• 대한기계학회논문집
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• 제17권10호
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• pp.2624-2633
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• 1993

Mass transfer experiment by naphthalene sublimation method has great advantages in measurement of local transfer coefficients in the region of a three dimensional flow or for a model of complex geometry, which is considered to be very difficult with conventional heat transfer measurements. Mass transfer data obtained by naphthalene sublimation technique are converted to the heat transfer data through heat/mass transfer analogy. This analogy is valid for a simple or laminar flow, but new insight is needed when applying to a turbulent flow or complex flow such as separation, reattachment and recirculation, The purpose of this research is to investigate how geometries and flow conditions incorporate heat/mass transfer analogy. Mass transfer experiments are performed using naphthalene sublimation technique for a flat plate, a circular cylinder, and rectangular cylinders. And mass transfer data are compared with earlier heat transfer measurements for the same geometries. Usefulness of analogy relation between heat and mass transfer is examined with these results.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1258-1266
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• 2004

It is important to completely understand heat/mass transfer from a flat plate because it is a basic element of heat/mass transfer. In the present study, local heat/mass transfer coefficient is obtained for two flow conditions to investigate the effect of boundary layer using the naphthalene sublimation technique. Obtained local heat/mass transfer coefficient is converted to dimensionless parameters such as Sherwood number, Stanton number and Colburn j-factor. These also are compared with correlations of laminar and turbulent heat/mass transfer from a flat plate. According to experimental results, local Sherwood number and local Stanton number are in much better agreement with the correlation of turbulent region rather than laminar region, which means analogy between heat/mass transfer and momentum transfer is more suitable for turbulent boundary layer. But average Sherwood number and average Colburn j-factor representing analogy between heat/mass transfer and momentum transfer are consistent with the correlation of laminar boundary layer as well as turbulent boundary layer.

• Nuclear Engineering and Technology
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• 제38권3호
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• pp.251-258
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• 2006

This study presents an idea of using analogy concept to the heat transfer studies regarding the HTGR development. Theoretical backgrounds regarding the idea were reviewed. In order to investigate the predictability of a mass transfer system for heat transfer system phenomenology, an electroplating system coupled with a limiting current technique was adopted. Test facilities for laminar forced convection and natural convections under laminar and turbulent conditions were constructed, for which heat transfer correlations are known. The test results showed a close agreement between mass transfer and heat transfer systems, which is an encouraging indication of the validity of the analogy theory and the experimental methodology adopted. This paper shows the potential of the experimental method that validates the little-understood heat transfer phenomena, even in complex geometries such as HTGR.

• 대한기계학회논문집
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• 제14권5호
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• pp.1300-1310
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• 1990

본 연구에서는 양각과 레이놀즈수를 변화시켜 가면서 사각관 각 면에서의 국 소물질전닭계수를 측정하여, 유동의 정체, 가속, 박리, 재부착, 와류유출등의 복잡한 유동현상이 물질전달에 미치는 영향을 고찰하고자 한다. 한편 Igarashi의 열전달 측 정 결과와 비교하여 열전달과 물질전달의 유사성을 고찰하고, 복잡한 유동이나 3차원 유동영역에서의 열전달해석에 나프탈렌승화법을 이용한 물질전달실험의 응용 가능성을 검토하고자 한다.

• Journal of Advanced Marine Engineering and Technology
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• 제22권4호
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• pp.445-450
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• 1998

In the present paper the effects of combined heat and mass transfer on the fin efficiency were calculated. Sector method was used for calculating the fin efficiency of the continuous fin. The parameter Lewis No. and C which describe the combined heat and mass transfer is derived by using the heat and mass transfer analogy and effects of Lewis No. and C on the fin efficiencies were calculated.

