Ingenieria

ESFuelCell2012-91216

EXERGY ANALYSIS OF A COMBINED POWER AND COOLING CYCLE

Armando Fontalvo L.
Department of Mechanical Engineering
Universidad del Norte
Barranquilla, Colombia
aefontalvo@uninorte.edu.co

Jorge Duarte
Department of Mechanical Engineering
Universidad del Norte
Barranquilla, Colombia
jduarte@uninorte.edu.co

˙
W

ABSTRACT
In recent years, because of theenvironmental issues, new
configurations for the traditional cycles have been proposed with
the aim of making better use of energy resources. The combined
use of energy for simultaneous production of cooling and power
is one of the working fields for increase energy efficiency and
be able to use alternatives energy sources such as solar radiation
and other low-temperature heat sources. Among thesenew cycle
configurations, a modified ammonia-water refrigeration cycle
for power and cooling production was proposed by Goswami in
1998. Since it was first proposed in 90’s, the Goswami cycle
has been subject of several research studies. A model for exergy
analysis of a combined power and cooling cycle has been developed for this work. The model was validated with other studies
and, based on thecycle parameters presented by other authors, a
study of the overall exergy destruction of the cycle and its components was carried out. The effect of the isentropic efficiency
of the turbine in the total exergy destruction cycle was determined. It was also determined the percentage of participation of
the total exergy destruction for each component. The effect of
the presence or absence of thesupherheater was also determined.

Power

Greek Symbols
η
Efficiency
ψ
Exergy flow
Subscripts
d
destroyed

INTRODUCTION
In recent years, because of the environmental issues, new
configurations for the traditional cycles have been proposed with
the aim of making better use of energy resources. The combined
use of energy for simultaneous production of cooling and power
is one of theworking fields for increase energy efficiency and
be able to use alternatives energy sources such as solar radiation
and other low-temperature heat sources. Among these new cycle
configurations, a modified ammonia-water refrigeration cycle for
power and cooling production was proposed by Goswami [1] and
is shown in Figure 1 in which a binary ammonia-water mixture
is pumped to high pressure (1–2)and partially boiled in a boiler.
The vapor generated (5) consists mostly of the volatile component. A rectifier condenser is used to make the vapor richer in
the volatile component, by partially condensing the vapor. The
remaining vapor is superheated (7–8) and expanded in a turbine
(8–9) to low temperatures. The low temperature vapor can be
used for refrigeration by transferring heat in arefrigeration heat
exchanger (9–10). The weak liquid from the boiler is passed

Keywords: Goswami Cycle, Exergy Analysis, Exergy Destruction, Power and Cooling.
NOMENCLATURE
m
˙
Mass flow
x
Ammonia mass concentration
h
Enthalpy
˙
Q
Heat rate
1

Copyright © 2012 by ASME

through a heat exchanger to recover heat from it (11–12), and
throttled back to the absorber (13–14). The vaporfrom the refrigeration heat exchanger (10) is absorbed into the weak solution in the absorber. The condensed liquid in the rectifier is also
throttled back into the absorber in this schematic. Alternately, it
could be recirculated back to the boiler.

1:
Schematic
power/cooling cycle

FIGURE

description

of

the

if an absorption condensation process is employed.
Rogdakis andAntonopoulos [7] proposed a triple stage
power cycle which is similar to the Kalina cycle. However, they
replaced the distillation condensation of the Kalina cycle with an
absorption condensation process. Kouremenos et al. [8] analyzed
this absorption type of power cycle as a bottoming cycle with a
gas turbine topping cycle. Since this cycle still uses ammoniawater vapor mixtures going through...