Dissertation 2005
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A Comparative Study of Hydrodynamics and Gasification Performance of Two
Types of Spouted Bed Reactor Designs. (May 2005)
By: Mr. P. Abdul Salam (Sri Lanka)
Supervisor: Prof. S. Kumar (Chairman) and Prof. S. C. Bhattacharya (Co–Chairman)
Committee: Prof. Mario T. Tabucanon and Prof. Surapong Chirarattananon
A comparative hydrodynamic and gasification study of spouted bed reactors having
central jet (conventional) and circular slit (modified) distributors has been carried out.
Specifically the study aimed: (i) to carry out a comparative hydrodynamic study of
spouted beds with central jet and circular slit distributors, (ii) to carry out a comparative
study on gasification of charcoal in spouted beds with central jet and circular slit
distributors, and (iii) modeling of hydrodynamic behaviour and gasification performance
of spouted beds with central jet and circular slit distributors by using Artificial Neural
Network (ANN).
The hydrodynamic study compared the minimum spouting velocity, pressure drop across
the bed and across the distributor at minimum spouting velocity and maximum spoutable
bed height of the central jet spouted bed with the circular slit spouted bed. Central jet and
circular slit distributors with four different air inlet areas were used. Three sizes of
crushed coconut shell particles, two sizes of sand, two sizes of dolomite and one size of
silica gel, in a specially constructed transparent spouted bed of 13.3 cm inner diameter,
were used for the study.
The results of the hydrodynamic study showed that (i) for a particular bed height and air
inlet area, the minimum spouting velocity of circular slit spouted bed is significantly (i.e.
1.2 – 3.8 times) higher than that of central jet spouted bed, (ii) as bed height increases, the
minimum spouting velocity of central jet and circular slit spouted beds tends to become
equal, (iii) the pressure drop across the bed of circular slit spouted bed at minimum
spouting velocity is almost independent of its air inlet area, (iv) for a given particle size
and air inlet area, maximum spoutable bed height for central jet spouted bed is higher
than that of circular slit spouted bed, and (v) for a specific particle size, as the air inlet
area increases the maximum spoutable bed height decreases in case of central jet
distributor, whereas the bed height is almost constant in case of circular slit distributor.
A comparative experimental study on air gasification of charcoal in spouted bed reactors
having central jet (conventional) and circular slit (modified) distributors was also carried
out. The gasification study showed that: (i) for a particular superficial spouting velocity,
the bed temperature of central jet spouted bed is higher than that of circular slit spouted
bed, (ii) the circular slit distributor design is associated with higher CO concentration (i.e.
12.31 – 16.02 vol.% for central jet and 15.32 – 18.42 vol.% for circular slit) in the gas and
higher carbon conversion in comparison with the central jet distributor, (iii) char carry
over rate in case of circular slit spouted bed is higher than that of central jet spouted bed,
(iv) at higher spouting velocities, the gasification efficiency of the circular slit spouted bed
is slightly more as compared to the central jet spouted bed, (v) the gasification efficiency
of both the types of spouted bed designs is low (i.e. 40 to 52 % for central jet and 43.6 to
54.1 % for circular slit) because of higher energy loss associated with the char carry over
(i.e. 14 – 28 % for central jet and 24 -36 % for circular slit); in practical systems, the carry
over loss could be reduced by recycling the char particles, and (vi) the efficiency of the
circular slit spouted bed with carry over recycling is expected to be significantly higher
compared to central jet spouted bed for gasification of solid fuels.
A two-layered artificial neural network (ANN) model was developed for predicting the
minimum spouting velocity (Ums), minimum fluidization velocity (Umf) and charcoal
gasification efficiency. The model was trained by using a back propagation learning
algorithm. About two-thirds of the available data was used for training the model and the
remaining was used to test and validate the model. The neural network model developed
predicts the Ums and Umf values better than the correlations available in the literature. The
model developed in this study also closely predicts the gasification efficiency.
The position of flow regime of circular slit spouted bed was also compared with the flow
regimes of central jet spouted bed and fluidized bed. The knowledge of the flow regime
of the circular slit spouted bed is important for identifying and designing practical
applications of spouted bed with circular slit distributor. The flow regime of the tested
circular slit spouted bed falls within the flow regime of the central jet spouted bed. This
implies that the circular slit spouted bed could be used for similar applications of central
jet spouted bed.
