킨다. 지금까지 bent duct에 대한 많은 연구가 진행되었지만, 입구와 출구가 같은 형상에 대해서 연구가 되어왔다. 이번 연구에서는 입구는 환형이지만, 출구는 원형을 가진 bent duct에 대해서 진행되었다. 입구 속도 54 m/s, 레이놀즈수 238,000에서 수행된 이번 연구에서는 bent duct 바깥에 태핑홀을 배치하여 정압분포를 확인하고, 입구와 출구에서 5공 프로브로 유동을 측정하여 스트림 방향 속도 프로파일과 전압 손실 계수를 얻었다. 본 연구에서는 전압 손실 계수, 0.243를 얻었다. Bent ducts add loss and decrease efficiency. Many researchers have been conducted the performances of bent ducts, but their shapes of inlet and outlet are same. However, in this investigation, the focus is on a bent duct which is annular at the inlet and circular at the outlet. The bent duct of these complex shapes has not been investigated, but has been used in many fields. The performance of such bent duct is investigated under inlet speed 54 m/s and Re = 238,000. Wall static pressure tappings are located surface of the bent duct to measure the static pressure and a probe is traversed at the inlet and outlet of the bent duct to measure the total pressure. As a result, it presents static pressure distribution on the bent duct surface, streamwise velocity profile at inlet and outlet of the bent duct and total pressure loss profile at outlet. In this investigation, the total pressure loss coefficient is 0.243.

지혈대 압력에 따른 인공 슬관절 치환술 후 발생한 피하출혈양의 관계

김지형 ( Jee Hyoung Kim ),이송 ( Song Lee ),김경태 ( Kyung Tae Kim ),고동오 ( Dong Oh Ko ),양종화 ( Jong Hwa Yang ),이정수 ( Jung Soo Lee ),김대근 ( Dae Geun Kim ) 대한슬관절학회 2011 Knee Surgery and Related Research Vol.23 No.1

Purpose: We wanted to evaluate the post-operative amount of subcutaneous bleeding according to the tourniquet pressure during total knee replacement. Materials and Methods: We analyzed 136 patients who had undergone total knee replacement at our hospital from March 4th, 2010 to September 16th, 2010. A tourniquet pressure of 250 mm Hg was applied to 69 patients (group I) and a tourniquet pressure of 320 mm Hg was applied to the other 67 patients (group II). Subcutaneous bleeding was evaluated on the 3rd and 6th days after the operations. All of the total knee replacements were performed by a single surgeon. Results: Among the group I patients, subcutaneous bleeding was seen in just 2 patients, yet among the group II patients, there were 32 patients with subcutaneous bleeding on the 3rd day and 33 patients with subcutaneous bleeding on the 6th day. According to the multiple regression analysis, there were no significant differences in ages, the tourniquet time and the orders between the two groups. Group 1 had significantly less subcutaneous bleeding than did group II on the 3rd and 6th days after the operations (p=0.001). Conclusion: There was a significant difference of the amount of subcutaneous bleeding amount according to the tourniquet pressure. We were able to decrease the post-operative amount of subcutaneous bleeding after total knee replacement by lowering the tourniquet pressure to 250 mm Hg.

Significance of operating pressure on process intensification in a distillation with side-reactor configuration

Hussain, Arif,Chaniago, Yus Donald,Riaz, Amjad,Lee, Moonyong Elsevier 2019 Separation and purification technology Vol.213 No.-

<P><B>Abstract</B></P> <P>Distillation with side-reactor (SRC) has already established its potential for understanding the energetic and economic performances of chemical processes. This study assesses the impact of operating pressure on reaction performances and overall economics in the SRC design. In conventional distillation operation, pressure is adjusted such that it permits the use of less expensive cooling water (318 K) in the condenser. However, the pressure of the nonreactive distillation column coupled to a side-reactor should be more carefully managed to obtain the process-intensification potential benefits. In the SRC design, the feed to the side-reactor is withdrawn from the column trays where the reactants are more abundant. Higher column pressure requires a more expensive heat source for the column base and causes temperature rise on the column trays. Depending on the kinetic parameters of the reaction, the pressure of the column can be adjusted to improve the conversion, selectivity, yield, and overall economics of the chemical process in an SRC design. A foremost trade-off between the operating pressure and reactor size/catalyst/heat load is demonstrated through three industrial-chemical processes. The outcome of this study affirmed the importance of understanding the impact, on process intensification, of selecting the appropriate operating pressure during the SRC conceptual design.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effect of operating pressure on process intensification in SRC design was studied. </LI> <LI> The dependence of side-reactor volume/catalyst weight/heat duty on pressure was studied. </LI> <LI> Three real chemical processes were simulated to analyze the results. </LI> <LI> Optimal design of SRC configurations was obtained by optimizing pressure. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

