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Measurement of Ground Temperature Distribution at Various Depths
사이드(S.M. Sayeed-Bin-Asad),신용한(Young H. Shin),정한식(Hanshik Chung),정효민(Hyomin Jeong) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Knowledge on ground temperatures is essential for many construction projects. These include the calculations of heat losses of buildings to the ground and the design of thermal energy storage equipment. This study discusses the factors affecting ground temperature and the summer temperature variation with depth. Temperatures were measured in Tongyeong, Korea, with thermocouples inserted in the ground which indicate that the short-period temperature variations are prominent to a depth of approximately 0.5 m. Because of the high thermal inertia of the soil, the temperature fluctuations at the surface of the ground are diminished as the depth of the ground increases. The annual temperature variation of the ground at a depth of 2m is between 15 to 25℃ while at a depth of over 15 m is negligible and the temperature remains constant at about 22℃.
나인(Md. J. Nine),이경환(G. H. Lee),정효민(H. M. Jeong),정한식(H. S. Chung) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The article represents an experimental investigation on pressure drop and friction loss behaviors of free airflow through a rectangular duct fitted with semicircular ribs of uniform height on one principle wall. The aspect ratio of the rectangular duct is AR= 5, duct height was of H= 30 ㎜ and uniform rib heights (e = 3.5 ㎜m) were used for three different rib pitches of 30 mm, 35 ㎜ and 42 ㎜. For this cases, the rib height to hydraulic diameter ratio were e/D = 0.07 and rib height to channel height ratio were e/H = 0.11. The experimental results show some significant effects of static pressure near the wall and at various configurations and different numbers of rib arrangements within test section. Each result is compared with another among different configurations of rib arrangement over the 90 ㎝ X 15 ㎝ copper plate test section. The Reynolds number in the inlet of calculation domain was in a range of 10000 to 30000. Digital micro manometer and pressure transducer were used for taking static pressure of this experiment. Darcy friction factor was used and isothermal pressure drop had been considered in data evaluation. These experiment will be the preliminary investigation for turbulence analysis as heat transfer enhancement using periodic semicircular ribs.
Pressure Features in 3_arm steel pipe in Reciprocating Hydrogen Compression System
M. Sq. Rahaman(라흐만),G. H. Lee(이경환),S. Wibowo(위보워),J. S. Woo(우주식),H. M Jeong(정효민),H. S. Chung(정한식) 한국마린엔지니어링학회 2009 한국마린엔지니어링학회 학술대회 논문집 Vol.2009 No.-
Compressing system is essential parts of hydrogen economy. High pulsation waveforms produced during hydrogen compression can be reduced by employing snubber in the system. There aresome pipes to flow hydrogen between snubbers. An experiment has been conducted to investigate the features of pressure in the pipe placed between snubbers in reciprocating compression system. The 32.6970 ~ 53.1210% pressure pulsation reductions are found with pressure losses 0.1092 ~ 1.4413% by experiment and detail of pressure are obtained by CFD analysis.
M. Sq. Rahman(라흐만),G. H. Lee(이경환),K. S. Lee(이광성),H. S. Chung(정한식),H. M. Jeong(정효민) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.10
Put Renewability and pollutant free energy source makes hydrogen energy popular rapidly. Hydrogen gas pressure which is after passing through reciprocating compressor part has high pulsation wave form. A unit, snubber is used as compressor components to reduce the harmful pulsation waveform and to remove the impurities in the hydrogen gas. An experiment has been conducted to investigate the pulsation reduction performance of different arrangement of snubber i.e. snubber array, single snubber in reciprocating compression system. The single snubber is able to reduce amplitude 55.947% ~ 58.248% (0.444, 0.786, 1.073 and 1.18 ㎪) with 0.475% ~ 1.966% pressure loss. It is found that the pressure fluctuations are reduced from 90.1977% ~ 92.6336% with pressure loss 1.5013% ~ 4.9034% for compressor operation at different speed which ensure the good performance of snubber-array as pulsation damper over single snubber in hydrogen compressing system.