General Flashcards
What kind of flame is the most common one in nature?
- Diffusion flames
- Non-premixed flames
What’s the activation energy?
The minimum quantity of energy which the reacting species ust possess in order to undergo a specified reaction.
What’s the Lewis number?
A measure of the relative influence of thermal diffusion to mass diffusion.
What’s the Prandtl number?
A measure of the relative influence of viscosity to thermal diffusion.
What is the Schmidt number?
A measure of the relative influence of viscosity to mass diffusion
What’s the Dahmköhler number?
Flow time / diffusion time (residence time) over the characteristic reaction time
What does the SSA state?
It assumes that one intermediate in the reaction mechanism is consumed as quickly as it is generated.
So, the concentration must remain the same in a duration of the reaction.
Which are the features of a chain branching reaction?
- The reaction is endothermic
- The reaction is sensitive to pressure
- Its activation energy is rather large.
What does the partial equilibrium approximation (PEA) state?
If the forward and backward rates of a reaction k are much alrger than the net reaction, then the net rection is almost 0
If the approximation is valid to a reaction, the reaction net rate is near zero.
Which are the major species of a reaction?
CO2 H2O H2 O2 CO
N2 is also a major specie though it dies not participate in the reactions to any significant extent.
What’s the Dufour effect?
The energy flux due to a mass concentration gradient
What is Fick’s law of mass diffusion?
Relation of diffusive flux to the concentration under the assumption of steady state
What’s the Soret effect?
A phenomenon observed in mixtures of mobile particles where the different particle types exhibit different responses to the force of a temperature gradient.
The elementary reaction difers from the global reaction as
- The elementary reaction is a one-step reaction, while the global reaction is always a multiple one
- Mass action law only works for elementary reactions
Differences between elementary reactions and global reactions
- The elementary reaction is a one-step reaction, while the global reaction is always a multiple one
- Mass action law only works for elementary reaction.
- Only for an elementary reaction, the reaction order can be obtained from the chemical reaction equation.
