• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.61-66
• /
• 2003

Fouling is very serious problem in heat exchanger because it rapidly deteriorates the performance of heat exchanger. Cross-flow heat exchanger with vortex generators is developed, which enhance heat transfer and reduce fouling. In the present heat exchanger, shell and baffle are removed from the conventional shell-and-tube heat exchanger. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients. The experiments are performed for single circular tube, staggered array tube bank and in-line array tube bank with and without vortex generators. Local and average Nusselt numbers of single tube and tube bank with vortex generator are investigated and compared to those of without vortex generator.

• 대한기계학회논문집
• /
• 제19권10호
• /
• pp.2657-2666
• /
• 1995

In this study, the effects of design factors of finned-tube heat exchanger, such as fin spacing and fin array on the frost growth and heat exchanger performance are investigated under a frosting condition. The results show that the amount of frost, frost density and blockage ratio of air flow passage increase with decreasing fin spacing. Heat transfer rate increases momentarily at the initial stage of frosting and then decreases. After that heat transfer rate continues to increase again to reach a maximum value and then decreases dramatically. It is shown that the time required for heat transfer rate to reach a maximum value becomes shorter with decreasing fin spacing, and after a maximum value, heat transfer rate decreases very fast. The maximum allowable blockage ratio is introduced to determine the operation limit of a finned-tube heat exchanger operating under frosting condition and is obtained as a function of fin spacing. It is also shown that heat transfer rate of heat exchanger with staggered fin array increases about 17% and the amount of pressure drop of air increases about 1~2 mmH$_{2}$O, compared with those of in-line type heat exchanger under frosting condition.

• 한국산학기술학회논문지
• /
• 제16권10호
• /
• pp.6641-6646
• /
• 2015

배열회수 보일러의 전열관군은 외부에 가스터빈에서 나온 고온의 배기가스가 흐르게 된다. 이러한 유체의 흐름으로 인해 전열관군에서 시간변화에 따라 양력의 변동이 발생하는데 이에 따라 유동 유발 진동이 발생한다. 이러한 진동이 배열회수 보일러의 전열관군에서 파손을 야기할 수 있어서 열교환기의 구조적 안정성을 위해 열교환기의 전열관군에서 유동 유발 진동 특성을 규명할 필요가 있다. 일반적인 열교환기 전열관군에서 유동 유발 진동에 관한 실험적 연구는 기존에 많이 진행되어 오고 있으며 유동 유발 진동에 대한 무차원 PSD(Power Spectral Density) 함수를 무차원 주파수인 Strouhal 수, fU/U의 함수로 실험적 결과들이 도출되어 있다. 본 연구는 열교환기 전열관군에서 유동 유발 진동에 관한 기존의 실험적 연구들의 결과를 전산유체해석을 통해 검증하고 배열회수 보일러의 전열관군의 유동 유발 진동 특성에 적용하기 위한 기반을 마련하는 것을 목적으로 한다. 이러한 것을 위해 기존 연구에서 실험에 사용한 전열관군에서 비정상 상태 유동해석을 수행하여 전열관군에서의 양력 변화 특성을 살펴보았다. 또한 전열관군에서 양력 변동 특성으로부터 유동 유발 진동에 따른 PSD 특성 결과를 도출하여 기존의 연구들과 비교를 통해 전열관군에서의 PSD 특성을 정립하였다.

• 설비공학논문집
• /
• 제16권4호
• /
• pp.340-348
• /
• 2004

The air and refrigerant side heat transfer performances are key parameters to improve heat transfer efficiency of the heat exchanger including the fan performance. Design of the fins, treatment of the tube inside, tube diameter and tube array effect heat transfer performance of the heat exchanger. The heat exchanger is used as a condenser at cooling mode and used as an evaporator at heating mode in the heat pump system. The heat pump system uses R410A as the refrigerant. The heat exchangers are consisted with 7 mm diameter tubes with slit-type fins. The study was conducted with variation of arrangement of the refrigerant path and air flow rate and refrigerant pressure drop and heat transfer rate were measured with a code tester. The capacity of the 3 path heat exchanger is more efficient than 2 or 4 path heat exchangers in heating or cooling modes.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회B
• /
• pp.2011-2016
• /
• 2008

A new method is presented for developing a simulation program which can analyze the heat transfer characteristics of fin-tube heat exchanger. This method is able to describe several types of refrigerant circuit arrangement. The delivery path of air and refrigerant properties is simplified by transforming three-dimensional array into one-dimensional array. By comparing simulated results with experiment results, the deviation was 8.2%. Several fin-tube heat exchangers of different design factors and operating conditions were simulated using this program. It was shown that this program could be used for designing practical fin-tube heat exchangers.

