AnswersDriveFluidised beds are used for several purposes, such as fluidized bed reactors (types of chemical reactors), fluid catalytic cracking, fluidized bed combustion, heat or mass transfer or interface modification, such as applying a coating onto solid items.
What is Afbc?
AFBC is atmospheric fluidised bed combustion, where the furnace pressure is atmospheric pressure. In case of CFBC, Circulating fluidised bed combustion, the furnace is pressurised and the furnace gas is recirculated to capture the unburnt carbon, to increase the thermal efficiency of the boiler.
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What is fluidized bed combustion?
Fluidized bed combustion (FBC) is a combustion technology used to burn solid fuels. The resultant fast and intimate mixing of gas and solids promotes rapid heat transfer and chemical reactions within the bed.
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What is an air fluidized bed?
air-fluidized bed. a bed with body support provided by thousands of tiny soda-lime glass beads suspended by pressurized, temperature-controlled air. The special bed is designed for use by patients with or at risk for posterior pressure ulcers or with posterior burns, grafts, or donor areas.
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What is bubbling fluidization?
Fluid cracking catalysts typically are in this category. These solids fluidize easily, with smooth fluidization at low gas velocities without the formation of bubbles. At higher gas velocity, a point is eventually reached when bubbles start to form and the minimum bubbling velocity, Umb is always greater than Umf.
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What is a packed bed?
In chemical processing, a packed bed is a hollow tube, pipe, or other vessel that is filled with a packing material. Packed beds can be used in a chemical reactor, a distillation process, or a scrubber, but packed beds have also been used to store heat in chemical plants.
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What is a fluid bed reactor?
A fluidized bed reactor (FBR) is a type of reactor device that can be used to carry out a variety of multiphase chemical reactions. This process, known as fluidization, imparts many important advantages to the FBR. As a result, the fluidized bed reactor is now used in many industrial applications.
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What is the minimum fluidization velocity?
Fluid flowed through bottom of a fixed bed. Fluidization is the balance of gravity, drag and buoyant forces. Suspended particles have larger effective surface area than a packed fixed bed. The smallest velocity at which fluidization occurs is the minimum fluidization velocity.
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What is particulate fluidization?
Particulate fluidization is a condition when particles in a fluidized bed are individually suspended. When the fluidizing fluid is liquid and is characterized by a large and uniform expansion of the bed at high velocities, this is known as particulate fluidization.
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What is a fluid bed dryer?
Fluidized Bed Dryers & Coolers. Materials processed in a Fluidized Bed Dryer or Cooler float on a cushion of air or gas. The process air is supplied to the bed through a perforated distributor plate and flows through the bed of solids at a sufficient velocity to support the weight of particles in a fluidized state.
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What is a fluidised bed filter?
A fluidized bed filter, sometimes called a "suspended particulate filter" or a "suspended sand filter," is a tube or box that hangs off the back of your fish tank, or a cylinder or canister which stands in your sump or on the floor beside or under your fish tank, and is connected to a water pump in the fish tank (or
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What is meant by superficial velocity?
Superficial velocity (or superficial flow velocity), in engineering of multiphase flows and flows in porous media, is a hypothetical (artificial) flow velocity calculated as if the given phase or fluid were the only one flowing or present in a given cross sectional area.
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What is the interstitial velocity?
Interstitial Velocity is the speed at which the molecules of water are progressing in the direction of movement.
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What is meant by slip velocity?
Slip ratio (or velocity ratio) in gas–liquid (two-phase) flow, is defined as the ratio of the velocity of the gas phase to the velocity of the liquid phase. In the homogeneous model of two-phase flow, the slip ratio is by definition assumed to be unity (no slip).
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What is the slip boundary condition?
From Wikipedia, the free encyclopedia. In fluid dynamics, the no-slip condition for viscous fluids assumes that at a solid boundary, the fluid will have zero velocity relative to the boundary. The fluid velocity at all fluid–solid boundaries is equal to that of the solid boundary.
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What is a slip wall?
The slip wall condition is for cases where viscous effects at the wall are negligible and/or your mesh size is much bigger than the boundary layer thickness (so you're not capturing the boundary layer effects anyway). The slip boundary is also the proper boundary condition for symmetry surfaces.
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What is the boundary layer in fluid mechanics?
Boundary layer, in fluid mechanics, thin layer of a flowing gas or liquid in contact with a surface such as that of an airplane wing or of the inside of a pipe. The flow in such boundary layers is generally laminar at the leading or upstream portion and turbulent in the trailing or downstream portion.
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What is the Nusselt number?
In heat transfer at a boundary (surface) within a fluid, the Nusselt number (Nu) is the ratio of convective to conductive heat transfer across (normal to) the boundary. In this context, convection includes both advection and diffusion.
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What is meant by fully developed laminar flow?
Fully developed flow: Fully developed flow implies that the velocity profile does not change in the fluid flow direction hence the momentum also does not change in the flow direction. In such a case, the pressure in the flow direction will balance the shear stress near the wall.
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What is fully developed laminar flow?
In case of laminar flow, the velocity profile in the fully developed region is parabolic but in the case of turbulent flow it gets a little flatter due to vigorous mixing in radial direction and eddy motion. The velocity profile remains unchanged in the fully developed region.
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Why are liquids usually transported in a circular pipes?
Liquids are usually transported in circular pipes because pipes with a circular cross- section can withstand large pressure differences between the inside and the outside without undergoing any distortion. Engine oil requires a larger pump because of its much larger density.