Browsing by Author "Malan, Daniel Johannes"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Die funksie van die metodiek in die christologie : 'n ondersoek aan die hand van E. Schillebeeckx se Jesus-boeke
    (Stellenbosch : Stellenbosch University, 1990-12) Malan, Daniel Johannes; Jonker, W. D.; Lategan, B. C.; Stellenbosch University. Faculty of Theology. Dept. of Systematic Theology and Ecclesiology.
    ENGLISH ABSTRACT: No abstract available.
  • Thumbnail Image
    Item
    Latent heat thermal energy storage for solar water heating using flat heat pipes and aluminum fins as heat transfer enhancers
    (Stellenbosch : Stellenbosch University, 2014-12) Malan, Daniel Johannes; Dobson, R. T.; Stellenbosch University. Faculty of Engineering. Department of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: Solar energy is a time dependent, high-temperature radiant energy resource. The utility of a solar thermal energy system increases if the hot temperature source is available when it is needed most. This is realized by the thermal storage of the solar energy. Thermal storage gives greater versatility to a solar energy system by decoupling the heat source from the heat sink. A large quantity of energy may be stored during the melting process in a phase change material (PCM) within a small temperature range. This molten PCM can then deliver its absorbed heat at a constant temperature in a heating application. In this study a phase change storage system (PCS) is developed and proposed for a solar water heating application. This PCS system stores more heat per unit mass than would be possible with water across the same temperature range. The heat transfer rate in and out of many PCMs is slow because of the low thermal conductivity of the PCM. However, heat transfer enhancers (HTE), such as heat pipes and fins may be added to enhance heat absorption and heat removal rates. Heat pipes have the inherent capability to transfer heat at high rates across large distances, even where the temperature difference is small. In this thesis a description is given of a PCS system consisting of paraffin wax as the PCM and which uses rectangular heat pipes in conjunction with aluminium fins to enhance heat transfer. The storage design is modular and each module has the characteristic that enhanced heat transfer in and out of the PCM is possible when the module is heated or cooled. It also has the capability to quickly absorb or alternatively to supply heat at a nearly constant temperature during the phase change of the module. A rectangular module was designed and built. The module was then analysed under controlled heat absorption and heat removal cycles. The heat up experiment involved an electrical kettle as the hot temperature source. The heat sink was a mains water heat exchanger. The experimental results were compared to those of a transient numerical model, which calculates theoretically how the module will perform thermally under the given test conditions. The numerical model of the experimental set-up was validated when it was found that the numerical model results resemble the experimental results. The numerical model was then adapted to simulate a novel solar water heater (SWH) with an additional PCS container. The improvement over previous designs is that the additional storage container can be heated to a higher temperature than the allowable geyser temperature. The system also heats up and cools down at a faster rate than would be possible without the HTEs. From the numerical simulation the size and performance of such a system is determined. This numerical analysis indicated that a phase change storage system in a SWH application will increase the hot water delivered by a given solar collector and geyser by increasing the storage capacity and by heating up the geyser overnight for early morning hot water use.
  • No Thumbnail Available
    Item
    Rome en "die geval Schillebeeckx" : 'n konfrontasie rondom die leer aangaande Christus
    (Stellenbosch : Stellenbosch University, 1982-10) Malan, Daniel Johannes; Jonker, W. D.; Stellenbosch University. Faculty of Theology. Dept. of Systematic Theology and Ecclesiology.
    AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.