Xylem Bell & Gossett Hoffman Speciality Series Engineering Data Manual page 25

26
Condensate Coolers
When heat exchangers are selected for opera-
tion above 2 psig, consideration should be
given to the addition of a condensate cooler.
The justification will vary depending on the
size of the heat exchanger and the actual
time the unit is in operation.
With a condensate cooler, the discharge from
the trap on the primary heat exchanger is
piped through a water-to-water heat exchanger.
This lowers the condensate temperature and
recovers wasted heat. A second trap is then
installed on the discharge of the condensate
cooler to maintain saturation pressure and
prevent flashing and water hammer in the
condensate cooler.
The water-to-water heat exchanger design dif-
fers from steam heat exchangers. The water-
to-water heat exchanger has internal baffles
to direct the water flow across the tubes to
improve heat transfer. The water-to-water heat
exchangers are externally distinguishable
because the top and bottom shell openings
are both the same size. The steam-to-water
heat exchangers have a large opening in the
top for the steam inlet and a smaller bottom
outlet for the condensate drainage.
Piping Detail of Condensate Cooler
When fluid being heated is too hot to cool condensate below 212°F., other heating
requirements may be circulated through the condensate cooler.
When a modulating steam regulator is used
on the steam-to-water heat exchanger, the
vacuum breaker will allow air to enter to pre-
vent an induced vacuum from holding up con-
densate. The F & T Trap must be installed 15
inches below the heat exchanger to provide
condensate drainage when the internal pres-
sure drops to O psig. A separate Thermostatic
Trap should be provided to allow the air to be
vented when the pressure increases above O
psig. This trap bypasses the condensate cool-
er to allow free passage of the air into the
gravity return line.
The fluid in the condensate cooler on the tube
side, may be the same fluid that is to be heat-
ed in the steam heat exchanger when the ini-
tial temperature is sufficiently low. When the
initial temperature of the fluid is too high to
cool the condensate below 212°F, other fluids
may be heated. Heating domestic hot water
or pre-heating boiler make-up water are two
possibilities.
TEMPERATURE
REGULATOR
HEAT EXCHANGER
F&T TRAP
HEAT EXCHANGER
CONDENSATE COOLER
STEAM LINE
THERMOSTATIC
TRAP
TO RETURN
LINE