Page 186 - Industrial Ventilation Design Guidebook

i 48 CHAPTER 4 PHYSICAL FUNDAMENTALS

The partial pressure of the component / is obtained from

For a nonideal liquid solution, multiplying Eq. (4.331) by the activity co-
efficient y gives

a i n t
For an ideal solution the activity coefficient is y i = 1.

where h mj is the mass transfer coefficient in m/s, which is calculated from the
heat and mass transfer analogy correlations, R is the universal gas constant,
and T is the absolute temperature (K).

4.4 WATER PROPERTIES AND TREATMENT

4.4.1 Introduction
It is essential that the industrial ventilating engineer have a basic under-
standing of the properties of water and its treatment. This is to ensure an
efficiently running and trouble-free plant. Additional to these issues are the
problems relating to the discharge of contaminated water to the surround-
ing environment.
Water treatment over the past 100 years has grown into a complex science.
It is of interest to note that in the 1880s a steamship left the port of Liverpool in
the UK with instructions that the boiler water was to be treated with a mixture
of cow dung and peat. A short time after leaving Liverpool, the ship's boiler ex-
ploded and the ship sank. It was not reported whether the explosion was due to
the unusual method of water treatment.

4.4.2 Common Water Impurities
The following factors indicate the problems that poor-quality water may cause
to the engineering plant and to human health:
• Metal corrosion
» Scale formation on the heat transfer surface
• Dezincification
• Plumbosolvency
• Biological health hazards
Water supplies should never be assumed to be chemically pure. Groundwa-
ter from wells and springs contains dissolved impurities. Its properties depend