• 한국압력기기공학회 논문집
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• 제14권1호
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• pp.8-14
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• 2018

Printed circuit heat exchangers (PCHEs) are widely used with an increasing demand for industrial applications. PCHEs are capable of operating at high temperatures and pressure. We consider a PCHE as a candidate intermediate heat exchanger type for a high temperature gas-cooled reactor (HTGR). For conventional application using stainless steels, design and manufacturing of PCHEs are well established. For applications to HTGR, knowledge of longitudinal conduction and deformation of channel is required to estimate design margin. This paper analyzes the effects of longitudinal conduction and deformation of channel on thermal performance using a code internally developed for design and analysis of PCHEs. The code has a capability of two dimensional simulations. Longitudinal conduction is estimated using the code. In HTGR operating condition, about ten percent of design margin is required to compensate thermal performance. The cross-sectional images of PCHE channels are obtained using an optical microscope. The images are processed with computer image process technique. We quantify the deformation of channel with dimensional parameters. It is found that the deformation has negative effect on structural integrity. The deformation enhances thermal performance when the shape of channel is straight in laminar flow regime. It reduces thermal performance in cases of a zigzag channel and turbulent flow regime.

• 설비공학논문집
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• 제11권5호
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• pp.561-569
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• 1999

The effects of longitudinal heat conduction on the performance of heat transfer surfaces are investigated by using a single-blow method. In the transient testing method for determining the heat transfer characteristics, exponential inlet temperature variations are made by using screen-mesh heater with small time constant and low frontal velocities of the test section, and the experimentally determined inlet temperature profile is used as the inlet fluid temperature condition. The effects of longitudinal heat conduction are negligible only if $\gamma^\act<0.05\;and \;N_{tu}\le3$ and should be considered if $N_{tu}\le3$ The test results ate compared with the existing theoretical and experimental data and the validity of this technique is confirmed by the good agreement.

• 설비공학논문집
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• 제26권12호
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• pp.600-604
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• 2014

Longitudinal heat conduction is known to be an important factor in the design of a printed circuit heat exchanger(PCHE) for cryogenic applications. Parasitic heat conduction through the heat exchanger frame needs to be considered because it is known to decrease the effectiveness of the heat exchanger. In this paper, a conjugate heat transfer problem in a simple counter-flow PCHE is analyzed by a computational fluid dynamics simulation. The effect of longitudinal conduction in a straight channel is compared with the theoretical effectiveness-NTU relationship that assumes a "thin" heat exchanger frame. The calculation results suggest that the theoretical model is valid in the present calculation conditions where NTU is < 13.

• 한국진공학회지
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• 제15권2호
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• pp.162-167
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• 2006

[ $GaAs_{1-x}N_{x}$ ]의 전도띠 바닥전자상태의 특성을 Ge 기판위에 성장시킨 $GaAs_{1-x}N_{x}(x{\leq}0.7)$ 박막에 대한 공명라만산란 실험을 수행함으로써 조사하였다. LO(longitudinal optical)-phonon 라만세기의 강한 공명상승이 $E_+$ 뿐만 아니라 $E_0$ 전이에너지 근처에서 관측되었다. 그러나 $E_+$ 전이에너지 아래와 근처에서 관측되는 분명한 LO-phonon 선폭 공명상승과 다양한 X와 L 영역경계 (zone-boundary) phonon의 활성화와는 대조적으로, $E_0$ 전이에너지 근처에서는 어떠한 LO-phonon 선폭 확장공명이나 날카로운 영역경계 phonon의 활성화가 관측되지 않았다. 관찰된 공명라만산란 결과는 GaAsN의 전도띠 바닥전자상태가 비국소화된 bulk GaAs와 거의 흡사한 ${\Gamma}$대칭 상태로 구성되었다는 사실을 의미한다.

