Dynamic thermal model for proton-exchange membrane fuel cell

In this paper, a mathematical model is developed to simulate the transient phenomena in a polymer electrolyte membrane fuel cell (PEMFC) system. Large transient changes are expected for practical application such as transportation vehicles due to acceleration and deceleration. Simple models are usually unable to capture these transient dynamics. For control purposes, a fuel cell model must include the dynamics of flow and pressure in the anode and cathode channels and mass/heat transfer transients. The proposed model can predict the transient response of cell voltage, temperature of the cell, hydrogen/oxygen out flow rates and cathode and anode channel pressures under sudden change in load current. It is implemented in SIMULINK environment. The model is tested by simulating a transportation-size fuel cell with 85 kW maximum power output. Results for maximum power and multi-step input current that simulate start up-shut down cycle are shown. The predicted power, pressure and temperature are matching the published data for the fuel cell. The model will be very useful for the optimal design and real-time control of PEM fuel cell systems in practical automotive or stationary applications

Particle Swarm-Based Micro Air Launch Vehicle Trajectory Optimization Method

The particle swarm-based micro air launch vehicle trajectory optimization method is carried out by formulating a parameter optimization problem, which is solved using a particle swarm optimization procedure. The optimization problem is formulated using a single objective function having the explicit objective to maximize the payload mass. Constraints on terminal conditions are imposed

Effectiveness of wheel-typed grain design for hybrid rocket motor performance

Although hybrid rockets are featured with distinct advantages over solid and liquid rockets, the issues specifically related to combustion instability and lowered regression rate are the most pronounced drawbacks which hinder it from being commercially viable. In the present work, we investigate the characteristics of hybrid rocket performance using generic algorithm code for preliminary design analysis purposes. An interior ballistic model is used for the analysis of the hybrid rocket performance. MATLAB® environment is used to develop the design and performance analysis codes, and visualize the temporal variation of performance characteristics. Hydroxyl Terminated Polybutadiene (HTPB) is used as a solid fuel and liquefied oxygen as an oxidizer for evaluation purposes. We have evaluated some other design features such as different expansion ratio for nozzle, different oxidizer initial flux and variation of initial mass. The valuation of variety port numbers are presented as well as comparison of multiple circular grain design. It was found that wheel-typed grain design improves 5% on the regression rate. The uses of many ports also improvise the regression rate but require a large diameter for structural integrity

Development of generic algorithm in wheel-typed hybrid rocket grain design for performance estimation

Hybrid rockets are featured by restarting capability, increased safety, high performance and moderate cost. These combined unique characteristics pose then as prominent candidates to replace solid rockets in tactical missiles and launch vehicles in the near future. However, the behavior of hybrid rockets is not fully understood, with issues specifically related to combustion instability and lowered regression rate. To investigate the characteristics of hybrid rocket performance we develop generic algorithm code. This script may serve as a valuable teaching resource in hybrid rocket motor design. This paper uses Hydroxyl Terminated Polybutadiene (HTPB) as a solid fuel and liquid oxygen as an oxidizer for evaluation purposes. Later, we introduce the results of the preliminary design and performance analysis of the hybrid rocket system. An interior ballistic model was used for the analysis of hybrid rocket performance. MATLAB® environment was used to develop the design and performance analysis codes, and visualize the temporal variation of performance characteristics

Enhancement of polymerase chain reaction using graphene nano-flakes

The excellent heat transfer properties of nanoparticles have potential applications in various fields including biology during the last two decades. Recently, the use of various nanoparticles in polymerase chain reaction (PCR) resulted in significant enhancement of its efficiency and specificity. In this research we have demonstrated the effects of a novel material, graphene nano-flakes on PCR. The rationale behind the use of graphene flakes is its unique physical and heat transfer properties. A number of experimental results including the effect of graphene flakes on denaturation of DNA and annealing step will also be discussed. The preliminary results clearly show that enhanced heat transfer effect of nano-flakes augment PCR yield and ultimately overall enhancement in reaction efficiency

apparatus and method to remotely control fluid flow in tubular strings and wellbore annulus

A method and apparatus for remotely and selectively controlling and altering fluid flow through tubular string disposed within a wellbore and further control fluid flow between the tubular string inner flow passage and the annular flow passage, and a method for selectively and remotely receiving and interpreting a form of command or information at a particular apparatus within the wellbore caused by the operator on earth surface through a change of a physical property of the environment. The apparatus comprising a body, a valve operable in plurality of states, an actuator, and an activator responsive to a change of a physical property of the environment caused by the operator on earth surfac

The IIUM low speed wind tunnel

The new IIUM low speed tunnel is of a closed-loop type having a test section of 1.5m × 2.3m × 6m and a maximum speed of 50 m/s. This paper describes measurement results for initial calibration and flow characteristics of this newly constructed wind tunnel. The results show that the total pressure varies within 0.999≤Cpt≤1.003, the dynamic pressure varies from -0.5 to 0.4 percent from the plane mean value, the flow angularity holds within ±0.2º and the boundary layer thickness is less than 2 percent of the equivalent hydraulic diameter of the test section