Drying agricultural produce consumes a considerable amount of energy. As an energyefficient syste... more Drying agricultural produce consumes a considerable amount of energy. As an energyefficient system, a heat pump can improve the energy efficiency of the drying process and hence reduce the energy consumption, especially in South Africa, where both sub-tropical and temperate weather conditions dominate. The objective of this research is to experimentally investigate the impacts of weather conditions on the operational conditions and thermal performance of an openloop air-source heat pump drying system. The experimental investigation was conducted in a climate chamber where the climate conditions were simulated from -10 • C to 20 • C with an interval of 10 • C for the typical temperature range of the harvesting season in South Africa. The findings indicate that ambient temperatures have a significant impact on both the operating conditions and thermal performance of an open-loop heat pump system; the change in ambient temperatures from -10 • C to 20 • C leads to a 141.6% improvement in the suction pressure, a 214.2% increase in the discharge pressure, and 30.1% increase in the compression ratio, as well as a consequent increase of 130.6% in the refrigerant mass flow rate (from 0.0067 to 0.0155 kg/s), resulting in a corresponding increase in the coefficient of performance (COP) of the heat pump drying system by about 42.1%. Therefore, this study suggests that, while using an open-loop air-source heat pump drying system utilising R134a refrigerant is feasible in South Africa, it may be practically limited to regions with warm climates or during warmer seasons.
Zenodo (CERN European Organization for Nuclear Research), Nov 28, 2022
The organizing committee, advisory board and review board, as well as the editors are grateful to... more The organizing committee, advisory board and review board, as well as the editors are grateful to the delegates who had submitted and presented papers. The conference papers included experimental as well as overview studies applicable to Energy and the application or enhancement of human habitat. Although the conference was open for inclusion of studies from an energy policy and energy economics perspective, almost all the papers received in this call were of a more technical nature. The conference received papers via its online submission platform and responded by related email. Reviews were double blind with two reviewers per paper and a third editorial review for decision to include the paper in the proceedings. Several paper abstracts were received but was not of sufficient quality to meet initial review requirements and some were also outside the scope of the conference. The conference received over 48 abstracts and received 38 papers as submissions. Only 21 papers were accepted and graded for inclusion in this Proceedings after peer review and these included only highly positive reviews with minimal corrective work.. The rejection ratio of papers was 44% rejection.The highest single institution papers accepted for publication was 28 %, hence meeting the South African DHET requirement. The authors were required to avail themselves for a face to face presentation with session chairs at the conference venue.
Zenodo (CERN European Organization for Nuclear Research), Nov 28, 2022
The organizing committee, advisory board and review board, as well as the editors are grateful to... more The organizing committee, advisory board and review board, as well as the editors are grateful to the delegates who had submitted and presented papers. The conference papers included experimental as well as overview studies applicable to Energy and the application or enhancement of human habitat. Although the conference was open for inclusion of studies from an energy policy and energy economics perspective, almost all the papers received in this call were of a more technical nature. The conference received papers via its online submission platform and responded by related email. Reviews were double blind with two reviewers per paper and a third editorial review for decision to include the paper in the proceedings. Several paper abstracts were received but was not of sufficient quality to meet initial review requirements and some were also outside the scope of the conference. The conference received over 48 abstracts and received 38 papers as submissions. Only 21 papers were accepted and graded for inclusion in this Proceedings after peer review and these included only highly positive reviews with minimal corrective work.. The rejection ratio of papers was 44% rejection.The highest single institution papers accepted for publication was 28 %, hence meeting the South African DHET requirement. The authors were required to avail themselves for a face to face presentation with session chairs at the conference venue.
The quality of spin casting products and mould life are critically dependent on thermal condition... more The quality of spin casting products and mould life are critically dependent on thermal conditions they undergo. In order to improve the performance of production and to optimise the spin-casting process, characteristics of the thermal process was firstly identified by means of the measurement and simulation. Furthermore the investigation of the developed control methods, including the thermal property substitute method and mixture method of the metal powder, was kept on the effect of air-cooling induced automatically from the spinning of the mould on the thermal process. The air cooling system was developed to optimise the thermal process during casting, utilising a theoretical analysis of the air-flow characteristics in a cooling tube submerged in a silicon mould and the characteristics of convection heat transfer associated with the mould and cast part. A numerical simulation of the casting process was also adopted in the analysis. The effect of the developed system on the thermal process was determined experimentally and it was found that a system of aircooling, automatically induced from the spinning of the mould, is feasible in optimisation of the thermal process. The developed control methods can be applied to the practice of spin casting individually or collectively according to the specific situations and requirements.
