http://hdl.handle.net/10092/840 2013-05-20T06:54:40Z http://hdl.handle.net/10092/7729 Title: The combustion of wood, mainly as assessed by fluidised-bed differential thermal analysis, with particular reference to rubber wood Authors: Tan, Ah Goh Abstract: The combustion characteristics of Rubber wood were studied using differential thermal analysis (DTA) carried out in fluidised-beds. Test samples up to 10 mm in diameter and fluidising gas of different oxygen concentrations were used. A number of tropical hardwoods were included in the study for comparison. Prior to the above study, investigations on the thermal behaviour of Rubber wood in an inert environment, in particular, the effect of particle size, were carried out. The particle sizes used ranged from smaller than 150 mesh to 19 mm diameter. The yields of the various degradation products and the temperature range within which they were formed were noted. The liquid and gaseous products were analysed, the former qualitatively (by proton and ¹³C NMR spectroscopy) and the latter quantitatively (by GLC). Thermogravimetric analyses of the test materials were performed in both inert and oxidative environments to provide information complementary to those obtained from DTA, in particular, char yield and burning time in a stationary bed. The ash contents of the wood species under study were determined. The adverse effect of ash on wood combustion was demonstrated in combustion experiments carried out in a down-draught incinerator using 5 cm thick blocks. Besides Rubber wood, three other species were used, including radiate Pine. 1986-01-01T00:00:00Z http://hdl.handle.net/10092/7728 Title: Modelling the effects of fuel types and ventilation openings on post-flashover compartment fires Authors: Yii, Ee Hieng Abstract: This thesis describes the details used to model a post-flashover fire compartment as a well-stirred reactor. In particular, it examines the two foremost important variables that dictate post-flashover fire behaviour inside the fire compartment. These two variables are: (1) the mass flow rate of air into the compartment via the vent opening and (2) the fuel mass loss rate inside the compartment. The vent flow analysis shows that the orifice analogy typically used to describe compartment vent flow is restricted to small wall opening applications. For large wall openings, such as a window occupying one whole wall, the flow rate is dictated by the plume entrainment with a flow rate -60% of the flow rate estimated from the orifice theory. A series of fire experiments using a reduced-scale compartment were conducted to study the vent flow behaviour in a compartment with a horizontal roof opening and a vertical wall opening. Based on the analytical and experimental studies, it is shown that in the case where the roof vent opening is not excessively large and a wall opening having a small downstand, the neutral-plane exists below the soffit of the wall opening giving outflow and inflow through the wall opening and outflow through the roof opening. In such a case, the flows through these openings can be adequately described using an extended form of the vent flow formulation that includes the roof vent opening. The area of the roof vent and the depth of the downstand between the ceiling and the soffit of the wall opening are found to be significant in determining the extra air inflow induced due to the existence of the roof vent opening. The cellulosic and pool fuels each have different burning behaviour inside a compartment. However, compartment fire temperatures and fuel mass loss rates, from both fuel types, are strongly dependent on the available fuel surface area to ventilation opening ratio and the fuel surface to enclosure area ratio. In the case of thermoplastic pool fires, the ratio between the heat of combustion of air for the fuel and the heat of gasification of the fuel is also found to be influential on the resulting fires. A post-flashover fire computer program, CFIRE, has been developed that incorporates these findings. The simulation studies performed using the CFIRE computer program show that the fire time-temperature histories of wood fires are highly dependent on the remaining fuel surface area over time. In the case of thin wood, a shorter and hotter fire is expected as it has greater surface area than thick wood, even with the same fuel load. The study also shows that for small ventilation opening, a pool fire inside a fire compartment is less severe than a wood fire because the thermoplastic fuel is easily vaporised under the radiation feedback from the hot surrounding environment and discharged outside the compartment. In the case of large openings, pool fires are more likely to produce a hotter fire in the compartment than wood fires because wood fuel would not have sufficient fuel surface area to achieve ventilation controlled burning. By comparing these simulated fires with the Eurocode parametric fires, the Eurocode parametric fires do not provide realistic decay rate. With the modified parametric fires, these fires are conservative as they provide envelopes for the simulated fire curves. However, these parametric fires do not clearly describe the fire behaviour of realistic furnishing inside the fire compartment. 