所屬科目：研究所、轉學考(插大)◆單元操作與輸送現象
(1)To write down the define of hydraulic radius and equivalent diameter , and what is the hydraulic radius for annulus between two concentric pipes? (4%)
2. A cylinder (cross-sectional diameter of 0.01128 m) containing chloropicrin (CCl3NO2) is placed in a hood. The hood has a blower system that continually circulates dry air at a constant temperature 25℃ and 1 atm pressure. Originally, the liquid surface is 0.0388 m from the top of the cylinder. After one day the liquid level is 0.0412 m below the top. The vapor pressure and density of CCl3NO2 are 3178.3 N/m2 and 1650 kg/m3, estimate the substances diffusivity in air. Molecular weight of CCl3NO2 is 164.39. (20%)
(3) If cooling water enters the condenser at 80°F and leaves at 150°F, how much cooling water is required?(7%)
4. A fan sends static air into a 45 m long； rectangular pipe of 200 mm x 300 mm. The air entering the pipe is 15℃and 750 mmHg absolute pressure, and the flow rate is 0.6 m3/s. What is the theoretical power required? For a smooth tube, f= 16/Re in laminar flow； f= in turbulent flow； Re is the Reynolds number. (20%)
5. What is flowing through a large circular conduit with a velocity profile given by the equation v = 9(1-r2/16) fps. What is the average water velocity in the 1.5-ft pipe? (10%)
6. A standard schedule 40, 2-in steel pipe (inside diameter 2.067 in and wall thickness 0.154 in) carrying steam is insulated with 2-in of 85% magnesia covered in turn with 2-in of cork. Estimate the heat loss per hour per foot of pipe if the inner surface of the pipe is at 250°F and the outer surface of the cork is at 90°F. The thermal conductivities ( in Btu/hr ㆍ ftㆍ°F) of the substances concerned are: steel, 26. 1； 85% magnesia, 0.04； cork, 0.03. (10%)
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, and what is the hydraulic radius for annulus between two concentric pipes? (4%)
in turbulent flow； Re is the Reynolds number. (20%)