Papers by Jasson Gryzagoridis
Proceedings of First Conference for Engineering Sciences and Technology: Vol. 2, 2018
This volume contains contributed articles of Track 4, Track 5 & Track 6, presented in the... more This volume contains contributed articles of Track 4, Track 5 & Track 6, presented in the conference CEST-2018, organized by Faculty of Engineering Garaboulli, and Faculty of Engineering, Al-khoms, Elmergib University (Libya) on 25-27 September 2018. Track 4: Industrial, Structural Technologies and Science Material Track 5: Engineering Systems and Sustainable Development Track 6: Engineering Management Other articles of Track 1, 2 & 3 have been published in volume 1 of the proceedings at this lin
Proceedings of First Conference for Engineering Sciences and Technology: Vol. 2, 2018
The use of Heat pipes, for a variety of applications, has increased worldwide due to them achievi... more The use of Heat pipes, for a variety of applications, has increased worldwide due to them achieving high thermal efficiencies. Heat pipes in evacuated tube solar collector systems, in modern domestic water heating, comprise of a sealed envelope of a copper pipe, which contain a small quantity of working fluid. The Heat pipe transfers energy by the latent heat of the evaporation of the working fluid in a heating section. This vapor travels to the cold portion of the heat pipe and condenses. The circulation is completed with the condensate flowing back through the container's inner wall to the heating section by gravity. Tests were conducted using a test apparatus specifically made for the purpose of comparing the relevant attribute of thermal performance of Heat pipes containing different working fluids. A commercially available heat pipe, with its proprietary working fluid, was used as a reference in comparing its thermal performance efficiency (57.1%) with those of identical heat pipes containing distilled water, methanol, acetone and ethanol as working fluids. The results from the experiments achieved thermal efficiencies of 63.1%, 60.5%, 57.6%, and 42.1% respectively.
2017 International Conference on the Domestic Use of Energy (DUE), 2017
The performance of a wall mounted space comfort heater has been studied with respect to the geome... more The performance of a wall mounted space comfort heater has been studied with respect to the geometry of its mounting condition. Tests were conducted in a laboratory with the heater positioned at various heights from the floor and the channel that is created by the various gaps with the wall on which the heater was mounted. Tests were also performed with the heater mounted on the wall whose emissivity was adjusted to low, medium and high values as well as placing insulation material on the wall directly behind the heater. The experiments revealed an acceptable geometry of the heater's mounting at least 200mm above the floor, and 50 mm off-set from the wall. The heater's mounting against the wall caused a drop in performance of about 15% of it's maximum “benchmark” performance (with an efficiency of about 41%) achieved when the heater was freely standing on the floor of the laboratory. This efficiency, based on the convective heat transfer generated by the heater's war...
This paper reports on a nondestructive application where the use of traditional ultrasonic testin... more This paper reports on a nondestructive application where the use of traditional ultrasonic testing may aid in characterizing the defects that are detected using the laser based optical interference technique known as Digital Shearography. The composite materials tested are both of the laminate and sandwich type construction. The portable Digital Shearography system employed with regard to evaluating the integrity of composite materials has proven to be particularly user friendly, revealing the whole field under test in almost real time. Barely visible or invisible impact damage, delaminations and cracks in composite specimens were localized using mild surface heating between the two captured images required by the Digital Shearography technique. Subsequent testing, using a portable ultrasonic tester, aimed at characterizing the defects as they were detected in terms of their extent and depth position relative to the near or test surface.
In this paper Induction Thermography is considered as a complementary and even as an alternate te... more In this paper Induction Thermography is considered as a complementary and even as an alternate technique to the conventional non-destructive techniques of Magnetic Particle and Dye Penetrant Inspections, for the detection of surface defects in the mechanical maintenance arena. Experiments using Induction Thermography, on metallic electromagnetic specimens were performed, in the laboratory as well as on a 304L stainless steel pipe specimen, an HP turbine stud and a CV-joint obtained from the power plant. The results delineated the presence of cracks as a solid line with higher contrast compared to other areas of the specimens. The technique revealed defects that were also detected with the conventional NDT of MPI and DPI techniques within a short period of time, and may be considered as a preferable NDT technique for large surface inspections.
