Engineering and Technology Journal

This study describes an experimental investigation of the thermal efficiency of stainless steel mesh and steel wool as a porous medium in the lower channel of a double pass solar air heater. An experimental setup was planned and developed. Various types of porous media with high thermal conductivity and with different porosities have been tested. The effects of the porosity of wire mesh, the thermal conductivity of porous media, mass flow rate, and the intensity of radiation have been studied. Experimental results show that thermal efficiency with using porous media is greater than without using porous media. When used steel wool as a porous medium, the thermal efficiency reached 79.82 percent while it can be achieved 76. The percent by using stainless mesh as porous material. The reduction in porosity increasing thermal efficiency. The thermal efficiency of multi-pass solar air collector when used steel wool as porous media is 6, 12.6 and31.7percent higher than without porous media at porosity 98.75, 97.5, and 96.25percent. While it can increase 8.1 and 28.5 percent at porosity 97.875 and 95.75 percent when using stainless steel as porous media.

This research has been done by reinforcing the matrix (unsaturated polyester) resin with natural material (date palm fiber (DPF)). The fibers were exposure to alkali treatment before reinforcement. The samples have been prepared by using hand lay-up technique with fiber volume fraction of (10%, 20% and 30%). After preparation of the mechanical and physical properties have been studied such as, compression, flexural, impact strength, thermal conductivity, Dielectric constant and dielectric strength. The polyester composite reinforced with date palm fiber at volume fraction (10% and 20%) has good mechanical properties rather than pure unsaturated polyester material, while the composite reinforced with 30% Vf present poor mechanical properties. Thermal conductivity results indicated insulator composite behavior. The effect of present fiber polar group induces of decreasing in dielectric strength, and increasing dielectric constant. The reinforcement composite 20% Vf showed the best results in mechanical, thermal and electrical properties.

These works study the characterization of thermal and acoustic insulation behavior of Polymer Blend/Recycled Natural Fibers. Acoustic insulation is an important property in design criterion in buildings and used to avoid the damage caused by the sounds of the explosion of rockets and bombs. This work is done through reinforcing 80% epoxy resin EP with 20% polycarbonate PC with two different recycled natural fiber RNF (hemp fiber H.F., cornhusk fiber C.H.F) at various weight fractions of (2,4,6) %, the samples, were formed by hand lay-up then the acoustic and thermal insulation tests carried out. The results show that altering both kinds of RNF can improve acoustic insulation. Also, it could be noticed that sound insulation efficiency can improve with increasing RNF weight fraction. Finally, the optimum results got at 6% hemp composite that shows better acoustic insulation than cornhusk composites. The thermal conductivity improved by increasing the fiber weight fraction. The maximum value of thermal conductivity for composite samples with (H.F., C.H.F) fibers at (6% wt) equal to (0.71609W/m. Kº) and (0.73686W/m. Kº), respectively. The composite samples with C.H.F. fibers have slightly higher thermal conductivity value than composite samples with H.F.

Paraffin wax is an important material used in thermal energy storage (TES) systems. The thermal conductivity of the material is an important parameter that decides the degree of exploitation of the paraffin wax in TES systems. The thermal conductivity is improved by the addition of silicon oxide nanoparticles (1%, 2%, 4%, and 6%) to the paraffin wax. The average size of the SiO2 particles is equal to 38 nm. The addition of SiO2 nano-particles at very small ratios was found to enhance the thermal conductivity of the paraffin wax considerably. SiO2 nanoparticles, add to paraffin wax, have a significant effect in enhancing the thermal storage characteristics of paraffin
Paraffin wax is an important material used in thermal energy storage
(TES) systems. The thermal conductivity of the material is an important
parameter
that
decides the degree of exploitation of the paraffin wax in TES
systems. The thermal conductivity is improved by the addition of silicon oxide
nanoparticles (1%, 2%, 4
%,
and 6%) to the paraffin wax. The average size of the
SiO
2
particles is equal to 38 nm. The a
ddition
of SiO
2
nano
-particles at very
small ratios was found to enhance the thermal conductivi
ty of the paraffin wax
considerably. SiO
2
nanoparticles, add to paraffin wax, have
a significant effect
in enhancing the thermal storage characteristics of paraffin

