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Effects of recessed blade tips on the performance and flow field in a centrifugal compressor
Jung, Yohan,Choi, Minsuk,Park, Joon-Young,Baek, Je Hyun SAGE Publications 2013 Proceedings of the Institution of Mechanical Engin Vol.227 No.2
<P>This article presents a numerical investigation of the influence of a recessed blade tip on the performance and flow field in a centrifugal compressor with a vaned diffuser. Steady computations were performed for three different blade tip geometries over their whole operating ranges. A flat tip blade was used as a baseline case to assess two different recessed blade geometries. It was found that recessed blade tip designs could improve the total-to-total pressure ratio and efficiency over whole operating ranges. The recessed tips were also effective in reducing the tip leakage flow. However, the recess cavity had an adverse effect on the efficiency due to the generation of a vortex in the cavity. As a result, the overall stage loss was reduced in the recessed cases because the positive effect of the reduced tip leakage flow ended up being superior to the negative effect of a strong vortex in the cavity. In addition, the diffuser performance of the centrifugal compressor could be enhanced with the recess cavity, because the pressure recovery coefficient was higher in the recessed cases than in the flat tip case. A parametric study was conducted to determine the geometry of a recess cavity with improved performance. This study revealed that as the cavity volume increases, the tip leakage flow continuously decreases but the strength of the cavity vortex increases. Therefore, it may be possible to optimize the recess cavity geometry further.</P>
Yohan Kim,Jung-Jin Lee,Sang-Gil Lee,Sang-Hyuk Jung,Joo-Hui Han,So Young Yang,Eunju Yun,Gyu-Yong Song,Chang-Seon Myung 대한생리학회-대한약리학회 2013 The Korean Journal of Physiology & Pharmacology Vol.17 No.3
As the abnormal proliferation of vascular smooth muscle cells (VSMCs) plays a critical role in the development of atherosclerosis and vascular restenosis, a candidate drug with antiproliferative properties is needed. We investigated the antiproliferative action and underlying mechanism of a newly synthesized naphthoquinone derivative, 5,8-dimethoxy-2-nonylamino-naphthalene-1,4-dione (2-nonylamino- DMNQ), using VSMCs treated with platelet-derived growth factor (PDGF). 2-Nonylamino-DMNQ inhibited proliferation and cell number of VSMCs induced by PDGF, but not epidermal growth factor (EGF), in a concentration-dependent manner without any cytotoxicity. This derivative suppressed PDGF-induced [<sup>3</sup>H]-thymidine incorporation, cell cycle progression from G<sub>0</sub>/G<sub>1</sub> to S phase, and the phosphorylation of phosphor-retinoblastoma protein (pRb) as well as the expression of cyclin E/D, cyclin-dependent kinase (CDK) 2/4, and proliferating cell nuclear antigen (PCNA). Importantly, 2-nonylamino-DMNQ inhibited the phosphorylation of PDGF receptorՂ(PDGF-RՂ) enhanced by PDGF at Tyr<sup>579</sup>, Tyr<sup>716</sup>, Tyr<sup>751</sup>, and Tyr<sup>1021</sup> residues. Subsequently, 2-nonylamino-DMNQ inhibited PDGF- induced phosphorylation of STAT3, ERK1/2, Akt, and PLCՃ1. Therefore, our results indicate that 2-nonylamino-DMNQ inhibits PDGF-induced VSMC proliferation by blocking PDGF-RՂ autophosp- horylation, and subsequently PDGF-RՂ-mediated downstream signaling pathways.
낮은 핀관과 Turbo-B 촉진관에서 임계 열유속까지의 풀 비등 열전달계수
이요한(Yohan Lee),박기정(Ki-Jung Park),정동수(Dongsoo Jung),심상은(Sang Eun Shim) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
In this work, nucleate pool boiling heat transfer coefficients(HTCs) of 5 refrigerants of differing vapor pressure are measured on horizontal 26 fpi low fin and Turbo-B square surface of 9.53 ㎜ length. Tested refrigerants are R245fa, R152a, R134a, R22, and R32 and HTCs are taken from 10 ㎾/㎡ to critical heat flux of each refrigerant. Wall and fluid temperatures are measured directly by thermocouples located underneath the test surface and by thermocouples in the liquid pool. Test results show that the nucleate pool boiling HTCs of refrigerants increase as the vapor pressure increase. However, as the heat flux increases, the nucleate boiling HTCs increase and then decrease after certain heat fluxes gradually. Critical heat fluxes(CHFs) of all enhanced surfaces were greatly improved as compared to that of a plain surface in all tested refrigerants. CHFs of all refrigerants on the 26fpi low fin surface were increased up to 240% as compared to that of the plain surface. CHFs of the Turbo-B enhanced surface were lower than that of the 26fpi low fin surface.