• 대한기계학회논문집
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• 제14권3호
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• pp.685-693
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• 1990

본 연구에서는 복사열전달 효과를 알아보기 위해 에너지 방정식을 수치적으로 풀었으며, 그 결과를 열전달계수 및 온도의 항으로 나타내었다. 수치 해석적 모델의 검증을 위해 여러사람들이 물질전달과정 해석을 위해 사용한 나프타린 승화법(naphth- alene sublimation technique)을 이용하여 실험을 수행하였다. 또한 실험에 사용된 다공질체(ceramic blocks)의 침투율도 측정하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.280-287
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• 2001

The present study investigates convective heat/mass transfer and flow characteristics inside the rib-roughened cooling passage of the gas turbine blades. A square duct with rectangular ribs is used and $\wedge-$ and V-shape ribs with $60^{\circ}$ attack angle are installed on the test plate surfaces. Naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wall and the vortices near the side-wall. The local heat transfer and the secondary flow in the duct are changed largely according to the rib orientation. A square duct with $\wedge$ and V-shape ribs has two pairs of secondary flow because of the rib arrangement. So, the duct has complex heat/mass transfer distribution. The average heat/mass transfer coefficient and pressure drop of $\wedge-$ and V-shape ribs are higher than those with $90^{\circ}$ and $60^{\circ}$ attack angles. The average heat/mass transfer coefficient on the $\wedge-shape$ ribs is higher than that on the V-shape ribs. Also, the uniformity of heat/mass transfer coefficient on discrete ribs is higher than that on continuous rib.

• Nuclear Engineering and Technology
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• 제55권1호
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• pp.180-189
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• 2023

We measured the heat load to a reactor vessel with and without the in-vessel debris bed under an IVR-ERVC condition. Mass transfer methodology was adopted based on heat and mass transfer analogy to achieve high Ra'_H of order ~10¹⁵ with compact test rigs. We postulated the in-vessel debris bed has a flat top and particulate debris was simulated as an identical diameter spheres. We conducted experiments varying the height of the debris bed and the results showed that Nusselt numbers decreased in both uppermost and curved surfaces with the increasing bed height. Once the debris bed is formed, it acts as an obstacle to the natural convective flow, which reduces the buoyancy. The reduction of driving force results in the impaired heat transfer in both upward and downward heat transfers.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1542-1551
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• 2002

The present study investigates the convective heat/mass transfer characteristics and pressure drop inside the rib-roughened cooling passage of gas turbine blades. The internal cooling passage is simulated using a square duct with h- and V-shaped rectangular ribs which have a 60。attack angle. A naphthalene sublimation technique is employed to determine the detailed local heat/mass transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wail. The secondary flow patterns and the local heat transfer in the duct are changed significantly according to the rib orientation. A square duct with ∧ - and V-shaped ribs have two pairs of secondary flow due to the rib arrangement. Therefore, the average heat/mass transfer coefficients and pressure drop of ∧ - and V-shaped ribs are higher than those of the continuous ribs with 90$^{\circ}$ and 60$^{\circ}$attack angles. The ∧-shaped ribs have higher heat/mass transfer coefficients than the V-shaped ribs, and the uniformity of heat/mass transfer coefficient are increased with the discrete ribs due to the flow leakage and acceleration near the surface.

• Nuclear Engineering and Technology
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• 제56권7호
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• pp.2524-2533
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• 2024

When analyzing containment thermal-hydraulics, computational fluid dynamics (CFD) is a powerful tool because multi-dimensional and local analysis is required for some accident scenarios. According to the previous study, neglecting steam bulk condensation in the CFD analysis leads to a significant error in boundary layer profiles. Validating the condensation model requires the experimental data near the condensing surface, however, available boundary layer data is quite limited. It is also important to confirm whether the heat and mass transfer analogy (HMTA) is still valid in the presence of bulk condensation. In this study, the boundary layer measurements on the vertical condensing surface in the presence of air were performed with the rectangular channel facility WINCS, which was designed to measure the velocity, temperature, and concentration boundary layers. We set the laminar flow condition and varied the Richardson number (1.0-23) and the steam volume fraction (0.35-0.57). The experimental results were used to validate CFD analysis and HMTA models. For the former, we implemented a bulk condensation model assuming local thermal equilibrium into the CFD code and confirmed its validity. For the latter, we validated the HMTA-based correlations, confirming that the mixed convection correlation reasonably predicted the sum of wall and bulk condensation rates.