Hot Gas를 이용한 히트펌프 성능개선에 관한 실험적 연구

전창덕 忠州大學校 2005 한국교통대학교 논문집 Vol.40 No.2

Frost formation easily occurs on the fin coils of outdoor heat exchanger under high humidity air below 5 ℃,it results in the decrease of geating capacity of heat pump. Several methods have been studied by far in order to solve this problem, one of the methods is hot gas bypass method. Two cases of experiments were performed, Case 1 is that outdoor fan speed is controlled under the poeration of hot gas bypass, Case 2 is that additional line is constructed so that refrigerant passes through thermal expansion valve and the hot gas bypass line independently. Outdoor fan speed is also controlled. In case 1, the optimal fan speed was 60% of rated fan speed, it showed about 1% decrease of average COPand 21% increase of heating capacity compared to time-controlled reverse cycle defrost. In case 2, the optimal fan speed is also 60% of rated fan speed, and it showed about 2% increase of average COP and 78% increase of heating capacity compared to time-controlled reverse cycle defrost. The reasons are that in Case 2, the defrost on the upper side of fin coilsoccurs rapidly in comparison with Case 1 under the operation of hot gas, it results in the increase of heating capacity and heating time.

Hot Gas를 이용한 히트펌프 성능개선에 관한 실험적 연구

전창덕 忠州大學校 2005 한국교통대학교 논문집 Vol.40 No.1

Frost formation easily occurs on the fin coils of outdoor heat exchanger under high humidity air below 5 ℃,it results in the decrease of geating capacity of heat pump. Several methods have been studied by far in order to solve this problem, one of the methods is hot gas bypass method. Two cases of experiments were performed, Case 1 is that outdoor fan speed is controlled under the poeration of hot gas bypass, Case 2 is that additional line is constructed so that refrigerant passes through thermal expansion valve and the hot gas bypass line independently. Outdoor fan speed is also controlled. In case 1, the optimal fan speed was 60% of rated fan speed, it showed about 1% decrease of average COPand 21% increase of heating capacity compared to time-controlled reverse cycle defrost. In case 2, the optimal fan speed is also 60% of rated fan speed, and it showed about 2% increase of average COP and 78% increase of heating capacity compared to time-controlled reverse cycle defrost. The reasons are that in Case 2, the defrost on the upper side of fin coilsoccurs rapidly in comparison with Case 1 under the operation of hot gas, it results in the increase of heating capacity and heating time.

휜-관 熱交換器의 蒸發特性에 關한 實驗的 硏究

장성운,전청덕 忠州大學校 2003 한국교통대학교 논문집 Vol.38 No.4

An experiment was carried out to investigate the characteristics of the evaporation heat transfer and pressure drop for refrigerant R407C in a fin-and-tube heat exchanger of commercial air-conditioning unit. Test was conducted at the conditions of inlet refrigerant evaporation temperature 7℃, inlet air relative humidity of 40~50%, and refrigerant mass flux varying from 150 to 250kg/m2s. The evaporation temperature of the refrigerant at the test section inlet were maintained at 7℃. Evaporation performance of R407C was 4.6~11.7%, 2.5~15% lower than compared to that of R22 for relative humidity 40% and 50% respectively and this difference was increased as the refrigerant mass flux increases. The experimental data were also useful in analyzing the effects of the temperature glide and length of two phase region for ternary non-azeotropic refrigerant mixture R407C, which is one of the potential candidates for the replacement of pure refrigerant R22.

심낭삼출을 동반한 CREST증후군 1례

윤덕구,박승국,박근용,전영준,이인규,박창호 啓明大學校 醫科大學 1986 계명의대학술지 Vol.5 No.2

CREST syndrome is variant of scleroderma characterized by calcinosis, Raynaud's phenomena, esophageal dysmotility, sclerodactyly & telangiectasia. In the past, it was believed that CREST patients live longer than scleroderma because rare involvement of internal organ, but recently noted that CREST patients may die early by involvement of internal organ. Recently, authors experience one case of CREST syndrome associated with pericardial effusion, herein presenting our experience and literature and reviewed.

후부요도 판막증 2례

유용덕,이창호,전윤수,이남규 순천향의학연구소 2004 Journal of Soonchunhyang Medical Science Vol.10 No.2

Posterial urethal valves represent the most common post-vesical obstructive malformation. One of the most credited pathological theories considers them an anomalous insertion of mesonephric duct into the cloca or incomplete involution of plicae colliculi. Urinary tract disorders that following posterior urethral valves include hydrouretheronephrosis and functional impairment of the entire urinary tract with consequent renal failure. Treatment of posterior urethral valves consists in their resection. In low-weight patients or in case of poor general condition, temporary external urinary bypass is feasible.

