Saturation Line:

The saturation line shows the states of saturated air at different temperatures. As an instance of fixing such a state on the chart, refer an atmosphere A at 20 ^oC and saturation as illustrated in Figure. From the steam tables at 20 ^oC, water vapours pressure

(a)       T-s diagram of water                                                             (b) Psychrometric Chart

                                                Saturated Air at 20 ^oC

p_s= p_v = 17.54 mm H_g =2342 N/m2

Partial pressure of dry air

p_a=p - p_v =101325-2342 = 98983 N/m2

Specific humidity at 20 ^oC saturation

Knowing t & ω, point a may be plotted. Similarly, saturation states at other temperatures might also be plotted to sketch the saturation line on the psychrometric chart.