• 설비공학논문집
• /
• 제20권12호
• /
• pp.833-843
• /
• 2008

A new method is presented for developing a simulation program which can analyze the heat transfer characteristics of fin-tube heat exchanger. This method is able to describe several types of refrigerant circuit arrangement. The delivery path of air and refrigerant properties is simplified by transforming three-dimensional array into one-dimensional array. By comparing simulated results with experiment results, the deviation was 8.2%. Several fin-tube heat exchangers of different design factors and operating conditions were simulated using this program. It was shown that this program could be used for designing practical fin-tube heat exchangers.

• 한국태양에너지학회:학술대회논문집
• /
• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
• /
• pp.68-73
• /
• 2011

This study was performed numerical analysis in order to analyze liquid film flow of heat exchanger tube arrangement and configuration of evaporative multi effect distillation system using medium-temperature. Simulation was accomplished the two-dimensional calculations using commercial analyses program FLUENT based on the FVM(finite volume method). Fresh water generator of this study used Shell & Tubes heat exchanger with Cu_Ni tube, configuration of tube used bare tube and corrugated tube, and arrangement of tube used in-line array and staggered array. Performance of heat exchanger through the formation of liquid film was compared and analyzed. Liquid film flow occurred that falling on heat exchanger tube wall. Result of simulation showed that liquid film thickness of in-line arrangement was found 0.57mm with bare tube and 0.67mm with corrugated tube, respectively. And liquid film thickness of staggered arrangement was found 0.39mm with bare tubes and 0.62mm with corrugated tubes, respectively. Liquid film thickness of corrugated tube showed thicker than bare tube, but heat transfer rates of corrugated tube showed higher than bare tube. The reason was considered that surface area of corrugated tube was wider than bare tube. And liquid film thickness of staggered arrangement showed thinner than in-line arrangement, so thermal performance of staggered arrangement showed higher than in-line arrangement.

• 한국산학기술학회논문지
• /
• 제17권2호
• /
• pp.712-718
• /
• 2016

배열회수 보일러의 전열관군은 외부에 가스터빈에서 나온 고온의 배기가스가 흐르게 된다. 이러한 유체의 흐름으로 인해 전열관군에서 시간변화에 따라 양력과 항력의 변동이 발생하는데 이에 따라 유동 유발 진동이 발생한다. 이러한 진동이 배열회수 보일러의 전열관군에서 파손을 야기할 수 있어서 열교환기의 구조적 안정성을 위해 열교환기의 전열관군에서 유동 유발 진동 특성을 규명할 필요가 있다. 일반적인 열교환기 전열관군에서 유동 유발 진동에 관한 실험적 연구는 기존에 많이 진행되어 오고 있으며 유동 유발 진동에 대한 무차원 PSD(Power Spectral Density) 함수를 무차원 주파수인 Strouhal 수, fD/U의 함수로 실험적 결과들이 도출되어 있다. 본 연구는 열교환기 전열관군에서 유동 유발 진동에 관한 기존의 실험적 연구들의 결과를 전산유체해석을 통해 검증하고 배열회수 보일러의 전열관군의 양력과 항력의 PSD 특성에 적용하기 위한 기반을 마련하는 것을 목적으로 한다. 이러한 것을 위해 기존 연구에서 실험에 사용한 전열관군에서 비정상 상태 유동해석을 수행하여 전열관군에서의 양력과 항력 변화 특성을 살펴보았다. 또한 전열관군에서 양력과 항력 변동 특성으로부터 유동 유발 진동에 따른 PSD 특성 결과를 도출하여 기존의 연구들과 비교를 통해 전열관군에서의 PSD 특성을 정립하였다.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2007년도 동계학술발표대회 논문집
• /
• pp.185-190
• /
• 2007

For the successful design of heat exchangers, it is very important to understand local heat transfer characteristics on the circular cylinder of the cross flow heat exchangers. In this study, the heat exchanger using screen is developed to enhance heat transfer. The naphthalene sublimation technique is employed to measure the local heat transfer coefficients in the heat exchanger. The experiments are performed for single circular tube, in-line array tube bank with and without heat transfer promoter. Local Nusselt numbers of single circular tube and tube bank with heat transfer promoter are investigated and compared to those of without heat transfer promoter.

• 한국안전학회지
• /
• 제16권4호
• /
• pp.22-28
• /
• 2001

Heat transfer and pressure distribution for heat exchanger type of domestic gas boiler are different from shape, pitch, thickness of fin and array of pipe respectively. In order to measure the pressure distribution across the heat exchanger, a suction type wind tunnel was constructed and velocity distribution was measured for pilot tube(4 point) of rack type. The experiments were performed for 5 different air flow mass, rpm=3,6,9,12,15 and transverse axis of heat exchanger(x-length) is 5cm respectively. Results showed that above 9.5m/s, pressure distribution dispersion for wet type of heat exchanger is on the increase and above 5.5m/s, pressure distribution dispersion for dry type of heat exchanger is on the increase. Also, pressure distribution dispersion by comparing two different types heat exchanger, dry type of heat exchanger showed a higher augmentation than wet type of heat exchanger.