Tube-in-Tube 미세관내 R-22 및 R-407C의 응축열전달 특성 (The Condensation Heat Transfer Characteristics of R-22 and R-407C Inside Small Diameter Tube-in-Tube Heat Exchangers)

서지정보

· 발행기관 : 대한설비공학회
· 수록지 정보 : 설비공학 논문집 / 33권 / 2호 / 80 ~ 89페이지
· 저자명 : 최광일, 오종택

초록

내경 4 mm인 세관을 이용한 tube-in-tube 열교환기 및 내경 8 mm인 이중관형 열교환기에서 R-407C와 R-22를 이용한 압력강하 및 응축열전달계수 실험 결과를 다음과 같이 요약할 수 있다.
(1) 응축포화온도가 낮고 질량유속이 증가할수록 압력강하는 증가하였으며, 내경이 4 mm×4 ch열교환기가 8 mm×1 ch보다 약 2.5배 증가하였다.
(2) 동일 실험조건에서의 R-407C가 R-22보다 압력강하가 낮게 나타났으며, 관경의 변화에 대한 압력강하는 4 mm보다 3 mm가 약 1.8배, 3 mm보다 2 mm가 약 1.3배 정도 높게 나타났다.
(3) 응축열전달계수는 응축포화온도가 낮고 질량유속이 증가할수록 증가하였으며, 질량유속의 영향이 응축포화온도의 영향보다 크게 나타났다.
(4) 응축열전달계수는 내경이 4 mm×4 ch 열교환기가 8 mm×1 ch보다 약 40% 이상 증가하였다. 또한 동일 실험조건에서의 3성분 혼합냉매인 R-407C가 단일 냉매인 R-22보다 평균열전달계수가 10% 정도 높게 나타났다.
(5) 실험데이터를 이용하여 R-22 및 R-407C 응축열전달계수 상관식을 제안하였으며, 각각 실험데이터와 MD 10.6% 및 10.1%와 AD -0.92% 및 -0.31%로써 비교적 잘 일치하였다.

영어초록

This paper focuses on the results of an experimental study of condensation heat transfer coefficients with the refrigerants R-22 and R-407C, and looks at the pressure gradient and heat transfer coefficients of horizontal tube-in-tube heat exchangers with the use of small tubes with inner diameters of 4 mm, 3 mm and 2 mm, in a 16.91 mm tube and length of 3,000 mm. Experiments were performed at an inlet saturation temperature of 35 to 45℃ and mass flux ranges from 200 to 600 kg/m2s. The use of an inner tube with a diameter of 4.0 mm resulted in a pressure gradient that was 2.5 times higher than that of an inner tube with a diameter of 8.0mm. In tube-in-tube HEX, the pressure gradients of R-22 measured higher than those of R-407C. The condensation heat transfer coefficients increase with an increase in mass flux, but they decrease with an increase in saturation temperature. Condensation heat transfer coefficients of R-407C were a little higher than those of R-22, and the condensation heat transfer coefficients of double tube HEX were about 40% higher than those of tube-in-tube HEX. The experimental results of this study were also compared with five existing correlations. New condensation heat transfer correlations were developed, and successfully predicted the experimental results with mean deviations of 10.6% and 10.1%, and average deviations are -0.92% and -0.31%, for R-22 and R-407C, respectively.

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