Currently, the cutting oil supply device is not equipped to cool the cutting oil. Therefore, additional cooling device should be connected to cool the cutting oil. This has the disadvantage of increasing the size of the device and reducing its cooling capability. To overcome these shortcomings, cooling coils are applied to the outside of the cutting oil filtering device to develop a heat exchanger filter for simultaneous coolant filtering and cooling to improve the compactness of the cutting oil supply device and cooling capability of the cutting oil. For the development of heat exchanger filter, flow and heat transfer analysis were performed. Due to the small heat transfer area of 10 cooling coils, less heat exchange occurred. In the 20 cooling coils, the coolant cooling coils prevented smooth flow of the cooling oil in the heat exchanger filter. The cooling efficiency of the 15 cooling coils were best, and the cooling temperature decreased non-linearly as the supply flow rate of the cutting oil increased.

As the demand for high-speed and high-precision machining increases, the need for cooling and filtering of cutting oil is high. A new concept of coolant heat exchange filter is developed by installing cooling coil through which refrigerant(R410-a) passes through the coolant filtering device. For structural safety evaluation of the heat exchanger filter for cutting oil suppling device of machine tool, thermal stress and vibration analysis were performed using ANSYS program. The results of structural and thermal stress analyses have led to the conclusion that the cooling system has structural stability. From modal analysis, first natural frequency is 12.37 hz and deformation is 22.041 mm. Sixth natural frequency is 26.887 hz and deformation is 25.563 mm.

In this study, the CFD analysis was performed by changing the geometry of coil-tube diameter ratio, coil winding number, coil pitch, and cross section of the tube to investigate the heat flow characteristics of forced convection in a helical coil-tube heat exchanger using RSM (Reynolds Stress Model). As a result, the secondary flow was developed in the tube caused by the influence of centrifugal force. It improved the heat transfer on the outer side of the tube, but on the inner side was not performed well. And the temperature rose locally in the tube region. Also the pressure drop in the tube was proportional to the diameter ratio of the coil-tube and the inlet velocity, and it was found that pressure drop and friction factor were inversely proportional. When the coil winding number and coil pitch were increased, it affected heat transfer in the low speed range of 0.1 ~ 0.2 m/s, but did not affect the flow condition after this range.

When the heat flux on the heating surface following changing heat condition in the boiling heat transfer system exceeds critical heat flux, the critical heat flux phenomenon is going over to immediately the film boiling area and then it is occurred the physical destruction phenomenon of various heat transfer systems. In order to maximize the safe operation and performance of the heat transfer system, it is essential to improve the CHF(Critical Heat Flux) of the system. Therefore, we have analysis the effect of improving CHF and characteristics of heat transfer following the nanoparticle coating thickness. As the results, copper nanocoating time are increased to CHF, and in case of nano-coatings are increased spray-deposited coating times more than in the fure water; copper nanopowder is increased up to 6.40%. The boiling heat transfer coefficients of the pure water are increased up to 5.79% respectively. Also, the contact angle is decreased and surface roughness is increased when nano-coating time is increasingly going up.

In this study, the performance of a small - sized wave heat exchanger to be applied to the white smoke reduction system was experimentally confirmed. The heat transfer rate, drain and pressure drop were measured according to the air flow rate, water flow rate and relative humidity change of the wave heat exchanger for two kinds of pitch numbers. A constant temperature and humidity calorimeter and a constant temperature water bath were used to measure the performance of the wave heat exchanger. The heat transfer rate and drain increased gradually with changes of water flow rate. Case 2 showed more than 50% higher heat transfer rate and drain than Case 1. The increase of air heat transfer rate and drain according to air flow rate was greatly increased when the number of pitches was the same or increased, unlike the result of water flow rate change. In the temperature visualization using a thermal imaging camera, it can be seen that as the water flow rate and the number of pitches increase, the heat transfer becomes more effective in Case 2.

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 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.

