Method: Vary heat flux. Varies cooling medium rate.
Process: Net vapor rate zero.
Advantages: Simple.
Disadvantages: High maintenance for louvers and variable-pitch
configurations. Variable speed rarely used due to cost.
Application: Most common method of control with air-fins.
Variants: Vary fan pitch, vary louver position, vary motor
speed.
Configuration notes: Variable position louvers tend to
be troublesome. Louvers must be designed for automatic control.
Do not refit an automatic positioner to a set designed for manual
operation. Variable fan pitch is also subject to maintenance problems
and fans have to be shut down before the pitch mechanism can be
worked on. Variable speed using a variable frequency motor is
the most reliable, but most expensive and is rarely used.
Operation: Variable flow rate varies air outlet temperature.
Variable LMTD controls heat removal.
Warnings:
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