• 한국산학기술학회논문지
• /
• 제16권7호
• /
• pp.4364-4374
• /
• 2015

본 연구에서는 복합 전열 촉진 핀 열교환기의 열전달 및 압력손실에 대하여 실험적으로 검토하였다. 비교를 위하여 널리 사용되는 루버 핀 열교환기에 대한 실험도 수행하였다. 핀 피치(1.5mm~1.7mm)와 열수(1열~3열)를 변화시키며 열전달 및 압력손실에 미치는 영향을 검토하였다. 실험범위에서 핀 피치가 j와 f 인자에 미치는 영향은 크지 않았다. 열수가 증가하면 j 인자는 감소하고 f 인자는 열수와 무관하였다. 루버 핀의 j와 f 인자가 복합 전열 촉진 핀의 값들보다 크게 나타났다. 1열의 경우 평균 j 인자와 f 인자는 23%, 27% 크고, 2열에서는 11%, 8%, 3열에서는 10%, 9% 크게 나타났다. 하지만 동일 압력 손실 대비 전열 성능은 복합 전열 촉진 핀 열교환기가 1열에서 6.4%, 2열에서 11.1%, 3열에서 13.6% 크게 나타났다. 기존 루버 핀 상관식은 j 인자를 과대 예측하고 f 인자를 과소 예측하였다.

• 한국기계가공학회지
• /
• 제20권11호
• /
• pp.121-126
• /
• 2021

In this study, the effect of thermal contact resistance between pin-channel tubes on the heat transfer characteristics was analytically examined around the channel tubes with the pins attached to two consecutive arranged channel pipes. The numerical results showed that the heat transfer coefficient decreased geometrically as the thermal contact resistance increased, and the corresponding temperature change on the contact surface increased as the thermal contact resistance increased. The thinner the pin, the more pronounced the geometric drop in the heat transfer coefficient. It was confirmed that the higher the height of the pin, the higher was the heat transfer coefficient, however, the greater the size of the thermal contact resistance, the smaller was the heat transfer coefficient. It was found that the temperature change in the inner wall of the channel tube did not significantly affect the heat transfer characteristics owing to the thermal contact resistance. Furthermore, the velocity of air at the entrance of the channel tube was proportional to the heat transfer coefficient due to a decrease in the convective heat resistance corresponding to an increase in the flow rate.

• 설비공학논문집
• /
• 제15권12호
• /
• pp.1043-1048
• /
• 2003

An experimental investigation was executed to determine the capacity degradation due to non-uniform refrigerant distribution in a multi-path evaporator. In addition, the possibility of recovering the capacity reduction by controlling the refrigerant distribution among refrigerant paths was assessed. The finned-tube evaporator, which had a three-path and three-depth-row, was tested by controlling inlet quality, exit pressure, and exit superheat for each refrigerant path. The capacity reduction due to superheat unbalance between each path was as much as 30%, even when the overall evaporator superheat was kept at a target value of 5.6$^{\circ}C$. It may indicate that the internal heat transfer within the evaporator assembly caused the partial capacity drop. For the evaporator having air mal-distributions, the maximum capacity reduction was found to be 8.7%. A 4.5% capacity recovery was obtained by controlling refrigerant distribution to obtain the target superheat at the outlet of each path.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집B
• /
• pp.7-12
• /
• 2000

The purpose of this study is to develop heat transfer analysis program of heat pipe elements and design a revolving heat pipe exchanger by the performance experiment of hot air production by means of middle-temperature waste heat. Experimental variables are the revolution per minute, normal velocity of inlet air and the temperature of waste heat. The revolving heat exchanger has designed as $2^{\circ}$ in inclination angle of heat pipe bundle and as 20% in working fluid quantity and as water in working fluid. Experimental value of the total heat transfer coefficient was $20w/m^2-^{\circ}C$

• 소음진동
• /
• 제9권6호
• /
• pp.1116-1122
• /
• 1999

HRSG, which is one of main components of the combined cycle power plant,is composed of an inlet duct, a main body and casing, an outlet duct and a stack. It is important to design HRSG wihtin the allowable noise limit. For this purpose, it is necessary to analyze and predict the noise reduction and radiation at HRSG. In this paper, the technology for the noise prediction at each part of HRSG has been based on the empirical and field data, and also the HRSG noise prediction program has been developed. In order to verify the developed technology and program a field test is conducted. The results of noise prediction show good agreement with the measured.

• 대한설비공학회지:설비저널
• /
• 제14권2호
• /
• pp.118-124
• /
• 1985

The motion of a fluid in the closed annular cavity formed by two concentric vertical cylinders with externally finned tube has been analysed by a numerical solutions of the equation of momentum and energy. For the calculation procedure, the fluid is assumed to have constant thermo-dynamic and transporties except for the density, which is temperature-dependent in the buoyancy term of the vertical momentum equation (Boussinesq approximation). The govern ins equations for velocity and temperature are solved by a finite difference technique which incoorporates a scheme for treating the coupled variables. Results are presented for a range of the Rayleigh number and for various values of the fin height and the number of fins.

