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TRG-TRC011-EN 57
period five
Application Considerations
notes
Special Considerations for Direct-Fired Chillers
The combustion process that occurs in the burner is key to the operation of a
direct-fired absorption chiller. It also introduces several additional
considerations when applying this type of chiller.
n Combustion air requirements: Combustion equipment is designed and
operated to ensure complete combustion. Incomplete combustion uses fuel
inefficiently, can be hazardous because of carbon monoxide production, and
contributes to air pollution. The quantity of air to provide for a particular
direct-fired absorption chiller installation is determined by such factors as
expected variations in fuel and air supplies, system application, burner
design, and control requirements.
n Venting of exhaust: A flue exhaust-gas duct and stack must be installed to
effectively vent the products of combustion out of the building. This duct
and stack must be designed and installed in compliance with municipal,
state, and federal regulations. Also, be careful not to locate the stack too
close to the cooling tower.
n Gas train: The main gas control train regulates the fuel flow to the burner
manifold and provides safe operation. The gas train is selected based upon
the pressure of the gas main and local code requirements.
n NO
x
emissions: Nitrogen oxides (NO
x
) are the combustion emissions
containing nitrogen and oxygen in direct-fired absorption chiller
applications. Due to environmental concerns, some local building codes
require low NO
x
emissions. Manufacturers have developed low-NO
x
burners that use various methods for reducing emissions. One cost-effective
method of achieving low emissions in commercial installations, flue-gas
recirculation, recycles flue gases to lessen NO
x
formation by reducing the
flame temperature and the amount of oxygen available for combustion.
direct-fired
absorption chiller
direct
direct
-
-
fired
fired
absorption chiller
absorption chiller
exhaust ductexhaust duct
exhaust duct
flue stackflue stack
flue stack
cooling
tower
cooling
cooling
tower
tower
Figure 65