What is a metastable flow in a nozzle?
The expansion of steam in an ideal nozzle is isentropic, which is accompanied by condensation process. The flow of supersaturated steam, through the nozzle is called supersaturated flow or metastable flow.
Why supersaturated phenomenon occurs in nozzle?
Detailed Solution The supersaturation phenomenon occurs in the nozzle due to delay in condensation as a result of which mass flow rate coming from the nozzle is more than the designed value. Thus this phenomenon is delayed and the vapor continues to expand in dry condition even beyond point C.
Why the turbine nozzles are made divergent after the throat?
So that Pe/Pt is less than 1 but greater than critical pressure ratio, the velocity increases in the convergent region of the nozzle, but mach number (m) is less than 1 at throat. So the divergent section acts as a sub-sonic diffuser in which the pressure increases and velocity decreases.
What is the effect of supersaturated flow in steam nozzle?
Effect of Supersaturated flow in nozzle: The effect of supersaturated is to reduce the heat drop slightly during the expansion and consequently a corresponding reduction in final velocity. The final dryness fraction and the entropy also increased and the measured discharge is greater than that theoretically calculated.
What is metastable state in physics?
metastable state, in physics and chemistry, particular excited state of an atom, nucleus, or other system that has a longer lifetime than the ordinary excited states and that generally has a shorter lifetime than the lowest, often stable, energy state, called the ground state.
What is the effect of friction on nozzle?
As the friction in the nozzle slows down the flow of steam in it, the mass flow rate also decreases due to nozzle friction.
What is the effect of friction on the flow through a nozzle?
in case of nozzle, friction will decrease the motion of flow, that is friction will decrease the velocity of floor. as a result, actual velocity of flow would be less than theoretical velocity of flow through nozzle.
Which of the following statement about metastable expansion of steam through a steam nozzle is false?
Which of the following statement about metastable expansion of steam through a steam nozzle is FALSE? Explanation: Metastable expansion of steam produces a supersaturated state where steam is undercooled to a temperature less than that corresponding to its pressure.
Why nozzles are made convergent and divergent?
Convergent-divergent type of nozzles are mostly used for supersonic flows because it is impossible to create supersonic flows (mach number more than one) in convergent type of nozzle and therefore it restricts us to a limited amount of mass flow through a particular nozzle.
Why metastable is important?
In a three-level laser, the material is first excited to a short-lived high-energy state that spontaneously drops to a somewhat lower-energy state with an unusually long lifetime, called a metastable state. The metastable state is important because it traps and holds the excitation energy, building up a…
Why there is a need for metastable state?
Metastable Meaning Due to this de-excitation process, the population inversion can not be achieved. Hence we need an intermediate energy level or the state where the atoms can stay a bit longer or atoms can have a longer lifetime.
What is the metastable state of a nozzle expansion?
In a nozzle expansion, the expansion is so quick that the vapor condensation doesn’t occur within the nozzle. The point at which the condensation occur maybe within the nozzle or after the vapor leaves the nozzle. The flow is neither stable nor unstable until the vapor condensation occurs. This state is called metastable state.
What is the difference between a nozzle and a steady state?
which is the expression for the steady state flow energy equation. Things to remember. Nozzle is a duct by flowing through which the velocity of a fluid increases at the expense of pressure drop. if the fluid is steam, then the nozzle is called as Steam nozzle.
How do you find the mass flow rate in a nozzle?
Mass-Flow Rate in a Nozzle: The steady flow energy equation is: If P 1 = P 2 the mass-flow rate is zero. Also if P 2 = 0, the mass flow rate is zero. If the graph is plotted for mass flow rate v s pressure ratio, it will be as shown in the figure.
What is the function of a nozzle?
Nozzle is a duct by flowing through which the velocity of a fluid increases at the expense of pressure drop. if the fluid is steam, then the nozzle is called as Steam nozzle. The flow of steam through nozzles may be takenas adiabatic expansion.