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

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 춘계 학술발표회
• /
• pp.615-624
• /
• 2010

In this paper, the applicability of cement grout has been studied as an alternative to bentontite grout to backfill ground heat exchangers. To provide an optimal mixture design, the groutabilty and thermal conductivity of cement grouts with various mixture ratios were experimentally evaluated and compared. The unconfined compression strength of cement grout specimen was measured, which are exposed to cyclic temperature variation ranging from $50^{\circ}C$ to $-5^{\circ}C$. In addition, the integrity of the interface between circulating HDPE pipes and cement grout by performing equivalent hydraulic conductivity tests, in which a pipe locates at the center of the specimen.

• Journal of Advanced Marine Engineering and Technology
• /
• 제32권6호
• /
• pp.847-853
• /
• 2008

Although combustion is essential in most energy generation processes, it is one of the major causes of air pollution. Circle fin exhaust pipes were designed to study the effect of cooling the recirculated exhaust gases (EGR) of Diesel engines on the chemical composition of the exhaust gases and the reduction in the percentages of pollutant emissions. The designs adopted in this study were exhaust pipes with solid and hollow fins around them direct surface force measurement in water using a nano size colloidal probe Technique The direct force measurement between colloidal surfaces has been an essential topic in both theories and applications of surface chemistry. As particle size is decreased from micron size down to true Carbon nano Colloid size (<10nm), surface forces are increasingly important. Nanoparticles at close proximity or high solids loading are expected to show a different behavior than what can be estimated from continuum and mean field theories. This paper use Water and CNC fluid at normal cooling system of EGR. Experimental result showed all good agreement at Re=$2.54{\times}10^{4}$.

• 설비공학논문집
• /
• 제26권10호
• /
• pp.460-466
• /
• 2014

This paper uses in-situ thermal response tests to present the characteristics of the ground thermal conductivities of three different SCW GHX. These SCW GHXs were installed in the same site in Seojong City. The three different cases are distinguished by the flow direction and the presence of a filler. The first type (A) is constructed for water to flow downstream. The second (B) and third (C) types are designed for water to flow upstream, and a filler is additionally inserted into the third type. The results of the in-situ thermal response tests, indicate that the ground thermal conductivity for types (A), (B) and (C) are of $4.84W/m{\cdot}K$, $3.40W/m{\cdot}K$, and $11.62W/m{\cdot}K$, respectively.

• 한국유체기계학회 논문집
• /
• 제18권6호
• /
• pp.19-26
• /
• 2015

The present paper presented and applied an exergy analysis method to evaluate the magnitudes and the locations of exergy losses in the conventional desuperheating and depressurizing process of high pressure and temperature steam delivery system. In addition, for the reduction of exergy losses occurred in conventional process, the present study proposed new alternative processes in which the pressure reducing valve and the desuperheater of conventional process are substituted with steam turbine and heat exchanger, and their effects on exergy loss reduction and exergy efficiency improvement are theoretically investigated and compared. From the present analysis results, the total exergy loss caused in conventional desuperheating and depressurizing process accounted for 66.5% of exergy input and 85% of the total exergy loss was due to the mixing between steam and cold water(e.g desuperheating). However, it was shown from the present analysis results that the present alternative processes can additionally reduce exergy loss by maximum 92.7% of the total exergy loss in conventional process, and can also produce additional and useful energy, the electricity of 220.6 kWh and the heat of 54.3 MJ/hr.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
• /
• pp.213-217
• /
• 2017

액체로켓엔진 고장에서 시동과정이 30% 이상을 차지하며 특히, 우주왕복선 주 엔진(Space Shuttel Main Engine, SSME)은 2%의 밸브위치 오차 또는 0.1초의 시간오차와 같은 작은 변화에도 급격하게 변화하는 매우 민감한 시스템으로 시동과정의 모델링이 중요하다. 하지만, 시동과정에서 비선형 질량 유량과 열전달 특성 때문에 많은 어려움이 발생한다. 본 논문에서는 이를 해결하기 위하여 부분적인 전산유체해석(Computational Fluid Dynamics, CFD) 방법을 사용하였으며 본 논문에서는 구성품의 모델링을 수행하여 정상상태에서 확인을 하였다.

• 실천공학교육논문지
• /
• 제10권2호
• /
• pp.125-129
• /
• 2018

이 논문은 LTP 퍼니스의 최적화 된 내부 유동과 온도의 균일성에 대한 수치 해석에 관한 것이다. 반도체 제조 공정에서 실리콘 웨이퍼를 어닐링하기 위한 기능을 수행한다. 특히 챔버 내부의 최고 온도를 약 $400^{\circ}C$의 고온으로 유지하여 웨이퍼를 보강한다. 공정이 고온에서 완료되면 열 교환기를 통해 온도를 낮추고 이를 수행하기 위한 작업이 반복된다. 이 논문에서 최종적인 목표는 LTPS 퍼니스의 유동 해석을 통해 챔버의 단열 공급과 배기 구조의 최적 설계를 도출하는 것과 교육과정 개발을 위한 사례 발굴에 있다.

• Geomechanics and Engineering
• /
• 제16권5호
• /
• pp.503-512
• /
• 2018

Globally there is an increasing need to reduce the greenhouse gas emissions and increase the use of renewable sources of energy. The storage of solar thermal energy is a crucial aspect for implementing the solar energy for space heating in high latitudes, where solar insolation is high in summer and almost negligible in winter when the domestic heating demand is high. To use the solar heating during winter thermal energy storage is required. In this paper, equations representing the single U-tube heat exchanger are implemented in weak form edge elements in COMSOL Multiphysics(R) to speed up the calculation process for modelling of a borehole storage layout. Multiple borehole seasonal solar thermal energy storage scenarios are successfully simulated. After 5 years of operation, the most efficient simulated borehole pattern containing 168 borehole heat exchangers recovers 69% of the stored seasonal thermal energy and provides 971 MWh of thermal energy for heating in winter.

• 조명전기설비학회논문지
• /
• 제22권11호
• /
• pp.23-29
• /
• 2008

This paper presents a new conceptual electromagnetic induction eddy current based stainless steel plate spiral type heater for heat exchanger or dual packs heater in hot water system boiler steamer and super heated steamer, which is more suitable and acceptable for new generation consumer power applications. In addition, an active clamping quasi-resonant PWM high frequency inverter using trench gate IGBTs power module can operate under a principle of zero voltage soft commutation with PWM is developed and demonstrated for a high efficient induction heated hot water system and boiler in the consumer power applications. This consumer induction heater power appliance using active clamping soft switching PWM high frequency inverter is evaluated and discussed on the basis of experimental results.

• Journal of Biosystems Engineering
• /
• 제13권4호
• /
• pp.30-37
• /
• 1988

A mathematical model was developed and programmed for computer simulation of a prototype hot water boiler system with rice hull furnace to predict the temperature distributions in the rice hull furnace and water tank, mass flow rate of hot water and thermal efficiency of the system under various operation and design conditions. The effects of feed rate of rice hull, thickness of the furnace wall, the type of heat exchanger, diameter of the water circulation pipe, etc, on the performance of the system can be evaluated with this model. The validity and simulation results of this model will be published in the next paper.