Is the Ergun equation accurate?
The Ergun equation is only able to accurately predict the pressure drop of single-phase flow over spherical particles, whereas it systematically under predicts the pressure drop of single-phase flow over non-spherical particles.
How is Ergun equation derived?
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.
How do you calculate bed voidage?
The actual calculation of voidage is simple: it is the amount of empty space divided by the total volume.
What is bed porosity?
A fixed granular bed (FGB) of sorbent, catalyst, or inert packing, which is charged into an industrial vessel, is a com- plex system. The free-volume fraction of the FGB is known as the porosity of the granular bed.
How do you measure the diameter of a packed bed reactor?
A bed with a height 2.5 m and an internal diameter of 0.035 m is packed with cylindrical particles of diameter Dp = 0.003m. The void fraction of the bed is ε = 0.33….THE EQUATIONS.
| Packed bed length, ft | 60 |
|---|---|
| Fraction voids in packed bed | 0.45 |
| Density of fluid at flowing conditions, lb/ft3 | 0.413 |
| Fluid viscosity, cP | 0.0278 |
What is the difference between packed bed and fluidized bed?
Excellent mixing of reactants in the fluidised bed helps to minimise temperature variations and renders this system attractive for carrying out gas–solid reactions. The fluidised bed reactors show better conversion of reactants in comparison with packed beds when solid reactants are used in the form of small pellets.
What is bed voidage?
(i) 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.
How do you calculate the volume of a packed bed reactor?
By definition, space velocity can be expressed mathematically as SV = Vo / V. In this expression, Vo represents the volumetric flow rate of the reactants entering the reactor and V represents the volume of the reactor itself.
How do you calculate pressure drop in a packed bed?
PD = particle diameter, in. PL = particle length, in. ΔP = total pressure drop in packed bed, lb/in. μ = fluid viscosity, cP (1 cP = 2.419lb/ft h)….THE EQUATIONS.
| Packed bed length, ft | 60 |
|---|---|
| Density of fluid at flowing conditions, lb/ft3 | 0.413 |
| Fluid viscosity, cP | 0.0278 |
Why is there pressure drop in a PBR?
Details. The pressure decreases down the length of the reactor, and thus the volumetric flow rate increases. As a result, the concentration of the reactant decreases (in addition to the decrease due to conversion), which lowers the rate of reaction.
How do you calculate bed porosity?
ε = 1 – (ρb/ρs). n = –3.6), which makes it possible to calculate the porosity of a bed of spherical grains with sufficient accuracy. where A, B, and n are constants dependent on the shape of the grains (see Table 1).
How do you calculate porosity?
There are two basic equations used to calculate porosity. The first equation uses the total volume and the volume of the void. Porosity = (Volume of Voids / Total Volume) x 100%. The second equation uses the total volume and the volume of the solid.
What is friction factor in packed bed?
The packed bed friction factor may be calculated using the packed bed Reynolds number as follows: f ∗ = 150 R e ∗ + 1.75 \displaystyle \displaystyle f^* = \frac{150}{Re^*} + 1.75 f∗=Re∗150+1.
What is G in Ergun equation?
G = superficial mass velocity. MW = molecular weight of fluid. NRe = Reynolds number, dimensionless. P = fluid pressure, psia.
Why do we use fluidization?
Fluidization has many applications with the use of ion exchange particles for the purification and processing of many industrial liquid streams. Industries such as food & beverage, hydrometallurgical, water softening, catalysis, bio-based chemical etc. use ion exchange as a critical step in processing.
What is the Ergun equation?
The Ergun equation, an extension of Darcy law, is the most popular equation used up to now to represent the relationship between pressure drop and fluid flow in fludized or packed beds.
Does the Ergun equation include the pressure drop due to inertia?
On the continuum level, the second order velocity term demonstrates that the Ergun equation also includes the pressure drop due to inertia, as described by the Darcy–Forchheimer equation . The extension of the Ergun equation to fluidized beds, where the solid particles flow with the fluid, is discussed by Akgiray and Saatçı (2001).
What is the relationship between Ergun and Kozeny-Carman equations?
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.
Is the Ergun correlation applicable for cylindrical packed beds with spherical particles?
An experimental study was conducted to determine the pressure drop characteristics of cylindrical packed beds through which turbulent pipe flow was passing. This study was planned to clarify the applicability of the well-known Ergun correlation proposed for beds composed with spherical particles on beds with non-spherical particles.