The aim of this work was to evaluate some mechanical and physical
properties of a composite material which consists of (epoxy/styrene-butadiene
rubber) blend as a matrix, reinforced with copper oxide (CuO) with a weight
fraction 3%, and the composite material was manufactured by hand lay-up.
The optimum mixing ratio was (75:25) % of epoxy and (SBR) was chosen to
accomplish the work due to its highest impact strength (2.1KJ/m2). The tests
that were performed on the material were: tensile test, impact test, thermal
conductivity test, and the absorption test, in addition to the microscopic
imaging using scanning electron microscope (SEM), to determine the surface
morphology of the specimens. Sodium hydroxide (NaOH) and hydrochloric
acid (HCl), both (0.1) normal concentration solutions, were used for the
immersion. The results showed that CuO nanofiller improved tensile and
impact properties of the blend, besides increasing resistance to diffusion of
chemicals into the material. The results showed that the immersion in HCl
solution increased the impact strength of the composite from (2.27KJ/m2) to
(3.38KJ/m2), and also increased the tensile strength from (9.2MPa) to (9.8
MPa), while immersion in NaOH solution decreased the tensile strength to
(7.3MPa), but increased the impact strength to (2.42KJ/m2). Thermal
conductivity was (0.21W/m.°C) before immersion in solutions, but changed to
(0.27W/m.°C) and (0.24W/m.°C) after immersion in HCl and NaOH
respectively. The weight gain after immersion in NaOH was higher than weight
gain after immersion in HCl.

The mechanical behavior of coconut shell (CS) particulate epoxy composites was concentrated on keeping in mind the end goal to create designing materials for modern application. Minute of the support with various weight portions (5, 10, 15, 20 and 25) wt%. Epoxy and composite materials were prepared by hand lay-up molding. The physical properties are thermal conductivity while the mechanical properties were hardness, tensile properties, impact properties, and flexural strength. The resulting composites of thermal conductivity 0.1005 W∕ m.c° that is lower than pure epoxy and commonplace materials utilized for home-structures. As for the mechanical properties, composite materials with (Epoxy+25%CS) has the maximum hardness of (76.6) shore D, The ultimate tensile strength of 33.42MPa was obtained from (Epoxy+25%CS), while the elongation at fracture with addition in filler concentration of 1.50 % was obtained from (Epoxy+25%CS) is lower than other composites. The highest impact strength, fracture toughness was 80J∕m2, 12.87 MPa.m-1/2 respectively. Flexural strength & shear stress of the composite materials with addition in reinforcement content at 5wt % &10wt% (39, 40.5)Mpa & (1.95,2.03)Mpa respectively while is other composites.

This work presents an investigation of possibility incorporate of synthetic fibers (glass, nylon and carbon) at two states (short: 1cm, long: 5cm) effects on the mechanical properties of mortars (cement: sand composition (1:3)). Fibers materials used at different weight percentages ranged of (0, 0.4, 0.8, and 1.2) wt%. Density, water absorption, porosity, thermal conductivity, compressive strength and flexural strength experimentally investigated for mortar specimens after curing for (28 days). The results showed that the incorporation of these fiber materials improvement mechanical and physical tests for all reinforced samples with short and long fibers, and that the highest value of the mechanical and physical properties obtained from long fiber (5cm) reinforced cement samples with (1.2%Nylon), reaching the rate of increase in values of compressive strength by (17.74%), flexural strength by (52.8%), and water absorption by (4.54%), while reaching the rate of decrease in values of density by (5.32%). The higher values for short fiber (1cm) reinforced samples reaching the rate of increase in values of compressive strength by (10.92%), flexural strength by (40.65%), and water absorption by (6.65%), while reaching the rate of decrease in values of density by (8.91%). Results of thermal conductivity test showed decrease in values conductivity for all mortar samples with long short synthetic fibers and that the minimum value of conductivity obtained with (1.2%Carbon), reaching the rate of increase in values of thermal conductivity by (41.84%) for long fiber reinforced samples, while the lowest value for conductivity by (75.98%) for short fiber reinforced samples.

