• 설비공학논문집
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• 제16권11호
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• pp.1077-1083
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• 2004

This study is to systematically analyze the effect of various kinds of design factors on the performance of stratified thermal storage tank. Taguchi method, known as a very reasonable tool in the parametric study, is employed in the present work. Three dimensional unsteady numerical experiment is conducted for 4 design parameters of stratified thermal storage tank: inlet Reynolds number, Froude number, diffuser size d with 3 levels (Re=400, 800, 1200, Fr=0.5, 1.0, 2.0 and d=150 mm, 200mm, 300 mm) and diffuser shape with 2 levels. Orthogonal array $L_{18}(2{\times}3^7)$ is adopted for the analysis of variance. The result gives quantitative estimation of the various design parameters affecting the performance and helps to select the main factors for the optimum design of stratified thermal storage tank. Reynolds number is found to be the most dominant parameter and the diffuser shape plays significant role on the performance of stratified thermal storage tank. Based on this finding, the prior questions on the contribution of the diffuser shape proposed by the authors become clear. The optimum condition for the performance is a set of d=300mm, Re=800, and radial regulated plate diffuser. Conformation test shows the repeatability in the analysis and $1.3\%$ difference between the estimated thermocline thickness and that of numerical result.

• 설비공학논문집
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• 제21권1호
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• pp.16-22
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• 2009

In order to investigate $CO_2$ heat transfer coefficient and pressure drop by PAG oil concentration during $CO_2$ evaporation, the experiment on evaporation heat transfer characteristics in a mini-channels were performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes($300{\sim}800kg/m^{2}s$), heat fluxes($10{\sim}40kW/m^2$) saturation temperatures($-5{\sim}5^{\circ}C$), and PAG oil concentration(0, 3, 5wt%). The variation of the heat transfer coefficient was different according to the oil concentration. With the increase of the oil concentration, the evaporation heat transfer coefficient decreased and the delay of dryout by oil addition was found. Pressure drop increased with the increase of the oil concentration and heat flux, and the decrease of saturation temperature.

• 설비공학논문집
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• 제21권2호
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• pp.79-86
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• 2009

The present study was investigates the effect of the parameters on the frost formation and heat transfer performance such as fin shape, air temperature and air velocity. Heat transfer rate and pressure drop by frost were experimentally investigated. Effect of the wet blub temperature and air velocity on the heat transfer performance has been also investigated. The heat transfer performance of the louver fin and tube type heat exchanger was higher by maximum of 0.85% than the corrugate fin type at the air temperature of $2.0/1.5^{\circ}C$. As the wet blub temperature of air were increased, the heat transfer rate, pressure drop and mass of frost of three test models were increased. Especially, the maximum heat transfer rate and maximum pressure drop were shown for the Type B louver fin heat exchanger. As an experimental result, the enhancement factor(EF) of louver fin and tube type heat exchanger was only $0.2{\sim}0.4$ due to the high pressure drop.

• 한국식품영양과학회지
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• 제33권5호
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• pp.911-916
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• 2004

우리나라 식단에 이용되는 채소 중 비교적 이용 빈도가 높은 양파와 콩나물, 당근의 통상적인 데치기를 통하여, 조리 후 냉장저장(cook/chill)하여 단체급식 현장에서 단순히 가열하여 제공하는 경우, 채소류의 조직감을 안정적으로 유지할 수 있었다. 양파와 콩나물, 당근 모두 7$0^{\circ}C$에서 각각 20분, 10분, 30분 동안 열처리하였을 때 조직강도가 높게 나타났으나, 실질적으로는 10분 이상으로 일정한 효과를 얻을 수 있을 것으로 판단된다. 또한 데치기 할 때 칼슘이온의 첨가로 조직감의 향상을 얻을 수 있었으며, 그 효과는 당근이 가장 크게 나타났고, 콩나물은 상대적으로 크지 않았다. 칼슘이온의 첨가에 의해 데치기 후 냉장조건에서 5일까지 저장한 후 재 가열하여도 초기의 조직강도 이상으로 유지되었다. 그러므로 데치기를 한 채소를 이용하여 대규모로 조리 한 뒤, 냉장 저장 후 단체급식현장에서 가열하여 제공하면, 고온에서 조리한 뒤, 저장하는 동안 채소의 연화에 의한 품질의 저하를 극복할 수 있을 것으로 기대된다.

