This document contains 3 problems related to mass transfer fundamentals:
1) Calculating the time required for a 2mm layer of water to disappear through evaporation into air, under different humidity and penetration conditions.
2) Calculating steady state fluxes and transport rates of N2 and O2 between two vessels connected by a tube, with different initial gas compositions.
3) Calculating the mass transfer rate of ammonia from a gas mixture into water, and how doubling the pressure would affect the rate.
This document contains 3 problems related to mass transfer fundamentals:
1) Calculating the time required for a 2mm layer of water to disappear through evaporation into air, under different humidity and penetration conditions.
2) Calculating steady state fluxes and transport rates of N2 and O2 between two vessels connected by a tube, with different initial gas compositions.
3) Calculating the mass transfer rate of ammonia from a gas mixture into water, and how doubling the pressure would affect the rate.
This document contains 3 problems related to mass transfer fundamentals:
1) Calculating the time required for a 2mm layer of water to disappear through evaporation into air, under different humidity and penetration conditions.
2) Calculating steady state fluxes and transport rates of N2 and O2 between two vessels connected by a tube, with different initial gas compositions.
3) Calculating the mass transfer rate of ammonia from a gas mixture into water, and how doubling the pressure would affect the rate.
This document contains 3 problems related to mass transfer fundamentals:
1) Calculating the time required for a 2mm layer of water to disappear through evaporation into air, under different humidity and penetration conditions.
2) Calculating steady state fluxes and transport rates of N2 and O2 between two vessels connected by a tube, with different initial gas compositions.
3) Calculating the mass transfer rate of ammonia from a gas mixture into water, and how doubling the pressure would affect the rate.
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Mass Transfer Fundamentals
Ch.E- 304
Muhammad Rashed Javed
2 Knudsen Diffusion
Mass Transfer Fundamentals
3 Knudsen Diffusion
Mass Transfer Fundamentals
4 Problem 1 There is a 2mm thick layer of water on the floor of a room. The water vaporizes and diffuses through a stagnant film of air of estimated thickness of 2.5 mm on the water surface. Under the conditions of evaporation, the water temperature is essentially equal to its wet-bulb temperature. If the ambient temperature is 28 C, calculate the time required for the water layer to completely disappear completely for the following cases: a) the ambient air has a relative humidity of 60% b) the floor has micropores and water penetrates the floor at a constant rate of 0.1 kg/m2.h, the ambient air having humidity as in part a. Wet bulb temperature is 22.5 C, diffisuvity of water in air is 0.853 ft2/h at 1 atm and 0 C. Vapor pressure, Pv (in bar) of water is given by: ln Pv = 13.8573 – 5160.2/T where T is temperature in K (Antoine Equation)
Mass Transfer Fundamentals
5 Problem 2 Two large vessels connected by a tube 5 cm in diameter and 15 cm in length. Vessel 1 contains 80% N2 and 20% O2. Vessel 2 contains 80% O2 and 20% N2. Temperature is 20 C and pressure is 2 atm Calculate: a) the steady state flux and rate of transport of N2 from vessel 1 to vessel 2. b) the same quantities for O2. c) the partial pressure of N2 and its gradient in the tube 5 cm from vessel 1. d) the net mass flux with respect to a stationary observer Diffusivity of N2-O2 pair is 0.23 cm2/s at 316 K and 1 atm.
Mass Transfer Fundamentals
6 Problem 3 Ammonia is absorbed in water from a mixture with air using a column operating at 1 bar and 295 K. The resistance to transfer may be regarded as lying entirely within the gas phase. At a point in the column, the partial pressure of the ammonia is 7.0 kN/m2. The back pressure at the water interface is negligible and the resistance to transfer may be regarded as lying in a stationary gas film 1 mm thick. If the diffusivity of ammonia in air is 236 x 10-5 m2/s, what is the transfer rate per unit area at that point in the column? How would the rate of transfer be affected if the ammonia air mixture were compressed to double the pressure?