기혼여성의 취업여부에 따른 시간압박감과 관련요인의 차이

차승은(Seung-Eun Cha) 가정과삶의질학회 2015 가정과삶의질연구 Vol.33 No.5

The purpose of this study is to examine the differences in perceived time pressure between employed and non-employed married women in Korea. The sample of married couple from the Korean Time Use Survey 2009 (n = 6,948 couple diaries) was used to examined the difference in the level of perceived time pressure over the life cycle of two group. This study also investigated the married womens time use, husbands time use as well as hour of domestic outsourcing and whether such factors are associated with lowering perceived time pressure of married women. Results showed employed wives felt almost 3 times more time pressed than non-employed wives, and the gap mostly remained over different life cycles. Total work hours were associated with increasing the time pressure of both groups of women, while regenerating time was associated with ameliorating time pressure. The result suggests that the time pressure gap between employed and non-employed wives can be partly due to the relative length of total labor hours and regenerating time among the two groups. Ordered logit analysis revealed that husbands paid work hours were not associated with wives feeling rushed, but husband unpaid work hours were positively linked with time pressure of their wives. Results indicated if employed or non-employed wives are feeling very busy, there is a high chance that husband might give them some help. We found employed wives spend more hours on housework outsourcing, and purchasing goods for housework was not associated with lowering the feeling of pressure of employed wives. There were both similarity and difference in factors associated with womens feeling pressed among employed and non-employed wives. It implies that social process and its strategies to alleviate the time pressure can be different by womens employment status.

이동작동기식 완전 이식형 인공 심장의 심실간 공간 압력 파형 해석에 관한 실험적 연구

조영호,최원우 대한의용생체공학회 1997 의공학회지 Vol.18 No.1

To regulate cardiac output of the Total Artificial Heart(TAH) physiologically, the hemodynamic information must be toed back to the controller. So far, our group has developed an automatic cardiac output control algorithm using the motor current waveform, It is, however difficult to detect the preload level such as a filling status of ventricular inflow and the variation of atrial pressures within normal physiologic range(0-15 mmHg) by analyzing the motor current which simultaneously reflects the afterload effect. On the other hin4 the interventricular volume pressure(IVP) which is not influenced by arterload but by preload is a good information source for the estimation of preload states. In order to find the relationship between preload and IVP waveform, we set up the artificial heart system on the Donovan type mock circulatory system and measured the IVP waveform, right and left atrial pressures, inflow and outflow waveforms and the signals represented the information of moving actuator's position. We shows the feasibility of estimating the hemodynamic changes of inflow by using IVP waveform. fife found that the negative peak value of IVP waveform is linearly related to atrial pressures. And we also found that we could use the time to reach the negative peak in IVP waveform, the time to open outflow valve, the area enclosed IVP waveform as unfu parameters to estimate blood filling volume of diastole ventricle. The suggested method has advantages of avoiding thrombogenesis, bacterial niche formation and increasing longterm reliability of sensor by avoiding direct contact to blood.

