A PDF file should load here. If you do not see its contents
the file may be temporarily unavailable at the journal website
or you do not have a PDF plug-in installed and enabled in your browser.
Alternatively, you can download the file locally and open with any standalone PDF reader:
https://ijlct.oxfordjournals.org/content/11/1/54.full.pdf
Transient simulation of a solar absorption cooling system
International Journal of Low-Carbon Technologies
Transient simulation of a solar absorption cooling system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . With non-renewable energy sources depleting quickly, solar energy could prove a viable option owing to its abundance and eco-friendliness. Modeling and simulation of a solar energy-driven single-stage absorption chiller was carried out using the transient simulation software 'TRNSYS'. An evacuated tube collector coupled with an insulated tank served as heat source for the absorption chiller. Experiments were conducted to evaluate the efficiency parameters of the collector as well as the loss coefficient for the storage tank. These parameters along with standard chiller performance data were used to model the system. The influence of climatic conditions, storage capacity and various control schemes with and without auxiliary heating on the output of the system is analyzed and presented in the paper.
solar cooling; evacuated tube collector; thermal storage; absorption chiller; controls; simulation; TRNSYS
New Delhi 110016, India
Abstract
1 INTRODUCTION
In tropical countries like India, which experience extreme
summers in the mainland, demand for electricity shoots up due
to the need for cooling. The high electricity demand not only
overloads the grid but harms the environment as well due to the
burning of fossil fuels, which are the primary source of power.
Solar energy for cooling applications provides an opportunity to
overcome this problem. The fact that cooling demand in
summer is proportional to the availability of solar energy has
been spurring the researchers to further exploit solar energy. In
cooling applications, different types of sorption systems can be
employed. Vapor absorption is a mature technology that can be
integrated with solar thermal collectors. A single-effect lithium
bromide – water (LiBr – H2O) absorption cooling system operates
at a generator temperature in the range of 70 to 958C and requires
water as cooling fluid in the absorber and the condenser [1].
A number of simulation and experimental studies [2 – 9] on
various solar-powered absorption systems have been carried out
by researchers to make this technology more competitive.
Assilzadeh et al. [2] presented the simulation and optimization
of a LiBr solar absorption cooling system with evacuated tube
collectors (ETCs) for the local weather conditions of Malaysia.
The simulation of the solar absorption cooling system was
carried out using TRNSYS software. The results showed that for
a continuous operation, a 0.8-m3 hot water storage tank is
essential and the optimum design for a 3.5 kW (1 TR) system
required 35-m2 evacuated tube solar collector sloped at 208.
Mazloumi et al. [3] simulated a parabolic trough collector-based
absorption cooling system with LiBr – H2O as absorbent
refrigerant pair. The results showed that the minimum value of the
required collector area was 57.6 m2, which could supply
the cooling loads for weather conditions of Ahwaz, Iran, in the
month of July when the maximum load reached 17.5 kW.
Martinez et al. [4] simulated a hot-water-fired, double-effect
LiBr – H2O absorption system using TRNSYS and also validated
the model with experimental data. The model predicted 30%
lower energy consumption as compared with experimental
results. This difference was attributed to steady state modeling,
which did not consider the transient performance. It was
deduced that the simulation time steps should be lower than
1 h. Monne et al. [5] conducted a two-year experimental analysis
(2007 and 2008) to study the effect of outdoor temperature of
Spain on the performance of LiBr – H2O absorber cooling
system. They found that the performance of the chiller was
better in the year 2007 because the heat rejection temperature
and the outdoor temperature were more favorable than those in
2008. Ge et al. [6] carried out simulation of a low-temperature
gas-fired ammonia – water absorption chiller using TRNSYS.
The chiller model was validated against experimental results
obtained on a 12 kW absorption chiller and was further used to
analyze the effect of important design and operating parameters
on its performance. The study concluded that the increase in
generator heat input from 20 to 30 kW increased the cooling
capacity from 11.26 to 14.85 kW and slightly decreased the COP
from 0.56 to 0.49. Florides et al. [7] modeled a solar absorption
cooling system using TRNSYS for the local climate of Nicosia,
Cyprus. The model predicted an optimized system consisting of
a 15-m2 compound parabolic collector tilted at 308 from the
horizontal and a 600-L hot water storage tank. The collector area
was determined by performing (...truncated)