본 연구에서는 원형휜-원형관 열교환기의 성능을 증가시키기 위하여 새로 고안된 V형 원형휜-원형관 열교환기의 열전달 및 압력강하 특성에 관하여 연구를 수행하였다. 단일 V형 원형휜-원형관 열교환기와 다열 V형 원형휜-원형관 열교환기에 대하여 실험 및 수치계산을 수행하였다. 단일 V형 원형휜-원형관 열교환기는 원형휜 면적대비 V형으로 접은 휜 면적의 비가 다른 4종과 V형으로 접은 각도가 다른 9종에 대하여 각각 수치계산하고 열전달, 압력강하, 국부열전달, 온도분포, 휜온도 및 속도분포에 대하여 분석하였다. 면적 4종에 대하여 면적비가 0.37인 경우, 수와 수는 Reynolds 수 8,900에서 기존의 원형휜보다 각각 40%와 24%증가한다. V각도 9종에 대하여 각도가 증가할수록 유동박리각은 후류방향으로 지연되며 V각도 55°의 경우, 동일한 팬 동력대비 열전달 성능이 가장 우수하여 원형휜보다 약 28%정도 증가한다. 공기흐름방향으로 4열의 엇갈림배열 V형 원형휜-원형관 열교환기의 V각도는 60°이며 수와 수는 Reynolds 수 19,160인 경우, 원형휜에 비하여 각각 31%, 16% 증가한다. 모형 V형 원형휜-원형관 열교환기의 압력강하 측정결과는 원형휜의 압력강하보다 약 2배 높고 수치해석 결과보다 평균 23.2% 크다.
In this research, the characteristics of heat transfer and pressure drop of V-bent circul ar fin-tube heat exchanger, which was newly designed to improve the performance of circular fin-tube heat exchanger, were studied. In this regard, an experiment and a numerical analysis were conducted on a single V-bent circular fin-tube heat exchanger and a multi-arrayed V-bent circular fin-tube heat exchanger. With regard to the single V-bent circular fin-tube heat exchanger, a numerical analysis and an analysis regarding heat transfer, pressure drop, local heat transfer, temperature distribution, fin temperature, and velocity distribution were conducted on four types of areas of which the ratios of the fin area folded in V shape in comparison to the circular fin area are different from each other and nine types of angles of which the angles folded in V shape are different from each other. As to four types of areas, in the case where the area ratio was 0.37, f factor and j factor, at the condition where Reynolds number was 8,900, increased by 40% and 24%, respectively, when compared to the existing circular fin. As to nine types of V angle, the flow separation angle was delayed to the direction of wake flow according to the increase in angle, and in the case where V angle was 55°, the heat transfer performance in comparison to the same fan power was most excellent, increasing by approximately 28% when compared to the circular fin. The V angle of the V-bent circular fin-tube heat exchanger, arrayed in a staggered arrangement, in four rows in the direction of air flow, was 60°; and f factor and j factor at the condition where Reynolds number was 19,160, increased by 31% and 16%, respectively, when compared to the circular fin. According to the measurement of pressure drop of V-bent circular fin-tube heat exchanger, a down scale model, it was found that the pressure drop was approximately two times higher than that of the circular fin, 23.2% higher in average when compared to the numerical analysis result.