Journal of Engineering, Design and Technology, 2021
Purpose The purpose of this paper is to validate an assumption of what to use as an effective (st... more Purpose The purpose of this paper is to validate an assumption of what to use as an effective (steady state) heat transfer coefficient of thermal conductivity for the honeycomb core sandwiched by Fiberglass face sheets composite. A one-dimensional model based on Fourier law is developed. The results are validated experimentally. Design/methodology/approach The results were obtained from the one-dimensional mathematical model of an overall or effective heat conductivity of the Honeycomb composite panel. These results were validated experimentally by applying heat flux on the specimen under controlled environment. The surface temperatures at different voltages were recorded and analysed. The skin of the sandwich composite material used in the investigation was Fiberglass sheet with a thickness of 0.5 mm at the bottom and 1.0 mm at the top surface. Both skins have a stacking sequence of zero degrees. Due to the presence of air cells in the core (Honeycomb), the model considers the cond...
Journal of Energy in Southern Africa, 2017
That solar tracking improves energy yields from solar harvest systems is not debatable. Nor is th... more That solar tracking improves energy yields from solar harvest systems is not debatable. Nor is the under powering of tropical Africa amidst plenty of energy resources – including solar. This paper presents a review of recent literature on tracking as applied to domestic solar harnessing devices. The purpose is to find basic requirements in design of a suitable solar tracker for the region’s rural homes. It is concluded that Single axis passive trackers possibly will stand better chances of acceptability in the region.
TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2016
TRNSYS stands for transient system simulation software. This paper describes a procedure that was... more TRNSYS stands for transient system simulation software. This paper describes a procedure that was used to validate a TRNSYS model for estimating electricity yields from a fixed slope photovoltaic (PV) panel. The objective was to find how close to reality predicted energy yield for a specified panel can be, at a location near one of the weather stations listed in the software's database. The software was used to predict daily total incident radiation on a horizontal plane and electrical energy yields from a 90 Wp panel when sloped at 34 • facing north at a test site in Cape Town, South Africa. The panel and other system components were then installed and tested to give actual electrical energy yields. The site was 5 km from a TRNSYS listed weather station. A local weather station logging 10-min data of actual total incident radiation on a horizontal plane enabled comparison with the model's estimate. Analysis of electrical energy yield gave statistical kappa values of 0.722 and 0.944 at actual to model acceptance ratio levels of 90% and 80%, respectively. Regression analysis of measured and model incident horizontal plane energy gave a coefficient of 0.782 across the year. It was thus concluded that within limits of meteorological phenomena behaviour, TRNSYS modelling reliably predicted energy yields from the PV panel installed in the neighbourhood of one of the software's listed stations.
Applied Energy, 2016
h i g h l i g h t s We estimate daily electrical energy requirements for start-up rural homes at ... more h i g h l i g h t s We estimate daily electrical energy requirements for start-up rural homes at 500 W h. We model PV panel and BOS components selection for optimisation to meet the load. We solve the model at 152 stations in sub-Sahara Africa and map the solutions. Optimal panel selections range between 160 and 275 Wp. Battery capacities range between 70 and 360 A h while 15 A charge controllers dominate.
International Journal of Heat and Mass Transfer, 1971
International Journal of Heat and Mass Transfer, 1973
International Communications in Heat and Mass Transfer, 1984
Natural convection from an isothermal hq~izontal surface facing downward, has been investigated u... more Natural convection from an isothermal hq~izontal surface facing downward, has been investigated using the inter-fe~0metric technique. Mach-Zehnder interf@~ograms were 6b£ained for a ~ectangular plate in air, and the experimentally determined local Nusselt numbers/showed a sur-prising_dependance on the temperature difference~ between the plate and the ambient, a fact that has not been reported by previous investigations of the phenomenon.
A State of the Art instrument using the tap testing technique ‘The Woodpecker WP-632AM’ developed... more A State of the Art instrument using the tap testing technique ‘The Woodpecker WP-632AM’ developed by Mitsui was used to compare detectability of manufactured defects (flat bottom holes) in Perspex and aluminium specimens/coupons. A modern infrared camera the ‘T440’ developed by FLIR was also employed to perform Thermography tests on the same specimens. In this paper the authors present a comparison of the test results obtained using the above mentioned NDT techniques. The two instruments proved to be very user friendly, require very little set up time and practically no surface preparation on the specimens was required. Testing the specimens, using either technique with its respective instrument, is performed rapidly and both instruments provide instantly, permanent records of the results.
