• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.3
• /
• pp.259-268
• /
• 2012

This study measured the natural-convection heat transfer of two vertically staggered cylinders with varying vertical pitch-to-diameter ($P_v$/D) and horizontal pitch-to-diameter ($P_h$/D) ratios. The measured heat-transfer rates for the lower cylinder agreed well with the existing heat-transfer correlations for a single cylinder. At the smallest $P_v$/D, the rising plume from the lower cylinder provides the upper cylinder with a preheated flow, and the heat-transfer rates of the upper cylinder decrease, but increase very sensitively with $P_h$/D. However, at the largest $P_v$/D, the velocity effect dominates, and the heat-transfer rates of the upper cylinder are larger than that of a single cylinder, and decrease less sensitively with $P_h$/D. Even if $P_h$/D is increased, the heat-transfer rate of the upper cylinder is higher than that of the lower cylinder because of the chimney and side flow effects. This work expanded the flow ranges to turbulent flows. The cupric acid-copper sulfate ($H_2SO_4-CuSO_4$) electroplating system was adopted for the measurements of the mass-transfer rates instead of the heat-transfer experiments based on the analogy concept. The measurements were made by varying $P_v$/D (1.02-5) and $P_h$/D (0-2) in both laminar and turbulent flows. The Rayleigh number ranged from $1.5{\times}10^8$ to $2.5{\times}10^{10}$, and the Prandtl number was 2,014.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.1
• /
• pp.33-42
• /
• 2011

In this study, we investigated the natural convection on the outer surface of a vertical pipe by performing mass transfer experiments using fluids with high Pr number using the concept of analogy between heat and mass transfer. A cupric acid-copper sulfate electroplating system was adopted as the mass transfer system. Tests were performed for $Ra_H$ numbers from $1.4{\times}10^9$ to $4{\times}10^{13}$, Pr numbers from 2,094 to 4,173, and diameters from 0.005 m to 0.035 m. The test results for laminar flow conditions were in good agreement with the correlations reported by King, Jakob and Linke, McAdam, and Bottemanne, and those for turbulent conditions with the correlations presented by Fouad for a vertical plate and also proved the dependence on Pr numbers. The obtained correlations were $Nu_H=0.55Ra^{0.25}_H$ for laminar and $Nu_H=0.12Ra^{0.28}_HPr^{0.1}$ for turbulent. The transition between laminar and turbulent occurs at $Ra_H$ of about $10^{12}$.

• Journal of Energy Engineering
• /
• v.21 no.1
• /
• pp.18-25
• /
• 2012

This work investigated the influence of the chimney dimensions(exit and entrance length, and diameter) on the heat transfer of a vertical cylinder in a duct. The measured mass transfer rates for the natural convection of vertical cylinder in a duct were presented for Prandlt number 2,094, Rayleigh number in the range of $4.55{\times}10^9$, $5.79{\times}10^{10}$, and $1.69{\times}10^{11}$. Experiments were performed using a copper sulfate electroplating system to simulate heat transfer based upon the analogy concept. The diameter of the duct was varied from 0.06 m to 0.14 m, and the heights from 0.30 m to 1.10 m. Nusselt numbers measured at open channel condition agreed well with the existing laminar heat transfer correlations for vertical plate developed by Le Fevre. The increase of the exit length enhanced the heat transfer up to a certain duct height but further increase does not affects the heat transfer. The heat transfer decreased with increasing the entrance length up to a certain duct height and was constant at further increase. The Nusselt number decreased with increasing the diameter of duct, until Nusselt number becomes similar to that at open channel beyond a certain diameter.

• Journal of Energy Engineering
• /
• v.20 no.3
• /
• pp.242-251
• /
• 2011

The effects of top and bottom lids on the natural convection heat transfer phenomena inside vertical cylinders were investigated experimentally for $Ra_{Lw}$ from $9.26{\times}10^9$ to $7.74{\times}10^{12}$. Using the concept of analogy between heat and mass transfer, a cupric acid-copper sulfate electroplating system was employed as mass transfer experiments replacing heat transfer experiments. The natural convection heat transfer of both-open cylinders in laminar and turbulent flows was in good agreement with the existing heat transfer correlations developed for vertical plates. The effects of top and bottom lids on the heat transfer rates were very similar to the studies of Krysa et al. and Sedahmed et al. and Chung et al. With the copper lids, the bottom-closed cavity showed the highest heat transfer rates and then followed both-closed, top-closed, both-open ones in both laminar and turbulent flows. However with the acryl lids, the similar trends were observed except that the heat transfer rates for both-open were higher than top-closed one. The use of the copper lids increased the heat transfer rates compared to the acryl lids due to the hydrodynamic interaction of the flows developed for the different heated faces. This study extended the ranges of flow conditions of the existing literatures and proposed the empirical correlations.

• Journal of The Korean Association For Science Education
• /
• v.18 no.3
• /
• pp.273-282
• /
• 1998

The purpose of this study is to compare the effect of concept formation between conflicted case and non-conflicted case as a method of learning science concepts. This study consists of 8 classes in 5th and 6th grade of elementary school children's in Kyoung-Buk, which were divided into conflicted group and non-conflicted group. The research procedure is as follows : first, two groups were asked the introducing problems-one was asked the conflicting problem, the other was asked the non-conflicting problems. Futhermore, the incorrect-answered students of conflicting problems were classified into conflict group am the correct-answered students of non-conflicting problems were classified into non-conflict group. Secondly, the demonstration and picture presentation about the introducing problems were carried out. Thirdly, the researcher introduced scientific concepts to the students. Afterwards, posttests, made up of the same items, were presented to the students-three times-posttest, delayed posttest(one week), second delayed posttest(one month). Finally, the degree of concept formation between the two groups was compared and analyzed by these results.

