The printed circuit heat exchanger is a plate type heat exchanger with a high performance and compact size. Heat exchangers such as this need a unique form of bonding and other techniques to be used in their construction. In this study, the process of joining plates, diffusion bonding, was performed and studied. A special furnace was manufactured for bonding purposes. The bonding process of copper metal was carried out under specific conditions of a high temperature up to 700 oC, high pressure of 3.45 MPa, and in an inert environment (Argon gas) to make tensile samples. The tensile samples are cylindrical shapes containing groves representing the flow channels in the printed circuit heat exchanger and checking their tensile strength in addition to the standard shape of the tensile specimen to check the yield and ultimate strength of the copper. A higher tensile strength was obtained for diffusion bonded specimens than the yield strength of copper, up to 1.35 times the copper yield strength. The tensile strength decreases with the increase in the number of groves and the decrease in the distance between one grove and another. This is because the stress is concentrated in the sharp corners. A prototype heat exchanger of two plates and a header to be tested for its compressive strength was also manufactured. The results showed that the bond bears an air pressure of up to 8 bar without fail. It was also found to withstand a hydraulic pressure of up to 60 bar until it reached failure.
Background: The Titanium and its alloys are suitable for dental implant and medical applications. Biocompatibility of the materials is a major factor in determining the success of the implant and has a great impact on their rate of osseointegration. The aim of this study was to evaluate the biocompatibility and cytotoxicity of Ti2AlC in comparison to CPTi & Ti6Al7Nb in rabbits. Materials and Methods: 10 male New Zealand White rabbits, weighing (2-2.5 kg), aged (10-12 months) were used in this study. Cylindrical implants were prepared from the study materials (CPTi, Ti6Al7Nb and Ti2AlC) with (8mm) height and (3mm) diameter for the evaluation of tissue response and disc specimens were prepared with (6 mm) diameter and (2 mm) thickness for ev
... Show Morein this paper the second order neutral differential equations are incestigated are were we give some new suffucient conditions for all nonoscillatory
The measurement of minority carrier lifetime (MCLT) ofp-n Si fabricated with aid of laser doping technique was reported. The measurement is achieved by using open circuit voltage decay (OCVD) technique. The experiment data confirms that the value of MCLT and proftle of Voc decay were very sensitive to the doping laser energy.
In this paper, a sufficient condition for stability of a system of nonlinear multi-fractional order differential equations on a finite time interval with an illustrative example, has been presented to demonstrate our result. Also, an idea to extend our result on such system on an infinite time interval is suggested.
Study of group action of stone columns using FEM
Background: For many decades, the ECG was the
workhorse of non-invasive cardiac test and today although
other techniques provide more details about the structural
anomalies in congenital heart diseases, ECG is likely to be
part of clinical evaluation of patients with such diseases
because it is inexpensive, easy to perform and in certain
situations may be both sensitive and specific.
Objective: this study carried out to identify the pattern of
ECG study in patients with TOF.
Methods: this is a retrospective study of 200 patients
with TOF, referred to Ibn Al-Bitar cardiac center from
April 1993 to May 1999. The diagnosis of TOF established
by echocrdiographic, catheterization and angiographic
study.
Abstract: This study aims to identify mainly the experience of development of the state of Zimbabwe. The purpose of this study is to explain African studies in our Arab countries . The approach followed in this study is analytical description using also the comparative method as needed. This research division an introduction ,fourth topics and conclusions .The first dealt with the geographical location of the state of the Zimbabwe and explain of the main cities and a general introduction to the Republic of the state of Zimbabwe . The second section reviewed the historical development since the advent of colonial British colonialism and the declaration of Rhodesia Nyasaland in 1953 . As well as to clarify the position of stats and interna
... Show MoreIn Libya, there are multiple sources of pollution, one of which is animal waste. The anaerobic digestion (AD) of organic wastes to produce biogas has the advantage of producing valuable, renewable energy while reducing the environmental impact of these wastes. Cowmanure have the potential to produce biogas due to their high organic content. This study aimed to study different concentrations for the feedstock (1:1 and 2:1 cow manure: water v/v) to monitor which one gives higher biogas production. A plastic tank with a capacity of 72 liters and a feedstock volume of 60 liters was used to create a pilot scale. The biogas was analyzed using a GC device at the end of the experiment in the Zawiya Oil Refining Company. The result indicated that th
... Show MoreThis work characterizes the fractographic features of the neat epoxy and ZrO2 epoxy nanocomposites. All samples were subjected to a tensile test to determine the tensile strength and tensile modulus. SEM images were used to study the morphology of the fractured surface. The fractographic of the fracture surfaces were studied by microstructure analysis program (j-images) to specify the effect of ZrO2 nanoparticles on tensile performance and failure mechanism for ZrO2 epoxy nanocomposites. The tensile test results show that the addition of ZrO2 nanoparticles (2, 4, 6, 8, and 10 vol.%) to the epoxy matrix leads to increase the tensile strength about 40% for optimal content of ZrO2 nanop
... Show More