Ciclo Economizador

© 2005, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.
org). Reprinted by permission from ASHRAE Journal, (Vol. 47, No. 7, July 2005). This article may not be
copied nor distributed in either paper or digital form without ASHRAE’s permission.

Is Economizer Cycle
Justified for
AC Applications
By Michael F. Taras, Member ASHRAE

R

-410A isbecoming increasingly popular in commercial air-conditioning applications. Although several design enhancement

options are feasible, R-410A still exhibits a performance deficiency
at certain environmental conditions in comparison to R-22 that is
being phased out. These issues present new challenges to system
designers and must be addressed in the most comprehensive and
cost-effective manner.For instance, performance degradation
issues for the equipment containing R410A become more profound at relatively
high ambient temperatures, where the
system performance is valued and needed
the most. This alone can drive technology
innovation and justify its application.
On the other hand, a low-pressure
refrigerant with a relatively high critical
point, such as R-134a, is a viablecan38

ASHRAE Journal

didate for R-22 substitution. However,
equipment size concerns, addressed at the
component level with respect to the compressor pump, piping and heat exchanger
design, become crucial considerations
and major obstacles for the implementation of R-134a.
These developments have prompted the
introduction of nonconventional methods
to significantly boost system efficiency,ashrae.org

as well as incremental improvements to
existing performance augmentation techniques. Consequently, new systems may
incorporate novel design approaches,
such as an economizer cycle, that in the
past would not have been considered for
similar applications.
T he choice of a particular system
design and configuration is defined by
essential performance characteristics,
componentreliability, applied cost and
specific application considerations.
This article evaluates the advantages
offered by the economizer cycle for airconditioning and heat pump applications,
and suggests that such an approach to enhance system performance has significant
potential. The benefits of the economizer
cycle are especially evident in the environment in which conventional methods
About theAuthor
Michael F. Taras is manager of technology and principal staff engineer at Carrier in Syracuse, N.Y.

July 2005

Until recently, the economizer cycle
was not considered a cost-effective
solution for air-conditioning installations where conventional technology
was pushed to the limit. Oversized
heat exchangers (condensers and
evaporators) reached their effectiveness plateaus andcompressor volumetric and isentropic efficiencies approached the respective maximums.

reach a plateau of rapidly diminishing returns on investment
or become physically impossible.
Economizer Cycle

The economizer cycle is well-justified for high compression
ratio conditions, such as refrigeration applications, where the
30% increase in performance provides a substantial advantage.
Untilrecently, the economizer cycle was not considered a
cost-effective solution for air-conditioning installations where
conventional technology was pushed to the limit. Oversized
heat exchangers (condensers and evaporators) reached their effectiveness plateaus and compressor volumetric and isentropic
efficiencies approached the respective maximums.
Now, however, the implementation of environmentallysound
refrigerants has negatively affected system performance at certain
environmental conditions, and industry standards and government regulations have raised the bar for the minimum efficiencies
of the air-conditioning equipment, a trend that will continue.
This course of events has opened the door to various kinds of
alternate technologies, encouraging a more serious evaluation
of the...