Daniel M. Madyira

• BSc. (Mechanical Enigneering), MSc. (Design of Turbomachines), PhD (Mechanical Engineering)
• Senior Lecturer at University of Johannesburg

The accelerating pace of climate change poses unprecedented challenges to global ecosystems and human societies. In response, this study reviews the power of Artificial Intelligence (AI) to develop advanced predictive models for assessing the multifaceted impacts of climate change. The study used the PRISMA framework to find, assess, and combine re...

This study focused on evaluating the combustion ignition, burnout, stability, and intensity of Hwange coal and Pinus sawdust blends within a drop tube furnace (DTF) through modelling. The cocombustion of coal with biomass is gaining attention as a strategy to improve fuel efficiency and reduce emissions. Hwange coal, a key energy source in Zimbabwe...

Process parameter optimization is of significant interest in the search for renewable energy from biomass. This study investigates the potential of three kinetic models to analyze and optimize biomethane production from acidic pretreated groundnut shells. First-order, logistic, and Gompertz models were investigated. Groundnut shells were pretreated...

Consumers’ consumption patterns and the global population’s livelihood have led to an increase in waste streams. Food waste (FW), agricultural residues, and livestock wastes are some of the major waste streams that require effective and economical management. This study investigated the biomethane potential, biodegradability, and synergistic effect...

This study investigates the effects of NaOH pretreatment on the microstructural distribution and biomethane released from Xyris capensis. Xyris capensis was pretreated with NaOH using 1, 2, 3, 4, and 5% w/w concentrations for 60, 45, 30, 20, and 15 min of exposure time, respectively, at a 90 °C autoclave temperature. The impacts of the pretreatment...

The study focuses on optimizing biomethane yield in the anaerobic digestion of alkali-pretreated groundnut shells, involving varied input parameters. Biomethane optimization will improve the economy of the technology, which will assist in managing the environmental challenges of fossil fuel combustion. Traditional methods prove challenging, inaccur...

Coal combustion is a major power source in the world, and energy conservation and environmental protection are now the top priorities in terms of carrying out the strategy for continuous and persistent development in power generation. The intricate coal combustion process must be investigated to present the process inside a live boiler as accuratel...

The mechanical separation of solids from liquids (filtration) is a critical process in many chemical process industries. The rotary drum filter can be considered a work-horse device which is one of the oldest filtration devices that has been used for centuries. Its reliability is affected by several process parameters leading to reduced life and po...

The global transition toward sustainable energy sources has prompted a surge in the integration of renewable energy systems (RES) into existing power grids. To improve the efficiency, reliability, and economic viability of these systems, the synergistic application of artificial intelligence (AI) methods has emerged as a promising avenue. This stud...

Nanolubricants were used to improve the performance of refrigeration systems in a household refrigerator. In this study, a pure lubricant is used as the base compressor lubricant, and nanoparticles of TiO 2 , Al 2 O 3 , and SiO 2 at 0.4g/L concentrations are used as nanolubricants in 50g isobutane (R600a) refrigerants. Power consumption was investi...

Wastewater treatment is now required because of the problems caused by water constraints. Wastewater is anaerobically digested to produce biogas, which can be used as a source of energy for things like lighting and heating. The upflow anaerobic sludge blanket (UASB) reactor has been recognized as an important wastewater treatment technology among a...

To enhance a home refrigerator’s refrigeration system’s performance, three types of nanoparticles (TiO 2 , CNTs, and SiO 2 ) were used to produce nanolubricants. The experiments were conducted with different charges of 50 and 60 g for R600a refrigerants, which a digital charging scale was used to measure. The inlet and exit temperature of the syste...

A combination of R290/R600 refrigerants with low global warming and zero ozone-depleting potential refrigerant was tested with a based lubricant and CNTs nanolubricant in a refrigeration system to improve its performance efficiency and minimise the environmental impact of refrigerants and energy demand by refrigeration systems. CNTs-nanolubricant,...

Synthetic refrigerants are being phased out gradually in accordance with international environmental protection protocols because of global warming and ozone layer depletion. adopting r290/r600 refrigerant, an environmentally friendly refrigerant, to replace r134a, a high global warming potential refrigerant, provides one of the solutions. in this...

Combustion of bituminous coal and pinus sawdust blends was investigated experimentally within a drop tube furnace (DTF) with the aim of determining particle residence times and temperatures during the process. Evaluation of these parameters gives useful information to engineers who want to optimise the co-combustion process of coal and biomass blen...

Anaerobic co-digestion of lignocellulose feedstock with livestock waste can assist in overcoming the challenges of digesting lignocellulose and balancing the nutrient contents of the process. This study investigated the optimum conditions for methane yield production from anaerobic co-digestion of alkali-pretreated groundnut shells and duck waste u...

