Page 156 - Introduction to Marine Engineering

14*2 Auxiliaries

Circulating
water outlet

Circulating water
inlet

Distilled water outlet
to tanks

Seawater
feed
u
Brine
discharge
Alternative
gr=| steam
t«rf connections
Jacket water outlet

Figure 7.6 Boiling process evaporator

remainder constantly overflows a weir and carries away the extra salty
water or brine. A combined brine and air ejector draws out the air and
brine from the evaporator.

Flash process
Flash evaporation is the result of a liquid containing a reasonable
amount of sensible heat at a particular pressure being admitted to a
chamber at a lower pressure. The liquid immediately changes into
steam, i.e. it flashes, without boiling taking place. The sensible heat
content, water pressure and chamber pressure are designed to provide a
desired rate of evaporation. More than one stage of evaporation can take
place by admitting the liquid into chambers with progressively lower
pressures.