Question

An airplane wing is coated with a volatile surfactant that reduces friction during flights. The mass transfer coefficient (kc’) for the transport of evaporated surfactant is 3.7 x 10-5 m/s and the vapor pressure of the surfactant is 0.003 atm under the flight conditions. During the flight, the temperature is typically –50 oC at the altitude of the flight path, while the pressure is 0.2 atm.

(i) What is the flux of surfactant if the system is under equimolar counter diffusion?

(ii) What is the flux if the system is under stationary condition?

(iii) If the resistance to the overall mass transfer occurs in a distance of 1 cm, what is the diffusivity of the surfactant in the gas phase?

(iv) If 14.2 kmol of surfactant is used to coat a plane wing of 45 m2, how long will the surfactant last on the wing?

Answer 1