• Journal of the Korean earth science society
• /
• v.26 no.6
• /
• pp.461-468
• /
• 2005

The purpose of this study is to investigate the abilities of 6th grade students to assess the relationship between spatial capability, concept of celestial motion, and science process skills, which can help find a better teaching strategy for students in understanding the concept of celestial motion. The results are as follows. First, in terms of level of accomplishment of these three skills, male students show higher level of accomplishment than female students, but significant differences are found. Second, according to the analysis of the effect of spatial capability and concept of the movement of heavenly bodies, the former has a stronger influence on the students' cognition of celestial motion. Minor elements of spatial capability that influence the conception of celestial motion are device analogy, calculation of wood cut, and revolving light. Third, spatial capability is very influential on the level of accomplishment in science process skills. Among the minor elements of spatial capability that is influential to science process skills, calculation of wood cut is the highest, especially when various elements are interactively related to each other.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.11 no.1
• /
• pp.9-16
• /
• 1991

The concept of damage is all-pervasive in structural engineering. It can be considered a state variable and defined to vary from 0(no damage) to 1(failure). Thus, the factor of safety against failure, the most important aspect of a structure, cannot be assessed without evaluating the damageability of a structure under load. It is the objective of the research reported herein to study the behavior of concrete under repeated load applications. Concrete is known to deteriorate under such loading, i.e., it suffers damage of increasing degree. Its response to future loading is a function of the amount of damage sustained during previous load exposures. The same can be said about reinforced concrete members and entire structures, but here we wish to consider only plain concrete and express some of its material properties as functions of the degree of sustained damage. The work described herein is based on the stipulation that the energy dissipation capacity of plain concrete is a material property and the damage accumulates in direct proportion to the degree to which the energy dissipation capacity is being exhausted, in some analogy to both high- and low-cycle failure behavior of materials.

• Archives of design research
• /
• v.15 no.4
• /
• pp.139-148
• /
• 2002

This study deals with the occurrence and application of 'Fun' as a linguistic function through form-giving. As a linguistic function, Fun could be defined, in a broad sense, as an emotion of desire when in relation to artifacts, and, in a narrow sense, as a physical or mental response when a person discovers unexpected information or artifacts. Hence, the occurrence of 'Fun' could be an analogy of a removal of a 'mental block' from using (or perceiving) artifacts. As an aspect of cognitive psychology, the context of form-giving, which has meanings in both artifact and design activity, will deal with an important factor of form-giving. From that, the elements of the context and the transformation of the elements are suggestive of 'Fun-oriented form-giving'. Hence, this study will show how to deal with that elements, what is required condition on it, 'Fun' in form-giving, and the Mechanism of Occurrence of 'FUN' based on this study, will be expected to apply them for product-concept effectively and Form-Giving fashionably.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.24 no.2
• /
• pp.76-88
• /
• 1982

The stream morphological characteristics of a basin have important influence upon the analysis of runoff. In this study, the laws of stream morphology-the law of average stream fall and the law of least rate of potential energy expenditure-which were derived based on the analogy of entropy in thermodynamics are introduced and their validity is analysised with the data taken from the topographic maps covering the whole Geum River system. The first law is the Law of Average Stream Fall which states that under the dynamic equilibrium condition the ratio of average fall between any two different order stream in the same river basin in unity. The second law is the law of least rate of energy expenditure which states that all natural streams are intended to choose their own course of flow such that the rate of potential energy loss per unit mass of water this course is a minimum. The parameters representing the morphological characteristics of 13 tributaries in the Geum River system such as stream bifurcation ratio and stream concavity were Computed from the Horton-Strahler's laws and are used to check the law of average stream fall. The result showed that the law of average stream fall agrees reasonably well with law of Horton-Strahler. Concavity of a river basin is shown to be the determinative factor to the formation of a stream system. Concavity of a river basin is shown to be the determinative factor to the formation of a stream system. Based on Horton's Law and the law of average stream fall, longitudinal stream profiles can be calculated.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.68-73
• /
• 2002

In standard teletherapy, a treatment plan is generated with the aid of a treatment planning system, but it is common to perform an independent monitor unit verification calculation (MUVC). In exact analogy, we propose and demonstrate that a simple and accurate MUVC in Intensity Modulated Radiotherapy (IMRT) is possible. We introduce a concept of Modified Clarkson Integration (MCI). In MCI, we exploit the rotational symmetry of scattering to simplify the dose calculation. For dose calculation along a central axis (CAX), we first replace the incident IMRT fluence by an azimuthally averaged fluence. Second, the Clarkson Integration is carried over annular sectors instead of over pie sectors. We wrote a computer code, implementing the MCI technique, in order to perform a MUVC for IMRT purposes. We applied the code to IMRT plans generated by CORVUS. The input to the code consists of CORVUS plan data (e.g., DMLC files, jaw settings, MU for each IMRT field, depth to isocenter for each IMRT field), and the output is dose contribution by individual IMRT field to the isocenter. The code uses measured beam data for Sc, Sp, TPR, (D/Mu)$\_$ref/ and includes effects from MLC transmission, and radiation field offset. On a 266 MHZ desktop computer, the code takes less than 15 sec to calculate a dose. The doses calculated with MCI algorithm agreed within +/- 3% with the doses calculated by CORVUS, which uses a 1cm x 1cm pencil beam in dose calculation. In the present version of MCI, skin contour variations and inhomogeneities were neglected.