• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.1226-1231
• /
• 2009

This paper presents operating characteristics of internal heat exchanger(IHX) for $CO_2$ geothermal heat pump in the heating mode. Mass flow rate of $CO_2$, inlet temperatures of $CO_2$ at high and low pressure side were selected as main effect factors by using fractional factorial DOE(Design of Experiments). And RSM(Response Surface Method) was used in optimization phase. The results show that heat transfer rate of IHX increases when either inlet temperature of low pressure side decreases or inlet temperature of high pressure side increases. Effectiveness of IHX increases with increasing of inlet temperature of either high pressure side or low pressure side. Finally, performance contour map was provided over the operation ranges of the main design factors.

• 대한기계학회논문집B
• /
• 제39권1호
• /
• pp.37-43
• /
• 2015

현열 뿐만 아니라 잠열을 이용하는 증발냉각은 배기열 회수에 매우 유용하게 사용될 수 있다. 본 연구의 목적은 증발냉각을 이용한 배기열 회수장치의 성능을 실험적으로 규명하는 것이다. 성능실험장치는 플라스틱 열교환기, 물 분무 노즐, 공기유동용 홴, 물 순환용 펌프, 수조, 온도 습도 유량 측정 센서 등으로 구성되었다. 증발이 없는 현열 회수에서의 유용도와 증발을 수반하는 전열 회수에서의 유용도를 여러가지 작동조건에서 측정하여 비교하였다. 현열냉각과 증발냉각의 유용도는 공기의 유량이 증가함에 따라 감소하고, 대향류에서의 유용도가 평행류에서의 유용도 보다 휠씬 높다. 증발냉각의 경우 물 유량이 증가함에 따라 유용도는 증가하고, 평행류가 대향류보다 물 유량에 더 민감함을 알 수 있다.

• 설비공학논문집
• /
• 제19권10호
• /
• pp.687-694
• /
• 2007

Cycle simulation is peformed for two types of the desiccant cooling system incorporating a regenerative evaporative cooler. The cooling capacity and COP are evaluated at various effectiveness values of the regenerative evaporative cooler, the desiccant rotor and the sensible heat exchanger. As either of the effectiveness of the regenerative evaporative cooler or the humidity effectiveness of the desiccant rotor increases, both the cooling capacity and COP increase, but the enthalpy leak ratio gives the opposite effect on the system performance. It is found that COP of cycle A mainly depends on the humidity effectiveness of the desiccant rotor, while for cycle B enthalpy leak ratio of desiccant rotor has the major impact on COP. The effect of the sensible heat exchanger on the cooling capacity is small about 1/10 compared with those of other components.

• 설비공학논문집
• /
• 제21권5호
• /
• pp.282-290
• /
• 2009

A ceramic monolith heat exchanger is studied to find the performance of heat transfer and pressure drop by numerical computation and $\xi$-NTU method. The numerical computation was performed throughout the domain including fluid region in exhaust gas-side rectangular ducts, ceramic core and fluid region in air-side rectangular duct with the air and exhaust in cross flow direction. In addition, the heat exchanger was also analyzed to estimate the performance by conventional $\xi$-NTU method with several Nusselt number correlations for flow in rectangular duct from literature. By comparisons of both performances by the numerical computation and the $\xi$-NTU method, the effectiveness by $\xi$-NTU method was closest to the result by numerical computation within a relative error of 2.14% when Stephan's Nusselt number correlation was adopted to the $\xi$-NTU method among the several correlations.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
• /
• pp.31.2-31.2
• /
• 2005

• 설비공학논문집
• /
• 제22권7호
• /
• pp.482-491
• /
• 2010

In conventional air-handling units, when the circulated air from the air-conditioned space pass through the cooling coil, the air is over-cooled to eliminate the moisture as well as to decrease the temperature. The purpose of this study is to estimate the thermal performance and energy saving of the cooling/reheating system using heat exchanger which can save both cooling energy and reheating energy by exchanging heat between the cooled air and reheated air. The energy balance equations to estimate the state of the air for each components were provided and the heat transfer rates and the energy saving rates for the system were calculated from the equations. The results showed that the energy saving was up to 40% under present conditions, and saving rates were significantly affected by the air velocity, inlet conditions and the effectiveness of heat exchanger.