본 연구에서는 저온소성 코팅을 적용한 SUS 304 판을 사용하여 고가의 티타늄 판 대체에 대한 성능평가를 수행하였다. 전산유 동해석 결과, 저온소성 코팅을 적용한 SUS 304 판은 100 마이크론 두께의 코팅까지는 티타늄 판에 비해 더 뛰어난 열전달 성능을 보이는 것으로 나타났다. 실제 열교환기를 이용하여 열전달 성능에 대한 실험을 한 결과, 코팅을 적용한 SUS 304 판이 티타늄 판에 비해 더 우수 한 열전달 성능을 나타냄을 확인하였다. 또한 개방검사를 통해서 판의 부식 및 스케일 생성 정도를 확인하였을 때, 코팅을 적용한 SUS 304 판의 내부식 성능은 티타늄 판과 거의 동등하게 나타났으며, 해수에 의한 스케일의 생성 억제 효과는 코팅을 적용한 SUS 304 판에서 더욱 우수하게 나타났다.

In this study, a numerical approach for automotive louvered fin heat exchanger is carried out to investigate the effect of louvered angle on the heat transfer characteristics. The numerical simulation code STAR-CCM+ is utilized to calculate flow and temperature fields with polyhedral meshes. The results show that the flow efficiency is increased as the louver angle is high. Also, the outlet temperatures are nearly the same according to louver angles because the average Nusselt numbers are nearly equivalent regardless of louver angle.

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.

생물학적 위험등급 3등급 BL3용 공조기의 급배기는 밀폐 연구시설 사이의 교차오염을 막기 위하여 관계 규정에 의거 전외기 방식을 택하고 있다. 이와 같은 전외기 방식의 공조기는 에너지 소비가 많으며 게다가 BL3의 경우 하루 24시간 운전으로 인하여 에너지 소비가 매우 많으며 또한 연구시설의 대형화로 인하여 에너지 소비는 더욱 증가하게 될 것이다. BL3용 공조기에서의 에너지 절약에 관한 연구로는 국외의 경우 전외기 방식에서 급기와 배기덕트 사이에 부동액 등을 사용한 핀-튜브 열교환기를 사용하여 배기로부터 열회수를 통한 에너지 절약에 관한 연구를, 국내의 경우 생물학적 안전성을 기반으로 하는 재순환에 의한 에너지 절약에 관한 연구를 시도하고 있다. 본 연구에서는 기존의 BL3용 공조기에서 주로 사용하는 핀-튜브 열교환기와 마이크로 채널 열교환기에 대한 특성을 비교, 연구하였고 마이크로 채널 제작을 위한 열교환기 설계 프로그램을 개발하였다.

The heating & cooling performance of vapor compression heat pump using seawater heat source has been investigated experimentally for fish farm heat supply system. The principal parts of the heat pump systems are compressor, condenser, expansion devices and evaporator. The evaporator and condenser are both heat transfer devices. We used double pipe H/E(CASE-1) and shell&coil H/E(CASE-2) as evaporator, condenser of heat pumps. The experimental results were higher Uvalue 25% of double pipe heat exchanger compared to shell & coil H/E. The COPc is 4.74 and the COPH is 6.18 of the heat pump with shell & coil H/E.

본 연구에서는 화력발전소에서 온배수의 형태로 배출되는 폐열을 히트펌프의 열원으로 이용하여 온실의 난방에 활용할 수 있는 히트펌프 시스템을 설계 제작하였으며, 난방 성능을 분석하여 PE 파이프 열교환기의 설계기준을 제시하고자 하였다. PE 파이프 열교환기의 내경은 20mm, 두께는 2mm였으며, Roll의 직경은 1,000mm로 하였다. 연구결과 PE파이프 열교환기의 적정 길이는 1.0RT당 75m로 설계하는 것이 바람직할 것으로 판단되었으며, 이때 히트펌프시스템의 난방성능계수(COPh)는 3.8로 나타났다.