Digital Shearography is an Optical non-destructive testing technique, suitable for the inspection... more Digital Shearography is an Optical non-destructive testing technique, suitable for the inspection of manufactured components for defects. The technique employs the correlation of speckle images before and after object deformation and is particularly suited for inspecting composites for a range of defects including internal debonds and delaminations. The Department of Mechanical Engineering at the University of Cape Town has developed a portable Digital Shearography system which has the ability to perform phase stepped inspections. In addition, a software project has just been completed which complements the existing software by unwrapping the phase fringes into a displacement gradient map. This paper describes the principle of Digital Shearography, before highlighting the development of the portable Digital Shearography system. Selected aircraft composite samples from a carbon fibre helicopter rotor blade are then subjected to phase stepped shearography inspections using the new sys...
Smart Materials and Structures, 2007
ABSTRACT This paper presents the results of measurements of free displacement and blocked force g... more ABSTRACT This paper presents the results of measurements of free displacement and blocked force generated from piezo-composite unimorph actuators made from three different substrate materials (aluminium, brass and mild steel) of different thicknesses. Values of free displacement and blocked force were compared with the results from a finite-element analysis. An actuator with stiffer substrate material provides relatively larger force and less displacement. Conversely, greater displacement and less force are obtained from a less stiff substrate. It is hoped that this information will be useful to designers in selecting the appropriate size and substrate material in applications, depending on whether the desired goal is large displacement or large force.
This paper demonstrates the non destructive evaluation of selected glassfibre reinforced plastic ... more This paper demonstrates the non destructive evaluation of selected glassfibre reinforced plastic piping for structural defects. The items selected were constructed from glassfibre and polyester resin and include a tubular elbow, and a hollow cube with pre-manufactured delaminations. By inspecting the objects on non vibration isolating surfaces the paper also investigates the feasibility of a Portable NDT unit capable of performing both Electronic Speckle Pattern Interferometry (ESPI) and Shearography, which are the chosen methods of inspection. The resultant interferograms are presented and their features highlighted. A discussion and interpretation of the fringe patterns supports the detected defect areas. The paper is concluded by comparing the two methods of inspection and discusses their advantages and limitations.
2016 International Conference on the Domestic Use of Energy (DUE), 2016
This paper describes work carried out to test the performance of a newly invented solar tracker. ... more This paper describes work carried out to test the performance of a newly invented solar tracker. It is a gravity driven, bladder-flow controlled, Hooke coupled inclined non polar axis solar tracker. The performance of the tracker when coupled with a PV panel was first modelled in MATLAB® using the Perez anisotropic diffuse radiation and the King cell temperature models. Experiments with two identical 90 Wp panels were done over a 40 day period in outdoor conditions. One PV panel was fixed on optimised slope, the other, was driven by the tracker about a similarly sloped axis. Weather data consisting of total and diffuse radiation, ambient temperature and wind speed was also collected using a Campbell Scientific weather station adjacent the panels. This data was used to simulate performances of the panels in the MATLAB® model. TRNSYS simulations were also done for the two panels. The three sets of results were compared. It was found that the tracked panel yielded 34% more energy than the fixed one and that the experimental results correlated more closely with the MATLAB® models than with TRNSYS ones. Results also indicated that the efficacy of the tracking device could be influenced by the timing of cloudiness during the day and by wind speed.
Digital Shearography is an optical, non-contacting NDE inspection tool which can be used to detec... more Digital Shearography is an optical, non-contacting NDE inspection tool which can be used to detect material discontinuities and other defects within objects. The authors present a portable Digital Shearography Camera, which has just been completed and is currently undergoing evaluation. After presenting the preliminary results of laboratory based evaluation and testing of the Digital Shearography System, the authors report on the findings of the first on-site inspection, which was conducted at the regional airforce base in Cape Town. The results in the form of images exhibiting fringe patterns are presented, discussed and the presence or absence of flaws is highlighted. The performance and suitability of the Digital Shearography System for on-site application appears quite promising.
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Papers by Jasson Gryzagoridis