Showing items 1 - 20 of 1748

Your selections:

Thermal diffusivity behaviour of multi-walled carbon nanotube reinforced Ti6Al4V metal matrix composites

  • Authors: Adegbenjo, A. , Obadele, B. , Olubambi, P. , Adejuwon, S.
  • Date: Shongwe, M. , 2019
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/405073 , uj:33998 , Citation: Adegbenjo, A. et al. 2019. Thermal diffusivity behaviour of multi-walled carbon nanotube reinforced Ti6Al4V metal matrix composites. IOP Conf. Series: Materials Science and Engineering 499 (2019) 012002. doi:10.1088/1757-899X/499/1/012002
  • Description: Abstract: This study investigated the thermal diffusivity behaviours of spark plasma sintered (SPS) multi-walled carbon nanotubes (MWCNTs) reinforced Ti6Al4V composites containing 0, 1, 2 and 3 wt. % of the reinforcement respectively, over a range of 50 – 300 °C. The MWCNTs were dispersed into the Ti6Al4V matrices by high-energy ball milling (HEBM) technique and the milled composite powders were consolidated by SPS under a vacuum atmosphere. The sintering conditions employed were heating rate (100 °C/min), holding time at temperature (5 min), sintering temperature (850 °C) and applied pressure of 50 MPa. The relative densities of the composite discs were measured according to Archimedes’ principle while the thermal diffusivities of as-sectioned composite samples were measured using the Laser Flash equipment. Relative densities of the synthesized nanocomposites deteriorated with increase in the weight fraction of MWCNTs added to Ti6Al4V. The thermal diffusivities of the composites containing 1 and 2 wt. % MWCNTs improved with increase in temperature and weight fraction of MWCNTs contents. A reverse trend was observed in the composite containing 3 wt. % MWCNTs, as the measured thermal diffusivities continued to drop with increase in temperature. Although this composite exhibited the best thermal diffusivities compared to the other composites up to 200 °C, a significant drop in thermal diffusivity was recorded between 250 and 300 °C respectively with the values lower than that of the unreinforced Ti6Al4V alloy. However, the thermal diffusivities of MWCNTs/Ti6Al4V composites were generally not dependent on their densification as the composites with higher weight fractions of the reinforcement had higher thermal diffusivities in spite of their lower relative densities.
  • Full Text:

Assessment of a range of design models for predicting creep in concrete

Numerical analysis of the hydrodynamics of the flow in an axially rotating heat pipe

Turbidity removal at twenty-one South African water treatment plants

  • Authors: Van Staden, S. J. , Amod, A. , Ceronio, A. D. , Haarhoff, J.
  • Date: 2002
  • Subjects: Water treatment plants , Turbidity removal
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/16583 , uj:15787 , Citation: Van Staden, S.J. et al. 2002. Turbidity removal at twenty-one South African water treatment plants. 8th Biennial Conference of the Water Institute of Southern Africa, 19-23 May 2002, ICC, Durban, WISA 198, 10p.
  • Description: Abstract: The Water Research Group at the Rand Afrikaans University undertook an ambitious sampling and monitoring programme at twenty-one South African water treatment plants during 2000 and 2001. At some of these plants, there were parallel but different treatment trains due to plant extensions being made at different times. A total of 25 full or partial treatment trains could therefore be monitored. A total of 115 plant visits were made over a period of fifteen months, with samples taken throughout the plant, covering the complete treatment train from raw to final water. Amongst other parameters, the turbidity of each sample was determined on site immediately upon sampling. This paper will summarise and interpret the resulting data set of approximately 1300 turbidity values. The paper will firstly characterise the raw and final waters respectively. In other words, how does typical raw water vary, and how good is the typical final water produced? The second part will summarise the typical performance of each of the treatment processes. In other words, what reduction in turbidity is typically achieved during settling, dissolved air flotation and filtration? The paper will make a practical contribution in providing a benchmark to all operators of treatment plants by: · being able to immediately "position" themselves within a typical range of raw water values. · judging their final water quality against what is generally achieved, and · evaluating and troubleshooting their individual process units against what is generally achieved.
  • Full Text:

