Keywords : Heat Transfer
Computational Single and Multiphase Approaches to Investigate the Hydrothermal Behavior of Hybrid Nano-fluid in Plain and Wavy Tubes
Engineering and Technology Journal,
2023, Volume 41, Issue 7, Pages 1-17
DOI:
10.30684/etj.2023.136449.1316

Numerical Investigation of Thermal-Hydraulic Performance of Printed Circuit Heat Exchanger with Different Fin Shape Inserts
Engineering and Technology Journal,
2023, Volume 41, Issue 1, Pages 23-36
DOI:
10.30684/etj.2022.132688.1137

Numerical and Experimental Investigation of Heat Transfer Enhancement by Hybrid Nanofluid and Twisted Tape
Engineering and Technology Journal,
2023, Volume 41, Issue 1, Pages 69-85
DOI:
10.30684/etj.2022.131909.1069

Recent Development in Hydrodynamic and Heat Transfer Characteristics in the Three-phase Fluidized-bed System
Engineering and Technology Journal,
2022, Volume 40, Issue 9, Pages 1179-1204
DOI:
10.30684/etj.2022.132506.1125

The Influence of Convection Heat Transfers for Vertical Mini-Tubes Using Solvent Carbon Dioxide and Porous Media at Supercritical Pressure
Engineering and Technology Journal,
2021, Volume 39, Issue 9, Pages 1409-1419
DOI:
10.30684/etj.v39i9.2068
Porous media and solvent CO2 at supercritical pressure were investigated experimentally to study the effect of convection heat transfer in vertical mini-tubes. Mini-tubes diameter (5 and 8 mm) with medium porosity of 0.5 are proposed in experimental investigation. Experimental conditions consisted of bulk fluid, wall temperatures ranged from 33 to 55 oC, and 8 to 10 MPa of pressure. Reynolds number, Mass flow rate, and heat flux were 1750 to 21000, 0.5 to 4.5 Kg/h, and 3.25×104 to 1.1×105 W/m2 respectively. Some chemical additives like Ethanol, Chloroform, Acetone, Dimethyl sulfoxide, and Methanol were considered. A special focus was dedicated to studying the influence of heat flux, inlet temperature, and mass flow rate at measured values of wall and fluid bulk temperatures, and coefficients of local heat transfer for mini-tubes and porous media. A higher effect was noticed on the convection heat transfer by buoyancy and properties of the thermophysical variable of solvent CO2 in mini-tube at vertical position. However, when these results were compared with the controls (empty tube) shoewn dramatically different results. Heat transfer coefficient was bigger about 4 times when using the porous media tube compared with the empty type in the case of using a 5% of acetone solvent.
An Elaborate Review for Micro-Fin Heat Sink
Engineering and Technology Journal,
2020, Volume 38, Issue 1, Pages 105-112
DOI:
10.30684/etj.v38i1A.331
Heat sinks are low cost, the process of manufacturing reliability, and design simplicity which leads to taking into consideration various cutting-edge applications for heat transfer. Like stationary, fuel cells, automotive electronic devices also PV panels cooling and other various applications to improve the heat sinks thermal performance. The aim is to focus on some countless fundamental issues in domains such as; mechanics of fluids and heat transfer, sophisticated prediction for temperature distribution, high heat flux removal, and thermal resistance reduction. The outcome of this survey concluded that the best configuration of heat sinks has a thermal resistance about (0.140 K/W to 0.250 K/W) along with a drop of pressure less than (90.0 KPa) with a temperature gradient about 2 °C/mm. Heat sinks with square pin fins lead to enhance the effectiveness of heat dissipation than heat sinks with microcolumn pin fins. While other researches recommend the use of high conductive coating contains nano-particles. The present survey focuses on the researches about future heat sink with micro fin and the development to resolve the fundamental issues. The main benefits and boundaries of micro fins heat sink briefed.
Enhancement of Thermal Storage Properties of Phase Change Material by Using Metallic Swarf
Engineering and Technology Journal,
2018, Volume 36, Issue 5A, Pages 586-595
DOI:
10.30684/etj.36.5A.15
The phase change materials (PCM) is commonly used for storage heat as a latent heat, the main disadvantage of this method is slow response time during charging and discharging; this due to the PCM thermal properties. This work studied experimentally the enhancement of thermal properties of PCM by adding various metallic swarf such as copper, aluminum and iron swarf. Metallic swarf used as thermal conductivity promoter to produce modified paraffin wax samples. The addition of the previous enhancers was conducted with a weight fraction of (7.5%, 12.5% and 17.5%) to the whole weight of the mixture. The experimental results showed that adding of metallic swarf to the PCM decrease the charging time by (5.5 - 22.1%) for weight fractions from (7.5-17.5%) respectively. The addition of metallic swarf to PCM showed enhancement of discharging time by (27 - 77 %) compared with the case of pure wax for copper swarf weight fraction of (7.5 – 17.5%) respectively. Thermal conductivity of PW was enhanced by using aluminum, copper, and iron swarf, where it is found that the maximum enhancement about (53 times) due to the addition of (17.5%) of aluminum swarf. This method is considered a successful economic way due to the use of manufacturing waste.
