2-4 I Description
How the Closed Circuit Works
Closed Circuit models maintain the process temperature by electrically heating and indirectly
cooling fluid in the process circuit. Cooling water supplied by a chiller, tower or other water source,
is mixed with the process fluid only during the initial filling or when water is needed to make up
process fluid loss. A brazed-plate heat exchanger replaces the mixing tank used on direct injection
units.
1 The temperature of the process fluid is measured as it
leaves the unit’s heater tank. The fluid then flows through
the “To Process” line A to the mold or process. The fluid
returns to the unit through the “From Process” line B for
reheating or cooling.
2 If the temperature is above the setpoint value, the cool-
ing valve opens. Cool water enters the heat exchanger
via the “Cooling In” line. Process fluid is always being
circulated through the process side of the heat exchanger.
The process fluid is indirectly cooled via conduction from
the colder water now running through the cooling side of
the heat exchanger. If the measured temperature is below
the setpoint, the heater elements inside the heater tank are
energized.
3 The pump moves water from the heat exchanger to the
heater tank. Pressure is measured before and after the pump
with pressure gauge E and F.
D
A
B
C
E
F
TW-S Closed Circuit
Optional From Process RTD
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