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Jong-Hark?Park Seong-Yeon?YooEmail author 《Journal of Mechanical Science and Technology》2004,18(7):1258-1266
It is important to completely understand heat/mass transfer from a flat plate because it is a basic element of heat/mass transfer.
In the present study, local heat/mass transfer coefficient is obtained for two flow conditions to investigate the effect of
boundary layer using the naphthalene sublimation technique. Obtained local heat/mass transfer coefficient is converted to
dimensionless parameters such as Sherwood number, Stanton number and Colburnj-factor. These also are compared with correlations of laminar and turbulent heat/mass transfer from a flat plate. According
to experimental results, local Sherwood number and local Stanton number are in much better agreement with the correlation
of turbulent region rather than laminar region, which means analogy between heat/mass transfer and momentum transfer is more
suitable for turbulent boundary layer. But average Sherwood number and average Colburnj-factor representing analogy between heat/mass transfer and momentum transfer are consistent with the correlation of laminar
boundary layer as well as turbulent boundary layer. 相似文献
2.
Park Seong-Yeon; Belsky Jay; Putnam Sam; Crnic Keith 《Canadian Metallurgical Quarterly》1997,33(2):218
In this study, the authors examine temperament (12-13 months) and mothering and fathering (15, 21, 27, 33 months) antecedents of inhibition of children at age 3 years prospectively in a sample of 125 firstborn boys and retrospectively in only the most and least inhibited children. High negativity coupled with low positivity in infancy predicted high inhibition, as did parenting that was supportive (e.g., high sensitivity, low intrusiveness). Parenting appeared more influential in the case of children who were highly negative as infants. The importance of distinguishing positive and negative emotionality in infancy and of studying mothering and fathering are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
Seong-Yeon Yoo Hwa-Kil Kwon Jin-Hyuk Kim 《Journal of Mechanical Science and Technology》2007,21(3):505-512
Cross-flow over tube banks is commonly encountered in practice in heat transfer equipments. The local and average heat transfer
characteristics for staggered tube banks are investigated in the present study. A naphthalene sublimation technique is employed
to obtain the local heat transfer coefficients, and experiments are performed for various tube spacings, tube locations and
Reynolds numbers. The variation of the local heat transfer coefficients is quite different from the first tube to the third
tube, but they are similar afterwards. The average Nusselt number increases more than 30% and 65% on the second and third
tubes, respectively, in comparison with that of the first tube. And the empirical correlations for average heat transfer coefficients
are compared with the conventional heat transfer correlations. 相似文献
4.
Seong-Yeon Yoo Jin-Hyuck Kim Myoung-Seok Jie 《Journal of Mechanical Science and Technology》2010,24(4):887-892
When circulated air passes through the cooling coil in an air-conditioning system, the air is over-cooled to eliminate the
moisture and decrease the temperature. The cooled air is then reheated to recover the temperature. The purpose of the present
study was to evaluate the performance of a cooling/reheating system with regard to both cooling and reheating energy savings
affected by exchanging heat between the cooled air and the reheated air with a compact heat exchanger. The thermal and dehumidification
behaviors of the system were evaluated experimentally and then compared with simulation data. The results show that the energy
saving rate was as high as 50% under the present experimental conditions and was affected by the face velocity of the heat
exchanger, the inlet temperature, the inlet humidity ratio, and the effectiveness of heat exchanger. Furthermore, the experimental
data were found to be in fairly good agreement with the simulation data. 相似文献
5.
Seong-Yeon?YooEmail author Dong-Seong?Park Min-Ho?Chung Sang-Yun?Lee 《Journal of Mechanical Science and Technology》2002,16(1):109-115
Vortex generators are fabricated on the fin surface of a fin-tube heat exchanger to augment the convective heat transfer. In addition to horseshoe vortices formed naturally around the tube of the fin-tube heat exchanger, longitudinal vortices are artificially created on the fin surface by vortex generators. The purpose of this study is to investigate the local heat transfer phenomena in the fin-tube heat exchangers with and without vortex generators, and to evaluate the effect of vortices on the heat transfer enhancement. Naphthalene sublimation technique is employed to measure local mass transfer coefficients, then analogy equation between heat and mass transfer is used to calculate heat transfer coefficients. Experiments are performed for the model of fin-circular tube heat exchangers with and without vortex generators, and of fin-flat tube heat exchangers with and without vortex generators. Average heat transfer coefficients of fin-flat tube heat exchanger without vortex generator are much lower than those of fin-circular tube heat exchanger. On the other hand, fin-flat tube heat exchanger with vortex generators has much higher heat transfer value than conventional fin-circular tube heat exchanger. At the same time, pressure losses for four types of heat exchanger is measured and compared. 相似文献
6.