To enhance the efficiency of the anaerobic digestion process of lignocellulose feedstocks, there is a need for appropriate pretreatment methods. The influence of nanoparticles additive on biogas yield of new novel Xyris capensis grass as biogas feedstock was investigated. A laboratory-batch experiment was set up at mesophilic conditions (37 ± 2° C)...

This study examined the influence of DES pretreatment using choline chloride and ethyl glycerol with the molar ratio of 1: 1 at different solid:liquid ratios and temperatures on groundnut shells’ microstructural arrangement and biomethane yield. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy...

Without a doubt, lightweight materials of high strength are in high demand in the automotive, aerospace, biomedical, and other industries that require such materials. Processing or manufacturing such materials has been a vital topic in contemporary research, as well as material development in the industry. A possible solution for the processing of...

Synthetic refrigerants are being phased out gradually in accordance with international environmental protection protocols because of global warming and ozone layer depletion. adopting r290/r600 refrigerant, an environmentally friendly refrigerant, to replace r134a, a high global warming potential refrigerant, provides one of the solutions. in this...

3CR12 is a low cost special stainless steel containing 12% chromium. It is widely used in material handling, road transport, rail transport, power generation and petrochemical applications due to its favorable corrosion performance. 3CR12 is a weldable material, but it has challenges such as poor ductility, poor toughness of 3CR12 stainless steel w...

The efficiency of R600a, an eco-friendly refrigerant with TiO2, Al2O3, and SiO2 nanolubricants, was investigated and evaluated as a substitute for R134a in a vapour compression refrigerator system. Pressure gauges and K-type thermocouples were used to monitor the temperature and pressure. The power consumption of the refrigerator was observed using...

nanolubricants, was investigated and evaluated as a substitute for R134a in a vapour compression refrigerator system. Pressure gauges and K-type thermocouples were used to monitor the temperature and pressure. The power consumption of the refrigerator was observed using the digital wattmeter. Using NIST refprop version 9.0, the refrigerant's enthal...

This study investigated the effect of the anaerobic co-digestion of duck waste and alkali-pretreated groundnut shells at mesophilic temperature for methane yield optimization and waste management. Co-digestion of duck waste and alkali-pretreated groundnut shells was carried out using 100, 75: 25, 50: 50, 25: 75, and 100% duck waste: alkali-pretreat...

This study examined the possibilities of enhancing methane yield from anaerobic digestion of Xyris capensis and duck wastes based on improved feeding composition and the C/N ratio. Batch anaerobic digestion of Xyris capensis and duck wastes was conducted at mesophilic temperature (37 ± 2 °C) with the mixing ratios of 100:0, 75:25, 50:50, 25:75, and...

This study investigated the application of Response Surface Methodology (RSM) for optimizing and predicting methane yield from oxidative pretreated Xyris capensis. Input process parameters of retention time, temperature, and pretreatment condition were considered, with methane yield as the response. The results show that all three process parameter...

Macroalgae can be grown without the use of fertilizer, fresh water, or arable land. These qualities support its use for biofuel production because it frees up land for other traditional energy sources and food crops. It has been investigated as biogas feedstock to substitute for fossil fuels burning with attendant effects on the ecosystem. The micr...

Renewable energy production from lignocellulose materials is a significant interest of modern research because it can assist in reducing the global challenges of climate preservation and energy demand. Lignocellulose materials are recalcitrant and are not easy to digest during anaerobic digestion, and this necessitated their pretreatment before ana...

Agricultural residues have been identified as potential substrates for anaerobic digestion, which indicates them as alternative energy sources. But enzymatic hydrolysis of these residues has been observed as the rate-limiting step due to their recalcitrant characteristics. Therefore, pretreatment before anaerobic digestion is required to reduce the...

Biogas production from lignocellulose feedstocks has become an acceptable energy source globally due to their availability and economy. Lignocellulose materials have a complex arrangement that hinders digestion during the process. Therefore, applying the pretreatment process to lower the recalcitrant properties is required to utilize the full poten...

Enzymatic hydrolysis of lignocellulose feedstocks has been observed as the rate-limiting stage during anaerobic digestion. This necessitated the need for pretreatment before anaerobic digestion for an effective and efficient process. Therefore, this study investigated the impact of acidic pretreatment on Arachis hypogea shells, and different condit...

To solve the problem that it is difficult to accurately identify the rotor eccentric fault, demagnetization fault and hybrid fault of a permanent magnet synchronous motor (PMSM) with a slot pole ratio of 3/2 and several times of it, this paper proposes a method to identify the rotor fault based on the combination of branch current analysis and a ma...