Condensation Heat Transfer of R22, R407C, and R410A in Slit Fin - and - Tube Heat Exchanger

Chang-Duk Jeon,Jinho Lee 대한설비공학회 2003 International Journal of Air-Conditioning and Refr Vol.11 No.4

Experimental Study of Heat Transfer Characteristics in the Louvered - Fin Heat Exchanger

Chang Duk Jeon,Jin-Ho Lee 대한설비공학회 1997 International Journal of Air-Conditioning and Refr Vol.5 No.-

Condensation Heat Transfer of R22, R407C, and R410A in Slit Fin-and-Tube Heat Exchanger

Jeon, Chang-Duk,Lee, Jin-Ho The Society of Air-Conditioning and Refrigerating 2003 International Journal Of Air-Conditioning and Refr Vol.11 No.4

R410A and R407C are considered to be alternative refrigerants of R22 for the air-conditioners. An experimental study is carried out to investigate the effect of the change of mass flow rate on the characteristics of heat transfer and pressure drop in three row slit finned-tube heat exchanger for R407C, R410A and R22. R407C, a non-azeotropic refrigerant mixture, exhibited a quite different condensation phenomenon from those of R22 and R410A and its condensation heat transfer coefficient was much lower than that of R22 and R410A. On the other hand, the condensation heat transfer coefficient of R410A, near-azeotropic refrigerant mixture, was a little higher than that of R22. R410A also showed the lowest condensation pressure drop across the test section. For all refrigerants, the condensation heat transfer coefficient and pressure drop increase as the mass flux increases. The condensation heat transfer coefficient correlation proposed by Kedzierski shows the best agreement with the experimental data within $\pm$20%.

광센서를 이용한 서리높이 예측 상관식 개발

전창덕(Jeon, Chang-Duk) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.10

본 연구에서는 KS C 9306에 따른 난방 제상능력 시험조건(건구온도 2℃/습구온도 1℃)에서 확대모형이 아닌 실제 열교환기의 전방에 디지탈 현미경과 광센서의 발광부와 수광부를 나란히 설치하여 광센서 출력전압과 서리 높이간의 연관성 을 규명하기 위한 실험을 수행하였다. 150개의 실험 데이터로부터 서리높이를 예측할 수 있는 선형 상관식을 개발하여 계산 한 결과, 측정값의 54%가 상관식으로 예측한 값의 ±10% 이내에서 일치하였으며 서리 높이가 0.3mm 이상의 실험데이터에서 는 데이터의 90% 이상이 ±10% 이내에서 일치하였다. Xiao 등의 상관식과 비교하였을 때 출력전압 변화에 따른 서리 높이의 변화를 나타내는 기울기는 2.3% 오차 범위에서 일치하였으나 Xiao 등의 상관식은 실제 열교환기가 아닌 모사 열교환기를 사용한 이상적인 조건에서 개발되었기 때문에 절편 값에서는 큰 차이를 보였다. In this study, experiments were conducted to investigate the correspondence between the output voltage of the photoelectric sensor and the frost height under heating and defrosting capacity test condition (dry bulb temperature 2℃, wet bulb temperature 1℃) described at KS C 9306, where a real heat exchanger was used as a test rig instead of a large-scale model. A digital microscope and a photoelectric sensor unit consisting of an emitter and a transistor (receiver) were installed in the front of it. A linear correlation is proposed to predict the frost height based on 150 experimental data, approximately 54% of the measured data are consistent with the predicted frost heights within a relative deviation of ±10%, it yields good agreement with 90% of the measured data when the frost height larger than 0.3mm with in a relative deviation of ±10%. Compared with Xiao's correlation, the slope namely, the change of frost height in accordance with the change of output voltage is consistent within the error of 2.3%. But vertical intercept shows big difference with Xiao's correlation, because it was developed with a large scale model instead of a real heat exchanger.

온도차 감지 제상법과의 비교를 통한 광센서 제상법의 타당성 검증을 위한 연구

전창덕(Chang-Duk Jeon),김동선(Dong-Seon Kim) 대한설비공학회 2014 설비공학 논문집 Vol.26 No.9

Experiments were performed to verify if performance and characteristic curves obtained from the temperature differential defrosting method, where surface temperature is measured to judge defrosting condition, can be reproduced by the photoelectric technology where defrosting condition is judged by photoelectric sensors. The output voltage of a phototransistor and heating capacity, power consumption, and surface temperature of the outdoor heat exchanger are compared. The results showed that the photoelectric sensors can be used as a defrost control device. On-off control timings in temperature differential defrosting method are in good agreement with those predicted by the high and low threshold output voltages of the photoelectric sensor.