Title of Thesis
Experimental Investigation and Mathematical Modeling of a Low Energy
Consuming Hybrid Desiccant Cooling System for the Hot and Humid
Areas of Pakistan
Department of Mechanical Engineering / NED University of Engineering & Technology, Karachi
|Number of Pages|
|Keywords (Extracted from title, table of contents and
abstract of thesis)|
Investigates, Mathematical, Desiccant,
Significantly, Demonstrated, Absorber, Staggered, Desiccant, Hybrid, Mathematical, Modeling, Humid
This experimental and simulation study investigates the potential of
using a solar assisted hybrid desiccant cooling system (SHDCS) for
air conditioning applications for Pakistan. A review of literature
reveals that compared to the conventional vapour compression cycle
this cycle could offer saving in overall primary energy. Since the
cycle is based on supply of conditioned ventilation air it has
significantly lower environmental impact.
A gas fired hybrid desiccant cooling test rig has been installed at
the Energy Conservation Laboratory
NED to study the performance of various components. These
experiments enabled understanding of the system and helped develop
effect of individual components on the system performance. Important
parameters of system components established from the experiments
were used as input to the TRNSYS simulation model.
The simulation studies have been based on a well established
transient energy software TRNSYS.Specific to this work a
mathematical model of Modified Cooler was prepared from basic
principles and added as module to TRNSYS. Addition of this component
resulted in an increases of the COPp-s by a factor of 1.065 for the
weather of Lahore. Besides COP; all system parameters showed an
improvement due to the addition of this component.
Six case studies based on SHDCS have been performed for Karachi and
Lahore. The results so obtained established that the advantage of
using SHDCS depends on the climatic conditions. SHDCS offers
considerable promise for Lahore i. e., it shows that of the seven
month summer cooling season the desiccant cooling system alone
suffices for three month – April, May and October. However for
Karachi summer, characterized by high humidity, SHDCS does not
provide acceptable temperature and humidity conditions without
auxiliary air conditioning.
The source of thermal energy needed for regeneration plays an
important part in the overall success of the desiccant cooling
scheme. To reduce the use of conventional energy, in this case
natural gas, a solar collector has been included in the study. Micro
analysis of the flow and heat transfer phenomenon taking place
inside inclined solar air collector was studied using CFD software,
which demonstrated that low heat transfer between air and absorber
can be improved by using staggered fins. It was also shown that the
fin configuration coupled with low flow velocity helped increase
heat transfer in the absorber duct by increasing heat transfer area,
mixing and residence time.
Energy, economic and environmental impact of the solar collectors
was also studied and payback periods for energy, Carbon emission and
monetary investment have been found to be 1.5 years, 1 year and 14
The success of the desiccant cooling system is strongly associated
with cost of the thermal energy. Combined heat and power systems
offer an opportunity of providing this energy at no additional cost.
The latter study has been suggested to be taken up as future work.