Kim, Yohan,Lee, Jung-Jin,Lee, Sang-Gil,Jung, Sang-Hyuk,Han, Joo-Hui,Yang, So Young,Yun, Eunju,Song, Gyu-Yong,Myung, Chang-Seon The Korean Society of Pharmacology 2013 The Korean Journal of Physiology & Pharmacology Vol.17 No.3
As the abnormal proliferation of vascular smooth muscle cells (VSMCs) plays a critical role in the development of atherosclerosis and vascular restenosis, a candidate drug with antiproliferative properties is needed. We investigated the antiproliferative action and underlying mechanism of a newly synthesized naphthoquinone derivative, 5,8-dimethoxy-2-nonylamino-naphthalene-1,4-dione (2-nonylamino-DMNQ), using VSMCs treated with platelet-derived growth factor (PDGF). 2-Nonylamino-DMNQ inhibited proliferation and cell number of VSMCs induced by PDGF, but not epidermal growth factor (EGF), in a concentration-dependent manner without any cytotoxicity. This derivative suppressed PDGF-induced $[^3H]$-thymidine incorporation, cell cycle progression from $G_0/G_1$ to S phase, and the phosphorylation of phosphor-retinoblastoma protein (pRb) as well as the expression of cyclin E/D, cyclin-dependent kinase (CDK) 2/4, and proliferating cell nuclear antigen (PCNA). Importantly, 2-nonylamino-DMNQ inhibited the phosphorylation of PDGF receptor${\beta}$(PDGF-$R{\beta}$) enhanced by PDGF at $Tyr^{579}$, $Tyr^{716}$, $Tyr^{751}$, and $Tyr^{1021}$ residues. Subsequently, 2-nonylamino-DMNQ inhibited PDGF-induced phosphorylation of STAT3, ERK1/2, Akt, and $PLC{\gamma}1$. Therefore, our results indicate that 2-nonylamino-DMNQ inhibits PDGF-induced VSMC proliferation by blocking PDGF-$R{\beta}$ autophosphorylation, and subsequently PDGF-$R{\beta}$-mediated downstream signaling pathways.
R1234yf와 R1234yf/R134a의 자동차 에어컨 작동 조건에서의 성능 평가
박기정(Ki-Jung Park),이요한(Yohan Lee),최대성(Daeseong Choe),정동수(Dongsoo Jung) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.12
In this study, performance of R1234yf and R1234yf/R134a mixture is measured on a heat pump bench tester in an attempt to substitute R134a used widely in mobile air conditioners (MACs). The bench tester is equipped with a open type compressor providing a nominal capacity of 3.5 ㎾. All tests are conducted under the summer cooling and winter heating conditions of 7/4 5℃ and -7/41℃ in the evaporator and condenser, respectively. For R1234yf/R134a mixture, measurements are made at 5%, 10%, and 15% of R134a by mass. Test results show that the coefficient of performance (COP) and capacity of R1234yf are up to 2.7% and 4.0% lower than those of R134a, respectively. For R1234yf/R134a mixture, the COP and capacity are up to 3.9% lower and 3.6% higher than those of R134a. For R1234yf and R1234yf/R134a mixture, the compressor discharge temperature is 4.1~6.7℃ lower than that of R134a while the amount of charge is reduced up to 11% as compared to R134a. 90%R1234yf/10%R134a is a better refrigerant than pure R1234yf in that it is less flammable and more compatible with existing R134a system. Based upon the results, it is concluded that R1234yf and R1234yf/R134a mixture are long term environmentally friendly solutions to mobile air-conditioners due to their excellent environmental properties with acceptable performance.
평활관과 낮은 핀관에서 R245fa의 풀 비등 열전달계수
박기정(Ki-Jung Park),이요한(Yohan Lee),임병덕(Byeongdeok Lim),정동수(Dongsoo Jung) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.3
In this work, pool boiling heat transfer coefficients(HTCs) of R22, R123, R134a, and R245fa are measured on both horizontal plain and 26 fpi low fin tubes. The pool boiling temperature is maintained at 7℃ and heat flux is varied from 80 ㎾/㎡ to 10 ㎾/㎡ with an interval of 10 ㎾/㎡. Wall temperatures are measured directly by thermocouples inserted through holes of 0.5 ㎜ diameter. Test results show that HTCs of high vapor pressure refrigerants are usually higher than those of low pressure fluids in both plain and low fin tubes. On a plain tube, HTCs of R245fa are 23.3% higher than those of R123 while on a 26 fpi low fin tube, HTCs of R245fa are 46.3% higher than those of R123. The fin effect is more prominent with low vapor pressure refrigerants than with high vapor pressure ones due to a sweeping effect.