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RISS 인기검색어
- 검색키워드
- 저자 : M. Mostaqur Rahman (검색결과 3 건)
- 무료
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M. Mostaqur Rahman,Keishi Kariya,AKIO MIYARA 대한설비공학회 2017 International Journal Of Air-Conditioning and Refr Vol.25 No.3
Experiments on condensation heat transfer and adiabatic pressure drop characteristics of R134a were performed inside smooth and microfin horizontal tubes. The tests were conducted in the mass flux range of 50 kg/m2s to 200 kg/m2s, vapor quality range of 0 to 1 and saturation temperature range of 20 ∘ C to 35 ∘ C. The effects of mass velocity, vapor quality, saturation temperature, and microfin on the condensation heat transfer and frictional pressure drop were analyzed. It was discovered that the local heat transfer coefficients and frictional pressure drop increases with increasing mass flux and vapor quality and decreasing with increasing saturation temperature. Higher heat transfer coefficient and frictional pressure drop in microfin tube were observed. The present experimental data were compared with the existing well-known condensation heat transfer and frictional pressure drop models available in the open literature. The condensation heat transfer coefficient and frictional pressure drop of R134a in horizontal microfin tube was predicted within an acceptable range by the existing correlation.
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Computation of transonic internal flow around a biconvex airfoil with cavity
M. Mostaqur Rahman,A. B. M. Toufique Hasan,A.K.M. Sadrul Islam,S. Matsuo,T. Setoguchi 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.6
At transonic flow conditions, unsteady self-excited shock waves are frequently observed in several modern internal aeronautical applicationssuch as in turbine cascades, compressor blades, butterfly valves, fans, nozzles, diffusers and so on. The appearance of shock oscillationoften causes serious problems such as aero-acoustic noise, non-synchronous vibration (NSV), intense drag rise, high cycle fatiguefailure (HCF) and buffeting. In recent years, the effect of various passive means on the airfoil are investigated both experimentally andnumerically to find the effectiveness as a shock control device. In the present study, the transonic internal flow around an airfoil using acavity as a passive means of shock control was investigated numerically. Computational results are validated with available experimentaldata. Results showed that the airfoil with cavity significantly reduced the flow field unsteadiness such as the amplitude of pressure oscillationand root mean square of pressure oscillation.
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Pavement Performance Evaluation Models for South Carolina
Md Mostaqur Rahman,M. Majbah Uddin,Sarah L. Gassman 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.7
This paper develops pavement performance evaluation models using data from primary and interstate highway systems in the state of South Carolina, USA. Twenty pavement sections are selected from across the state, and historical pavement performance data of those sections are collected. A total of 8 models were developed based on regression techniques, which include 4 for Asphalt Concrete (AC) pavements and 4 for Jointed Plain Concrete Pavements (JPCP). Four different performance indicators are considered as response variables in the statistical analysis: Present Serviceability Index (PSI), Pavement Distress Index (PDI), Pavement Quality Index (PQI), and International Roughness Index (IRI). Annual Average Daily Traffic (AADT), Free Flow Speed (FFS), precipitation, temperature, and soil type (soil Type A from Blue Ridge and Piedmont Region, and soil Type B from Coastal Plain and Sediment Region) are considered as predictor variables. Results showed that AADT, FFS, and precipitation have statistically significant effects on PSI and IRI for both JPCP and AC pavements. Temperature showed significant effect only on PDI and PQI (p < 0.01) for AC pavements. Considering soil type, Type B soil produced statistically higher PDI and PQI (p < 0.01) compared to Type A soil on AC pavements; whereas, Type B soil produced statistically higher IRI and PSI (p < 0.001) compared to Type A soil on JPCP pavements. Using the developed models, local transportation agencies could estimate future corrective actions, such as maintenance and rehabilitation, as well as future pavement performances.
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