Fiber optic interferometry has been used to detect small displacements in diverse applications. C... more Fiber optic interferometry has been used to detect small displacements in diverse applications. Counting the number of fringes in fiber-optic interferometry is challenging due to the external effects induced in dynamic systems. In this paper, a novel interference fringe counting technique is developed to convert the intensity of interference data into displacements in the range of micrometers to millimeters while simultaneously resolving external dynamic effects. This technique consists of filtering the rough experimental data, converting filtered optical interference data into displacements, and resolving dynamic effects of the experimental system. Filtering the rough data is performed in time by using the moving average method with a window size of 400 data points. Filtered optical data is further converted into displacement by calculating relative phase differences of each data point compared to local maximum and local minimum points. Next, a linear curve-fit is subtracted from the calculated displacement curve to reveal dynamic effects. Straightness error of the lead screw driven stage, dynamics of the stepper motor, and profile of the reflective surfaces are investigated as the external dynamic effects. Straightness error is characterized by a 9th order polynomial function, and the effect of the dynamics of the stepper motor is fitted using a sinusoidal function. The remaining part of the measurement is the effect of roughness and waviness of the reflective surfaces. As explained in the experimental setup part, two fiber-optic probes detect the vertical relative displacements in the range of 1-50 mm, and the encoder probe detects 13.5 mm horizontal displacement. Thus, this technique can detect three order of magnitude different dynamic displacements with sub-micrometer resolution. The current methodology can be utilized in different applications which require measuring straightness error of lead-screw driven stages, large area surface profile of specimens, and vibration of actuators such as stepper motors.
Dimensional optimization of silicon microchannel heat sinks is performed by minimizing the total ... more Dimensional optimization of silicon microchannel heat sinks is performed by minimizing the total thermal resistance. Intel Core i7-900 Desktop Processor of chip core dimensions of 1.891 cm × 1.44 cm is considered as a reference processor which is reported to dissipate 130 W of heat. The properties are evaluated at the area weighted average of the fluid inlet and iteratively calculated outlet temperatures. The effects of the thermal and hydrodynamic entrance regions on heat transfer and flow are also investigated. The study is unique in that the optimization has been performed for localized multiple heat sources, as well as for a uniform heat load condition. The results of the optimization agreed very well with available ones in the literature.► Analytical optimization of microchannel heat sink dimensions by thermal resistance minimization. ► Effects of hot spots in multiple local heat sources are included. ► Effects of the hydrodynamic and thermal entry regions, and property variations are considered. ► Intel Core i7-900 Desktop Processor is the reference processor. ► A wider range of pumping powers and temperatures are handled compared to the optimization studies available in the literature.
A nanofluid is a new class of heat transfer fluids that contain a base fluid and nanoparticles. T... more A nanofluid is a new class of heat transfer fluids that contain a base fluid and nanoparticles. The use of additives is a technique applied to enhance the heat transfer performance of base fluids. The thermal conductivity of the ordinary heat transfer fluids is not adequate to meet today's cooling rate requirements. Nanofluids have been shown to increase the thermal conductivity and convective heat transfer performance of the base liquids. One of the possible mechanisms for anomalous increase in the thermal conductivity of nanofluids is the Brownian motions of the nanoparticles inside the base fluids. It is shown in this study that the heat diffusion assumption that has been used in the macro-and micro-composite systems is not valid in the nanofluid systems. Apart from heat diffusion the nanoconvection diffusion that it is due to the indirect effect of Brownian motion is responsible of enhancement in thermal conductivity of nanofluid systems.
ASME/STLE 2009 International Joint Tribology Conference, 2009
ABSTRACT The aim of this study is to develop an interferometric technique to measure micron level... more ABSTRACT The aim of this study is to develop an interferometric technique to measure micron level clearances occurring in small piston-cylinder arrangements; such as hermetically sealed compressors. A Cartesian model of the piston cylinder arrangement is manufactured and lateral and vertical motions are generated via a step motor, and micrometers, respectively, to simulate the piston motion and the change of clearance during the motion. Experiments are conducted in air and a lubricant. Measurements show the important effect of surface waviness of the mirror and the effect of the motion of the carriage at micron level measurements.
Volume 11: Micro and Nano Systems, Parts A and B, 2007
ABSTRACT Transient analysis of the radiative transfer problem in participating media has become e... more ABSTRACT Transient analysis of the radiative transfer problem in participating media has become essential due to the recent applications involving extremely small time scales. In classical radiation problems, the time derivative term in the radiative transfer equation has a negligible order of magnitude compared to the others. Lasers of pico- to femtosecond pulse durations are now being used to investigate the properties of scattering and absorbing media in such applications as, optical tomography, combustion product analysis, and remote sensing. For such applications, the time derivative in the radiative transfer equation can no longer be neglected. Numerous approaches such as, integral formulation, direct numerical approach, discrete ordinates method, Monte Carlo simulations, and Galerkin technique have been introduced for the solution of transient radiative transfer problems in participating media. In the present work, Laguerre-Galerkin solutions for both rectangular and Gaussian incident pulse profiles are presented.
Journal of Quantitative Spectroscopy and Radiative Transfer, 2007
An assessment is made of the Galerkin technique as an effective method of solution for transient ... more An assessment is made of the Galerkin technique as an effective method of solution for transient radiative transfer problems in participating media. A one-dimensional absorbing and isotropically scattering plane-parallel gray medium irradiated with a short-pulse laser ...