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Influence of Facts Controllers, Generation and Load Directions on Static Voltage
Stability Margin. (December 2005)
By: Arthit Sode-Yome (Thailand)
Supervisor: Dr. Nadarajah Mithulananthan (Chairperson)
Committee: Prof. Surapong Chirarattananon, Dr. Weerakorn Ongsakul and
Dr. Issarachai Ngamroo
Voltage instability has been a major concern in power systems, especially in planning and
operation, as there have been several major power interruptions associated with this
phenomenon, in the recent past. Voltage instability due to the lack of the ability to foresee
the impact of contingencies is one of the main reasons for the recent and worst North
American power interruptions on August 14th, 2003. Hence, electric power utilities
around the world have been devoting a great deal of efforts in voltage stability assessment
and margin enhancement.
Major contributory factors to voltage instability are power system configuration,
generation pattern and load pattern. Power system network can be modified to alleviate
voltage instability by adding reactive power sources i.e. shunt capacitors and/or Flexible
AC Transmission System (FACTS) devices at the appropriate locations. There are various
types of FACTS devices; each of them has its own characteristic and limitations.
Adequate representations of FACTS devices have a great impact on voltage stability
margin. Moreover, appropriate type, placement and correct size of the devices are
important and become necessary for power system, especially in a de-regulated
environment, to achieve maximum loading margin and other benefits. Generation pattern
is easier to control by system operators compared to other factors, as long as there is
enough margin left in the generators. Conventionally, in typical voltage stability studies,
generation of participating generators are raised at the same rate or predefined rate.
Increasing generation at this rate may not lead to highest voltage stability margin or
lowest operating cost. Increasing generation at a more appropriate direction would result
in a better power system performance in terms of loading margin and operation cost.
Adding to this, load pattern is another factor that also contributes to voltage instability.
Load is mostly dependent on the customers, thus it can not be controlled as operator wish.
Traditionally, in static voltage stability study, the load is increased at the same rate.
Increasing the load at this rate, however, may not represent the realistic load increase in
the practical power system. This may lead to a non-realistic voltage stability assessment
as well as voltage stability margin. Based on the above observation, attention is drawn in
this dissertation to study the
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Radiant Cooling for Thermal Comfort in Tropical Climate. (December 2005)
By: Prapapong Vangtook (Thailand)
Supervisor: Prof. Surapong Chirarattananon (Chairperson)
Committee: Prof. Sivanappan Kumar and Prof. Vilas M. Salokhe
In hot and humid region, air-conditioning is increasingly used to attain thermal comfort.
Air-conditioning is highly energy intensive and it is desirable to develop alternative
lowenergy means to achieve comfort.
This dissertation reports on experimental and simulation studies for the application of
radiant cooling using natural air for ventilation in the hot and humid climate of Thailand.
To avoid condensation of moisture on the cooling panel, the temperature of water
supplied to the panel was limited to 24 ºC. This led to the expectation that the low heat
reception capacity of the panel would limit its use only to situations when loads were low.
Experiments were conducted in an experimental room over the hot and dry period of
March, the humid period of May, and the cool period of December. The results generally
confirm good potential for application of radiant cooling. However, the room was served
by radiant panels with a total area of 7.5 m2. Its capacity was grossly inadequate during
the hot period, even for application exclusively at night time. A special configuration was
devised to achieve thermal comfort for the area served by the panel. The well-known
TRNSYS program was used to simulate the use of cooling panels and conventional
airconditioning in the experimental room. Simulation results matched experimental
results very well. Using comfort criteria adopted by ASHRAE and International
Standards Organization, results from experiments and simulation show that thermal
comfort could be obtained with application of radiant cooling.
Results of a series of whole-year simulations using TRNSYS computer code on
applications of radiant cooling to a room model that represents the actual experimental
room are reported. Admitting the inability of radiant cooling to accept latent load, chilled
water at 10 oC was supplied to the cooling coil to precool ventilation air in the daytime in
addition to the water cooled by the cooling tower that was used for radiant cooling. At
night, cooling water from the cooling tower alone supplied for radiant cooling was found
to be sufficient to achieve thermal comfort. Such applications are considered to be more
amenable to residential houses.
Results of an experimental study on the application of solar regenerated desiccant for
dehumidification and radiant cooling for thermal comfort are also reported. A set of
packed beds of solid desiccant were exposed to solar radiation during day time. The
packed beds were connected to the inlet ventilation duct of an experimental room in the
Energy Park at AIT for dehumidification of the ventilation air during night time. This
dehumidification setup was used in conjunction with the use of a panel supplied with cool
water for cooling to achieve thermal comfort. This combination enables quiet quality
thermal comfort to be achieved. The use of packed beds of solid desiccant reduced
moisture in the ventilation air resulting in the reduction of humidity in the room. This
allows cold water of lower temperature to be used on the radiant panel, thus increasing
the capacity of the panel. With the lower temperature, the capacity to achieve thermal
comfort is enhanced.
