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

• 한국전산유체공학회지
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• 제19권1호
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• pp.47-56
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• 2014

Since a typical plate heat exchanger is made up of a huge number of unitary cells, it may be impossible to predict the aero-thermal performance of the full scale heat exchanger through three-dimensional numerical simulation due to the enormous amount of computing resources and time required. In the present study, a simple flow-network model using the friction factor correlation and a thermal-network model based on the effectiveness-number of transfer units (${\varepsilon}$-NTU) method has been developed. The complicated flow pattern inside the cross-corrugated heat exchanger has been modeled into flow and thermal networks. Using this model, the heat transfer between neighboring streams can be considered, and the pressure drop and the heat transfer rate of full-scale heat exchanger matrix are calculated. In the calculation, the aero-thermal performance of each unitary cell of the heat exchanger matrix was evaluated using correlations of the Fanning friction factor f and the Nusselt number Nu, which were calculated by unitary-cell CFD model.

• Journal of Advanced Marine Engineering and Technology
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• 제29권6호
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• pp.685-691
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• 2005

In this study, high performance waste heat recovery heat exchanger was developed using the bayonet tube with spiral serrated fins. Especially, heat exchanger of the bayonet tube type was operated well because of double water passes mechanism and characteristics. A cooling water Passes down inner tubes to thimble-form tubes, then flows back up as it boils. The heat exchanger of bayonet tube type was composed of steel tube with 7channels$(I.D_1\;14mm.\;I.D_2\;31.6mm)$ and spiral serrated fins. The performance tests were conducted under the following conditions A cooling water flow rate was 273kg/h and engine l·pm was varied from 750rpm to 3500 rpm. From the experimental result. waste heat recovery was 9.21kW when engine rpm was 3500. and pressure drop was $15\~260mmHg/m^3$ The effectiveness of heat exchanger was about /$0.7\~0.9$. The performance of heat exchanger was evaluated by using the $\varepsilon-NTU$ method. In the study the NTU of the heat exchanger was $1.57\~2.33$.

• 한국자동차공학회논문집
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• 제10권3호
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• pp.51-60
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• 2002

An analysis method to predict performance of a vehicle cooling system which is composed of radiator, A/C condenser, cooling fan, and etc. is suggested. Air flow through the heat exchanger system and heat rejection rate which dominate the cooling performance are analyzed. Heat transfer with A/C refrigerant phase change is also considered in the analysis. Some predicted results are compared with experimental data for various operating conditions. This evaluation procedure will be useful for the design of optimal vehicle cooling system.

• 대한기계학회논문집B
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• 제37권5호
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• pp.503-511
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• 2013

연료전지 시스템에서 공급기체 가습은 연료전지 성능효율과 전해질막 수명 향상 측면에서 중요하다. 판형 막 가습기는 일반적으로 유동 방향에 따라 직교류와 대향류로 구분되고 판과 막 사이에서 고온 다습한 공기와 저온 건조한 공기의 열 및 물질전달이 이루어진다. 본 연구에서는 현열 및 잠열 ${\varepsilon}$-NTU 법을 이용하여 입구 온도와 유량 변화에 따른 열 및 물질전달 성능 변화를 유동 방향에 따라 비교하였다. 이를 통하여 저유량 일 때 대향류는 직교류 보다 열 및 물질전달 성능이 높은 것을 알 수 있었고 유량이 증가함에 따라 성능 차이가 감소되는 것을 확인할 수 있었다. 그리고 입구온도가 증가함에 따라 열전달 성능 변화는 작은 반면 물질전달 성능 변화는 비선형으로 크게 감소되는 결과를 얻었다.

• 한국수소및신에너지학회논문집
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• 제14권1호
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• pp.53-60
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• 2003

Performance evaluation on thermal transport of a plate heat exchanger has been carried out. The $\varepsilon$-Ntu method is employed to evaluate the performance of a brazed type of plate heat exchanger. This problem is of particular interest in the design of a plate heat exchanger. The characteristics of heat transfer as well as pressure drop are studied in the wide range of Reynolds numbers in the cold side while that of hot side is fixed at 620. f-factor correlation in a plate heat exchanger is obtained from the pressure drop data. It is also found that the effectiveness of the plate heat exchanger is increased as the Ntu is increased.

