Browsing by Author "Van der Merwe, Daniel"
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- ItemDeveloping a toolkit to assist in the decision-making process of LSPs to shift to the use of bimodal transport in South Africa(Stellenbosch : Stellenbosch University, 2021-12) Van der Merwe, Daniel; Van Eeden, Joubert; Smith, Zane; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.ENGLISH ABSTRACT: South Africa experiences high externality costs associated with transport due to its reliance on the use of trucks for long-distance freight transport. The use of a bimodal system could help to alleviate this. Only a limited amount of visible research has been done on the use of bimodal technology in South Africa. This thesis seeks to contribute to research on the topic by developing a toolkit that allows Logistics Service Providers (LSPs) to conduct investigations into the suitability of the RailRunner bimodal technology for use in their business. The toolkit was developed by first investigating the road-to-rail industry both locally and in- ternationally, including the RailRunner system and its technology. This information was used to construct selection criteria for potential users of the RailRunner system. Secondly, a prelim- inary toolkit was set up using the selection criteria and the knowledge gained from the previous investigations. Exploratory interviews were done to flesh out the preliminary toolkit so that a more comprehensive finalised toolkit could be constructed. Validation interviews were then conducted to confirm the usefulness and validity of the finalised toolkit. A toolkit containing the following tools was successfully developed and validated: Abstract South Africa experiences high externality costs associated with transport due to its reliance on the use of trucks for long-distance freight transport. The use of a bimodal system could help to alleviate this. Only a limited amount of visible research has been done on the use of bimodal technology in South Africa. This thesis seeks to contribute to research on the topic by developing a toolkit that allows Logistics Service Providers (LSPs) to conduct investigations into the suitability of the RailRunner bimodal technology for use in their business. The toolkit was developed by first investigating the road-to-rail industry both locally and in- ternationally, including the RailRunner system and its technology. This information was used to construct selection criteria for potential users of the RailRunner system. Secondly, a prelim- inary toolkit was set up using the selection criteria and the knowledge gained from the previous investigations. Exploratory interviews were done to flesh out the preliminary toolkit so that a more comprehensive finalised toolkit could be constructed. Validation interviews were then conducted to confirm the usefulness and validity of the finalised toolkit. A toolkit containing the following tools was successfully developed and validated: Explanation of the RailRunner system/technology; . Selection criteria for LSPs that can benefit from the RailRunner system; . Stakeholder analysis of the role players that may have an interest in or influence on the decision to use the RailRunner system; . Financial model comparing the operating costs of road-only systems with systems involving the RailRunner technology; . Decision matrix that assists LSPs in quantifying and visualising their attitudes towards different transport methods; . Frequently asked questions that help to clear up any misconceptions of the RailRunner system or technology. The toolkit can now be used by LSPs as a basis for their investigations into the viability of the use of the RailRunner system in their business. RailRunner will also be able to use the toolkit to identify potential customers and to see what the deciding factors are for them choosing to use the system. Preliminary results show that RailRunner would have to make sure that the reliability of their system is equal to or better than that of road transport alone. LSPs must also note that the RailRunner system is not a one-size-fits-all solution. Many factors need to be considered in the decision to use the system. Lastly, this research also provides a basis for numerous potential future research topics related to a road-to-rail shift.
- ItemEvaluation of natural draught wet-cooling tower performance uncertainties(Stellenbosch : Stellenbosch University, 2007-03) Van der Merwe, Daniel; Reuter, H. C. R.; Kroger, D. G.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical & Mechatronic Engineering.ENGLISH ABSTRACT: A natural draught wet-cooling tower (NDWCT) was modelled using the Merkel method with an improved energy equation as recommended by Kloppers and Kroger (2005a) - referred to as the Improved Merkel method. The improved energy equation is used for calculating the heat rejection rate of the tower and includes the energy associated with water evaporation. The sensitivity indexes of a NDWCT were calculated numerically with the Improved Merkel method model. It was found that the perfonnance of a NDWCT is most sensitive to the fill Merkel number. The "Natklos" fill test facility at Stellenbosch University was used to estimate typical uncertainties found in fill performance characteristics. The zeroth order uncertainty for the Merkel number and loss coefficient was calculated to be 0.2100 m-1 and 0.4248 m- 1 , respectively, while the first order uncertainty for the Merkel number and loss coefficient was calculated to be 0.1933 m- 1 and 0.2008 m-1 , respectively. ASME requires that the uncertainty in tower capability has to be less than 6 % for a NDWCT perfonnance test to be deemed ASME approved. Propagating typical measurement uncertainties found in NDWCT test standards and experimental data into the tower capability showed that the 6 % uncertainty limit imposed by ASME is unrealistic and too stringent. Performance curve generator (PCG) is a software package developed that generates NDWCT perfonnance curves. With these performance curves it is possible to easily and effectively adjust the off-design test results in order to detennine whether the NDWCT has met its guarantee or not.