tailieunhanh - Evaporation Condensation and Heat transfer Part 2

Tham khảo tài liệu 'evaporation condensation and heat transfer part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 30 Evaporation Condensation and Heat Transfer vaporization. Since the pressure drop between the inlet and outlet of the test section was measured using a differential pressure transducer installed across the test section the measured pressure drop was the sum of the pressure drops across the test section. The total measured pressure drop could be divided into five components the test section inlet pressure drop cpiniet the single-phase frictional pressure drop the two-phase frictional pressure drop the acceleration pressure change pàcc and the test section outlet pressure change .poutiet Pexp- Rnlet Pf ẩpl I PfttpP feỄả Poutlet 5 The inlet pressure change dueto the sudden contraction at the inlet was estimated as 2 _ - 2 v _ _ _ Goutf ACross oute IX n Pinlet Rn R ũĩ 2 A fnlet n 6 where G is the mass flux g- is the specific volume of liquid and A is the cross-sectional area of the channel. The irreversible contraction loss coefficient Kiniet can be obtained from the literature Blevins 1984 and the subscripts in and out refer to the corresponding fluid connection. The single-phase region can befurther divided into developing and fully developed regions. For the present study the Rạmolds number of the test range was within the laminar flow range and the length of th e single-phase developing region can be neglected due to its small value. The single-phasefrictional pressure drop was calculated as Pf sp 7 2 uh where f is the dimensionless friction factor Lsp is the length of the single-phase region including the adiabatic length before the heated region and Dh is the hydraulic diameter of the channel. The dimensionless friction factor fRe for single-phase liquid flow was obtained from single-phase adiabatic experiments of the present study. The pressure increment caused by the sudden enlargement at the outlet can be calculated Collier Thome 1994 A IỈ a Poutlã Poẫ Pin 0n cross lng1 cross OU A_ 5 1 cros s in u rA 1 A cross out qA I a 7 where