ITP Metal Casting: Advanced Melting Technologies: Energy Saving ...

A vertical tube-within-tube convective recuperator is an alternative arrangement of the
convective recuperator where the cold combustion air is heated in a tank of parallel vertical tubes
extending
in to the path of flue gas stream. The tube is easy to replace during full operation,
minimizing cost, inconvenience, and equipment damage from forced shutdowns in case of
recuperator failures. 67
4.3.2 Refrigeration
Absorption chillers use heat instead of mechanical energy to provide cooling for applications
such as air conditioning.
They transfer their thermal energy from the heat source to the heat sink
through an absorbent fluid and a refrigerant. The two most common refrigerant/absorbent
mixtures used in absorption chillers are water/lithium bromide and ammonia/water. The
absorption chiller creates refrigerating effect by absorbing and then releasing water vapor into
and out of a refrigerant solution (Exhibit 25). 68
Source: Gulf Coast CHP Application Center
Exhibit 25: Simplified absorption cycle
Absorption chillers are economically attractive because they utilize
inexpensive thermal energy
(waste heat). Mechanical chillers must be driven by motor or engine; however,
absorption
chillers primarily use low-grade waste heat at a temperature between 100°C and 200°C (212°F
and 392°F). These chillers can change a building’s thermal and electric energy and cost profile
by shifting cooling needs from an electric load to a waste-heat thermal load.
4.3.3 Regenerators
A regenerator is a container that is capable of absorbing and storing large amount of thermal
energy. It is charged with
the hot exhaust gas during the melting operation cycle; when the
regenerator is fully charged, it stops the flow of the exhaust gas and starts allowing in
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