• 설비공학논문집
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• 제20권1호
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• pp.49-56
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• 2008

When the outdoor air temperature decreased less than the freezing temperature, frost forms at the surface of heat exchangers and it makes the performance degradation of a heat pump system. In this study, a heat pump system has been developed which has a refrigerant heating device as an auxiliarly heating equipment. To reduce power consumptions of the system, a liquid pump, rather than a compressor, was used to drive refrigerant in the heat pump cycle. Ratio of refrigerant mass flow between a refrigerant heating heat exchanger(GHX) and a outdoor plate heat exchanger(PHX) was varied and the system performance was measured and analyzed. As results, when the refrigerant flow rate to the GHX was decreased, the system performance is decreased due to heat absorption capability restriction of the GHX and small variation of the power consumption in the compressor. The effect on the evaporating and condensing pressure by the distribution ratio of the refrigerant to the each heat exchanger is small compare to the effect by the frequency change in the compressor. When the compressor was replaced by the liquid pump, the capacity of the system decreased a little, however the power consumption decrease approximately 80% compare with the power used in the compressor.

• 설비공학논문집
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• 제25권5호
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• pp.279-288
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• 2013

Heat transfer and pressure drop characteristics of fin-and-tube heat exchangers having sine wave fins and oval tubes were investigated. Oval tubes having an aspect ratio of 0.6 were made, by deforming 12.7 mm round tubes. Twelve samples, having different fin pitch and tube row, were tested. The effect of fin pitch on the j and f factors was negligible. The effect of the tube row on the j factor, however, was different from that of common fin-and-tube heat exchangers having plain fins and round tubes. The highest j factor was obtained for a two-row configuration, while the lowest one was obtained for a one-row configuration. A possible reason was attributed to the flow mixing characteristics of the sine wave channel of the present geometry. Comparison with a plain fin-and-tube heat exchanger having 15.88 mm O. D. round tube reveals that the present oval fin-and-tube heat exchanger shows generally superior thermal performance, except for the one-row configuration.

• 설비공학논문집
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• 제25권5호
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• pp.269-278
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• 2013

In this study, in order to examine the applicability of computational fluid dynamics with the porous model to the analysis of APR+ (Advanced Power Reactor Plus) internal flow, simulation was conducted with the commercial multi-purpose computational fluid dynamics software, ANSYS CFX V.14. In addition, among the various reactor internals, the effect of flow skirt geometry on reactor internal flow was investigated. It was concluded that the porous model for some reactor internal structures could adequately predict the hydraulic characteristics inside the reactor in a qualitative manner. If sufficient computation resource is available, the predicted core inlet flow distribution is expected to be more accurate, by considering the real geometry of the internal structures, especially located in the upstream of the core inlet. Finally, depending on the shape of the flow skirt, the flow distribution was somewhat different locally. The standard deviation of the mass flow rate (${\sigma}$) for the original shape of flow skirt was smaller, than that for the modified shape of flow skirt. This means that the original shape of the flow skirt may give a more uniform distribution of mass flow rate at the core inlet plane, which may be more desirable for the core cooling.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2003년도 심포지엄
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• pp.9-18
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• 2003

A method for rapid propagation of mature Jack fruit was developed. Four types of explants (mature embryos, apical meristems of young seedlings, apices from mature plants and nodal segments) were used. It has been found 88% of young apical meristems produced shoots in Campbell and Durzan (CD) medium compared to 60% in Murashige and Skoog (MS) medium. Only 1/3 of them produced multiple shoots. Shoot idtiation from nodal segments was very rare. Mature apices produced callus. Although removed of the sheathing cover around mature buds enhanced the shoot initiation but success rate was low in growth regulator free medium. Embryos respond to the CD medium but not to the MS medium. Embryos from seeds soaked in water for 24 hours produced shoots after 8 weeks of incubation and the success rate was 70% while embryos from dry seeds only produced roots. There was no significant effect of cold storage (refrigeration) for 7 days on shoot initiation from mature embryos (65%) but the ability for shoot induction declines with storage time (55% after 21 days of cold storage). Mature axillary buds were established in Modified Campbell and Durzan (CD) medium supplemented with 0.5mg/1 and IBA. There was a significant difference in the growth performance of shoots according to the period of the year in which explants were collected. Highest (60%) was observed in November-January period. It was only 30% when the explants were collected in February-April or May-July and decreased to 20% in August-October. The shoots produced in November-January showed a higher vigor than those produced in other months. Since Jak fruit show seasonal changes in fruit bearing and shedding of leaves, it can be suggested that the difference in growth performances of tissues cultured in artificial culture media would have been affected by endogenous rhythms.

