The shell & tube-type heat exchanger has been frequently used because it shows simple structure, easy manufacturing and wide operation conditions among many heat exchangers. This study aims to investigate the characteristics for thermal flow of coolant and the possibility of damage for tube equipped with shell due to thermal stress. For these purposes, The thermal flow of coolant in tube was simulated using ANSYS-CFX program and thus the behaviors of coolant were evaluated with standard k-ε turbulence model. As the results, as the flow rate of coolant in tube was increased, the mean relative pressure was also increased with quadratic curve, however, as the surface temperature of tube was increased, mean temperature difference was linearly increased. Finally it showed that the damage of tube could be predicted, that is, which tube was the most weak due to thermal stress.

In this study, gas flow pattern and temperature distribution in a laboratory scale low temperature furnace for carbonization were numerically analyzed. The furnace was designed for testing carbonization process of carbon fibers made from polyimide(PI) precursor. Nitrogen gas was used as a working gas and it was treated as an ideal gas. Three-dimensional computational fluid dynamics analysis for steady state turbulent flow was used to analyze flow pattern and temperature field in the furnace. The results showed that more uniform velocity profile and axisymmetric temperature distribution could be obtained by varying mass flow rate at the inlets.

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.

This research is to investigate the performance analysis of methanol fuel cell for flow channel with four different types of the channel (Serpentine I, II, Inter-digitated, Parallel) in the fuel cell stack. Velocity, pressure, temperature and density distributions of fluid over the flow domain of the flow channel are numerically calculated for the optimum design of flow channel with uniform inlet velocity. According to better water discharge and mutual gas reaction with low pressure drop and high density difference between inlet and outlet in the flow channel, Serpentine I type is of highest performance of the flow channel shapes in the present methanol fuel cell models.

This research is to investigate the performance analysis of micro gas turbine for power generation with three different numbers of the nozzle vane in the micro gas turbine. Velocity, pressure. and temperature distributions of fluid over the flow domain of the turbine and turbulent kinetic energy of three different turbine blades are numerically calculated for the optimum design of turbine blade with two different rotational speeds of the turbine blade (10000 and 20000 RPM). Ultimately, the energy-efficient and maximum power-generated shape of the nozzle vane are determined through two different rotational speeds of the turbine with three shapes of the nozzle vane (6, 8, and 12 EA).

In this research, the heat and flow analysis in a condenser of vehicle HVAC system was investigated numerically regarding the different shapes of the condenser tube. The velocity, pressure, and temperature distribution of the test fluid(R-134A) inside the tube were numerically calculated for the optimum design of the condenser tube for two different length with four different inlet velocities. In addition, the local pressure and temperature distributions for total tube length were calculated and the variation of pressure drop of the R-134A with flow rate were also calculated numerically. The tube at case 1 with less curved elbows was determined for the better design than case 2 in the aspect of energy-effective shape of the condenser tube.

3차원 실내공간의 상부에서 일정유속이 유입하여 양측면 하부쪽으로 유출될 경우, 책상형의 가열 장애물 영향에 의한 유동장의 변화와 온도분포를 수치계산 한 결과 다음과 같은 결론을 얻었다. (1)표준 k-ε 2 방정식 모델로 난류유동장을 해석한 결과 장애물을 기준으로 상하부에는 독립적인 큰 재순환 영역이 존재함을 알 수 있었다. (2) 유입류의 속도 변화에 따른 전제적인 유동패턴은 큰 변화없이 상사적인 분포를 하는 것을 알 수 있었다. (3) 유입속도가 감소함에 따라서, 공간에 대한 발열체의 온도영향이 커진다. (4) Re수가 작은 범위 (10 상(4)-10 상(5)에서는 열전달이 급격히 상승하여, Re수가 10 상(5)이상이 도면 열전달이 거의 일정하다.