Shape optimization is needed to enhance the performance or efficiency of many industrial products, for instance, such as small-scale electric parts, automotive design and so on. In, especially, small-scale apparatus with heat transfer, it is not easy to decide optimal shape of apparatus. Therefore, the shape of power auxiliary apparatus in automotive engine was investigated using numerical analysis which includes k- model and unsteady state. The relations between temperature and heat transfer were simulated in case of 3 Type and 3 Point for power auxiliary apparatus. As the results, the heat transfer was decreased due to flow recirculation in case of Type-1. Further high temperature did not always mean high heat transfer when the shape interacted with surrounding fluid.

In this study, the heat transfer characteristics of pilot wave heat exchanger for white smoke reduction system was investigated. The performance of the wave and honeycomb heat exchanger combined with the first stage, second stage and third stage was tested using a calorimeter. Air and water inlet/outlet temperature and flow rate, pressure drop and dehumidification amount were measured to compare the heat transfer performance according to the type and the combination of heat exchanger. The heat transfer rate and dehumidification amount of the wave heat exchanger were higher than that of the honeycomb heat exchanger, and the pressure drop was low. As the stage increased, the heat transfer rate and the increase of the dehumidification amount were more pronounced, and the pressure drop linearly increased. The wave heat exchanger had a lower flow resistance than the honeycomb heat exchanger with the honeycomb structure and had a higher heat transfer effect due to the convection, so the water outlet temperature was higher in the wave heat exchanger.

In the present study, single-phase heat transfer characteristics for downstream flow in the support grid of 6×6 rod bundle were investigated. It has been known that a turbulence generation due to a support grid with split mixing vanes enhances heat transfer in rod bundle but its heat transfer enhancement actually affects to relatively shorter distance. On the other hand, it has been also turned out that a support grid with large scale vortex flow (LSVF) mixing vanes results in heat transfer enhancement to a longer distance. Based on the results of literatre survey, single-phase water heat transfer experiments were performed for Reynolds numbers at around 30,000, and the heat transfer enhancement effect with both i) the split mixing vanes and ii) the LSVF mixing vanes was compared in this study. The key results showed that the effect of heat transfer enhancement in rod bundle region by the split mixing vanes was maintained up to the length of 15Dh behind the spacer grid. For the Reynolds numbers at around 30,000, it was also observed that the effect using the LSVF mixing vanes was stronger at about 3% when compared to the case using the split mixing vanes only for the distance ranging from 1 to 15Dh behind the spacer grid.

The heat transfer characteristics of forced convection according to the geometric shapes with four rectangular blocks in a horizontal PCB channel was analyzed numerically using SST (Shear Stress Transport) turbulence model. As the boundary condition for CFD (Computational Fluid Dynamics) analysis, the inlet temperature and air velocity were respectively 300 K and 3.84 m/s and the heat flux of the block surface was 358 W/㎡. The shape factors of block were width, height, spacing and channel entrance height. As the results, the heat transfer rate was decreased as the width ratio (x/h) was increased, while it was increased as the height ratio (h/x) is increased. Also as the block spacing ratio (s/x) was increased, the heat transfer effects was not significantly affected. And as the channel entrance height ratio (H/x) was increased, the heat transfer performance was decreased.

In this study, the heat flow characteristics of wave heat exchanger was investigated by being applied to the white smoke reduction system. Through numerical analysis, the heat transfer and flow characteristics of the wave heat exchanger with the change of inlet condition of air-side and water-side were analyzed. To investigate the temperature, the absolute humidity, heat transfer rate, pressure drop and turbulence characteristics of the wave heat exchanger, the simulation analysis was conducted by using the commercial computational fluid dynamics software (Solidworks Flow Simulation) under uniform flow conditions. As the inflow rate of air decreased and the inflow temperature of water increased, the heat transfer coefficient of the wave heat exchanger decreased. When the experimental conditions of water-side were the same, the air outlet temperature and absolute humidity of the wave heat exchanger increased with increasing inflow rate of air. To reduce the white smoke, the air outlet temperature and absolute humidity of the wave heat exchanger must be reduced. Therefore, the lower the air velocity and the water inflow temperature into the wave heat exchanger, the more effective it is.

단동 이중비닐하우스에서 수막에 의한 열전달 특성 및 가온효과를 구명하기 위하여 작물이 재배되는 수막온실의 실내외 기온과 수막의 수온 등을 계측하였고, 단위 피복면적당 수막에 의한 총 공급열량, 열관류율, 관류열량, 온실 내부로 전달되는 열량비율 변화를 비교·분석하였다. 1중과 2중사이의 기온은 외부기온보다는 수막유량과 공급수온에 따라 결정되는 것으로 나타났다. 수막유량이 증가할수록, 공급수온이 높을수록 수막과 2중 하우스 내부와의 열관류율(UW-IN)은 유의하게 증가하는 경향을 보였다. 그러나 수막유량과 공급수온이 일정조건(수 막유량 0.00266L·m-2·s-1, 공급수온 19.8oC) 이상에서는 UW-IN 값이 10W·m-2·oC-1 정도로 수렴되는 것으로 나타났다. 수막과 1·2중 공기 사이의 열관류율(UW-B)의 경우에도 수막유량 및 공급수온에 따라 증가하는 경향을 보였으나, 경향성은 상대적으로 작은 것으로 분석되었다. UW-B는 연구자에 따라 전체적으로 큰 차이를 보이고 있으며, 본 연구에서는 3.27~4.44W·m-2·oC-1의 범위를 보였다. 수막에 의한 총 공급열량(QW)과 온실 내외부로 전달 되는 관류열량(QW-IN, QW-B)의 경우, QW 값이 QW-IN과 QW-B의 합과 매우 유사하게 일치하고 있어 본 연구에서 제시한 결과가 신뢰성이 있음을 확인할 수 있었다. 수막에 의해 내부공기를 가열하는데 사용되는 열량은 최대 57% 수준으로 분석되었고, 우리나라 수막재배온실의 경우 약 22~28% 수준으로 판단된다. 본 연구는 농업인이 실제 사용하는 수막온실과 가장 유사한 조건에서 수막에 의한 온도변화, 열관류율과 관류열량을 계량화함으로써 향후 경제적인 수막온실 설계 시 활용할 수 있을 것으로 기대된다.