The stability of biodiesel is dependent on storage conditions such as contact with ambient air an... more The stability of biodiesel is dependent on storage conditions such as contact with ambient air and metals, exposure to sunlight and high temperature conditions which accelerate oxidation reactions. In addition, biodiesels are more susceptible to degradation when compared to fossil diesel because of the presence of unsaturated fatty acid chains which are prone to oxidation. The stability of biodiesel is categorised according to oxidation stability, storage stability and thermal stability. Oxidation instability can led to the formation of oxidation products such as aldehydes, alcohols, shorter chain carboxylic acids, insolubles, gums and sediments in the biodiesel. Thermal instability is concerned with the increased rate of oxidation at higher temperature, which in turn increases the weight of oil and fat due to the formation of insolubles. Storage stability is the ability of liquid fuel to resist change to its physical and chemical characteristics brought about by its interaction with its storage environment, such as contamination with metals. These fuel instabilities give rise to the formation of undesirable substances in biodiesel beyond acceptable limits as per global biodiesel standards such as those of the American Society for Testing and Materials (ASTM D6751) and European Standards (EN 14214). When such fuel is used in the engine, it impairs engine performance through fuel filter plugging, injector fouling, and deposit formation in the engine combustion chamber and various components of the fuel system. We review the stability of biodiesel made from less common vegetable oils of African origin and synthetic antioxidants used in improving the stability of produced biodiesels.
Zenodo (CERN European Organization for Nuclear Research), Nov 28, 2022
The organizing committee, advisory board and review board, as well as the editors are grateful to... more The organizing committee, advisory board and review board, as well as the editors are grateful to the delegates who had submitted and presented papers. The conference papers included experimental as well as overview studies applicable to Energy and the application or enhancement of human habitat. Although the conference was open for inclusion of studies from an energy policy and energy economics perspective, almost all the papers received in this call were of a more technical nature. The conference received papers via its online submission platform and responded by related email. Reviews were double blind with two reviewers per paper and a third editorial review for decision to include the paper in the proceedings. Several paper abstracts were received but was not of sufficient quality to meet initial review requirements and some were also outside the scope of the conference. The conference received over 48 abstracts and received 38 papers as submissions. Only 21 papers were accepted and graded for inclusion in this Proceedings after peer review and these included only highly positive reviews with minimal corrective work.. The rejection ratio of papers was 44% rejection.The highest single institution papers accepted for publication was 28 %, hence meeting the South African DHET requirement. The authors were required to avail themselves for a face to face presentation with session chairs at the conference venue.
Characterisation and thermal performance of a R290 transport refrigeration unit with charge amount in South Africa
The transport of perishable goods mainly foodstuffs, requires refrigeration and insulated vehicle... more The transport of perishable goods mainly foodstuffs, requires refrigeration and insulated vehicles, especially countries with high ambient temperatures have a growing demand for efficient and safe refrigerated transport. Refrigerated transport plays an paramount roles in direct and indirect reduction of greenhouse gases emission. Currently, the available technologies for transport refrigeration systems in South Africa are inefficient units using refrigerants with high global warming potential (GWP) and having high leakage rates. The Transport Refrigeration Project sponsored by GIZ aims to improve the overall performance of transport refrigeration in South Africa: Efficient transport refrigeration systems for small and large trucks have been developed using the low-GWP hydrocarbon refrigerant R290. During the project, the thermal performance of R290 were tested and compared to the R404A for a refrigeration unit when the charge amount varies. The results indicate that the charge amount is dramatically reduced meanwhile the refrigeration capacity and performance are still maintained at an equivalent or higher level, investigation results also shows the opportunity for further performance improvement.