• 공업화학
• /
• 제17권5호
• /
• pp.476-482
• /
• 2006

본 연구에서는 핀-관 열교환기의 공기측 열전달 및 마찰특성을 조사하기 위하여 8종의 열교환기에 대하여 난방조건에서 실험을 수행하였다. 핀-관 열교환기의 성능 비교평가를 위하여 공기엔탈피식 칼로리미터를 이용하였다. 실험에 사용된 핀은 슬릿, 루버, 평판형이며, 관경은 7.0 mm, 열수는 1, 2, 3열 그리고 4종의 관회로에 대해 j 계수와 마찰계수를 획득하였다. 실험을 통해서 핀형상, 핀피치, 열수 그리고 관회로의 변화에 대한 핀-관 열교환기의 공기측 열전달 및 마찰거동을 조사하였다. 실험결과는 관회로의 구성이 열교환기의 열전달과 마찰과 관련이 있음을 보여주었다. 동일 핀피치의 열교환기의 경우에 저 Re 수에서는 1열의 열전달성능이 우수하나 Re 수가 증가할수록 j 계수의 거동은 역전함을 보였다. 그리고 2열의 열교환기에서 핀종류에 따라 공기측 열전달성능과 마찰계수가 다르게 나타남을 확인하였다.

• 한국산학기술학회논문지
• /
• 제16권9호
• /
• pp.5778-5788
• /
• 2015

본 연구에서는 복합 전열 촉진 핀 열교환기의 습표면 열전달 및 압력손실에 대하여 실험적으로 검토하였다. 비교를 위하여 널리 사용되는 루버 핀 열교환기에 대한 실험도 수행하였다. 핀 핏치(1.5mm~1.7mm)와 열수(1열~3열)를 변화시키며 열전달 및 압력손실에 미치는 영향을 검토하였다. 실험범위에서 핀 핏치가 j와 f 인자에 미치는 영향은 크지 않았다. 열수가 증가하면 j와 f 인자 모두 감소하였다. 복합 전열 핀 열교환기의 j와 f 인자가 루버 핀 열교환기의 값들보다 크게 나타났다. 1열의 경우 평균 j 인자와 f 인자는 11%, 43% 크고, 2열에서는 8%, 50%, 3열에서는 17%, 53% 크게 나타났다. 동일 압력 손실 대비 전열 성능은 복합 전열 촉진 핀 열교환기가 1열에서 2.0%, 2열에서 3.1%, 3열에서 8.4% 크게 나타났다. 실험 자료를 기존 루버 핀 상관식과 비교하였다.

• 한국자동차공학회논문집
• /
• 제20권3호
• /
• pp.20-25
• /
• 2012

As a kind of distributed energy system, the co-generation system based Diesel engine using after-treatment device was devised for its environmental friendly and economic qualities. It is utilized in that the electric power is produced by the generator connected to the Diesel engine, and waste heat is recovered from both the exhaust gases and the engine itself by the finned tube and shell & tube heat exchangers. An after-treatment device composed ceramic heater and DOC(Diesel Oxidation Catalyst) is installed at the engine outlet in order to completely reignite the unburned fuel from the Diesel engine. In this study, mutual relation of each experimental condition was derived through minimum number of experiment using Taguchi Design and ANOVA recently used in the various fields. It is found that the total efficiency (thermal efficiency plus electric power generation efficiency) of this system reaches maximum 94.4% which is approximately higher than that of the typical diesel engine exhaust heat recovery system.

• Journal of Mechanical Science and Technology
• /
• 제17권6호
• /
• pp.925-934
• /
• 2003

An experimental study is performed to investigate the characteristics of near wake flow behind a circular cylinder with serrated fins using a constant temperature anemometer and flow visualization. Various vortex shedding modes are observed. Fin height and pitch are closely related to the vortex shedding frequency after a certain transient Reynolds number. The through velocity across the fins decreases with increasing fin height and decreasing fin pitch. Vortex shedding is affected strongly by the velocity distribution just on top of the finned tube. The weaker gradient of velocity distribution is shown as increasing the freestream velocity and the fin height, while decreasing the fin pitch. The weaker velocity gradient delays the entrainment flow and weakens its strength. As a result of this phenomenon, vortex shedding is decreased. The effective diameter is defined as a virtual circular cylinder diameter taking into account the volume of fins, while the hydraulic diameter is proposed to cover the effect of friction by the fin surfaces. The Strouhal number based upon the effective diameters seems to correlate well with that of a circular cylinder without fins. After a certain transient Reynolds number, the trend of the Strouhal number can be estimated by checking the ratio of effective diameter to inner diameter. The normalized velocity and turbulent intensity distributions with the hydraulic diameter exhibit the best correlation with the circular cylinder's data.