In this study, different percentages (2, 4, 6, 8, and 10% by weight of the soil) of chopped polymeric (plastic bottles with maximum particle size 2.36 mm and 1.18 mm in addition to rubber tires of 0.6 mm max particle size) wastes are incorporated with soil to produce lightweight clay bricks, to find the optimum percentage satisfying the requirements of bricks grade C using for non-structural walls (partitions).The effects of different types and percentages of the polymeric wastes on firing shrinkage, density, water absorption, compressive strength and thermal conductivity of the fired bricks were studied. Results indicate that it is possible to incorporate not more than 8% of chopped rubber tires or not more than 6% of chopped bottles to the clay soil to produce lightweight fired clay bricks satisfying the compressive strength and water absorption requirements for grade C of bricks (used for partitions) according to the Iraqi specification IQS 25/1988, in addition to reducing the thermal conductivity by 13-17% which is desirable as it will reduce the energy required for heating and cooling. Also, found that the size of the incorporated particles of plastic wastes in clay, used for bricks manufacturing, did not have a significant effect on the different studied properties of bricks. In addition to, the incorporation of chopped rubber tires, having smaller particles size and more sphere particles shape, produce fired clay bricks with more homogeneous pores distribution and smaller size compared with clay brick incorporating chopped plastic wastes having flaky shape and larger particles size, leading to produce clay brick with higher density and strength, with lower water absorption. As a total results, the incorporation different types of polymeric wastes (chopped plastic bottles with 2.36 and 1.18 max size and chopped rubber tires) with percentages (2, 4, 6, 8, and 10% by weight of soil) , cause the firing shrinkage and water absorption to increase by (0.6-20.2%) and (3-43.5%) respectively, while the density, compressive strength, and thermal conductivity decrease by (3.5-25.1%), (0.4-2.3%), and (2.1-31.9%) respectively with respect to the reference fired clay bricks, depending on the percentage, particles size, and type of the polymeric wastes addition.

In this work prepared and study a polymer composite, where use polyester resin with asbestos fiber ratio (5%, 10% and 15%). First study effect of changing reinforcement percentage by asbestos fiber on coefficient thermal conductivity (k) of polymer composite. Result show decrease in the coefficient thermal conductivity (k) of composite materials with increase of weight percentage of asbestos fiber. Second, study effect of it above reinforcement ratio on the some of mechanical properties (Impact, tensile, fracture and hardness) for polymer composite. The result indicate increase value of mechanical properties with increase weight percentage of asbestos fiber. The impact strength was (2.7 kj/m2) for pure resin where reach to maximum value (7.83 kj/m2) at 15wt% of fiber .Hardness and tensile reach to maximum value at 15% weight percentage for asbestos fiber. The result illustrate improvement mechanical properties after reinforcing by asbestos fiber and these properties rises with increased in reinforcement percentage.

This work was carried out to investigate effect of glass fiber (GF) and carbon fiber (CF) on kaolin-clay firebrick properties. GF and CF are considered inorganic fibers with application of high temperatures. Kaolin clay is mixed with short GF and CF separately by different percentages (0, 0.5, 1, 1.5 and 2) wt%. Kaolin-GF and kaolin-CF mixtures were compacted by using the semi-dry pressing method. The compacted specimens were fired at different temperatures (1100, 1200 and 1300)°C. Properties which include bulk density, apparent porosity, water absorption, thermal conductivity and fracture strength were obtained from the firebrick specimens. The results show that the addition of GF has beneficial in lowering of firing temperature, and consequently accelerating the densification via enhanced grain boundary diffusivity. Increasing GF content in the firebrick mixture enhances the fracture strength due to increase amount of glassy and mullite phases. Incorporation of CF has inversely affected than GF on the firebrick properties. As the percentage of CF increased the density of firebrick decreased, and the porosity and water absorption increased.

Different concentrations of cadmium ferrite (2%, 5%, 8%, 10% and 15%) were incorporated into epoxy resin. Cadmium ferrite was prepared by conventional ceramic technique. Composites are prepared by mixing the ferrite with epoxy by hand lay - up method at different percentages. The effect of ferrite content on tensile strength, hardness, thermal properties such thermal conductivity, thermal diffusivity and specific heat beside the dielectric strength were investigated. Using ferrite powders as filler to form particulate composite could lead to composite properties improvement. All the measured properties were improved with the increasing of the filler content. The results showed the important role of perfect adhesion between the filler and the polymer on the composite properties. It is found that the uniform distribution of filler particles in all directions of composite leads to the improved properties.

In this work attempt was made to formulate water based boehmite (AlOOH) nanofluid in one and two steps methods. Boehmite is the first born alumina phase as prepared by sol gel route using aluminum isopropoxide precursor, exhibit a combination of excellent consistency and dispersibility in water. Plain nanofluids containing boehmite at different concentrations were investigated for colloidal, suspensions and/or dispersions stability and thermal conductivity enhancement. X-ray diffraction analysis, laser diffraction particle size analysis, viscosity, thermal conductivity measurements, TG/DSC thermal analysis and sedimentation balance were used as characterization tools. The results show promising long-term fluid stability and thermal conductivity enhancement relative to starting based fluid following non-linear dependence on particles concentration. The maximum 2.7 times enhancement in thermal conductivity occurred at narrow boehmite concentration range as a result of achieving optimum nanoparticles aggregation level where neither the case of nanoparticles homogenous dispersion nor the case of fully aggregated clusters could retain these enhancements values. This far beyond behavior from Maxwell's model was explained on the basis of the known mechanisms of thermal conductivity enhancement of nanofluids.

