Welty, James R.; Wicks, Charles E.; Wilson, Robert E. Fundamentals of Momentum, Heat, and Mass Transfer, third edition. New York: John Wiley and Sons.

Example 2

Evaluate the diffusion coefficient of carbon dioxide in air at 20C and atmospheric pressure. Compare this value with the experimental value reported in Appendix Table J.1.

Will be using the following diffusivity equation:

We have temperature and pressure. We can calculate the molecular weights via a periodic chart. and can be obtained from Tables K.1 and K.2.

From K.2 of the appendix values and are obtained:

Carbon dioxide: in , 3.996 and in K, 190

Air: in , 3.617 and in K, 97

T = 20 + 273 = 293 K

P = 1 atm

This value was obtained by interpolation

From Table K.1

and

and

Interpolate

We have all variable except molecular weights. Considering the most prevalent gasses:

Now, we have all the information needed to calculate the diffusivity of in air when using:

Now, we want to compare to the experimental value that is reported in Table J.1

Since the value is reported at 273 K, must use a conversion equation to compare at 293 K

at and

at and from Table Table K.1

Once again, interpolation of Table K.1 is needed

Since we have all the values for the conversion equation

The diffusivity of carbon dioxide in air

Calculated: and Corrected Experimental:

Percent Difference

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