• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1447-1452
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• 2003

Vortex is very interesting flow phenomena on the heat transfer enhancement. In the present study, naphthalene sublimation technique is used to determine the average and local mass transfer coefficients on the flat plate with vortex generator. A parametric study with Reynolds number and angle of attack is carried out to investigate the heat transfer enhancement. The heat transfer coefficients on the flat plate with rectangular type and delta type vortex generator are compared with those of the flat plate without the vortex generator. Comparing heat transfer coefficients between rectangular type and delta type vortex generator, rectangular type vortex generator has much higher value than delta type vortex generator at the same condition.

• 대한기계학회논문집B
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• 제29권6호
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• pp.696-702
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• 2005

The effect of incidence angle on the endwall heat (mass) transfer characteristics within a turbine rotor cascade passage has been investigated by employing the naphthalene sublimation technique. The experiments are carried out at the Reynolds number of $2.78{\times}10^5$ for two incidence angles of -5 and 5 dog. The result shows that the incidence angle has a considerable influence on the transport phenomena over the endwall. The positive incidence angle tends to promote development of the pressure-side leg of a leading-edge horseshoe vortex. The endwall thermal load is augmented by 7.5 percents at i = -5 deg but is reduced by 2.5 percents at i = 5 deg, in comparison with that at the design condition.

• 대한기계학회논문집B
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• 제21권8호
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• pp.973-982
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• 1997

Effect of vortex generator on the heat transfer enhancement of electronic chips is investigated using naphthalene sublimation technique. Experiments are performed for a single chip and chip arrays, and shape of vortex generator, position of vortex generator, stream wise chip spacing and air velocity are varied. Local and average heat transfer coefficients are measured on the top surface of simulated electronic chips, and compared with those obtained without vortex generator. In case of a single chip, heat transfer augmentation is seen only on the upstream portion of chip surface, while heat transfer enhancement is found on the whole surface for chip arrays. Rectangular wing type vortex generator is found to be more effective than delta wing.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.119-124
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• 2000

The heat transfer characteristics of confined turbulent slot jet impingement on the flat plate with square rods(turbulence promoter) have been experimentally investigated. The effects of jet Reynolds number (Re=3900, 5800, 7800, 9700), dimensionless slot-to-plate distance(H/B=4, 6, 8) clearance(c) between square rods and the plate, and the length(d) of a side of the square rod were examined. Measurement or heat transfer rate were conducted using naphthalene sublimation technique. When square rods were inserted over the heat transfer surface, heat transfer rate was slightly increased in the wall jet region.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.61-66
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• 2003

Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.408-413
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• 2003

Naphthalene sublimation technique is used to investigate the average and local heat transfer from the circular rod, and to determine the average and local heat transfer from the circular rod with and without square wing type mixing vane in axial flow. The experiments are performed for a circular rod and flat plate with and without mixing vane in wind tunnel. In comparison with flat plate and circular rod in axial flow, averaged Nusselts number is increased 2 times as the increase of Reynolds number with mixing vane. Longitudinal vortex induced by square wing type has the stronger vortex strength, so square wing type vortex generator shows an effect further in downstream.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.185-190
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• 2007

For the successful design of heat exchangers, it is very important to understand local heat transfer characteristics on the circular cylinder of the cross flow heat exchangers. In this study, the heat exchanger using screen is developed to enhance heat transfer. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients in the heat exchanger. The experiments are performed for single circular tube, in-line array tube bank with and without heat transfer promoter. Local Nusselt numbers of single circular tube and tube bank with heat transfer promoter are investigated and compared to those of without heat transfer promoter.

• 설비공학논문집
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• 제11권6호
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• pp.861-870
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• 1999

An experimental study was carried out to investigate the effects of using various shapes of turbulence promoter on the heat-transfer enhancement of 2-D and 3-D arrays of rectangular modules in a rectangular channel for design of noiseless and low-powered cooling fan in the electronic systems. Measurements of heat/mass transfer coefficients were made using a naphthalene sublimation technique, and the friction factors were measured for Reynolds numbers in the range$3.3{\time}10^3$~$1.6{\time}10^4$. Flow visualization was peformed by oil-film method. It was found that heat transfer and pressure drop increased remarkably due to the existence of the promoter. The results of the performance evaluation based on equal pumping power were showed that substantial heat-transfer enhancement was obtained at low Reynolds number range by use of a turbulence promoter.

• 설비공학논문집
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• 제24권12호
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• pp.837-845
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• 2012

The purpose of this research is to investigate the heat transfer enhancement by the multiple tripping wires installed on a flat plate. Naphthalene sublimation technique is used to measure the local mass transfer coefficients, and then heat transfer coefficients are calculated using heat/mass transfer analogy. Experiments are performed for the developed and developing flow conditions. Local and average heat transfer coefficients from the flat plate with three tripping wires are compared with those of no and one tripping wire. Remarkable heat transfer enhancements are found resulting from the boundary layer separation by the tripping wires, especially in the laminar boundary layer.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.433-436
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• 2010

본 논문에서는 막냉각홀이 설치된 동익 표면에서의 열/물질전달 특성을 나프탈렌 승화법들 이용해 고찰하였다. 실험에는 저속 환형풍동이 이용되었으며, 풍동 내에는 16개의 동익으로 구성된 터빈단이 설치되어 있다. 동익의 선단부에는 막냉각을 위한 홀이 3열로 배치되어 있으며, 막냉각유체의 분사비를 1.0에서 2.0으로 조절하며 국소 열/물질전달계수를 측정하였다. 전반적인 열/물질전달 계수는 분사비가 높아짐에 따라 증가하며, 박리기포에 의해 압력면에 형성된 낮은 열/물질전달 계수를 갖는 영역은 분사비의 증가와 함께 사라진다.