Browsing by Author "Savransky, Max"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Numerical Simulations of Thermo-Fluid Phenomena in Microwave Heated Packed and Fluidized Beds
    Savransky, Max (Virginia Tech, 2003-09-01)
    Microwave heating is implemented in various fields such as drying, material processing, and chemical reactors. Microwaves offer several advantages over conventional heating methods: 1) microwaves deposit heat directly in the material without convection or radiation, 2) microwave heating is easy and efficient to implement, and 3) microwave processes can be controlled.In order to understand how to use microwaves more efficiently, we must understand how they affect the material with which they interact.This requires the ability to predict the temperature distribution that is achieved within the material.In recent years packed and fluidized beds have been used as chemical reactors to achieve various tasks in industry.Recent studies have shown that microwave heating offers the potential to heat the bed particles to a higher temperature than that of the fluid.This results in enhanced reaction rates and improves the overall efficiency of the reactor.T he focus of this work is to determine the temperature distributions within the packed and fluidized beds, and to determine whether the catalyst particles can be heated to a higher temperature than the gas in catalytic reactions. The beds are modeled with multiphase flow equations.The gas velocity profiles along with the solid and gas temperature profiles for packed and fluidized beds are provided. F or the fluidized beds, the hydrodynamics is modeled using FLUENT and the solid velocity profiles are also determined.
  • Thumbnail Image
    A study of transient heat conduction and thermal noise in an Earth radiation budget radiometer
    Savransky, Max (Virginia Tech, 1996)
    The suite of three Clouds and Earth’s Radiative Energy System (CERES) radiometers measure the radiation reflected from and emitted by the Earth from Earth orbit. The instruments are based on a two-mirror reflecting telescope which focuses incident radiation on a thermistor bolometer thermal radiation detector. The CERES radiometers scan back and forth across the Earth and surrounding space as the satellite orbits the Earth. Each scan has a period of about six seconds. This not only results in a transient radiation signal arriving at the detector surface from the scene, but also in temperature transients in the instrument structure. The instrument “zero” is obtained during the “space look” when it views cold space at each end of the scan. Some of the surfaces of the instrument structure are visible from the detector, either directly or through reflections. As a result, the radiation emitted by these surfaces will reach the detector. This form of radiation is called thermal noise and is undesirable. In order to determine whether the thermal noise is significant to cause concern, the transient response and temperature variations of the various components of the instrument must be known. The transient response is determined from observing the temporal variation of the temperature distribution within the instrument structure. Since the instrument orbits the Earth, both the Earth and space make up the environment of the instrument. This means that the temperature distributions for both the space look and Earth scene must be studied. Pseudo time constants were determined from the transient space-look temperatures. The transient thermal noise was then determined from the pseudo time constants and the steady-state space-look and earth-scene temperatures. The thermal noise was shown to vary with magnitude on the order of nanowatts. This means that the thermal noise is not sufficiently large to be of concern.