대학 보디빌딩 선수의 대사적 수용기 자극에 따른 심혈관 반응

김성민(Kim, Sung-Min),최현민(Choi, Hyun-Min),김종경(Kim, Jong-Kyung),노호성(Nho, Ho-Sung) 한국체육과학회 2012 한국체육과학회지 Vol.21 No.3

Previous studies have shown that resistive exercise training such as isometric handgrip exercise or weight lifting decreases arterial blood pressure. However, the mechanisms responsible for reduction in arterial blood pressure have not been investigated. One mechanism that may lower arterial blood pressure is a neural mechanism termed the muscle metaboreflex that is activated when oxygen delivery to active skeletal muscle falls below a critical level. The muscle metaboreflex, a component of exercise pressor reflex, increases the sympathetic activity to heart and vasculature and then increases arterial blood pressure, cardiac output, and ventilation during exercise. Therefore, the purpose of this study was to investigate the effect of the muscle metaboreflex on hemodynamics following fatiguing rhythmic handgrip exercise and circulatory arrest in 10 male collegiate body builders and 10 age-matched controls. All subjects performed 3 min rhythmic handgrip exercise at the exercise intensity of 60% maximal voluntary contraction and 2 min of postexercise circulatory occlusion while heart rate (HR), stroke volume (SV), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured followed by the calculation of cardiac output, mean arterial pressure (MAP), and total vascular conductance (TVC). From resting baseline values, the changes in SBP, DBP, and MAP in body builders during PEI were significantly smaller compared to contol group (SBP: ? 31.2 ㎜Hg vs. ? 36.2 ㎜Hg; DBP: ? 9.9 ㎜Hg vs. ? 18.2 ㎜Hg; MAP: ? 17.0 ㎜Hg vs. ? 24.2 ㎜Hg, respectively). However, there was no difference in CO between two groups (? 2.2 l/min vs. ? 2.2 l/min) and TVC tended to be higher in body builders compared to control group (? 9.0 ml/min/㎜Hg vs. ? 3.9 ml/min/㎜Hg). This study suggest that chronic resistance training may improve the muscle metaboreflex. The mechanism in which the pressor response mediated by the muscle metaboreflex with resistance training is attenuated is due to peripheral vasodilation.

Influences of Mach Number and Flow Incidence on Aerodynamic Losses of Steam Turbine Blade

Yoo, Seok-Jae,Ng, Wing Fai Ng The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.4

An experiment was conducted to investigate the aerodynamic losses of high pressure steam turbine nozzle (526A) subjected to a large range of incident angles ($-34^{\circ}\;to\;26^{\circ}$) and exit Mach numbers (0.6 and 1.15). Measurements included downstream Pitot probe traverses, upstream total pressure, and end wall static pressures. Flow visualization techniques such as shadowgraph and color oil flow visualization were performed to complement the measured data. When the exit Mach number for nozzles increased from 0.9 to 1.1 the total pressure loss coefficient increased by a factor of 7 as compared to the total pressure losses measured at subsonic conditions ($M_2<0.9$). For the range of incidence tested, the effect of flow incidence on the total pressure losses is less pronounced. Based on the shadowgraphs taken during the experiment, it' s believed that the large increase in losses at transonic conditions is due to strong shock/ boundary layer interaction that may lead to flow separation on the blade suction surface.

압력면익단소익이 터빈 동익 압력면스퀼러팁 하류의 팁누설유동 및 압력손실에 미치는 영향

천주홍(Joo Hong Cheon),이상우(Sang Woo Lee) 대한기계학회 2016 大韓機械學會論文集B Vol.40 No.10

본 연구에서는 압력면익단소익의 폭이 터빈 동익 압력면스퀼러팁 하류의 팁누설유동 및 압력손실에 미치는 영향에 대하여 연구하였다. 팁간극비 h/s = 1.36%에 대하여, 흡입면스퀼러의 높이는 hp/s = 3.75%로 일정하게 유지하고, 압력면익단소익의 폭은 w/p = 2.64%, 5.28%, 7.92%, 10.55% 등으로 변화시키면서 실험을 수행하였다. 일반적으로 압력면익단소익의 폭이 증가할수록, 통로와류 영역에서의 압력손실은 감소하였지만 팁누설유동 영역에서는 압력손실이 오히려 증가하였다. 그 결과 익단소익의 폭이 증가할수록, 질량평균 압력손실은 매우 소폭 감소하는 경향을 보였다. 본 연구 결과, 압력면스퀼러팁에 설치된 압력면익단소익은 압력손실 저감에 거의 기여를 하지 못함을 확인할 수 있었다. Effects of pressure-side winglet width on the tip leakage flow and aerodynamic loss downstream of a turbine blade with a pressure-side squealer rim have been investigated for the tip gap-to-span ratio of h/s = 1.36%. The pressure-side squealer has a fixed height-to-span ratio of hp/s = 3.75% and the pressure-side winglet, which is installed at an elevation of tip surface, has width-to-pitch ratios of w/p = 2.64%, 5.28%, 7.92% and 10.55%. The results show that with increasing w/p, aerodynamic loss in the passage vortex region decreases, whereas that in the leakage flow region increases. As a result, the mass-averaged loss coefficient all over the measurement plane tends to decrease minutely with the increment of w/p. It is concluded that the pressure-side winglet for the pressure-side squealer tip can hardly contribute to the tip-leakge loss reduction.

