• 한국정밀공학회지
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• 제25권3호
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• pp.126-133
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• 2008

The main objective of the present study is to achieve linear temperature distribution of cooling surface of plunger. K type thermocouples are attached at the surface of plunger to measure temperature. Nozzle and insulating material are inserted in the pin hole of the plunger for this study. Cooling water flow enters at one nozzle and leaves at three nozzles. Flow through nozzle can be activated in the pin hole, temperature of hot point around hole is decreased. Meanwhile, insulating material blocks off heat transfer, temperature of cold point around hole is increased. By combination of nozzle and insulation, heat transfer of hole is controlled effectively, as result its, temperature of plunger surface shows linear temperature distribution.

• The Korean Journal of Pain
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• 제28권2호
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• pp.96-104
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• 2015

Background: The present experiment was conducted to identify the cooperative effect of serine histogranin (SHG) and noradrenaline in alleviating peripheral neuropathic pain. Methods: Chronic constriction injury of the right sciatic nerve was used to induce chronic neuropathic pain. For drug delivery, a PE10 tube was inserted into the subarachnoid space. Acetone drops and a $44^{\circ}C$ water bath were used to evaluate the cold and heat allodynia, respectively. Placing and grasping reflexes were used to assess the locomotor system. Results: SHG at 0.5 and $1{\mu}g$significantly (P < 0.05) decreased the thermal allodynia. The cold allodynia was also significantly reduced by intrathecal injections of 0.5 (P < 0.05) and $1{\mu}g$(P < 0.001) of SHG. $1{\mu}g$of noradrenaline, but not $0.5{\mu}g$, significantly alleviated the cold (P < 0.01) and thermal (P < 0.05) allodynia. The ameliorating effect of noradrenaline or SHG disappeared when the two compounds were administrated in equal concentrations. A significant difference (P < 0.01 in the acetone and P < 0.05 in the heat) was observed in the groups under equal doses of the two compounds, with a lower effectiveness of the combination therapy. Conclusions: Our findings suggest that the simultaneous administrations of noradrenaline and SHG do not result in synergistic analgesia, and combination therapy may not be a good approach to the treatment of chronic neuropathic pain syndrome.

• 설비공학논문집
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• 제19권7호
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• pp.545-554
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• 2007

Flow condensation heat transfer coefficients(HTCs) of R22, propylene, propane, DME and isobutane are measured on a horizontal plain tube. The main test section in the experimental flow loop is made of a plain copper tube of 9.52 mm outside diameter and 530 mm length. The refrigerant is cooled by passing cold water through an annulus surrounding the test section. Tests are performed at a fixed refrigerant saturation temperature of $40{\pm}0.2^{\circ}C$ with mass fluxes of 100, 200, $300kg/m^2s$ and heat flux of $7.3\sim7.7kW/m^2$. The data are obtained in the vapor Quality range of $10\sim90%$. Test results show that at same mass flux the flow condensation HTCs of propylene, propane, DME and isobutane are higher than those of R22 by up to 46.8%, 53.3%, 93.5% and 61.6% respectively. Also well-known correlations developed based upon conventional fluorocarbon refrigerants predict the present data within a mean deviation of 30%. Finally, the pressure drop increase as the mass flux and Quality increase and isobutane shows the highest pressure drop due to its lowest vapor pressure among the fluids tested.

• 한국수소및신에너지학회논문집
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• 제33권4호
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• pp.413-418
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• 2022

This paper presents two-phase condensation heat transfer and pressure drop characteristics of R32 and R454B as an alternative refrigerant to R410A in a 9.52 mm OD microfin tube. The test facility has a straight, horizontal test section with an active length of 2.0 m and is cooled by cold water circulated in a surrounding annular space. The heat transfer coefficients of the annular space were obtained using the modified Wilson plot method. Average condensation heat transfer coefficient and pressure drop data are presented at the condensation temperature of 35℃ for the range of mass flux 100-400 kg/m²s. The average condensation heat transfer coefficients of R32 refrigerant are 35-47% higher than R410A at the mass flux considered in the study, while R454B data are similar to R410A. The average pressure drop of R32 and R454B are much higher than R410A and they are 134-224% and 151-215% of R410A, respectively. R32 and R454B have relatively low GWP and high heat transfer characteristics, so they are suitable as alternatives for R410A.