Fiber optic interferometry has been used to detect small displacements in diverse applications. C... more Fiber optic interferometry has been used to detect small displacements in diverse applications. Counting the number of fringes in fiber-optic interferometry is challenging due to the external effects induced in dynamic systems. In this paper, a novel interference fringe counting technique is developed to convert the intensity of interference data into displacements in the range of micrometers to millimeters while simultaneously resolving external dynamic effects. This technique consists of filtering the rough experimental data, converting filtered optical interference data into displacements, and resolving dynamic effects of the experimental system. Filtering the rough data is performed in time by using the moving average method with a window size of 400 data points. Filtered optical data is further converted into displacement by calculating relative phase differences of each data point compared to local maximum and local minimum points. Next, a linear curve-fit is subtracted from the calculated displacement curve to reveal dynamic effects. Straightness error of the lead screw driven stage, dynamics of the stepper motor, and profile of the reflective surfaces are investigated as the external dynamic effects. Straightness error is characterized by a 9th order polynomial function, and the effect of the dynamics of the stepper motor is fitted using a sinusoidal function. The remaining part of the measurement is the effect of roughness and waviness of the reflective surfaces. As explained in the experimental setup part, two fiber-optic probes detect the vertical relative displacements in the range of 1-50 mm, and the encoder probe detects 13.5 mm horizontal displacement. Thus, this technique can detect three order of magnitude different dynamic displacements with sub-micrometer resolution. The current methodology can be utilized in different applications which require measuring straightness error of lead-screw driven stages, large area surface profile of specimens, and vibration of actuators such as stepper motors.
Dimensional optimization of silicon microchannel heat sinks is performed by minimizing the total ... more Dimensional optimization of silicon microchannel heat sinks is performed by minimizing the total thermal resistance. Intel Core i7-900 Desktop Processor of chip core dimensions of 1.891 cm × 1.44 cm is considered as a reference processor which is reported to dissipate 130 W of heat. The properties are evaluated at the area weighted average of the fluid inlet and iteratively calculated outlet temperatures. The effects of the thermal and hydrodynamic entrance regions on heat transfer and flow are also investigated. The study is unique in that the optimization has been performed for localized multiple heat sources, as well as for a uniform heat load condition. The results of the optimization agreed very well with available ones in the literature.► Analytical optimization of microchannel heat sink dimensions by thermal resistance minimization. ► Effects of hot spots in multiple local heat sources are included. ► Effects of the hydrodynamic and thermal entry regions, and property variations are considered. ► Intel Core i7-900 Desktop Processor is the reference processor. ► A wider range of pumping powers and temperatures are handled compared to the optimization studies available in the literature.
A nanofluid is a new class of heat transfer fluids that contain a base fluid and nanoparticles. T... more A nanofluid is a new class of heat transfer fluids that contain a base fluid and nanoparticles. The use of additives is a technique applied to enhance the heat transfer performance of base fluids. The thermal conductivity of the ordinary heat transfer fluids is not adequate to meet today's cooling rate requirements. Nanofluids have been shown to increase the thermal conductivity and convective heat transfer performance of the base liquids. One of the possible mechanisms for anomalous increase in the thermal conductivity of nanofluids is the Brownian motions of the nanoparticles inside the base fluids. It is shown in this study that the heat diffusion assumption that has been used in the macro-and micro-composite systems is not valid in the nanofluid systems. Apart from heat diffusion the nanoconvection diffusion that it is due to the indirect effect of Brownian motion is responsible of enhancement in thermal conductivity of nanofluid systems.
ASME/STLE 2009 International Joint Tribology Conference, 2009
ABSTRACT The aim of this study is to develop an interferometric technique to measure micron level... more ABSTRACT The aim of this study is to develop an interferometric technique to measure micron level clearances occurring in small piston-cylinder arrangements; such as hermetically sealed compressors. A Cartesian model of the piston cylinder arrangement is manufactured and lateral and vertical motions are generated via a step motor, and micrometers, respectively, to simulate the piston motion and the change of clearance during the motion. Experiments are conducted in air and a lubricant. Measurements show the important effect of surface waviness of the mirror and the effect of the motion of the carriage at micron level measurements.
Volume 11: Micro and Nano Systems, Parts A and B, 2007
ABSTRACT Transient analysis of the radiative transfer problem in participating media has become e... more ABSTRACT Transient analysis of the radiative transfer problem in participating media has become essential due to the recent applications involving extremely small time scales. In classical radiation problems, the time derivative term in the radiative transfer equation has a negligible order of magnitude compared to the others. Lasers of pico- to femtosecond pulse durations are now being used to investigate the properties of scattering and absorbing media in such applications as, optical tomography, combustion product analysis, and remote sensing. For such applications, the time derivative in the radiative transfer equation can no longer be neglected. Numerous approaches such as, integral formulation, direct numerical approach, discrete ordinates method, Monte Carlo simulations, and Galerkin technique have been introduced for the solution of transient radiative transfer problems in participating media. In the present work, Laguerre-Galerkin solutions for both rectangular and Gaussian incident pulse profiles are presented.
Journal of Quantitative Spectroscopy and Radiative Transfer, 2007
An assessment is made of the Galerkin technique as an effective method of solution for transient ... more An assessment is made of the Galerkin technique as an effective method of solution for transient radiative transfer problems in participating media. A one-dimensional absorbing and isotropically scattering plane-parallel gray medium irradiated with a short-pulse laser ...
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