The enhancements of heat transfer coefficient and Nusselt number in a heat exchanger system were achieved by using Titanium-dioxide (TiO2) nanoparticles with an average diameter of 10 nm. TiO2 nanoparticles/water has a better thermal conductivity compared to conventional working fluids (water). The heat transfer rate in a vertical shell and tube heat exchanger counter flow under laminar and turbulent flow conditions were investigated. The liquid flow rate has been varied in the range of 50-300 l/h whilethe inlet temperature was between 20 to 60ºC. The effects of factors such as the Reynolds number and the peclet number on the heat transfer and flow characteristics were carried out and investigated. It was observed that the convection heat transfer increased remarkably with the increment of the temperature under various values of the Reynolds number.As well as,the Nusselt number increased about 17% as compared to pure water;at a nanofluid velocity of 0.0192 m/s at inlet temperature of 600C.

In present work alumina with grain size (50nm )and titanium dioxide with grain size (20nm ) are used tothermal conductivity is tested separately when mixed with water at different percent concentrations (0.05%, 0.1 %, 0.3%, and 0.5 W %),in order to investigate their effects on enhancement of heat transfer of pool boiling water and enhancement thermal conductivity of nanofluid.
The experimental results of thermal conductivity of water before and after adding of nanoparticles have been presented in this work. The results of a theoretical study of thermal conductivity of nanofluids with Al2O3 and TiO2 nanoparticles are also presented and compared with the experimental results. Both results showed an increment of 1.5% -1.8% enhancementshave been obtained when a small amount of nanoparticles is added to the pure water. The theoretical calculation is based on the mechanism of Brownian motion which is the reason for improvement of thermal conductivity.

Anew type of porous clay bricks is proposed , this research studies the effect of adding industrial wastes admixtures with different percentages on the thermal and acoustics insulation properties of clay bricks . Different types of admixtures were used in this work ,including plastic cuttings ,wood saw dust ,palm fiber with ( 5% ,10% ,15% ,20 ) percent of weight of each one . Acoustics insulation , thermal conductivity ,specific heat capacity ,porosity and variation of density have been examined for each samples at all percent of admixtures and comparing with the reference clay bricks samples . Form the obtained test result show the admixtures effect on the properties of clay bricks , the best material which can used from this paper is palm fiber to get the best properties of acoustic insulation , thermal conductivity and density for 20% admixtures percentage comparing with the standard bricks .

This research studies the effect of adding industrial wastes materials with
different percentages on the thermal and mechanical properties of clay
bricks . Different types of admixtures were used in this work, including
rubber cuttings, wood saw dust and barley reeds ash with ( 5%,10% 15%
,20% ) by weight of each one respectively. Thermal conductivity, specific heat
capacity, compressive strength, flexural tensile strength, porosity and variation
of density have been examined for each samples at all percent of addition
and comparing with the reference clay bricks samples . Test results show that
the admixtures effect on the properties of clay bricks, when used barley reeds
ash which the best additives because take good properties, the density of clay
bricks is reduced 33%,thermal conductivity reduced 46% and the compressive
strength increased 20% comparing with the standard bricks. The experimental
work carried in the industrial factory of clay bricks in the Nahrawon city in
Baghdad.

In this work a composite materials were prepared containing matrix of polymer blend (polypropylene 80% + polycarbonate 20%) reinforced by (carbon black) with different of weight fraction %. The specimen sheet, were obtained by hotcompression from extruded material, using single extruder operated at a temperature between (190-200)Co. The extrusion processes give homogeneous mixer through a regular selection of machine screw revolution per minute and temperature used in extrusion process. The weight fraction of the carbon blacks ranged from 0.0 up to 20 wt % with the polypropylene and polycarbonate blend. All samples related to, mechanical, thermal and electrical tests were prepared by single –extruder. By discharging a high voltage through the composite it was found that the resistivity of the composite decreased from (1.00E+09)-(1.00E+028). Carbon black–polypropylene and polycarbonate composites show significant differences from the neat blends measured in the frequency range. The study of physical test show that the thermal conductivity decreases with the increase of weight fraction
from (0.157-0.23).