• 한국작물학회지
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• 제27권4호
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• pp.314-339
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• 1982

Fluctuating climate is still most important environmental constrain, although improved modem agricultural technology has succeeded to increase crop production in the world. To stabilize the food production under fluctuating weather conditions, it is very needed to obain the quantitative information of interactions between crops and climate. The main purpose of this paper is three hold. Using the JIBP-data, the dry matter accumulation of rice crops is studied in relation to weather indexes (\SigmaTa and \SigmaSt). Temperature dependence of the yield index of rice is analyzed as to air temperature and water temperature. \SigmaT$_{10}$ -fluctuations are studied using meteorological data at various stations. The possible shift of \SigmaT$_{10}$ -isopleths due to climate fluctuation is evaluated. The second interest is in the plant climate of rice crops. Using results of canopy photosynthesis, it is pointed that the canopy structure has most important implication in plant climate. Leaf-air, stomatal, and mesophyll resistances of rice crops are described in relation to weather conditions. The change in light condition and aerodynamical property of rice crops with the growth is illustrated. The energy partition is also studied at different growing stages. Third point is to show in more detail effective countermeasures against cold irrigation water and cool summer. Heat balance of warming pond and polyethylene tube as a heat exchanger is studied to make nomo-grams for evaluating the necessary area and necessary length. Effects of windbreak net on rice crops are illustrated by using experimental and simulation results.lts.

• 소성∙가공
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• 제23권7호
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• pp.405-412
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• 2014

As a major type of heat exchanger, the steam generator (SG) produces steam from heat energy of a nuclear power plant reactor. The steam produced by the steam generator flows into a turbine, and plays an important role in electric power generation. The heat transfer tubes in the steam generator consist of approximately 10,000 U-shaped tubes, which perform a structural role and act as thermal boundaries. The heat transfer tubes conduct the thermal energy between the primary coolant (about $320^{\circ}C$, $157kgf/cm^2$) obtained from the reactor and the secondary coolant (about $260^{\circ}C$, $60kgf/cm^2$) as part of the secondary system. Recently, the heat transfer tubes in the steam generator of the pressurized water reactor (PWR) are primarily produced from Alloy 600 and Alloy 690 seamless tubes. As a pilot study to find process parameters for the cold U-bending process using rotary draw bending, numerical and experimental investigations were conducted to produce U-shaped tubes from long straight SUS304L seamless tubes. 3D finite element simulations were run using ABAQUS Explicit with consideration of the elastic recovery. The process parameters studied were the angular speed, the operation period and the bending angle. Experimental verifications were conducted to insure the suitability of the final U-shaped configurations with respect to both ovality and wall thickness.

• 한국입자에어로졸학회지
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• 제13권3호
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• pp.105-110
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• 2017

본 연구에서는 고온희석-상온희석 2단 희석의 다공 튜브형 희석장치를 제작하여 실제 배기가스와 시험챔버의 다양한 고수분 환경에서의 희석 조건에 따른 응축성 물질의 생성 억제와 생성된 응축 입자의 제거 특성에 관하여 살펴보았다. 디젤 엔진의 배출 입자는 응축 성분의 핵화 모드와 고체상의 응축성장 모드의 이중모드 분포를 나타내었고, 다공 튜브형 희석장치의 1차 고온희석 유량을 증가시킴으로써 핵화 모드 입자의 생성을 억제시키고 응축성장 모드의 입자만을 측정할 수 있었다. 석탄보일러에서 배출되는 미세먼지에 대해서도 다공 튜브형 희석장치를 적용하여 응축성 성분의 입자 생성 없이 응축성장 모드의 입자만을 측정할 수 있었고, $3{\mu}m$ 크기 이상의 입자에 대해서 기존 이젝터 방식에 비해 상대적으로 입자 손실이 적음을 확인할 수 있었다. 또한 $30m^3$ 시험챔버에서 가습기로 인위적으로 발생시킨 물입자가 측정하고자 하는 고체 입자와 공존할 때 다공 튜브형 희석장치를 사용하여 물입자를 증발시켜 제거함으로써 고체 입자만을 정확하게 분리하여 측정할 수 있음을 확인할 수 있었다.

