Experiment 5 Gas Diffusion
EXPERIMENT 5
GAS DIFFUSION COEFFICIENT
OBJECTIVES:
Determine the gas diffusion coefficient of acetone using the established Winkelmann’s method
KEYWORDS
Diffusivity, Gas Diffusion Coefficient, Winkelmann’s method
OVERVIEW
The knowledge of physical and chemical properties of certain materials is important because very often process engineering deal with the transformation and distribution of these materials in bulk. One such property is diffusivity. Mass transfer by diffusion takes place when there is a concentration gradient of the diffusing component. Naturally, the diffusion in gas phase is much faster than the diffusion in liquid phase due to the small spaces between the molecules that hinder other molecule movement. Other factors that will effect the diffusion are temperature, density, concentration and other external factors.
1. INTRODUCTION
This experiment has been designed for students experiment on the technique of determining diffusivity of the vapor of a volatile liquid based on the established Winkelmann’s method. In this method the volatile liquid is allowed to evaporate in a vertical glass tube over the top of which a stream of vapor-free gas is passed. A water bath is provided for maintaining a steady temperature so that there is no eddy current in the vertical tube and mass transfer takes place from the surface by molecular diffusion alone. The rate of evaporation can be followed by the rate of fall of the liquid surface. A traveling microscope is provided for determining, the liquid fall. With the knowledge of the concentration gradient, the diffusivity of the vapor of the volatile liquid can then be calculated.
2. THEORY
When a concentration gradient exists within a fluid consisting of two or more components, there is a tendency for each constituent to flow in such a direction as to reduce the concentration gradient. This is called mass transfer. Mass transfer takes place in either a gas phase or a liquid phase or in both
GAS DIFFUSION COEFFICIENT
OBJECTIVES:
Determine the gas diffusion coefficient of acetone using the established Winkelmann’s method
KEYWORDS
Diffusivity, Gas Diffusion Coefficient, Winkelmann’s method
OVERVIEW
The knowledge of physical and chemical properties of certain materials is important because very often process engineering deal with the transformation and distribution of these materials in bulk. One such property is diffusivity. Mass transfer by diffusion takes place when there is a concentration gradient of the diffusing component. Naturally, the diffusion in gas phase is much faster than the diffusion in liquid phase due to the small spaces between the molecules that hinder other molecule movement. Other factors that will effect the diffusion are temperature, density, concentration and other external factors.
1. INTRODUCTION
This experiment has been designed for students experiment on the technique of determining diffusivity of the vapor of a volatile liquid based on the established Winkelmann’s method. In this method the volatile liquid is allowed to evaporate in a vertical glass tube over the top of which a stream of vapor-free gas is passed. A water bath is provided for maintaining a steady temperature so that there is no eddy current in the vertical tube and mass transfer takes place from the surface by molecular diffusion alone. The rate of evaporation can be followed by the rate of fall of the liquid surface. A traveling microscope is provided for determining, the liquid fall. With the knowledge of the concentration gradient, the diffusivity of the vapor of the volatile liquid can then be calculated.
2. THEORY
When a concentration gradient exists within a fluid consisting of two or more components, there is a tendency for each constituent to flow in such a direction as to reduce the concentration gradient. This is called mass transfer. Mass transfer takes place in either a gas phase or a liquid phase or in both