In this study, the cooling performance change according to the arrangement of the fin-tube heat exchanger using a single tube and the cooling performance change according to the air flow rate were studied. The arrangement of basic heat exchanger was set to 4 columns and 4 rows, and the performance change was studied while changing the columns and rows. In addition, the performance change was investigated by changing the air flow rate of the basic heat exchanger.

본 연구는 절탄기 튜브의 저온부식 손상을 방지하기 위해 Inconel 625 용사재료를 활용하여 아크 열용사 코팅기술 적용 후 실링 처리를 실시하였다. 용사코팅(TSC) 층의 내식성 분석을 위해 0.5 wt% 황산 수용액에서 다양한 전기화학적 실험을 진행하였다. 양극분극 실험 후에는 주사전자현미경과 EDS 성분분석을 통해 부식 손상 정도를 파악하였다. 자연전위 계측 시 TSC+실링처리(TSC+Sealing)의 안정적인 전위 형성을 통해 실링처리 효과를 확인하였다. 양극분극 실험 결과 TSC와 TSC+Sealing에서 부동태 영역이 확인되었으며, 부식 손상 역시 관찰되지 않아 내식성이 개선되었다. 더불어 타펠분석에 의해 산출된 부식전위와 부식전류밀도 분석 결과 TSC+Sealing의 내식성이 가장 우수하게 나타났다.

One simple way of increasing the heat transfer for a fin-and-tube heat exchanger is to increase the fin surface area. In this study, a series of tests were conducted on wide slit fin heat exchangers having an increased fin area (Pl/Pt = 0.87), and the results were compared with those of standard slit fin heat exchangers (Pl/Pt = 0.6). Thermal performances of wide silt-finned samples were superior to those of standard slit fin samples. For one row configuration, the j factor of the wide slit fin sample was 11% larger, and the f factor was 33 % smaller than those of the standard slit fin sample. The difference decreased as the number of tube row increased, although wide slit fin sample always yielded superior performance, The reason was attributed to the many narrower slits formed on the wide fin sample. Furthermore, the effect of fin pitch on j and f factor was not significant, and j factor decreased with the increase of the number of tube row.

This study was to develop the automatic fin tube cutting machine, equipped with semi-automatic supplying board, automatic transfer equipment, fin tube holder, and cutting equipment assembly for the effective and safe fin tube cutting. The development of the automatic fin tube cutting machine resulted in improving 150% of productivity, 300% of cutting length precision, and 230% of a vertical angle precision on the cutting plane. In addition, we were able to secure safety of the workers and to automate production management, and further to reduce environmental pollution by recycling cutting chips.

In this paper, the hybrid tube expander unit for fin and tube type heat exchanger are developed by means of enlarging and inserting the smooth tube with a small diameter to a finned tube having larger diameter. In other word, the tube expander tool that is easy to attach and remove from tube is developed. The hybrid tube expander unit developed in this study can move easily and enlarge the tube without fixing at tube sheet. Also, this unit has a function removing scales inside tube by replacing a tube expander ball.

Heat transfer enhancement of fin-tube heat exchangers with vortex generators is investigated using naphthalene sublimation technique. Experiments are performed for the fin-flat tube and the fin-circular tube heat exchangers with and without vortex generator. Vortex generators are found to enhance heat transfer rate on the fin surface dramatically. Their effect is relatively high in the fin-flat tube heat exchanger compared to fin-circular tube heat exchanger. Performance test is done for the prototype of air-conditioning heat exchanger and gas boiler heat exchanger with and without vortex generators .Fin-flat tube heat exchanger with vortex generator promote local heat transfer coefficient by 75% and increase friction factor, but friction of fin-flat tube heat exchanger with vortex generator is lower than that of fin-circular tube heat exchanger without vortex generator by 45%