Abstract: Phenomenon of flame acceleration of premixed combustible air-acetylene mixture towards the open end of adiabatic microchannel has been studied by solving Navier-Stokes (NS) system of equations with single step chemistry model. A two dimensional unsteady reactive NS solver has been developed using modified upwind slitting methods (AUSM+) and second order Runge-Kutta method to achieve the unsteady solutions. The predicted mechanism of flame acceleration, flame propagation speed and maximum outflow velocities are well in agreeemtnt with the conclusion drawn on the available literature related to the maximum flame acceleration configuration of the adiabatic microchannel

Abstract: High speed combustion characteristics of premixed stoichiometric air-acetylene mixtures inside microchannels are numerically studied by solving a Navier-Stokes (NS) system of equations with a single-step chemistry model. A two dimensional explicit finite volume solver has been developed using modified advection upwind splitting methods (AUSM+) to predict the complex interactions among hydrodynamic processes, shock structures and combustion in microdimensions. The effects of channel aspect ratio and wall temperature on high speed microcombustion have been studied in this work. The increase in wall temperature due to wall friction in reduced dimensions initiates the chemical reaction of the combustible mixture near the wall region, and the reacted zone reaches the centerline for smaller height-to-length ratios of the microchannels. The wall temperature plays an important role in hypersonic combustion at the microscale.
Permalink: https://doi.org/10.1002/ceat.200600389

Abstract: The heat transfer characteristics of supersonic to hypersonic gas flow in microchannels are numerically studied by solving a two-dimensional Navier-Stokes (NS) system of equations utilizing Maxwell’s velocity slip with thermal creep, and a corresponding temperature jump relationship derived by von Smoluchowski. An explicit Finite Volume (FV) solver has been developed using modified advection upwind splitting methods (AUSM+) to simulate the high speed microscale gas flow. The influence of the inlet Mach number on overall hydrodynamics and heat transfer is also studied. The supersonic test case has been compared with the Direct Solution Monte Carlo (DSMC) and Finite Element (FE) results available in the literature. The study of high speed flow through microchannels demonstrates an increase in temperature due to the wall friction and that fluid flow decelerates throughout the microchannels. The wall temperature jump and the centerline temperature are higher for larger inlet Mach numbers.
Permalink: https://doi.org/10.1002/ceat.200600229

Abstract: Fluid flow behavior and heat transfer characteristics of pressure driven flow in partially heated microchannels have been investigated using the explicit Finite Volume Method (FVM). The developed flow solver utilizes the compressible Navier-Stokes (NS) system of equations with Maxwell’s first order slip boundary condition and the corresponding temperature jump relation derived by von Smoluchowski to achieve the solutions. The effects of Knudsen number and gas species have been studied for partially heated microchannels similar to the classical Graetz problem. The existence of nonlinear pressure distribution and dominant heat diffusion for higher Knudsen number regime are predicted by the solution. The fluid flow and heat transfer characteristics of the partially heated microchannels greatly depend on the transport properties of the medium under similar flow conditions.
Permalink: https://doi.org/10.1002/ceat.200600366

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Abstract: [Norwegian] Det er utviklet kurver som viser sammenhengen sammenhengen mellom behovet for lys og alder, når deteksjonskriteriet er opprettholdelse av fargesyn. Det er videre utviklet kurver for luminanskontrasten som funkjon av alder og lys.

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Abstract: Textbook chapter about Demand controlled ventilation (DCV)