Coal is the primary source of energy in South Africa today. In the extraction and processing of coal, significant amounts of coal fines waste are generated. Currently, waste coal fines have no economic value. As a result, they are disposed of in landfills or underground. Furthermore, if coal fines are not properly managed, they have a negative envi...

The usage of natural fibers requires that they should be pretreated in preparation for their application as reinforcement in Natural Fiber-Reinforced polymer composites. The treatment modifies the fiber surface to improve bonding between the fibers and the polymer matrix. This paper reports on the effects of sodium hydroxide (NaOH) treatment on the...

Polymer-based nanocomposites are widely investigated owing to their unique and remarkable mechanical properties. Yet, obtaining polymer nanocomposites with improved impact strength and acceptable hardness properties is a major challenge. This is because various types of polymers and nanoparticles can be combined to, or sometimes, fail to achieve su...

This paper presents a review of existing plastic deformation displacement analysis models for materials and components. Plastic deformation analysis is important in the study of failed components. This is because it provides insight on how materials and components behave after the yield point has been exceeded and the deviation of the plates from t...

Vibrating screens have significantly improved the particle separation process in the mining industry. However, they operate under demanding conditions. Components such as the cross bracket, used to transmit the excitation from the actuation motors to the screen frame, are prone to failure. To improve the welded joints, a newly developed vibrating s...

Developing and designing engineering materials with desirable properties, such as high strength to weight ratio, formability, corrosion resistance and biocompatibility, among many other properties, is crucial, especially in modern engineering and material science industries. This is influenced by the demand for high-performing and more efficient ma...

Designing and developing a new material can be challenging due to several aspects that require consideration. Materia behavior, material properties (physical or chemical), and other material characteristics are the factors to consider when developing new materials. In this work, polymer-based nanocomposite material is developed using High-Density P...

Powder metallurgy (PM) is an alternative approach to ingot metallurgy (IM) in the production of metal products. It is of paramount importance for PM to be able to produce fully dense products for it to make headway in becoming an equal alternative to IM and be a better option economy-wise. Cold rolling is an inexpensive post-sintering densification...

Anaerobic digestion (AD) is one of the most widely used technologies in the world for converting solid organic waste into energy and other value-added products. In the treatment of municipal wastewater, the disposal of sewage sludge is a problem of growing importance, as it contributes significantly to the operating costs of a wastewater treatment...

Hydrofluorocarbon refrigerants will be phased out of domestic refrigeration shortly, by the Montréal and Kyoto Protocols, due to their high global warming potential (GWP), making them environmentally unfriendly. This study looked into the possibility of using graphene-nanolubricant in a domestic refrigerator system to improve liquefied petroleum ga...

Beer is one of the most consumed beverages in the globe reaching an average consumption of 23L per person per year. This makes brewing industry one of the leading economic contributors to most countries. Large amount of organic waste that pollute the environment are produced in beer making processes. The brewing by-products may reach 3%–30% of the...

Co-digestion of organic rich wastewater sludge and brewery spent yeast is a prospectively viable bioenergy substrate, which can enhance future green energy and boost the emerging circular economy. Multi-objective optimization of wastewater treatment plant (WWTP) cost and its environmental footprint are considered significant and vital in modern WWT...

Biomethane production from thermally pretreated Arachis hypogea shells was modeled using response surface methodology (RSM) and artificial neural network (ANN). RSM and ANN models were investigated based on; temperature, retention time, and pretreatment conditions as input variables, and biomethane yield as the response. The ANN model gave the best...

This study experimented biogas production from Arachis hypogea shells subjected to combined pretreatments, namely particle size reduction and Fe3O4 additives. Further to this, the biogas production based on organic dry matter biogas (oDMBY), fresh mass biogas (FMBY), organic dry matter methane (oDMMY), and fresh mass methane (FMMY) were modeled usi...

A smart energy recovery process can achieve maximum energy recovery from organic wastes. Pretreatment of feedstock is essential to biogas and methane yields during the anaerobic digestion process. This work combined particle size reduction with Fe 3 O 4 nanoparticles to investigate their influence on biogas and methane yields from anaerobic digesti...

Optimum energy recovery and economical use of lignocellulose feedstocks required an efficient breakdown of their recalcitrance characteristics. This study investigated the alkali pretreatment of underutilized Arachis hypogea shells’ structural arrangement and methane yield. The NaOH pretreatment was carried out with 1%, 2%, 3%, and 4% (w/w), an exp...

Cocombustion of bituminous coal (HC) and Pinus sawdust (PS) was investigated in this paper with the aim of determining the kinetic parameters relevant to cocombustion reactions of their fuel blends. PS was used because it is a waste biomass product capable of generating energy. Motivated by the need to partly substitute HC used in existing boilers...

