Siaw Wee

Temperature and voltage responses of a molten carbonate fuel cell in the presence of a hydrogen fuel leakage

A two dimensional (2-D), dynamic model of a molten carbonate fuel cell (MCFC) was developed using COMSOL Multi-physics. The model was used to investigate the dynamic behaviour of the MCFC in the presence of hydrogen fuel leakage. A leakage was modelled as a known outflow velocity at the anode gas channel. The effects of leakage velocity and the leakage location were investigated. The simulations show that anode electrode temperature increases as the leakage velocity increases. The voltage generated is shown to decrease at the start of the leakage occurrence due to loss of hydrogen gas. Later the voltage increases as the anode temperature increases. The results also show that the changes of temperature and voltage are more significant if a leakage occurs nearer to the inlet compared to that at the outlet of anode gas channel.

Theory to practice on finite element method and computational fluid dynamics tools

Abstract Computer-aided engineering has become increasingly important in engineering practices, where processes such as mathematical modelling, stress and deformation analysis can be performed by an individual engineer, without the need for a range of specialists. A case study was conducted at Curtin University Sarawak (CSM) to evaluate the performance of mechanical engineering students in the usage of finite element method and computational fluid dynamics tools. CSM is a branch campus of Curtin University, Australia, where the course structures and all assessments are identical to those of her mother campus. The curriculum design and teaching materials are developed by Curtin University, Australia. Similar teaching contents are delivered in CSM. The aim of the study is to investigate the students’ comprehension in the theoretical knowledge and its applications in practical engineering problems. This paper describes the learning experience of mechanical engineering students, in particular, the correlation between theoretical knowledge and engineering practice. Teaching experience of academic staffs was also detailed, discussed and mapped against the students’ views to give a comprehensive picture of the students’ learning experience. Based on the study, it was shown that the teaching methodology plays a crucial role in ensuring effective learning. An initial study which compared graphical user interface and programming teaching approach was conducted, in which the latter has showed to be more effective.

The study of solid circulation rate in a compartmented fluidized bed gasifier (CFBG)

Biomass waste has been abundantly available in Malaysia since the booming of palm oil industry. In order to tackle this issue, gasification is seen a promising technology to convert waste into energy. In view of the heat requirement for endothermic gasification reaction as well as the complex design and operation of multiple fluidized beds, compartmented fluidized bed gasifier (CFBG) with the combustor and the gasifier as separate compartments is proposed. As such, solid circulation rate (SCR) is one of the essential parameters for steady gasification and combustion to be realized in their respective compartments. Experimental and numerical studies (CFD) on the effect of static bed height, main bed aeration, riser aeration and v-valve aeration on SCR have been conducted in a cold- flow CFBG model with only river sand as the fluidizing medium. At lower operating range, the numerical simulations under-predict the SCR as compared to that of the experimental results. Also, it predicts slightly different trends over the range. On the other hand, at higher operating range, the numerical simulations are able to capture those trends as observed in the experimental results at the lower operating range. Overall, the numerical results compare reasonably well with that of the experimental works.

Experimental Analysis of Impedance-Driven Reverse Flow Dynamics

Impedance pump is a type of valveless pumping device, in which it utilizes a bio-inspired mechanism for pumping of fluid based on resonant wave interactions along a flexible media. By inducing a periodic asymmetrical compression on the flexible media will produce a unidirectional flow within the system. The impedance pump has many beneficial characteristics which make it an effective driving mechanism, especially for micro-fluidic systems. In addition, the wave-based mechanism through which pumping occurs infers many benefits in terms of simplicity of design and manufacturing. Adjustment of simple parameters such as the excitation frequency or compression location will reverse the direction of flow, providing a very versatile range of flow outputs. This paper describes the experimental analysis of such impedance-driven flow with emphasis on dynamical study of the reverse flow in open-loop environment. In this study, tapered section with converging steps is introduced at both ends of the flexible media to amplify the reverse flow. Study conducted shows that the reverse peak flow is rather significant with estimate of 23% lower than the forward peak flow. The flow dynamics on the other hand has shown to exhibit different characteristics as per the forward peak flow.