Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : model


Characteristics of Air Impingement From an Orifice on a Target Plate

Adnan A. Abdul Rasool

Engineering and Technology Journal, 2013, Volume 31, Issue 7, Pages 1331-1350

The present work is an experimental and numerical CFD study of air impingement from orifices of different sizes in the range of (10-40) mm with a step increase of 10 mm. The impinging jet strikes the target plate at the stagnation point, converted to a wall jet beyond the stagnation zone in the outward radial direction on the target plate. Measurements of pressure coefficient (Cp) at points in plate centre and other points in the radial direction from stagnation point on the target plate show that pressure coefficients reduces gradually in the outward direction reflecting the same behavior of velocity distribution of the impinging jet ..The calculated average values of the pressure coefficients Cpavg on the total target plate area are reduced as the target plate – orifice distance is increased and its values are in the range of 0.3-0.7 with the higher jet velocity having the greater value of Cpavg for the tested axial distances in the range of 50-120 mm. Average pressure coefficient for different axial distances are calculated and are in the range of 0.4-0.6 with the higher values are noticed to be for the smaller tested orifice sizes reflecting a concentration of pressures for the small sizes of the orifice. This concentration of pressure of small orifices is attributed to the flow condition of the small orifice relative to the big orifice size where the presence of cross flow within the stagnation region of big orifice sizes tends to reduce static pressures and reduce peak heat transfer coefficients, this cross flow is confirmed by the velocity analysis using CFD numerical analysis zone at the stagnation zone. The percentages of the wall jet relative to the impinging jet velocities are discussed, where smaller orifice sizes are shown to have greater velocity percentages especially at the higher tested jet velocities.

Comparative Study of Temperature Control in a Heat Exchanger Process

Afraa H. Al-Tae; Safa A. Al-Naimi

Engineering and Technology Journal, 2012, Volume 30, Issue 10, Pages 1707-1731

In the present work the dynamic behavior of a plate heat exchanger (PHE)
(single pass counter current consists of 24 plates) studied experimentally and
theoretically to control the system. Different control strategies; conventional
feedback control, classical fuzzy logic control, artificial neural network (NARMAL2)
control and PID fuzzy logic control were implemented to control the outlet
cold water temperature. A step change was carried in the hot water flow rate which
was considered as a manipulated variable. The experimental heat transfer
measurements of the PHE showed that the overall heat transfer coefficient (U) is
related to the hot water flow rate (mh) by a correlation having the form:
U mh
0.7158 =11045
In this work the PHE model was found theoretically as a first order lead and
second order overdamped lag while the experimental PHE represented dynamically
(by PRC method) as a first order with negligible dead time value. A comparison
between the experimental and the theoretical model is carried out and good
agreement is obtained. The performance criteria used for different control modes
are the integral square error (ISE) and integral time-weighted absolute error (ITAE)
where the ITAE gave better performance. As well as the parameters of the step
performance of the system such as overshoot value, settling time and rise time are
used to evaluate the performance of different control strategies. The PID fuzzy
controller gave better control results of temperature rather than PI, PID and
artificial neural network controller since PID fuzzy controller combines the
advantages of a fuzzy logic controller and a PID controller. MATLAB program
version 7.10 was used as a tool of simulation for all the studies mentioned in this
work.

A Manual Kinetic Study for Pyrolysis of Scrap Tires by Use of TG Technique

Mohammed A.Abass

Engineering and Technology Journal, 2011, Volume 29, Issue 2, Pages 341-358

The kinetic study of pyrolysis involved the use of a homemade
thermogravimertic analysis (TG) system and showed that the reaction is
first order at high temperature range (390- 450) ºc.
The reaction rate constant has been increased with temperature
(0.15903- 0.9183) min-1 at the same range of temperature above according
to Arrhenius model equation modeled Bovier and Gelus, which can be
used to estimate the kinetic parameters .the activation energy of reaction
is found to be 1.33 kcal/mol. , whereas the frequency factor is equal to 1x
10-8 l/mol. sec.
From comparison between theoretical and experimental conversion due to
the same model above it could be seen that there is a good agreement
between theoretical and experimental results and higher temperatures
(390-450) ºc but become worse of low temperatures (200-350) ºc.