Numerical analysis of the convective heat transfer in a combustor cooling jacket

  • Authors: Gutierrez, Gustavo , Jen, Tien-Chien , Yan, Tuan-Zhou
  • Date: 2003
  • Subjects: Combustor cooling , Convective heat transfer , Numerical analysis
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/16022 , uj:15729 , Citation: • Gutierrez, G., Jen, T.C., and Yan, T., 2003, “Numerical Analysis of the Convective Heat Transfer in a Combustor Cooling Jacket,” International Mechanical Engineering and Congress Exposition, November 16-21, 2003, Washington, D.C., Vol. 3, pp. 29-37. IMECE2003-42912. ISSN: 0-7918-3718-1.
  • Description: Abstract: In any combustors and chemical reactors, to achieve high efficiency it is very important to maintain the high gas temperature inside the combustion chamber without significant deterioration of the materials of the walls. Thus, a critical aspect of the design of a combustor or reactor is the development of a method to cool the inner walls of a combustor such that the temperatures on the inner wall are well below the temperature a material can sustain. A typical method to cool a combustor chamber is to use a cooling jacket adjacent to the inner wall of the combustor. In general, the efficiency of this cooling jacket depends on the heat removal capability of the cooling water and the flow channel geometry. It is critically important to control these parameters to enhance the performance of the combustion chamber by decreasing the inner wall temperature below its material limit Sφ : source term in the generic property φ Vr ,Vθ , Vz : reduced velocities in the r, θ , and z direction respectively [m/s] T : temperature [ºC] Tinn : inner temperature [ºC] T∞ : ambient temperature [ºC] U0 : inlet velocity [m/s] Greek ρ : density [kg/m3] φ : generic property μ : dynamic viscosity [kg/m-s] Γ : diffusivity for the generic property φ Ω : angular velocity [rad/s] This study considers a cylindrical combustor, rotating around its axis. A detailed investigation of the fluid flow and heat transfer processes throughout the cooling jacket is performed. A two-dimensional axial symmetric Navier-Stokes equations and energy equation as a conjugate problem are solved. The flow patterns and temperature distributions of the cooling jacket under the effect of rotation are presented. Also, local friction factor and Nusselt number are calculated along the axial direction.
  • Full Text:

Predicting creep deformation of concrete : a comparison of results from different investigations

  • Authors: Fanourakis, George C. , Ballim, Yunus
  • Date: 2003
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/463056 , uj:41315 , Citation: Fanourakis, G.C. & Ballim, Y. 2003. Predicting creep deformation of concrete : a comparison of results from different investigations.
  • Description: Abstract: Creep deformation of concrete is often responsible for excessive deflection at service loads which can compromise the performance of elements within a structure. Hence, the realistic prediction of both the magnitude and rate of creep strain is an important requirement of the design process. Although laboratory tests may be undertaken to determine the deformation properties of concrete, these are time-consuming, often expensive and generally not a practical option. Therefore, relatively simple empirically based national design code models are relied upon to predict the magnitude of creep strain. This paper reviews the accuracy of creep predictions yielded by eight commonly used international “code type” models, all of which do not consider the same material parameters and yield a range of predicted strains, when compared with actual strains measured on a range of concretes in seventeen different investigations. The models assessed are the: SABS 0100 (1992), BS 8110 (1985), ACI 209 (1992), AS 3600 (1988), CEB-FIP (1970, 1978 and 1990) and the RILEM Model B3 (1995). The RILEM Model B3 (1995) and CEB-FIP (1978) were found to be the most and least accurate, respectively.
  • Full Text:

The acceleration of micro- and nano-particles in supersonic De-Laval-Type nozzle

Thermal performance of heat pipe drill : experimental study

An improved filter media test for troubleshooting and rehabilitation of problem filters

  • Authors: Van Staden, Samantha , Haarhoff, Johannes
  • Date: 2004
  • Subjects: Water treatment filters , Floc retention test
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/16754 , uj:15808 , Citation: Van Staden, S.J. & Haarhoff, J. 2004. An Improved Filter Media Test for Troubleshooting and Rehabilitation of Problem Filters. 2004 Water Quality Technology Conference, 14-18 November 2004, San Antonio, Texas, USA, 12p.
  • Description: Abstract: A standard “floc retention test” was made available by the American Water Works Association1 to provide a routine measure of filter media cleanliness. This would allow early detection of the potential for serious problems. The test is performed by preparing a 50g media sample and shaking it vigorously in 100ml of water. The resultant suspension is then decanted and, after five repetitions, the turbidity of the combined suspension is measured, doubled and reported as NTU (nephelometric turbidity units)/100g of sand. The turbidity, according to AWWA guidelines, ranges from < 60 (clean filters) to 300 NTU/100g (filters with a possible mudball problem)2. At many South African plants, filters appear to be inadequately cleaned by routine backwash procedures. The hypothesis is that the root of this phenomenon lies in the high degree of biological activity within filter beds. This presumably results in a sticky biofilm on the media grains, which is difficult to remove. The floc retention test proved to be an indispensable tool for a systematic survey of water filtration plants currently being carried out to test this hypothesis. To improve reproducibility and insight into the reasons for media fouling, the floc retention test was refined in a number of ways, which is the main focus of this presentation.
  • Full Text:

Contactless power coupling system

Heat transfer augmentation in 3D inner finned helical pipe

Rogowski coil power application

What simple media tests can tell you about filter problems and rehabilitation

A study of insulation failure in a high voltage current transformer

Alternating current source to voltage source converter

Current transformer used as a voltage source

Feeder's load balancing using an expert system

Health and safety (H&S) awareness and implementation in Botswana's construction industry

Overview of tapping methods from high voltage transmission lines

Simulation results for permutation trellis codes using M-ary FSK

  • Disclaimer
  • Privacy
  • Copyright
  • Contact