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수평증발관내 R22/R114 혼합냉매의 열전달 특성에 관한 연구
윤치한,이종인,하옥남 대한설비공학회 2000 설비공학 논문집 Vol.12 No.5
Evaporation heat transfer characteristics were studied in a horizontal tube using R22/R114 non-azotropic refrigerant mixture. the heat transfer coefficient was high in the upper part for pure refrigerants, and heat transfer coefficient was low in the lower part for refrigerant mixtures. In the low quality region where nucleate boiling was dominant, the average heat transfer coefficient was low. In the region where forced convection was dominant, heat transfer coefficient was high. Results show that the heat transfer coefficient for pure refrigerants obtained by experiments were lower than those of Yoshida et al. but agreed well with Jung et al., and Chen et al. data. But the heat transfer coefficients for refrigerant mixtures were lower about 20% than those predicted by the equation for pure refrigerant.
하옥남,이행남,이종인,윤치한 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1
본 연구에서는 글리세린 수용액(45%)을 사용하여 2차원 분기관 유로의 정상 층류에서의 분기부의 유동 상태를 알아보기 위하여 레이놀즈 수, 분기 각도, 유량 분배비등이 손실 계수에 미치는 영향을 실험으로 구하고, 다음과 같은 결론을 얻었다. 레이놀즈 수 100을 기준으로 하여 100 이하에서 T형과 Y형의 값은 직선적으로 감소하고, 유량 분배비의 영향은 적으며, 100 이상에서는 유량 분배비에 따라 거의 일정한 값, 즉 본관에서는 0.3∼1.3 지관에서는 1.70∼2.45의 수치에 접근한다. 그러나, 분기각의 영향은 레이놀즈 수 100 이하에서는 크지만, 100 이상에서는 매우 적어서 일정한 값, 즉 본관에서 액 0.9, 지관에서 약 1.8의 값을 갖는다. The purpose of this research is to study the characteristics of the dividing flow in the laminar flow region. Using glycerine-water solution(45%) for Newtonian fluid, this research investigates the flow state of the dividing tube in steady laminar flow region of the two dimensional dividing tube by measuring the effect of Reynolds number, dividing angle, and the flow distribution ratio on the loss coefficient. The results of the research is as follows. In T-type and Y-type tube, the loss coefficient of the glycerine-water solution decreases in constant rate when the Reynolds number is below 100. The effect of the flow distribution rate is negligible. But when the Reynolds number is over 100. the loss coefficient as to the flow distribution rate converges to a constant value. In the main tube the value lies in the range of 0.30-1.30. In the lateral tube the value lies in the range of 1.7-2.45. The effect of the dividing angle is considerable when the Reynolds number is below 100. But it is very small and converges to a constant value when the number is over 100: in the main tube approximately 0.9, and 1.8 in the lateral tube.
R22/R114 혼합냉매의 수평증발관내 강제대류 전열특성에 관한 연구
하옥남,윤치한,이종인 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.1
It was studied on the heat transfer characteristic of forced convection in horizontal tube using the pure refrigerant and non-azeotropic refrigerant mixture, and compared the heat transfer coefficient. The inside wall temperatures and the heat transfer coefficients of horizontal evaporation tube were obtained from the experiments using the pure refrigerant, R22 and R114, and the non-azeotropic refrigerant mixture, R22/Rl14. In case of the pure refrigerant R114, with increasing the quality, the local heat transfer coefficient of bottom of the tube was the highest value without being influenced by flow rate. In case of the pure refrigerant R22, in the low flow rate region the local heat transfer coefficient of bottom of the tube were the highest, and these were decreased as quality was increased, and in the high flow rate region the reverse results were obtained. In case of the refrigerant mixture, the local heat transfer coefficient of the bottom of tube were the highest regardless of flow rate. Two phase convection heat transfer coefficients of 76mol%R22-24mol%R114 refrigerant mixture were lower about 20% than these of Chen's.