How do you calculate bed voidage?
Divide the volume of the container into the volume of water added. For example, if the container has a volume of 2 liters (2000 milliliters) and you added 500 milliliters of water, you have 500/2000 = 0.25. The voidage is therefore 0.25. Express the voidage as a percentage by multiplying by 100.
How do you calculate the flow rate of fluidization for a fluidized bed gasifier?
The inside cross-sectional area of the fluidized-bed gasifier, Ab, is found by dividing the volumetric flow rate of the product gas flow, Vg, by the chosen superficial gas or fluidization velocity through it, Ug, at the operating temperature and pressure.
How do you calculate fluidization velocity?
5.2 Minimum Fluidization Velocity. The minimum fluidization velocity is determined empirically by the intersection of the pressure drop versus the superficial velocity curve and the pressure drop equals the weight of the bed line, as illustrated in Fig. 5.2.
How does a fluidised bed work?
Typically, pressurized gas or liquid enters the fluidised bed vessel through numerous holes via a plate known as a distributor plate, located at the bottom of the fluidised bed. The fluid flows upward through the bed, causing the solid particles to be suspended.
What is bed voidage?
Voidage, e, is defined as the fraction of the total volume which is free space available for the flow of fluids, and thus the fractional volume of the bed occupied by solid material is (1 − ε). Depending upon the nature of the porous medium, the voidage may range from near zero to almost unity.
What is the relationship between sphericity and Voidage?
It is found that as the sphericity decreases, the bed voidage increases. Increasing the particle density and initial bed height causes the voidage to decrease due to the strong compression in the bed. The decrease in the voidage can lead to a decrease in the minimum fluidization velocity.
Which factor is considered in Ergun equation when the Reynolds number is less 20?
Explanation: The pressure drop through the fixed beds has been correlated by Ergun equation. 8. Which factor is considered in Ergun equation when the Reynolds number is less 20? Explanation: Since viscous forces predominate, 150 factor is considered.
What is the minimum fluidization velocity?
The minimum fluidization velocity (Umf), defined as the superficial gas velocity at which the drag force of the upward moving gas becomes equal to the weight of the particles in the bed, is one of the most important parameters associated with a fluidized bed system.
How do you calculate the minimum fluidization velocity?
The minimum fluidization velocity can be calculated by equating the pressure–drop across the fixed packed–bed, calculated from Ergun’s equation to that from the expression for fluidized bed under particulate (smooth) conditions.
What are 3 benefits of using fluidized sand as a method of separation?
Despite these challenges, fluidized beds offer three distinct advantages over other process technologies: superior heat transfer, the ability to easily move solids like a fluid, and the ability to process materials with a wide particle size distribution.
What is Ergun equation used for?
The Ergun equation tells us a number of things. It tells us the pressure drop along the length of the packed bed given some fluid velocity. It also tells us that the pressure drop depends on the packing size, length of bed, fluid viscosity and fluid density.
How is the Ergun equation extended to fluidized beds?
The extension of the Ergun equation to fluidized beds, where the solid particles flow with the fluid, is discussed by Akgiray and Saatçı (2001). Ergun, Sabri.
How to calculate the pressure drop in the Ergun equation?
The void fraction of the bed is ε = 0.33. A gas of density ρ = 0.9487 kg/m 3 and dynamic viscosity μ = 3.1 × 10 −5Pa s flows through the bed with a superficial mass flow velocity of 1.4 kg/m 2 s. Determine the pressure drop in the bed.
How is the Ergun equation related to Kozeny-Carman equation?
This arrangement of the Ergun equation makes clear its close relationship to the simpler Kozeny-Carman equation which describes laminar flow of fluids across packed beds via the first term on the right hand side.
Who is the creator of the Ergun equation?
Ergun equation. The Ergun equation, derived by the Turkish chemical engineer Sabri Ergun in 1952, expresses the friction factor in a packed column as a function of the modified Reynolds number.