2002-01-01T00:00:00Z http://hdl.handle.net/10092/7727 Title: Thermodynamics of alkane solutions Authors: Weiguo, Shen Abstract: An apparatus for static vapour pressure measurements on pure liquids and on binary and ternary mixtures containing one involatile component has been designed and constructed. The apparatus and corresponding experimental techniques have been tested and experimental errors have been discussed. Measurements have been made of the vapour pressures of binary mixtures of n-hexane + n-hexadecane at 298.15 K and 303.15 K and of binary mixtures of n-hexane + n-octane, n-octane + n-hexadecane, and ternary mixtures of n-hexane + n-octane + n-hexadecane at 298.15 K. The experimental measurements of pressures (P) vs mole fractions (x) have been fitted to the Redlich-Kister equation by Barker's method to obtain activity coefficients of each component in the liquid phase, the excess Gibbs functions, and the mole fractions in the vapour phase. The results for n-hexane + n-hexadecane at 303.15 K have been compared with those of previous work (Williamson, 1957) and the agreement is reasonably good. The excess volumes of n-hexane +benzene, n-dodecane + 2-methylpentane and pseudo n-dodecane prepared from equimolar numbers of n-decane + n-tetradecane + each of four branched hexane isomers at 298.15 K have been obtained from measurements of the densities of pure compounds and mixtures with a vibrating tube densimeter. Two methods for preparation of mixtures of which densities are required to be accurately measured have been designed and compared with each other. The excess enthalpies of 2-methylpentane with n-dodecane and with each of three pseudo n-dodecanes prepared from equimolar mixtures of n-decane + n-tetradecane, n-undecane + n-tridecane, and n-octane + n-hexadecane, and the excess enthalpies of equimolar decane + tetradecane mixture with each of the other three branched hexane isomers at 298.15 K have been measured with an isothermal displacement calorimeter. The experimental results of binary mixtures have been discussed in term of the principle of congruence with Hijmans' graphical method and Bellemans and Mat's analytical formula. New graphical tests of the principle of congruence and a modified Bellemans and Mat equation for ternary mixtures have been developed and applied to the experimental p-x data of ternary systems. The agreement between the experimental values and those predicted by the principle are excellent. The modified Bellemans and Mat equation seems to be more powerful than and preferable to the Redlich-Kister equation for the systems investigated in this work. 1988-01-01T00:00:00Z http://hdl.handle.net/10092/7725 Title: Spatial and temporal lag effects in bedload sediment transport Authors: Phillips, Brett Clayton Abstract: Spatial lag effects and temporal lag effects are investigated under bedload sediment transport conditions. This investigation, which involves both experimental and theoretical studies, culminates in the formulation of a numerical model which includes schemes which successfully describe spatial and temporal lag effects. An equation which characterises spatial lag effects and two possible relations for the spatial lag coefficient are investigated. Values of the spatial lag coefficient are calculated from measured data and compared with values predicted by the theoretical relations. This investigation verifies the proposed spatial lag equation and indicates the form of the spatial lag coefficient relation. A temporal lag scheme which is able to predict the temporal variation of bed roughness and sediment transport capacity under non-steady flow conditions is developed and calibrated against measured data. An impulse model is used to predict the temporal variation of the variable which chracterises the temporal response of the alluvial system, the equivalent steady flow rate. The performance of the temporal lag scheme is tested against additional measured data which verifies the proposed temporal lag scheme. A numerical model which incorporates the spatial lag equation and the temporal lag scheme is formulated. This model also incorporates an upstream sediment boundary scheme which takes account of the zone of separation in a scour hole. The performance of the numerical model is tested against data measured by a previous investigator. The ability of the numerical model to predict the spatial and temporal variation of the bed elevation and the bedload sediment transport rate under both steady and non-steady flow, non-equilibrium sediment transport conditions is verified. 1984-01-01T00:00:00Z