• 한국가시화정보학회지
• /
• 제10권3호
• /
• pp.16-20
• /
• 2012

In the past decades, extensive studies on convection heat transfer on internal flow have been conducted by using high specific surface area, by increasing heat transfer coefficient and swirl flow, and by improving the transport properties. In this study, we applied a tangential slot swirl generator to improve heat transfer in a horizontal circular copper tube. The Al-Mg particles (approximately $100{\mu}m$ to $130{\mu}m$) were employed for this experimental work. The copper tube was heated uniformly by winding a heating coil with a resistance of 9ohm per meter for heat transfer. Using Al-Mg particles, experiments were performed in the Reynolds number range of 5,000 to 13,130, with and without swirl. Experimental data transfers or comparisons between Nusselt numbers with and without swirl along the test tube and Reynolds numbers are presented. The Nusselt number is improved by increasing Reynolds numbers or swirl intensities along the test tube.

• 한국추진공학회지
• /
• 제24권5호
• /
• pp.1-12
• /
• 2020

본 논문에서는 재생냉각 연소기에서 냉각제 및 연료로 사용되는 Jet A-1의 열전달 특성에 대해 실험적으로 연구하였다. 냉각채널 가열을 위한 인가 전류, 모사 시편 지름, 시편 후단 압력, Jet A-1 유속을 변화시키며, 시편에서의 벽면 온도 및 시편 전/후단에서의 Jet A-1 온도를 측정하였다. 시편 지름과 유속이 열전달 특성에 중요한 인자임을 알 수 있었으며, 시편의 후단 압력은 열전달 성능에 영향을 주지 않음을 확인할 수 있었다. 열전달 실험결과는 기존 Nu수 경험식들과 비교하였으며, 최종적으로 새로운 Nu수 경험식을 도출하였다.

• 대한설비공학회지:설비저널
• /
• 제17권4호
• /
• pp.448-455
• /
• 1988

A study has been conducted experimentally on natural convection heat transfer characteristics of a vertical flat plate with horizontal rectangular fins in air. The effects of fin heights and Rayleigh numbers are mainly investigated. The experimental results are as follows; 1. The mean fin, plate and total Nusselt numbers decrease as dimensionless fin heights H/S increase at $0.50{\leq}H/S{\leq}2.00$. 2. The mean fin surface Nusselt number in case of H/S = 0.50 and $Ra_c=4.33{\times}10^3$ shows its maximum at $X_1$, surface where there is no interference with other fins. 3. Owing to the interference of fins the mean plate Nusselt numbers at H/S=0.50 and 2.00 for $Ra_S=6.57{\times}10^3$ are 35% and 80% respectively less than the mean fin Nusselt numbers. 4. The mean fin, plate and total Nusselt numbers of horizontal rectangular fins show higher values at short fins, but lower values at long fins than those of upward vertical fins.

• 대한기계학회논문집B
• /
• 제37권7호
• /
• pp.637-646
• /
• 2013

본 연구에서는 밀폐된 정방형관 내에서 자성유체의 자연대류현상에 대하여 수치해석적으로 접근하였다. GSMAC(Generalized-Simplified Marker and Cell method)법을 이용하여 자성유체의 지배방정식을 풀었으며 외부에서 인가자장의 세기 및 방향에 따른 자연대류현상과 열전달 특성을 수치해석적으로 규명하였다. 자성유체의 자연대류현상은 인가자장의 세기 및 방향에 따라 제어되었다. 자장이 수직방향으로 인가될 경우 자장의 세기 H가 4000일 때 평균 Nusselt 수가 최소가 되었고 자장이 수평방향으로 인가될 경우 자장의 세기 H가 12000일 때 평균 Nusselt 수가 최소가 되었다. 또한, 이 지점을 기준으로 자장의 인가방향과 관계없이 자장의 세기가 증가할수록 평균 Nusselt 수가 증가하였다.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
• /
• pp.225-226
• /
• 2014

An experimental study has been conducted to investigate the heat transfer characteristics of syngas/air mixture impinging jet flame with 10% hydrogen content. Effects of impinging distance, Reynolds number as major parameters on surface temperature of stagnation point were examined experimentally by the data acquisitions from k-type thermocouple. There were 2 times of maximum peak point of stagnation point with respect to the impinging distance for the investigation. As reynolds number increases, the nusselt number and convective heat transfer coefficient increased accordingly.

