Procedures for Tower Sizing

The number of diffusion units is computed from the relation /dT/(Hs -H). It is determined from process conditions imposed on the tower alone, not by the tower s performance. Htu is the only parameter determined experimentally. 

We first need to construct an enthalpy-temperature plot. The enthalpies of saturated air can be computed from the following relation (see Chapter 3)  

For T = 50°F, the partial pressure of water can be obtained from the Steam Tables  

The enthalpy of air above 0°F can be obtained from the following relation Hs = Tair + Ms A + 0.24 

Following this procedure, enthalpy and humidity data at saturation conditions can be computed for a range of temperatures. Table 5.4 gives the required data for this example. 

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