• Nuclear Engineering and Technology
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• 제44권4호
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• pp.393-404
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• 2012

After the Fukushima nuclear accident in 2011, there has been increasing concern regarding severe accidents in nuclear facilities. Severe accident scenarios are difficult for operators to monitor and identify. Therefore, accurate prediction of a severe accident is important in order to manage it appropriately in the unfavorable conditions. In this study, artificial intelligence (AI) techniques, such as support vector classification (SVC), probabilistic neural network (PNN), group method of data handling (GMDH), and fuzzy neural network (FNN), were used to monitor the major transient scenarios of a severe accident caused by three different initiating events, the hot-leg loss of coolant accident (LOCA), the cold-leg LOCA, and the steam generator tube rupture in pressurized water reactors (PWRs). The SVC and PNN models were used for the event classification. The GMDH and FNN models were employed to accurately predict the important timing representing severe accident scenarios. In addition, in order to verify the proposed algorithm, data from a number of numerical simulations were required in order to train the AI techniques due to the shortage of real LOCA data. The data was acquired by performing simulations using the MAAP4 code. The prediction accuracy of the three types of initiating events was sufficiently high to predict severe accident scenarios. Therefore, the AI techniques can be applied successfully in the identification and monitoring of severe accident scenarios in real PWRs.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 추계학술발표회논문집(1)
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• pp.534-539
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• 1997

A CHF table method has been assessed in this study for rod bundle CHF predictions. At the conceptual design stage for a new reactor, a general critical heat flux (CHF) prediction method with a wide applicable range and reasonable accuracy is essential to the thermal-hydraulic design and safety analysis. In many aspects, a CHF table method (i.e., the use of a round tube CHF table with appropriate bundle correction factors) can be a promising way to fulfill this need. So the assessment of the CHF table method has been performed with the bundle CHF data relevant to pressurized water reactors (PWRs). For comparison purposes, W-3R and EPRI-1 were also applied to the same data base. Data analysis has been conducted with the subchannel code COBRA-IV-I. The CHF table method shows the best predictions based on the direct substitution method. Improvements of the bundle correction factors, especially for the spacer grid and cold wall effects, are desirable for better predictions. Though the present assessment is somewhat limited in both fuel geometries and operating conditions, the CHF table method clearly shows potential to be a general CHF predictor.

• 한국분무공학회지
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• 제17권1호
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• pp.35-44
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• 2012

To improve the mixing and atomizing performance at the center region of the conventional coaxial shear injector spray, the concept of a coaxial porous injector was invented. This novel injection concept for liquid rocket engines utilizes the Taylor-Culick flow in the cylindrical porous tube. The 2-dimensional injector, which can be converted in three injection configurations, was fabricated, and several cold flow tests using water-air simulant propellant was performed. The hydraulic characteristics and the effects of a gas flow condition on the spray pattern and the Sauter mean diameter (SMD) was analyzed for each configuration. The atomizing mechanism of coaxial porous injector was different with the coaxial shear injector, and it was explained by the momentum of the gas jet, which is injected normally against the center liquid column, and by the secondary disintegration at the wavy interface of liquid jet, which was generated at the recessed region. The SMD of 2D coaxial porous injector, which has higher gas momentum, was measured and it shows better atomizing performance at the center and outer side of spray than the 2D coaxial shear injector.