Question

1. (10 points) A water manometer is being designed to measure the pressure on a system. What minimum tube diameter (mm) is necessary to keep the capillary height change of the water less than 2 mm? Water surface tension and specific gravity are 72.8 dyne/cm and 1.0, respectively. The contact angle for the water-air-glass interface is 15º.

Answer 1

Q. Given :- A water manometer is being designed. capillary higght change of water should be less than amm, h< 2 mm. water surface tension (6) = 72.8 dynelem specific gravity of water =s.g= 1.0. density, Iwater 1000 kg/m² contaret angle of interface, 0 = 15°. - We know, formula for capillary height change (h) - h = 20 coso o coso S.I.R s.g.D where D is diameter. 8-9.81m1s (gravity) Surface tension. =72.8 dyne = 0.0728 N/m. cm a) h<2mm 40 coso 22 mm. IgD 4 (0.0728 N/m) cos 15) (1000 kg m)) (9.8\mis)() < 2x10²m. D > 0.01434 m D> 14.34 mm] Thus, the diameter of the tube is equal to 14.34 mm.