Heat Transfer Performance Improvement in the Split Units in Humid Environment through Drain Water Circulation
Engineering and Technology Journal,
2017, Volume 35, Issue 2A, Pages 130-133
DOI:
10.30684/etj.2017.127323
The only way to ease extremely hot days during the summer is to resort to cooling systems to feel comfort. This idea brings an end to failure in cooling process to hot summer days, energy saving, and lets you rest. By recycling the water drained from the indoor unit through simple distributor fixed on the outdoor unit. There is two advantages due to rapid vaporization of the compensating draining by fan during hot air of weather: avoid the corrosion due to using the drain water in the cooling process, and get rid and consumption of the draining water to avoid any problem where place drained. The drain water is almost high purity (TDS < 50 ppm), and dust-free by filters of indoor unit lead to no salts accumulation, and reduce probability of fins corrosion of outdoor heat exchanger in salt medium. Experimental results indicate that the increasing of the heat transfer is obtained by using low temperature water, which ranging (5-15 oC) and the decreasing depend upon the hot air (30-55 oC), over the temperature during the summer in Iraq as well as the difference values in heat capacities between air and water. Applying this idea will result in power consumption reduction by the range (1 – more than 4 Amperes).
Development of Hydrodynamic and Heat Transfer Profiles for Fischer–Tropsch Synthesis in a Fixed Bed Reactor of Different Scales
Engineering and Technology Journal,
2016, Volume 34, Issue 14, Pages 2585-2596
DOI:
10.30684/etj.34.14A.4
Comprehensive hydrodynamic and heat transfer study of Fischer–Tropsch synthesis (FTS) on a home-based cobalt catalyst, with the presence of water–gas shift (WGS), is conducted with a fixed bed reactor. Two different diameters have been used for the reactor, 4 and 7 inches. To meet the requirements of industrial applications, simulation has been used to scale up the effect on the commercial scale reactor. Synthetic gas was used as a feed stream and its conversion to H2 was considered. Temperature and velocity profiles were obtained for the different scales.
An Experimental Study on Heat Transfer Enhancement for Porous Heat Exchange in Rectangular Duct
Engineering and Technology Journal,
2014, Volume 32, Issue 11, Pages 2788-2802
DOI:
10.30684/etj.32.11A.15
Forced convection heat transfer of air in porous rectangular duct was investigated experimentally . The pad consist of (zig-zag ) metallic wire mesh insert with two different porosities ( ε) namely ( 0.97 ) and ( 0.99) .The experiments were carried out for Reynolds number (7682,12497 and 17323 ) and constant heat flux (192,297 and 422 W/m2 ) .The results indicated that Nusselt number was increased with increasing Reynolds number and heat flux but decreased with increasing pad porosity .The Nusselt number in the porous duct was increased up to (144% ) for (ε=0.97) and (72% ) for (ε=0.99) when compared to clear duct at the same tested condition . For optimization between heat transfer enhancement and pad weight added into clear duct , it is found that [ (Nuporous - Nuclear ) / weight of pad ] equal to (84.34 ) and ( 40.49 ) for (ε=0.99 and ε=0.97) respectively and this is good improvement in heat transfer through porous rectangular duct and reducing size and weight of original duct .
Modeling the Behavior of Frost Growth on Finned Tube Heat Exchanger
Engineering and Technology Journal,
2014, Volume 32, Issue 1, Pages 215-229
DOI:
10.30684/etj.32.1A.16
A quasi-steady finite-volume model was developed for modeling a plain-finround-tube heat exchanger under frosted conditions. In this study, the heat and mass transfer characteristics of heat exchangers during frost formation process are analyzed numerically. Unsteady heat and mass transfer coefficients of the air side, heat transfer coefficient of the refrigerant side, frost layer thickness, the surface efficiency of the
heat exchanger and the mass flow rate of the frost accumulated on the heat exchanger surface are calculated. The total conductivity (UA) and pressure drop of the heat exchanger are reported for different air inlet and refrigerant temperature. Results have shown that frost layer growth is faster with lower inlet air temperature. Using the developed mathematical model, the algorithm and the computer code, which have
been experimentally validated, it is possible to predict a decrease of exchanged heat flux in the heat exchanger under frost growth conditions. The model could be further extended to simulate direct expansion evaporators with varying operating conditions and variable heat exchanger geometry.
Influence of Corrosion Rate on the Double Butt Welding Shapes Design for Low Carbon Steel
Engineering and Technology Journal,
2011, Volume 29, Issue 6, Pages 1094-1106
The aim of this paper is to demonstrate the influence of butt welding shapes
on the corrosion rate, microstructure and temperature of carbon steel type
St37.The double butt welding was performed by V angles 15°,30° and 45°. The
finite element analysis via ANSYS software is performed, this analysis includes a
finite element model for the thermal welding simulation. The temperature
distribution was obtained. From the results of the microscopic structure it is
evident that the geometric shape has an important role in the welding process,
when the geometric value of the welding region gets bigger, the faults get less due
to increase of heat quantity in the welding region and the corrosion rate for the
rain water is less than of sea water. The work presents the finite element model for
numerical simulation of welding in carbon steel St37 double butt welding.