Development of Lightweight Insulation Body for Refrigerated Vehicles by Using Composite Materials
Key Engineering Materials, May 1, 2017
Energy demand in refrigerated vehicles account for about 5% of fossil fuel consumption globally a... more Energy demand in refrigerated vehicles account for about 5% of fossil fuel consumption globally and this percentage is expected to rise as perishable raw food continue to enjoy significant patronage of refrigerated vehicles which provide low temperature condition for its sustenance. Sustaining the shelf life of fresh food remains a herculean task to most farmers as cold chain must remain unbroken in order to maintain the quality of fresh food. The concept of this research is to reduce energy consumption in refrigerated vehicles through lightweight insulated panel as this medium could effectively reduce the payload of the entire vehicle. Part of the progress made in this work, is to develop five different composite cover sheet for insulated panel using fibre loading and orientation as manufacturing parameters and results show that the oriented reinforced composite materials offer significant weight reduction compared to unoriented composite cover sheet. The panel weight of these new materials were estimated using all the conceptual parameters of a refrigerated vehicle and the results indicate that composite reinforced with 10%wt. of fibre at 30o orientation in the matrix, offers the best panel weight reduction with 5.2380kg/m2 and 6.7380kg/m2 for 50mm and 100mm insulation thicknesses, respectively.
Notice of Retraction: Application of laser sintering technology in heat exchanger design and manufacture
ABSTRACT Notice of RetractionAfter careful and considered review of the content of this paper by ... more ABSTRACT Notice of RetractionAfter careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE's Publication Principles.We hereby retract the content of this paper. Reasonable effort should be made to remove all past references to this paper.The presenting author of this paper has the option to appeal this decision by contacting TPII@ieee.org.Laser sintering technology is being widely applied in different industries. There is, however, a resistance to the application of this technology and the applications are limited due to the nature of the process. For example, the surface roughness of the final laser sintered product is often a major technical issue. The disadvantages in one area can probably displayed as the advantages in another area. The use of laser sintering technology in the design and manufacture of heat exchangers is such an example. In the areas of thermodynamics, heat transfer, and fluid mechanics, the enhancement of heat transfer is the key research topic. Heat exchangers are commonly used in engineering applications from power generation to computer processors. Some types of heat exchangers, such as finned-tube heat exchangers, helical internal or external tube heat exchangers and double tube heat exchangers, are recommended in many areas. In mass and volume critical applications such as aerospace, aeronautic, marine, biomedical, and computer engineering, the need for weight and volume efficient designs is paramount. Unfortunately these heat exchangers are difficult to be manufactured in the traditional ways, and the heat transfer is restricted by the existing contact thermal resistance between different assembles and the required rough surface is always beyond the control. The use of laser sintering technology in the design and manufacture of some kinds of heat exchangers is presented in this paper. The results show that the laser sin- ering technology is the feasible way to manufacture some high quality heat exchangers to reach high surface area to volume ratios through the use of unique geometries and some specific heat exchangers can be successfully manufactured, meanwhile the challenges facing the laser sintering are also identified for further investigation.
Investigation of T-history Method Application for Sub-zero Phase Change Material Thermal Properties
Proceedings of the International Conference on Advanced Technologies
The T-history method, first proposed by Zhang & Jiang, is a simple method used to determine the l... more The T-history method, first proposed by Zhang & Jiang, is a simple method used to determine the latent heat, specific heat, thermal conductivity, melting point, and degree of supercooling of a phase-change material (PCM). The method is based on the measurement of the temperature of the material over time. It assumes that the PCM sample and the reference material exchange thermal energy with the environment in a similar manner, because it is based on the lumped capacitance method, and the temperature distribution inside the sample is uniform. There are multiple advantages that the T history method has over conventional methods; however, the T history method also has some downfalls, which have been improved over the years by different authors. This study experimentally investigates the reliability of this technique for PCM with a phase change temperature below 0 ° C. The technique is used to first determine the properties of denoised water with a phase change temperature of 0 ° C, usi...
Zenodo (CERN European Organization for Nuclear Research), Nov 28, 2022
According to data sourced from Statistics South Africa's 2016 Community Survey, 11.4 percent of S... more According to data sourced from Statistics South Africa's 2016 Community Survey, 11.4 percent of South Africa's black population live in informal dwellings. 5.7 percent of the coloured population, 0.9 percent Indian citizens and 0.3 percent of the white population. Summer temperatures in South Africa range from 15°C to 36°C, while winter temperatures range from-2°C to 26°C. Extreme heat is a serious public health concern and one of the leading causes of weather-related mortality. This study investigated the temperature fluctuations around a metal sheet house, by experimental measurements and simulation analysis. Energy plus software was used to simulate the integration of Phase Change Material (PCM) into the shacks walls with the aim to reduce temperature fluctuations inside the shack. The results showed that by integrating a 20mm PCM layer, the temperature fluctuations ranged within ±2°C.
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