Page 99 - Industrial Ventilation Design Guidebook

64 CHAPTER 4 PHYSICAL FUNDAMENTALS
Lydersen, A. L., Mass Transfer in Engineering Practice. Wiley, New York, 1983.
Nyvlt, J., Industrial Crystallisation from Solutions. Butterworths, London 1971.
Oliver, E. D., Diffusional Separation Processes: Theory, Design and Evaluation. Wiley, New York, 1966.
Reid, R. C., Prausnitz, J. M., and Sherwood, T. K., The Properties of Gases and Liquids.
McGraw-Hill, New York, 1977.
Sherwood, T. K., Pigford, R. L., and Wilke, C. R., Mass Transfer. McGraw-Hill, New York, 1975.
Sissom, L. E., and Pitts, D. R., Elements of Transport Phenomena. McGraw-Hill New York, 1972.
Treybal, R. E., Mass Transfer Operations. McGraw-Hill, New York, 1968.

4.2 STATE VALUES OF HUMID AIR; MOLLIER DIAGRAMS AND THEIR APPLICATIONS

4.2.1 Properties of Air and Other Gases
The analysis of dry atmospheric air varies with location, altitude, time of year,
and other factors. Table 4.4 gives the molecular weights of the constituents
and the volumetric and gravimetric analyses.
For general engineering work for altitudes up to 1500 m it is sufficiently
accurate to use the following:

The above values are based on the assumption that argon is combined with n
trogen, adjusting the molecular weight to 28.16. Other gases present in the atmc
sphere air are normally ignored, as these represent less than 0.003% {by volumi
27.99 ppm). Table 4.5 provides some basic information on these trace gases.
The gases also have other constituents mixed with them, typical ones beinj
dusts, pollens, bacteria, viruses, mold spores, smoke particles, and the produc
of industrial activity such as SO 2, H 2, and S. Volcanic activity also adds variou
gases and dusts to the atmosphere.

4.2.2 Fundamentals
Air is seldom dry; it normally contains varying amounts of moisture. Humid a;
is a mixture of dry air and water vapor. The term dry air denotes the mixture <
all gases present in air (nitrogen, oxygen, carbon monoxide, and inert gases), e>
cept water vapor.

TABLE 4.4 Analysis of Air at Sea Level

Volumetric Gravimetric
Constituent Symbol Molecular weight (M) analysis % analysis %

Nitrogen N 2 28.016 78.09 75.55
Oxygen 32.00 20.95 23.13
0 2
Argon Ar 39.944 0.93 1.27
Carbon dioxide CO 2 44.01 0.03 0.05
Total 100 100
Source: R.B. Keey, Drying Principles and Practice, 1972