Thesis May 2005
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Development of a Rating Scheme for Energy-Star Houses.
By: Mr. Yossawee Sanohdontree (Thailand)
Supervisor: Prof. Surapong Chirarattananon
Study on Air Movement and Natural Ventilation Model for Energy Simulation of
Residential Houses.
By: Mr. U Aye Chan (Myanmar)
Supervisor: Prof. Surapong Chirarattananon
Renewable Energy Hybrid System for Decentralized rural Electrification Using A
GIS Based Model.
By: Ms. Tania P. Urmee (Bangladesh)
Supervisor: Prof. S. Kumar
Application of FACTS Devices for Congestion Management in the Deregulated
Electricity Market.
By: Mr. Naresh Acharya (Nepal)
Supervisor: Dr. N. Mithulananthan
Overcurrent, Overvoltage Protection and Reliability Improvement in Distribution
Network of Binh Duong Province-Vietnam.
By: Mr. Le Anh Dung (Vietnam)
Supervisor: Dr. Weerakorn Ongsakul
Energy-Environmental Analysis of Alternative Transport Scenarios: Case of
Greater Bangkok Region.
By: Mr. Damrongsak Rinchumpoo (Thailand)
Supervisor:Prof. Ram M. Shrestha
Least Cost Vehicular Mix Analysis for Hanoi Passenger Road Transportation
Development and External Cost
By: Ms. Nguyen Thi Thanh Hue (Vietnam)
Supervisor: Prof. Ram M. Shrestha
A Study of a Si-PV-Thermal System in Thai Hospitals
By: Mr. Kamonpan Chumpolrat (Thailand)
Supervisor: Prof. S. Kumar
Power Flow and Transient Stability Analyses for 500kV Transmission Plan of
Southern Vietnam.
By: Mr. Ho Thanh Dieu (Vietnam)
Supervisor: Dr. N. Mithulananthan
Cleaner Production in Seafood Processing Industry a Study in Vietnam.
By: Ms. Nguyen Thi My Trang (Vietnam)
Supervisor: Prof. S. Kumar
Optimal Power Flow with FACTs Devices Using Parallel Improved Evolutionary
Programming.
By: Mr. Peerapol Tanapongporn (Thailand)
Supervisor: Dr. Weerakorn Ongsakul
Assessment of Renewable Energy Resources and GIS Mapping for the Kingdom of
Bhutan.
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By: Mr. Norbu Tshering (Bhutan)
Supervisor: Prof. S. Kumar
Renewable Energy Based Water Purification System.
By: Mr. Prakash Das (India)
Supervisor: Prof. S. Kumar
Field Assessment of Thermal Comfort in Common Spaces in AIT.
By: Mr. Nyi Nyi Naing Myo Tun (Myanmar)
Supervisor: Prof. Surapong Chirarattananon
Thermal Comfort Assessment in Subtropical Classroom: A Case Study.
By: Mr. Rizwan Ahmed (Pakistan)
Supervisor: Prof. Surapong Chirarattananon
Experimental Investigations on a Rock-bed Thermal Storage System for Air Heating
and Drying Applications.
By: Ms. Chrystalyn Ivie S. Ramos (Philippines)
Supervisor: Prof. S. Kumar
Renewable Energy Resources Assessment and Its Application in the Kingdom of
Cambodia.
By: Mr. Sok Nattha
Supervisor: Prof. S. Kumar
Voltage Profile Improvement in Electric Power System: A Case Study of Central
Area PEA Power System, Thailand.
By: Mr. Vipa Udomwongpaiboon (Thailand)
Supervisor: Dr. N. Mithulananthan
December 2005
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Optimal Placement of Distributed Generation in Distribution System.
By: Pukar Mahat (Nepal)
Supervisor: Dr. Weerakorn. Ongsakul
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Optimal Distributed Generation Placement in LMP Based Electricity Market.
By: Gautum Durgar (Nepal)
Supervisor: Dr. N. Mithulananthan
Voltage Stability Study in Deregulated Electricity Marker Environment.
By: Sarina Adhikari (Nepal)
Supervisor: Dr. N. Mithulananthan
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Research Study
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Greenhouse Gas Emission and Environmental Impact Assessment of Pha Lai
Thermal Power Plant.
By: Mr. Nguyen Chi Hieu (Vietnam)
Supervisor: Dr. N. Mithulananthan