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The evaporation pressure drop of CO2 (R-744) in a horizontal tube was investigated experimentally.The main components of the refrigerant loop are a receiver, a variable-speed pump, a mas flow meter, a and an evaporator (test section). The test section consists of a smooth, horizontal stainless steel tube of 4.57 mm inner diameter. The experiments were conducted at saturation temperature of -5℃ to 5℃, and heat flux of 10 to 40 kW/m2. The test results showed that the evaporation pressure drop of CO2 are highly dependent on the vapor quality, heat flux and saturation temperature. The measured pressure drop during the evaporation process of CO2 increases with increased mas flux, and decreased saturation temperature. The evaporation pressure drop of CO2 is much lower than that of R-22. In comparison with test results and existing correlations, the best fit of the present experimental data is obtained with the previous correlation. But existing correlations failed to predict the evaporation pressure drop of CO2. Therefore, it is necessary to develop reliable and accurate predictions determing the evaporation pressure drop of CO2 in a horizontal tube.접수일 : 2006년 10월 28일, 채택확정 : 2007년 2월 8일구학근(책임저자) : 동명대학교 환경설비공학과E-mail : hgkur@tu.ac.kr, TEL : 051)620-3521손창효 : (주)티알이엔씨기호 설명d : 관경 [m]f : 마찰계수G : 질량유속 [kg/m2s]P : 압력 [Pa]Re : 레이놀즈수 [Gdi/μ]T : 온도 [℃]x : 건도Xtt : 파라메타dz : 소시험구간의 길이 [m]그리스 문자α : 보이드율μ : 점성계수ρ : 밀도ν : 비체적 Φ : 이상류 압력강하 변수하첨자e : 증발exp : 실험값f : 마찰 i : 내측in : 입구l : 액상lo : 액상만loc : 국소값a : 운동량m : 측정값re : 냉매tp : 이상류v : 기상수평관내 이산화탄소의 증발 압력강하- 64 -