• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.664-673
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• 2005

The heat transfer characteristics of rarefied flows in a micro-actuator are studied numerically. The effect of Knudsen number (Kn) on the heat transfer of the micro-actuator flows is also examined. The Kn based on gas density and characteristic dimension is varied from near-continuum to highly rarefied conditions. Direct simulation Monte Carlo calculations have been performed to estimate the performance of the micro-actuator. The results show that the magnitude of the temperature jump at the wall increases with Kn. Also, the heat transfer to the isothermal wall is found to increase significantly with Kn.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.844-853
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• 1998

Natural and forced convection experiments were carried out in order to investigate the effects of channel spacing gap between protrusions and number of rows of protrusion, In natural convection the optimum channel spacing was found to be approximately 20mm regardless of the protrusion gaps. For optimum channel spacing the heat transfer coefficients were converged to an asymptotic value after the fourth row. The heat transfer coefficient for each row approaches to constant values for protrusion gaps larger than 10 mm. An experimental correlation has been suggested by using a modified Rayleigh number based on the dimensionless characteristic length(G/L). In forced convec-tion the heat transfer coefficients were not merged to an asymptote until the fifty row and increases as the channel spacing at the constant Reynolds number decreases.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.795-801
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• 2004

An experimental study has been carried out to examine heat-transfer characteristics of an axisymmetric, under-expanded, sonic jet impinging on a flat plate and the local measurement of surface pressures and heat transfer coefficients on a plate have been achieved together with a visualization test of shock structure in a jet. As a result, it has been found that the Nusselt number distribution has different aspects depending on the under-expansion ratios and the nozzle-to-plate distances.

• 대한기계학회논문집
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• 제10권1호
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• pp.96-101
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• 1986

본 연구에서는 2차원 충돌분류에 있어서 전열면상에 비교적 큰 스케일을 가진 트랜스버스 리브(transverserib)형의 피형돌기를 만들고 충돌영역을 포함하여 통상열전달율이 현저하게 낮아지는 하류역까지의 넓은 영역에 걸쳐 전달회진을 목적 으로 전달특성을 실험적으로 조사하고 전보에서 다룬 거형의 트랜스버스 리브를 갖는 전열면에서의 결과와 비교 검토하였다. 한편 돌기면상의 유동형태의 상세를 smoke wire법에 의해 충돌분류 특유의 종과류와 그 신장에 대하여 조사하고 표면부유법 (surface floating method)에 의해 비교적 큰 스케일의 돌기에 따른 흐름의 박이 및 재부착에 관해서 조사하여 이들과 전열기구와의 관계를 정성적으로 검토하였다.

• 설비공학논문집
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• 제19권11호
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• pp.743-750
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• 2007

In this study, ice slurry generator using air cylinder was designed and manufactured to investigate the heat transfer characteristic of the ice slurry generator. The ice slurry generator has the same shape as the shell-and-tube type heat exchanger. Refrigerant is flowing in the shell side and ethylene glycol solution in the tube side. The experiment was conducted on performance of ice slurry generator using air cylinder with standard condition and the results are plotted on the time scale. The experimental tests on the various concentration of ethylene glycol solution, the various solution velocity in the tube side and the various tube size have been carried. For the above experimental conditions, ice making characteristics of the ice slurry generator are evaluated in terms of the overall heat transfer coefficient. And the experimental results show that the overall heat transfer coefficient of the system is increased as the tube size and the concentration of ethylene glycol decreases.

• 대한기계학회논문집
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• 제16권8호
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• pp.1566-1574
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• 1992

본 연구에서는 원형수직 충돌분류에 의한 가열평판의 전열특성을 해석하기 위 하여 최근 표면온도 측정에 많이 사용되고 있는 liquid crystal을 이용하였다. 즉 liquid crystal의 감온특성과 영상처리 기법을 이용하여 레이놀즈수 및 노즐과 충돌판 사이의 거리(L/D) 변화에 따른 전열면의 온도장 변화를 측정하였다.

• 동력기계공학회지
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• 제9권2호
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• pp.93-98
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• 2005

The performance of cooling tower is dependent on the thermal performance of the packings. It's assessed by heat transfer rate and fan power. In this study, new packing was developed for application in compact type cross-flow cooling tower. The packing characteristic curve and the pressure drop curve were obtained by measuring packing characteristic values and pressure drops of small sized filler in comparison to existing mid-large sized filler. The heat transfer characteristics on small sized filler are about 66% higher than existing mid-large sized filler. The pressure drop characteristics on small sized filler are about two times of the pressure drop characteristics on existing mid-large sized filler.

• 대한기계학회논문집
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• 제17권2호
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• pp.438-444
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• 1993

The circuit board of an electronic equipment were simulated with a vertical channel which had thermal blocks protruded from one of the channel walls. A rought front plate was made of a circuit board attached with short wires to simulate the back side of a printed circuit board. Natural convection experiments were carried out to study the effects of channel space and rough front plate and to find the suitable characteristic value after the fourth row. The effect of a rough front plate was negligble. There were negligible effects of the channel space on the first and second heaters. Heat transfer coefficients after the third row decreased as the channel space decreased. Heat transfer coefficients were almost constant for larger than 20 mm channel space. A characteristic length was suggested to non-dimensionalize Nu and Ra numbers in a vertical channel with protruded heaters. A correlation was obtained using the new characteristic lengths.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1997년도 추계 학술대회논문집
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• pp.92-98
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• 1997

A finite-difference method based on characteristic upwind flux difference splitting has been studied on the blowing effect on the wall heat transfer over blunt-bodies. As the blowing rates increased, the wall heat transfer rate decreased and the temperature gradient also decreased compared with no blowing case. The heat trasfer rate at Mach No. 20 was almost twice higher than that of Mach No. 15 at 50km altitude. The surface blowing can be an effective mechanism to reduce the surface heat transfer rate at hypersonic flight condition.

• 산업기술연구
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• 제26권B호
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• pp.29-34
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• 2006

A convective, radiating rectangular fin is analysed by using the one dimensional analytic method. Instead of constant fin base temperature, heat conduction from the inner wall to the fin base is considered as the fin base boundary condition. Radiation heat transfer is approximately linearized. For different fin tip length, temperature profile along the normalized fin position is shown. The fin tip length for 98% of the maximum heat loss with the variations of fin base length and radiation characteristic number is listed. The maximum heat loss is presented as a function of the fin base length, radiation characteristic number and Biot number.