• 한국가구학회지
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• 제19권1호
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• pp.91-96
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• 2008

This paper investigates the penetration of essential oil into radial and longitudinal directions of Castanea crenata. Present study was performed to know the essential oil penetration depth in radial and longitudinal direction of Castanea crenata. Essential oil penetration depth was found higher in longitudinal direction than in radial direction and it was about 53 times high at 15.0 second of penetration. In early wood, fiber conducted oil more than that of large vessel. In heartwood, fiber had played an important role for the conduction of oil. But in sapwood, small vessel conducted oil deeper than wood fiber, which was also significantly different from large. On the other hand, large vessel in heartwood had statistically lower penetration depth than that of fiber and small vessel. At the beginning of penetration the speed was high and gradually decreased in course of time.

• 설비공학논문집
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• 제1권1호
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• pp.64-72
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• 1989

Laminar natural convection heat transfer from a horizontal heat exchanger tube with one infinitely long vertical plate fin has been studied by a finite-difference numerical procedure. In predicting convective heat transfer from a circular tube, the thermal boundary condition at solid fluid interface is usually assumed to be isothermal. However, in reality, the thermal boundary condition is not isothermal, and the tube has the thickness and the conductivity. So the temperature at the interface is not known a priori to the calculation. This problem has the conjugate phenomena which occur between the tube conduction and external natural convection, and between the fin conduction and external natural convection. Numerical results are obtained to determine the effects of the conductivity of solid wall and the thickness of tube wall on heat transfer. It is found that the conduction causes significant influence on the natural convection heat transfer at low K and high ${\delta}$.

• 한국가구학회지
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• 제19권2호
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• pp.124-129
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• 2008

Moisture content of Larix kapempferi was maintained at 28% after air drying. 5% CCFZ solution penetration depth was observed through longitudinal tracheid and axial resin canal. Penetration depth was increased significantly from heartwood to sapwood and the penetration depth was found 1.3 times higher for sapwood measured at 15.0 second of penetration. On the other hand, liquid flow in sapwood and heartwood involved most liquid first entering the resin canals. Overall resin canal conducted 1.4 times more than tracheid. Latewood was found more permeable than in earlywood. At the beginning of penetration, the speed was high and then decreased in the course of time.

• 한국가구학회지
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• 제19권2호
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• pp.111-115
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• 2008

An experiment was conducted to know ultra-pure distilled water penetration depth through large vessel, small vessel, latewood fiber and earlywood fiber in longitudinal direction of Castanea crenata. In heartwood, latewood fiber transported water more than large and small vessel. While in sapwood, small vessel conduction depth was found the highest. Penetration depth of water after 15.0 seconds, no significant difference was observed among earlywood fiber, latewood fiber and earlywood vessel. Whilst in heartwood, no statistical difference was observed among earlywood fiber, latewood fiber and earlywood vessel. At the beginning, the speed of water penetration was high and then gradually decreased.

• 한국가구학회지
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• 제18권4호
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• pp.282-286
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• 2007

An experiment was conducted to compare the 1% safranine solution flow depth in radial and longitudinal direction of Prunus sargentii. Longitudinal flow of safranine solution was found higher than radial flow. Body ray parenchyma was found more permeable than marginal ray parenchyma and it was about 1.3 times higher. Intercellular space conducted safranine solution more than ray parenchyma. Vessel was found to be the main avenue for liquid conduction in longitudinal direction. Different anatomical features of ray, vessel and fiber affected the penetration depth of safranine solution. Moreover initial penetration depth was found to be high and thereafter decreased gradually.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.155-158
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• 1998

This paper is calculated at electron swarm simulation by Back Prolongation of Boltzmann equation for range of E/N values from 0.1~200[Td], pressure P= 1.0[Torr], temperature T=300[ 。K], the electron swarm parameter(drift velocity, longitudinal . transverse diffusion coefficients, characteristic energy, etc) in He gas is used by electron collision cross section, particularly explicate the simulation technique, and consider electrical conduction characteristic of He gas.