• 대한기계학회논문집B
• /
• 제35권9호
• /
• pp.947-954
• /
• 2011

차량에서 구동계의 의한 손실은 전체 연료 소비 손실에서 약 4%를 차지하며 그 중에서도 자동변속기는 구동계 손실에 큰 영향을 끼친다. ATF W/C 열교환기는 근래에 관심이 높아지고 있는 부품인데, 자동변속기 윤활유의 온도를 적정한 상태로 유지시켜 줌으로서 연비 개선 효과를 얻을 수 있다. 본 연구에서는 ATF W/C 열교환기 단품 특성을 실험적으로 파악하고, ATF W/C 열교환기가 실제 차에 장착되었을 때의 연비 개선 효과를 살펴보았다. 본 연구에서는 실험을 통하여 ATF 와 냉각수의 온도와 유량에 대한 유용도를 파악하고 유용도를 예측하기 위한 상관식을 도출하였다. MATLAB의 Simulink 프로그램을 통하여 실험의 결과를 바탕으로 ATF W/C 열교환기 유무에 따른 연료 소모량을 비교 하여 연비 개선 효과를 분석하였다. 그 결과 ATF W/C 열교환기가 장착된 자동차는 0.992% 연비 개선 효과가 나타났다.

• 대한기계학회논문집B
• /
• 제38권11호
• /
• pp.925-933
• /
• 2014

오늘날 고성능컴퓨터로 인해 많은 산업분야에서 전산해석이 사용되고 있다. 하지만 정해진 컴퓨터자원과 시간에 의해 3 차원 풀 스케일 해석에서는 많은 어려움 등이 있다. 본 연구에서 ${\varepsilon}-NTU$ 식과 열교환기 성능의 데이터베이스를 이용해 열교환기의 성능예측프로그램을 개발하였다. 다양한 타입의 열교환기 형상정보와 성능데이터베이스를 구축하였고, 이를 바탕으로 정해진 작동 조건에서 열교환기의 성능을 계산하였다. 계산된 정보를 바탕으로 최적의 사이즈를 갖는 형상을 찾기 위해 유전알고리즘(Genetic Algorithm)을 이용하였다. 계산을 위해 상용 소프트웨어인 MATLAB 과 REFPROP 이 사용되었다.

• 대한기계학회논문집B
• /
• 제20권4호
• /
• pp.1385-1394
• /
• 1996

A theoretical analysis was performed on the heat transfer by laminar oscillating flow in a simplified heat exchanger of a Stirling cycle machine and the results were compared with the experiment of Hwang. In the analysis the general solution to the temperature field obtained by Lee et. al was applied and extended to a more realistic situation. The results show that the heat transfer is influenced by the ratio of the swept distance of the fluid to the length of the heat exchanger as well as the oscillation frequency. This is well consistent with the result of Hwang's experiment. It is also revealed that there exist three distinct regimes having different heat transfer mechanisms. Through the scale analysis the main parameters governing the heat transfer in each regime are reduced and the dependency of the heat transfer on the parameters are examined.

• Nuclear Engineering and Technology
• /
• 제35권3호
• /
• pp.251-259
• /
• 2003

The Taguchi method was applied to investigate the effect of design factors on the performance of the shutdown cooling heat exchanger in the SMART-P. This method provided the simulation matrix for the KDESCENT program and an efficient tool for analyzing the simulation results. Levels of the design factors were selected by the effectiveness-NTU method. From 18 runs with the KDESCENT program, it was found that the performance of the system was greatly influenced by the inlet temperature at the shell side and the mass flow rate of the reactor coolant at the tube side. After applying the Taguchi method, we identified the important design factor that should be controlled and designed carefully. This method provides an efficient way to estimate the influence of each design factor on a system performance.