Influence of Butt Welding Shapes Design on the Microstructure and Stresses of Low Carbon Steel
Engineering and Technology Journal,
2010, Volume 28, Issue 15, Pages 5036-5047
The aim of this paper is to demonstrate the influence of butt welding shapes on the microstructure, temperature and equivalent stresses of carbon steel type St- 37.The single butt welding was performed by V angles 15°,30°,45° and U shape. The finite element analysis via ANSYS software is performed , this analysis includes a finite element model for the thermal and mechanical welding simulation. The equivalent stresses and temperature distribution were obtained. From the results of the microscopic structure it is evident that the geometric shape
has an important role in the welding process, when the geometric value of the welding region gets bigger, the faults get less due to increase of heat quantity in the welding region. The work presents the finite element model for numerical simulation of welding stresses in carbon steel St-37 butt welding. The welding simulation was considered as a direct coupled thermo- mechanical analysi.s
A Study of Chaotic Behavior of Heat Transfer In Gas-Solid Fluidized Bed
Engineering and Technology Journal,
2010, Volume 28, Issue 10, Pages 2027-2042
Fluidized beds are characterized by high heat transfer rates between the
bed and internal surfaces and have uniform temperature distribution that can be
achieved in fluidized bed systems. In the same time there is a chaotic behavior of
hydrodynamic and heat transfer in gas-solid fluidized bed.
Experimental work was carried out in gas-solid (air – sand) fluidized bed to
investigate the steady state heat transfer coefficient. The bed column used was
(172) mm in diameter and (1000) mm height, fitted with immersed cylindrical
heating element of (25.4) mm in diameter. The fluidizing medium was air flowing
at different velocities from fixed bed to fluidized bed of (0.006-0.078)m/s, and
three different sizes of fine sand particles were used (i.e. 63, 112, and 145 μm),
these average particles diameters were estimated by two methods (Wide and
Narrow Range Solids).
A comparison have been done with values of the minimum fluidizing velocity that
calculated analytically, empirical, and which got experimentally. The results show
a chaotic behavior of hydrodynamic gas-solid fluidized bed.
The heat transfer coefficient and the bed viodage increase with increasing gas
fluidizing velocity and the heat transfer coefficient decreases with an increase in
particle diameter.
Two empirical correlations are proposed which can calculate wide range solids and
narrow range solids based on experimental data. The Nusselt number presented
with some dimensionless groups as follows:-
For Wide Range Solids Nu = 0.81Re0.94 Pr0.35
Where the correlation coefficient (R) was equal to (0.92) and the average absolute
relative error was (12.62 %).
For Narrow Range Solids Nu = 0.45Re0.65 Pr0.33
Where the correlation coefficient (R) was equal to (0.86) and the average absolute
relative error was (24.2 %).
Heat Transfer from an Immersed Heater in Liquid – Liquid – Solid Fluidized Beds
Engineering and Technology Journal,
2009, Volume 27, Issue 10, Pages 1901-1914
Heat transfer from an immersed heating surface to a liquid-solid and liquid-liquidsolid fluidized beds have been studied. The experiments were carried out in a (0.22) m column diameter fitted with an axially mounted cylindrical heater heated electrically. The fluidizing medium was water as the continuous phase and kerosene as the dispersed phase. Low density (Ploymethyl-methacrylate) particles were used. Previous
published heat transfer correlations, obtained for fluidized beds containing highdensity particles, gave significant deviations compared with the present data. New correlations were developed to predict the heat transfer coefficients in liquid-solid and liquid-liquid-solid fluidized beds. The new correlation is,
The heat transfer coefficients obtained from the present work were compared with those estimated from other correlations reported in the literature. The comparison shows a good agreement with the data obtained for the gas-liquid-solid fluidized beds using low-density particles.
Thermal Effects on Diesel Engine Piston and Piston Compression Rings
Engineering and Technology Journal,
2009, Volume 27, Issue 8, Pages 1444-1454
This paper introduces an analytical study on the thermal effects on the diesel
engine piston and its compresion rings during the contact between the piston and its
compression rings .A three dimensional finite element model is built for the piston
and its compression rings using the ANSYS v. 8 Finite Element Analysis Code
that serves all engineering problems . The thermal analysis is made using contact
case between the piston and its compression rings .The work in this paper did not
include a convergence study.
The study includes the effects on the piston and piston compression rings
of the thermal conductivity of piston material , and the contact area .The conclusions
of this study are that the material type of high thermal conductivity is considered better
than the material type of low thermal conductivity. This means that the aluminum
alloy is considered better than the cast-iron alloy, and tapering the compression rings
from the inner side by 1 mm , leads to a reduction in the temperature values by
1.6% , 0.84% and 0.37% compared to rectangle compression rings.