• Asian-Australasian Journal of Animal Sciences
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• 제14권11호
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• pp.1527-1533
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• 2001

Garole is a prolific, rare, less known and small size Indian sheep breed found in low and humid Sunderban region of West Bengal. Although information on stored Garole ram liquid semen upto 24 h is available, but there is a need to further investigate the short-term and long-term preservability of Garole ram semen for extensive utilization of this valuable germplasm by artificial insemination. The aim of the present study was to apply computer-assisted sperm analysis technique for assessing the motion characteristics of Garole ram semen stored (i) in liquid state at refrigeration temperature for short-term preservation upto 48 h and (ii) in frozen state at $-196^{\circ}C$ for long-term preservation after packaging in mini straws. Short-term preservation had a significant effect on motility (p<0.01) as the motility progressively decreased from 90.1% at 0 h to 85.5% and 73.2% after 24 and 48 h of storage, respectively. Although the decline in rapid moving sperms was also significant (p<0.01) on storage but the decrease was more pronounced at 48 h as compared to 24 h of storage period. Storage of chilled semen had also a significant effect on % linearity (p<0.05), % straightness (p<0.01), sperm velocities (p<0.01), amplitude of lateral head displacement (p<0.01) and beat frequency (pO.Ol) of spermatozoa. The replication had a significant effect for all the variables except average path and straight line velocity. However, the interactions of short-term storage and replication were non-significant for most of the variables except % of medium moving sperms, sperm velocities and beat frequency. On long-term preservation of Garole ram spermatozoa under controlled conditions the mean post-thaw recovery of 70.4 and 71.4% motile spermatozoa was achieved having 48.8 and 48.9% of rapidly motile spermatozoa, respectively in both the replicates. The effect of replication on cryopreservation was significant (p<0.05) on amplitude of lateral head displacement and beat frequency, but there was no significant effect on motility, rapidly motile spermatozoa, linearity, straightness and sperm velocities of frozen-thawed spermatozoa. It can be concluded from these results that an average 70% motility can be achieved on storage of Garole ram semen in chilled liquid state upto 48 h or in liquid nitrogen after freezing under controlled conditions in straws. However, further studies are required to evaluate the fertility of short-term and long-term preserved Garole ram semen for extensive use of this prolific sheep breed.

• 생명과학회지
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• 제15권5호
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• pp.783-789
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• 2005

V. pnrahaemolyticus를 저해하는 천연산물 조합 추출물을 이용하여 고추장을 제조하였다. 각각의 천연산물 및 천연산물 조합 추출물의 항산화력 크기는 ORP system value를 이용하여 측정하였고, 천연산물 조합 추출물을 이용하여 제조한 고추장을 disk 법으로 IZD (Inhibition zone divided by diameter of disk)를 측정하여 제어의 정도를 비교하였다. 그 결과 한 가지 천연산물에서는 황백, 오미자, 녹차가 높게 나타났고, 이들 천연산물을 조합했을 때도 항산화력이 높게 나타나 기능성 고추장을 제조할 수 있을 것이라 판단하였다. 그리고 항산화력이 높게 측정된 황백, 오미자, 녹차 그리고 황금의 A조합과 A조합에 오가피를 첨가한 B조합의 IZD를 측정하였을 때 각각 $1.57\pm0.0051$과 $1.56\pm0.0071$로 제어력이 뛰어나 A조합과 B조합의 천연산물의 추출물을 이용하여 고추장을 제조하였다 고추장을 제조하였을 때 A조합(IZD: $1076\pm0.0103$)보다 B조합(IZD: $1079\pm0.0103$)이 좋게 나타났고, 이 고추장으로 식초를 첨가하여 초고추장을 제조하였을 때도 A조합(IZD: $2.15\pm0.0071$)보다 B조합(IZD: $2.44\pm0.0086$)이 뛰 어난 제어력을 보였다 여기에 chitosan, 마늘, 메주의 첨가는 유의성 있는 제어력을 나타내지 못하였다.