- TITLE:
PERFORMANCE OF DIFFERENT TWISTED TAPE INSERTS IN TURBULENT TUBE FLOW – CRITICAL REVIEW
- AUTHOR(S):
D. Kostadinova, V. Petkov
- ABSTRACT:
There are different kinds of inserts employed in the heat exchanger tubes such as helical/twisted
tapes, coil wires, ribs/fins/baffles, and winglets. This paper presents performance evaluation of some
twisted tape inserts, using a simple evaluation criterion to assess the possible energy benefit. Twisted
tape inserts, classical and modified, with different geometrical parameters with working fluids as air
or water in the range have been taken into consideration.
- TITLE:
DETERMINATION OF THE IMPULSE RESPONSE OF A COMMUNICATION CHANNEL IN THE PROCESS OF INFORMATION TRANSMISSION
- AUTHOR(S):
G. Cherneva, H. Spiridonova
- ABSTRACT:
The paper suggests an approach to determination the impulse response of a communication
channel in the process of information transmission, on the base of the processing the channel
response to amplitude-, phase- or frequency-manipulated signals.
- TITLE:
AUTONOMOUS AERIAL SYSTEM
- AUTHOR(S):
Sia Lozanova
- ABSTRACT:
Unmanned aerial system containing balloon filled with Helium connected to quadrocopter and
sensor module is experimentally investigated for a first time. This unusual construction design is an
effective solution to the deficiency of all multirotors from their limited battery capacity. It has been
established that the platform's flight time is proportional to the vertical Archimedes force. A drastic
increase of flight time is achieved with commensuration of weight and lifting force, and the shortest -
in the absence of a balloon. The operation of the system is safe, predictable and always reproducible.
The movement of a bear population in a forest area and a new archaeological mound is established
by the platform.
- TITLE:
MODEL-BASED STUDY OF LOSSES IN CYLINDRICAL SHAPED INDUCTORS
- AUTHOR(S):
D. Grozdanov, N. Hinov, K. Tarnev
- ABSTRACT:
Induction heating is a technology known for its highly efficient method of transferring energy
from the source to the operated part or area. Inductors performing the conversion of high-frequency
electrical energy into electromagnetic field are a major part of this technology. Determining their
basic parameters, such as inductance and loss of power at a selected operating frequency, is key in
the assessment and design of induction heating processes and systems. The calorimetric method for
estimating lost power in the inductor is one of the most accurate. This article explores a variation of
this method, which allows the real losses of a real inductor to be evaluated in the laboratory by
relatively small power sources. The follow-up experiment is compared to the results achieved by
simulating the environment through computer modeling. The main objective of the present study is to
achieve the correlation between theoretical modeling and experimental data in order to derive a
more general method for estimating the actual loss of power in a given inductor. This would
facilitate the design of processes and systems in terms of power requirements by allowing a realistic
assessment of the otherwise relatively complex interactions in the inductor between the electric
current and the electromagnetic field. The advantages of such an approach are especially striking
when working at high frequencies - at the order of 300 kHz, as phenomena such as a skin effect and
proximity effect have a significant influence on the resulting electric current, its distribution across
the cross section of the conductor, changing its effective cross section.
- TITLE:
ANALYSIS AND DESIGN OF CONTACTLESS TRANSMISSION ELECTRICAL ENERGY AND INFORMATION SIGNALS BY MULTIPLEXING THE FREQUENCY
- AUTHOR(S):
N. Madzharov, L. Petkov
- ABSTRACT:
In non-contact energy transmission systems, actual heading is the parallel bidirectional
communication between the transmitting and the receiving side using the same inductive coupling.
This removes the additional modules for transmitting information and control signals and improves
the technical and performance characteristics of the wireless power transfer systems. This report
presents the results of the frequency multiplexing method analysis, and for high frequency
modulation are used MOSFET transistors. A computer simulation of the developed system was
carried out and the effect of the value of the transmitted power on the bidirectional transmission of
control and information signals was determined.