For semigroups of linear bounded operators on Hilbert spaces, the problem of
being in Cp , 0 Keywords

The research work covers a study of the feasibility of producing
lightweight ceramic thermal insulation bodies used for lining the furnaces
by adding saw dust and AlF3 to the Dewechla clay (Kaolinite).AlF3 is a
chemical waste materials in the Akashat–factories in Rutba to the
Dewechla clay (kaolinite). Finely distributed Saw dust and ALF3 were
added to clay with different weight percentages (0, 15, 25, 35 & 40) Wt%.
Cylindrical shape samples (30mm diameter and 30 mm height) were
prepared by using the semi–dry method, moulding pressure was
(500Kg/cm²). After drying at (110C◦), the samples were burnt at (900, 950,
1000, 1050&1100) C◦. The fired samples were investigated to obtain their
properties, bulk density, porosity ,compressive strength and thermal
conductivity. It was possible to produce ligh-weight ceramic thermal
insulators with bulk density between (700 and 1300) Kg/m³ compressive
strength not less than (25) Kg/cm² and thermal conductivity between (0.2
and 0.4) Kcal/m.h.c.

This work is concerned with experimental and finite element investigation to determine the temperature distribution in hot weather through the section of the high performance lightweight concrete sandwich panels. In the experimental work thermal conductivity of unreinforced mortar, reinforced mortar and polystyrene concrete were
investigated, then the thermal conductivity of eight series of 1000mm length and 200mm width concrete sandwich panels with two reinforced mortar faces of 20 mm in thickness and core of 30 and 50mm in thickness from polystyrene concrete were calculated. A nonlinear one – dimensional finite element analysis has been used to conduct an analytical investigation on the temperature distribution through the section of concrete sandwich panels. ANSYS (version 8) computer programme was utilized and 2-node LINK elements were used.
The experimental results show that thermal conductivity of the concrete sandwich panels is low with average value of 0.446 W/m.K and the thermal conductivity of the panels with similar type and volume content of reinforcement decreases by about 17% when the core thickness increases from 30 to 50 mm. The finite element results of
temperature distribution show good agreement with the experimental measurements.

The weather in Iraq is hot in summer and cold in winter. Therefore , the
thermal insulation is of the main problems facing the engineers working in
building and housing sector
The paper presents an experimental investigation, It includes preparation of
several concrete mixes using lightweight aggregate (siporex and porcelinite &
suwdast ) to obtain light weight concrete of two densities ranging from (350-880
kg/m3), which provides a good thermal insulation. Based on the analysis of
experimental results several graphs and Tables have been prepared and presented
which can be used in the mix design of similar siporex concrete of densities from
(350-880 kg/m3) . The physical properties of siporex concrete , have been found
which included density (765-822kg/m3) , compressive strength (1.51-2.2 N/mm2)
& (2.8-3.7 N/mm2) ,thermal conductivity ( 0.19-0.39 W/M.K) for the two groups
respectively.

Thermal and electrical conductivity of an insulating polymer can be achieved by
dispersing conducting particles (e.g., metal, carbon black) in the polymer. The resulting materials
are referred to as conducting polymer composites. Electrical and thermal properties of epoxycarbon
black composites were studied in this work. The weight fraction of the carbon blacks
ranged from 0.0 up to 20 wt % with the epoxy resin. By discharging a high voltage through the
composite it was found that the resistivity of the composite decreased. Epoxy-carbon black
composites show significant differences from the neat epoxy resin measured in the frequency
range. Conductivity percolation threshold was found when carbon blacks is added in the range of
1 and 2 wt%. It was found that the epoxy/ carbon black composites have better thermal properties
than the neat epoxy.

In this research work a hybrid composite material was prepared contains a matrix which is Epoxy resin (EP) natural and fabricated fibers (Kevler fiber + Woven and short glass fiber + Palm fiber + Metal fiber), the volume fraction for all hybrid composite material was 25 %.
All samples were prepared by hand lay up process. Thermal tests were done by using Lee disk to determine the coefficient of thermal
conductivity at different temperatures, the results obtained showed good improvement of thermal conductivity values of the composite material consists of metal wires as result of improve the thermal conductivity. Also the results showed positive effect of the
directionality of fibers to the hybrid which contains fibers as compared with hybrid contents short fibers. To explain the effect of the ultraviolet (UV) radiation on the thermal properties,
the samples were exposed for a period of time to (UV); the results show that as the exposure time increased the thermal conductivity of samples decrease