• 한국분무공학회지
• /
• 제13권3호
• /
• pp.143-148
• /
• 2008

In the present study, the correlation between the Nusselt number and Reynolds number was developed for forced convection and nucleate boiling region in spray cooling. Also the effect of droplet subcooling on spray cooling heat transfer was investigated. Full cone spray nozzles were employed for spray cooling experiment, and water and FC-77 were used for developing the correlation. From the experimental results, the correlation between the Nusselt number and Reynolds number based on droplet-flow-rate was developed. The correlation shows good predictions with ${\pm}30%$ error for water and FC-77.

• Journal of Advanced Marine Engineering and Technology
• /
• 제25권3호
• /
• pp.581-587
• /
• 2001

Plate heat exchange(PHE) will be applied to the refrigeration and air conditioning systems as evaporators or condensers for their high efficiency and compactness. The purpose of this study is the analyze the characteristics of heat transfer and pressure drop of plate heat exchanger. Numerical work was conducted using the FLUENT code k-$\varepsilon$model. Also the dependence of heat transfer coefficient and friction factor on Reynolds number was investigated. As the Reynolds number increases, it is found that heat transfer coefficient also increases, but friction factor decreases. The study examines the internal flow, thermal distribution and the pressure distribution in the channel of plate heat exchanger. The results of CFD analysis compared with experimental data, and the difference of friction factor and Nusselt number in plate heat exchanger are 10% and 20%, respectively, Therefore the CFD analysis model is effective for the performance prediction of plate heat exchanger.

• Journal of Advanced Marine Engineering and Technology
• /
• 제15권2호
• /
• pp.64-72
• /
• 1991

The unsteady, two-dimensional laminar flow and heat transfer of an incompressible, constant-property fluid flowing around a circular cylinder are numerically analyzed. The Navier-Strokes equation and the energy equation are solved by the finite difference method. The range of the Reynolds number is 10 to 100 and the Prandtl number considered is 0.7. The contours of the flow pattern, equi-vorticity line and isotherm pattern around a circular cylinder are shown. Also, numerical solutions of the surface vorticity, pressure coefficient, drag coefficient, local Nusselt number and mean Nusselt number are obtained. The numerical results for the final time fo calculation are compared with the other available experimental and theoretical results for the steady state and are found to be in good agreement with them.

• 설비공학논문집
• /
• 제14권3호
• /
• pp.231-239
• /
• 2002

Experiments on the single phase cooling heat transfer and pressure drop with microfin tubes were performed using water as a test fluid. Experimental data were obtained in the range of Reynolds number 3000 ~40000 and Prandtl number 4-6. The data of microfin tubes presented the characteristics of rough surface tube in pressure drop and heat transfer Experimental data were compared with the heat transfer and friction factor correlations of smooth tubes. Heat transfer enhancements of microfin tubes were lower than pressure drop penalty factors. The helix angle is more significant parameter in both of the pressure drop and heat transfer than the relative roughness. The correlations of Nusselt number and friction factor were suggested for the tested microfin tubes. Maximum deviations between correlations and experimental data were within $\pm15$% for Nusselt number and $\pm10$% for friction factor.

• 대한기계학회논문집
• /
• 제7권3호
• /
• pp.301-312
• /
• 1983

Experimental results for the variation of the flow characteristics and heat transfer coefficients in the entrance region of concentric annular pipe with artificial roughness are compared with the theoretical results by numerical analysis. In the experiments, velocity profiles, pressure gradients and heat transfer coefficients were measured with variation of the Reynolds number for the constant ratio of pitch to height at the hydrodynamic entry region. Wall temperature of inner heated pipe with constant heat flux was measured at thermal entry region after the hydrodynamically fully developed region of flow. Experimental data agree well with numerical predictions. Both results show that turbulent flow of annular pipe with artificial roughness is fully developed thermally much faster than that of smooth pipe. Nusselt number of annular pipe with roughness is much higher than that of smooth pipe. However the ratios of Nusselt number of annular pipe with artificial roughness to that of smooth pipe does not vary with Reynolds number.