Seong-Yeon Yoo Jin-Hyuck Kim Kyu-Hyun Han 《Journal of Mechanical Science and Technology》2010,24(4):893-898
In closed wet cooling towers, the heat transfer between the air and external tube surfaces can be composed of the sensible
heat transfer and the latent heat transfer. The heat transfer coefficient can be obtained from the equation for external heat
transfer of tube banks. According to experimental data, the mass transfer coefficient was affected by the air velocity and
spray water flow rate. This study provides the correlation equation for mass transfer coefficient based on the analogy of
the heat and mass transfer and the experimental data. The results from this correlation equation showed fairly good agreement
with experimental data. The cooling capacity and thermal efficiency of the closed wet cooling tower were calculated from the
correlation equation to analyze the performance of heat exchanger for the tower. 相似文献
7.
Direct contact air conditioning systems, in which heat and mass are transferred directly between air and water droplets, have
many advantages over conventional indirect contact systems. The purpose of this research is to investigate the cooling and
heating performances of direct contact air conditioning system for various inlet parameters such as air velocity, air temperature,
water flow rate and water temperature. The experimental apparatus comprises a wind tunnel, water spray system, scrubber, demister,
heater, refrigerator, flow and temperature controller, and data acquisition system. The inlet and outlet conditions of air
and water are measured when the air contacts directly with water droplets as a counter flow in the spray section of the wind
tunnel, and the heat and mass transfer rates between air and water are calculated. The droplet size of the water sprays is
also measured using a Malvern Particle Analyzer. In the cooling conditions, the outlet air temperature and humidity ratio
decrease as the water flow rate increases and as the water temperature, air velocity and temperature decrease. On the contrary,
the outlet air temperature and humidity ratio increase in the heating conditions as the water flow rate and temperature increase
and as the air velocity decreases. 相似文献
8.
Sang-Tae Kim Young-Jin Kim Nam-Yong Joung Dong-Seok Im Kang-Pyo Kim Kyung-Min Kim Eun-Nam Bang Yaung-Soo Kim Seong-Yeon Yoo 《Fusion Engineering and Design》2013,88(11):2967-2971
A baking system for the Korea Superconducting Tokamak Advanced Research (KSTAR) plasma facing components (PFCs) is designed and operated to achieve vacuum pressure below 5 × 10?7 mbar in vacuum vessel with removing impurities. The purpose of this research is to prevent the fracture of PFC because of thermal stress during baking the PFC, and to accomplish stable operation of the baking system with the minimum life cycle cost. The uniformity of PFC temperature in each sector was investigated, when the supply gas temperature was varied by 5 °C per hour using a heater and the three-way valve at the outlet of a compressor. The alternative of the pipe expansion owing to hot gas and the cage configuration of the three-way valve were also studied. During the fourth campaign of the KSTAR in 2011, nitrogen gas temperature rose up to 300 °C, PFC temperature reached at 250 °C, the temperature difference among PFCs was maintained at below 8.3 °C, and vacuum pressure of up to 7.24 × 10?8 mbar was achieved inside the vacuum vessel. 相似文献
9.
Seong-Yeon Kim Seung-Boo Jung Chang-Chae Shur Yun-Mo Yeon Dae-Up Kim 《Journal of Materials Science》2003,38(6):1281-1287
This paper describes a fundamental investigation of friction welding pure copper to titanium. Friction welding was performed using a brake type friction welder. The effect of friction time and upset pressure on the mechanical and metallurgical properties were evaluated. Under constant upset pressure, the tensile strength made little difference with an increase in friction time, whereas at the constant friction time, the tensile strength increased with increasing upset pressure. Thus, the upset pressure plays a major role over the friction time and friction pressure on tensile strength. Though Cu3Ti intermetallic compound is formed at the copper/titanium interface during welding, the tensile strength of welded joint is not affected. It may be due to the thickness of intermetallic compound layer at interface being very thin and scattered. The tensile fracture of the welded joint occurred in copper side near the interface. 相似文献
10.
Seong-Yeon Yoo Kee-Young Yoon Kyung-Am Park 《Journal of Mechanical Science and Technology》1997,11(5):574-581
Flow characteristics of a swirl generator are studied using an open circuit flow loop, and influence of upstream swirl on the discharge coefficients of sonic nozzles is investigated using a high pressure gas flow standard measurement system. The open circuit flow loop consists of swirl generator, testsection, sonic nozzle, suction fan and LDV system. The gas flow measurement system comprises two compressors, storage tank, temperature control loop, sonic nozzle testsection, weighing tank, gyroscopic scale and data acquisition system. Experiments are performed at various nozzle throat diameters, inlet pressures and angles of swirl generator. As the angle of swirl generator becomes larger, axial velocities decrease near the wall and rapidly increase in the pipe core, and swirl velocities increase to form swirl flow. Influence of upstream swirl on discharge coefficients becomes greater as the intensity of swirl increases and as the nozzle throat diameter is enlarged. Variation trend with Reynolds number, however, is very similar each other regardless of swirl intensity. 相似文献
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