LPG's steady-state performance in a base lubricant and a graphene nanolubricant was investigated in this study. Step-by-step processes and procedures for preparing graphene nanolubricant concentrations and replacing them for the base lubricant in a domestic refrigerator system were presented as the measuring devices necessary and their uncertaintie...

Currently, 91% of the world population has access to clean and safe water. Despite this encouraging development exclusion and marginalisation of the poor appear not only to be deepening but also spreading. Low-income communities in urban areas are increasingly grappling with issues of reliability, sufficiency, and affordability of potable water. At...

Enzymatic hydrolysis of lignocellulose materials has been identified as the rate-limiting step during anaerobic digestion. The application of pretreatment techniques can influence the biodegradability of lignocellulose substrate. This study combined Fe3O4 nanoparticles, which serve as a heterogeneous catalyst during anaerobic digestion, with differ...

The complex lignocellulosic arrangement of Arachis hypogea shells is the major hindrance during its anaerobic digestion process. This work emphasizes the application of thermal pretreatment on Arachis hypogea shells before anaerobic digestion. Different temperatures of 90, 100, 110, and 120 °C, with 30 and 60 min duration were applied to the substr...

In this study, Response Surface Methodology (RSM) was used to examine the effects of temperature, hydraulic retention time, and particle size of Arachis hypogea shell on biogas and methane yields in a batch test. Further to this, an Adaptive Neuro-fuzzy Inference System (ANFIS) clustered with fuzzy c-means (FCM) was developed to predict organic dry...

Optimising biogas yields from anaerobic digestion of organic wastes is significant to maximum energy recovery in the biodigestion process and has become an important topic of interest. Substrate particle size is an important process parameter in biogas production, and it precedes other pretreatments methods for the majority of the lignocellulose ma...

The cocombustion of coal and pinus sawdust waste is an economically viable and sustainable option for increasing the share of biomass in energy production. This technology also has the potential to reduce the emission of greenhouse gases from existing coal fired power plants. The thermal synergistic effects of cocombusting Hwange bituminous coal (H...

A single evaporator household refrigerator with a total volume of 70 litres is used to evaluate multi-walled carbon nanotubes (CNTs) nanolubricant as a drop-in replacement for pure lubricant. Continuous running on the refrigerator is done with varying concentrations of multi-walled CNTs nanolubricant and different mass charges of R600a. The results...

The efficiency of R600a an eco-friendly refrigerant with graphene nanolubricant was investigated and compared in a domestic refrigerator with R134a refrigerant a zero Ozone Depleting Potential (ODP) but higher Global Warming Potential (GWP) refrigerant. Type K thermocouples were attached to the refrigerator components to track the temperature of th...

This study focused on the effects of introducing pine sawdust and bituminous coal in a down fired combustion reactor. Co-combustion of coal and biomass waste provides an alternative to biomass waste management as well as efficiency improvement with regards to boiler optimisation if correctly applied. A Computational Fluid Dynamics model, using ANSY...

The aim of this work was to evaluate the response of a vinasse mesophilic anaerobic digester to intermittent mixing. Physicochemical analysis were performed on the digestate, and on three samples collected at three different depths, providing a local insight of the digester before and after mixing. The mixing speed varied from 20 to 60 rpm. The bio...

The current investigation deals with proposing a numerical analysis for the geometrically nonlinear large-amplitude vibrations of arbitrary-shaped microplates having variable thickness with various patterns in the presence of couple stress type of microstructural size dependency. To accomplish this purpose, the isogeometric analysis (IGA) is employ...

A 100% overlap double pass friction stir process technique was developed for the fabrication of AA1100/17-4 PH stainless steel composites, using an H13 tool steel cylindrical threaded pin with shoulder diameter of 21 mm, pin diameter of 7 mm and pin height of 5 mm. Grooves of 2 mm width and 3.5 mm depth were machined on the 6 mm thick AA1100 plate,...

In line with Montréal and Kyoto protocol, the use of Hydrofluorocarbon refrigerants in domestic refrigeration will be phased out completely soon due to their high global warming potentials (GWP) which makes them unfriendly to the environment. This work investigated the possibility of improving liquefied petroleum gas (LPG) of propane and butane (60...

Vapour compression systems are associated with high energy demand and contribute to ozone depletion and global warming due to halogenated refrigerants used in them which are unfriendly to the environment. Hydrocarbon refrigerants have been proposed as a substitute to halogenated refrigerants due to their zero ozone depletion potentials, very low gl...

Energy consumption and environmental problems have been the major consideration for comfort systems manufacturers. This research work investigated a varied mass charge of R600a, an eco-friendly refrigerant with a low concentration of 0.4 and 0.6 g/L of CNT nanolubricant concentration in a domestic vapor compression refrigerating system working with...