테프론 코팅 전열관 표면으로의 열 및 물질 전달 특성에 관한 실험적 연구

서지정보

· 발행기관 : 대한기계학회
· 수록지 정보 : 대한기계학회논문집 B / 27권 / 8호
· 저자명 : 이장호, 김형대, 김정배, 김무환

초록

* 포항공과대학교 대학원 기계공학과†책임저자, 회원, 포항공과대학교 기계공학과E-mail: [e-mail]: [phone], FAX: [phone]The heat and mass transfer on two kinds of tube surfaces (bare stainless steel tube and Teflon coated tube) in steam-air mixture flow are experimentally studied to obtain design data for the heat exchanger of the latent heat recovery from flue gas. In the test section, 3-tubes are horizontally installed, and steam-air mixture is vertically flowed from the top to the bottom. The pitch between tubes is 67mm, the out-diameter of tube is 25.4mm, and the thickness is 1.2mm; blockage factor (cross sectional tube area over the cross sectional area of the test section) is about 0.38. All of sensors and measurement systems (RTD, pressure sensor, flow-meter, relative humidity sensor, etc.) are calibrated with certificated standard sensors and the uncertainty for the heat transfer measurement is surveyed to have the uncertainty within 7%. As experimental results, overall heat transfer coefficient of the Teflon (FEP) coated tube is degraded about 20% compared to bare stainless tube. The degradation of overall heat transfer coefficient of Teflon coated tube comes from the additional heat transfer resistance due to Teflon coating. Its magnitude of heat transfer resistance is comparable to the in-tube heat transfer resistance. Nusselt and Sherwood numbers on Teflon (FEP) coated surface and bare stainless steel surface are discussed in detail with the contact angles of the condensate. 기호설명A : 면적 [m2]Cp : 정압 비열 [kJ/kg-K] D : 확산계수 [m2/s]F : 노즐면적을 포함한 유량계수 hs : 현열 열전달 계수 [w/m2.K]hm : 물질 전달 계수 [kg/m2.sec]K : 열전도율 [W/m.K]Kq : 막힘 비율 (blockage factor)m : 질량유량 [kg/s]Nu : Nusselt 수 (식 (14)) P : 노즐차압 [Pa]Q : 열전달량 [W]Re : 최소 흐름 면적에서의 Reynolds 수 (udo/μ) Sc : Schmidt 수 ( / D)Sh : Sherwood 수 (식 (15))t, : 두께 [m]R : 열저항 [K/W]T : 온도 [K or oC]U : 불확실성 Pr : Prandtl 수 u : 유속 [m/s]

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