Projection of the rotation form Navier-Stokes equation onto the half-staggered grid

Ji Ryong Cho 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.7

A projection method for computing incompressible fluid flow is proposed. For the method, the rotation form Navier-Stokes equation (NSE), for which the velocity and the total pressure are employed, is discretized on the half-staggered, finite difference spatial grid. The total pressure couples the static pressure gradient and the convection of momentum in the continuous NSE while the half-staggered grid provides weak pressure-velocity coupling in discrete space. These two features interact synergistically for the discretized NSE to produce smooth pressure fields without additional numerical artifacts such as the momentum interpolation. The method preserves the kinetic energy at the inviscid limit condition. Numerical solutions of the decaying Taylor vortex, the inviscid Taylor vortex, the sudden expansion channel and the square-prism wake are presented.

원주방향 볼류트 입구 높이를 수정한 자동차용 터보차저 원심압축기의 성능 향상

Zhou Tianjun,이근식(Geun Sik Lee) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.2

자동차용 터보차저 압축기의 성능 개선을 위해 원주방향의 볼류트 입구 높이들이 수정되었고 디퓨저를 포함한 볼류트에 대한 유동장이 상용 소프트웨어를 사용하여 조사되었다. 기본적으로 잘 설계된 볼류트는 높은 압력회복계수와 낮은 전압력손실계수를 보여주어야 한다. 본 연구에서는 동일한 단면형상과 설단면각(Tongue Angle)을 가지나 원주방향으로는 서로 다른 볼류트 입구 높이를 갖는 두 경우의 원형단면 볼류트가 선정되었다. 하나는 90° 원주방향에서는 단면 중앙으로 유입되나 이후의 원주방향에서는 볼류트 단면 최하단부들을 잇는 접선과 동일한 높이를 유지하면서 점진적으로 하단부로 유입되는 볼류트 형상이다(케이스 1 볼류트). 다른 하나는 설단면에서는 접선방향으로 유입되도록 모든 원주방향에 대하여 입구 높이를 2 ㎜ 낮춘 형상이다(케이스 2 볼류트). 해석결과, 케이스 2 볼류트가 케이스 1 볼류트보다 높은 압력회복계수로 인한 높은 전압력비와 낮은 전압력손실계수로 인한 높은 등엔트로피 효율을 보여주었다. To enhance the performance of an automobile turbocharger compressor, the circumferential inlet heights of the volute were modified and the flow field for the combined region of the diffuser and volute was numerically investigated using commercial software. Basically, a well-designed volute should have a high pressure recovery coefficient and a low loss coefficient for the total pressure. In this study, two circular volutes with the same cross sectional shape and tongue angle, but circumferentially different volute inlet heights, were selected. One volute had the middle inlet in the cross-section at the circumferential angle of 90o but gradually lower inlet heights for the angles between 90° to 360 o with respect to the cross sectional center of the volute, while maintaining the same height between the tangential line connecting the lowest positions of the cross section and the line connecting the volute inlets in the circumferential direction (case 1 volute). The other volute has an inlet height that is 2 ㎜ lower than in case 1 volute such that the tongue section has a tangential inlet (case 2 volute). The results showed that the case 2 volute had a higher total pressure ratio because of its higher pressure recovery coefficient and higher isentropic efficiency, resulting from the lower loss coefficient along the circumferential position than the case 1 volute.