• International Journal of Air-Conditioning and Refrigeration
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• 제11권2호
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• pp.73-81
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• 2003

The performance of heat exchanger using oscillating heat pipe (OHP) for low temperature waste heat recovery was evaluated. OHP used in this study was made from low finned copper tubes connected by many turns to become the closed loop of serpentine structure. The OHP heat exchanger was formed into shell and tube type. R-22 and R-141b were used as the working fluids of OHP with a fill ratio of 40 vol.%. Water was used as the working fluid of shell side. As the experimental parameters, the inlet temperature difference between heating and cooling water and the mass velocity of water were changed. The mass velocity of water was changed from 30 kg/$m^2$s to 92 kg/$m^2$s. The experimental results showed that the heat recovery rate linearly increased as the mass velocity and the inlet temperature difference of water increased. Finally, the performance of OHP heat exchanger was evaluated by $\varepsilon$-NTU method. It was found that the effectiveness would be 80% if NTU were about 1.5.

• 설비공학논문집
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• 제13권5호
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• pp.368-376
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• 2001

Performance of heat exchanger was evaluated to heat exchanger using oscillating heat pipe for waste heat recovery of low temperature. Oscillating heat pipe used in this study was formed to the closed loop of serpentine shapes using copper tubes. Heat exchanger was formed to shell and tube type and composed of low finned tube. R-22 and R-141b were used to the working fluids of tube side and their charging ratio was 40%. And, water was used to the working fluid of shell side. As the experimental parameters, the inlet temperature difference of heating and cooling part of secondary fluid and the mass velocity of secondary fluid were used. The mass velocity of secondary fluid was changed from 90 kg/$m^2s\; to\;190 kg/m^2$s from the experimental results, heat recovery rate was linearly increased to the increment of the mass velocity of secondary fluid and the inlet temperature difference of secondary fluid. Finally, the performance of heat exchanger was evaluated by using $\varepsilon$-NTU method. It was found that NTU was about 1.5 when effectiveness was decided to 80%.

• 설비공학논문집
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• 제13권8호
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• pp.771-779
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• 2001

In this study, a simulation program has been developed to predict the performance of a parallel flow condenser of an air conditioning system for an automobile. The well-known correlations for he heat transfer rates and the pressure drops are included in this model. It is fond that the numerical model can predict the heat transfer rate and the pressure drop accurately. As the condensing pressure increases of fixed air inlet temperature, the heat transfer rate increases and the pressure drop decreases. The effect of he degree of subcooling on the performance of the condenser is greater than that of the degree of super-heating because the ratio of the area occupied by he tow-phase refrigerant the total area is significantly affected by he degree of subcooling rather than the degree of superheating.

• 한국산학기술학회논문지
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• 제21권7호
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• pp.270-276
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• 2020

3D 프린팅은 고분자, 세라믹, 금속 등 다양한 소재를 대상으로 복합적인 형상을 한 번의 공정으로 제작할 수 있는 적층 기반 제작 기술이다. 최근의 3D 프린팅 기술은 프린팅 속도의 향상과 적용 가능 소재의 지속적인 개발에 의해 양산형 제품 생산이 가능한 수준으로 발전하였다. 본 연구에서는 레이저를 활용한 3D 프린팅 기술을 적용하여 철도 차량용 공기 압축기에 쓰이는 열교환기 제작을 진행하였다. 먼저 3D 프린팅에 적합한 형상으로 경량화 및 컴팩트화를 주안점으로 열교환기의 최적 설계를 진행하였다. 그로부터 도출된 설계안을 기반으로 SLM 기법을 적용하여 AlSi10Mg 합금 소재로 열교환기 시작품을 제작하였다. 다음으로, 제작된 시작품을 기존 공기 압축기에 부착하여, 압축공기의 열교환 성능을 시험하였다. 3D 프린팅 시작품의 시험 결과는 기존 열교환기 대비하여 저압부와 고압부에서 열교환 성능은 각각 약 80% 및 85% 수준을 보였다, 하지만 외부 냉각공기 조건을 기존 열교환기와 유사한 조건으로 가정하였을 때 𝓔-NTU 법을 활용하여 계산한 열전달량은 기존 열교환기 대비하여 유사한 성능을 보여 주었다. 결과적으로, 3D 프린팅 제작 열교환기의 성능 효과 및 경량화 등의 장점을 확인할 수 있었다.