Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : thermal conductivity


Thermal Investigations of Double Pass Solar Air Heater with Two Types of Porous Media of Different Thermal Conductivity

Jalal M. Jalil; Shrooq J. Ali

Engineering and Technology Journal, 2021, Volume 39, Issue 1A, Pages 79-88
DOI: 10.30684/etj.v39i1A.1704

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.

Manufacturing of Thermal and Acoustic Insulation From (Polymer Blend/Recycled Natural Fibers)

Huda. M. khdier; Ahmed Hussein; Wafaa M. Salih

Engineering and Technology Journal, 2020, Volume 38, Issue 12, Pages 1801-1807
DOI: 10.30684/etj.v38i12A.1509

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.

A Study of Some Mechanical and Physical Properties for Palm Fiber/Polyester Composite

Samah M. Hussein

Engineering and Technology Journal, 2020, Volume 38, Issue 3B, Pages 104-114
DOI: 10.30684/etj.v38i3B.598

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.

Recycling of Waste Paraffin Wax by the Addition of SiO2 Nano-Powders to Improve Thermal Conductivity

Aseel B. Al-Zubaidi

Engineering and Technology Journal, 2019, Volume 37, Issue 9A, Pages 369-373
DOI: 10.30684/etj.37.9A.4

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

Enhanced thermal conductivity of cooling liquid using nano material's

Kheria M.Essa; Hashim Zydan Mohammed

Engineering and Technology Journal, 2015, Volume 33, Issue 7, Pages 1179-1192

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.

Study The Convective Heat Transfer of TiO2 /Water Nanofluid in Heat Exchanger System

Asmaa H.Dhiaa; Majid I. Abdulwahab; S.M.Thahab

Engineering and Technology Journal, 2015, Volume 33, Issue 7, Pages 1319-1329

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.

Experimental Stability and Thermal Characteristics Enhancement Analysis of Water Based Boehmite Nano fluid

Atia; Mohammed Hussein J. Al; Sarah A. Abed

Engineering and Technology Journal, 2015, Volume 33, Issue 7, Pages 1193-1210

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.

Mechanical, Electrical and Thermal Properties of Polypropylene and Polycarbonate Blend Filled with Carbon Black

Fadhil Abbas Hummdai

Engineering and Technology Journal, 2012, Volume 30, Issue 12, Pages 2076-2086

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).

Thermal Analysis of High Performance Lightweight Concrete Sandwich Panels

Wasan I. Khalil; Zain A. Raouf; Husain M.Husain

Engineering and Technology Journal, 2010, Volume 28, Issue 21, Pages 6439-6457

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.

Electrical And Thermal Properties Of Epoxy Resin Filled With Carbon Black

Waffa Abdul Kazem; Najat j. Salah; Adnan A. Abdul Razak

Engineering and Technology Journal, 2009, Volume 27, Issue 11, Pages 2223-2232

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.

Study of temperature and ultraviolet radiation effect on the values of thermal conductivity of hybrid composite materials

Engineering and Technology Journal, 2009, Volume 27, Issue 9, Pages 302-309

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