The purpose of this study was investigated heat flow and heat transfer coefficient characteristics of around tube when changing the tube arrangement type and heat transfer area. When  ≒1∼4, convective heat transfer coefficient of staggered and aligned arrangement was increased. Growth rate of the heat transfer coefficient becomes smaller in case of ≒5∼8 because a change in the turbulence was very small. At the staggered arrangement, all tubes were always arranged in front of the open passage between the back of the tube. Then, the entire surface area of the tube was exposed to the main flow. Thus growth rate of heat transfer coefficient appear larger than aligned arrangement.

The heat transfer characteristics of a louver fin for a radiator are numerically analyzed to investigate the performance of radiator for automotive. The commercial code FLUENT is utilized to simulate a louver fin to analyze both the flow fields of air and the solid region of lover fin. The numerical analysis is performed with the variation of air mass flow rate. The results show that as mass flow rate increases, louver fin efficiency is nearly constant. The correlation of the average Nu is derived. The results of numerical study is useful in louvered fin design.

Jet impingement heat transfer is a very effective technique for exchanging high heat fluxs between a heated plate and a fluid. The purpose of this study is to investigate the heat transfer characteristics of a rectangular free water jet normally or obliquely impinging onto a flat plate. The water jet issued from a rectangular slot nozzle with a cross section of 1.5mm⨉40mm. The mean velocities of nozzle exit were varied from 1.5m/s to 6.1m/s. The Reynolds number range based on the nozzle gap and the mean velocity was 2200∼8800. Various impingement angles between the vertical rectangular water jet and the inclined flat surface were investigated : 90˚, 70˚, 60˚ and 50˚ . The Nusselt number is high at the impingement line, and decreases with departures from it. The stagnation Nusselt numbers were compared to predictions of several correlations proposed by other researchers. The locations of the peak Nusselt numbers do not coincide with the geometric center of the rectangular jet on the surface.

The heat transfer characteristics of laminar syngas-fuel/air mixture with 10% hydrogen content impinging normally to a flat plate has been conducted experimentally. There were investigated by the effects of impinging distance, Reynolds number and equivalence ratio as major parameters on heat fluxes of stagnation point with the direct photos and data acquisitions from heat flux sensor. There were 3 times of maximum and 2 times minimum heat flux of stagnation point with respect to the impinging distance for the investigation of Reynolds number and equivalence ratio effect. The heat transfer characteristics between the stagnation and wall jet region in radial heat flux profiles was also investigated by the heat flux profiles.

In this research, the flow and forced convective heat transfer analysis of HEV battery pack were investigated numerically regarding the different shapes of the inlet, outlet, and battery case. The velocity ,pressure, and temperature distribution of the fluid at the inlet part of the battery module were numerically calculated for the optimum design of the battery pack for three different inlet shapes of the battery module. In addition, the local battery temperature for height and width and convective heat transfer coefficient of the air inside the battery pack were numerically obtained. Ultimately, the circle shape of the inlet and outlet were determined for the energy-effective shape of the battery pack.

The heat generated in contact type braking system can cause an unacceptable braking performance. Thermal behavior of ventilated disk brake system is presented in this paper. The temperature and velocity fields of 3-D unsteady simulated model are obtained using a software package "FLUENT". The numerical results show that there exits a temperature nonuniformity between the disk faces contacting with pads. The conduction rate through the disk and pad is calculated and the effect of material conductivity is also investigated.

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and TiO2 for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the TiO2 is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of TiO2.

The loop thermosyphon has been designed and tested for cooling several hundreds watt of heat. This cooling system is consisted of copper block, condenser which is fabricated with tubes and fins and transport lines. In this research, operational characteristics and limitation of the loop thermosyphon were investigated as a function of fill charge ratio, thermal load, vapor temperature and effective head. The experimental results shows that the heat transfer limitation is dominated by vapor temperature and effective head. Also, the correlation for the heat transfer limitation is presented and showed good agreement. The evaporating heat transfer coefficient is affected by vapor temperature and heat flux, but the fill charge ratio and liquid head are minor factor.

Experimental measurements of flame shape and heat transfer characteristics were performed for impinged inverse diffusion flame(IDF) using propane as a fuel. The purpose of this study is to identify the favorable co-axial inverse diffusion flame structure for impingement heating. The flame consisted of an entrainment zone and mixing and combustion zone. The heat flux which represents heat transfer rate is measured by using a heat flux sensor that is located at the center of the impingement plate. The inverse diffusion flame structure has been classified into six modes. In these modes, several favorable flames for impingement heating were identified. In this study, the parameters are overall equivalent ratio(Φ), nozzle to impingement plate distance(h/d), vertical distance from the stagnation point and Reynolds number(Re) of combustion air.