How many surface profiles are possible in Gvf?

A summary of the twelve possible water-surfaces profiles is shown in Table 2. The classification follows directly from the governing equation (Equation 10).

What is the difference between critical and subcritical flow?

If Fr is greater than 1.0, flow is supercritical; if it is under 1.0, flow is subcritical. Fr is 1.0 for critical flow conditions. 3. Critical Slope: Critical slope is that channel slope for a particular channel and discharge, at which the normal depth for uniform flow will be the same as the critical depth.

How do you know if a flow is supercritical or subcritical?

If flow is subcritical waves will appear in front of the stick. If flow is at critical waves will have a 45 o angle. If flow is supercritical no upstream waves will appear and the wave angle will be less than 45 o.

What is an adverse slope?

Adverse slope occurs when the upstream invert elevation of a pipe is actually below the downstream invert elevation. Normal depth is undefined for adverse slopes, since no amount of positive flow would result in a rising friction slope. Most flow conditions for adverse sloping pipes are subcritical.

What is meant by supercritical flow?

According to the website Civil Engineering Terms, supercritical flow is defined as follows: The flow at which depth of the channel is less than critical depth, velocity of flow is greater than critical velocity and slope of the channel is also greater than the critical slope is known as supercritical flow.

What is the formula of critical depth?

The governing equation for critical depth computation is [1](1) Q 2 g = A 3 B , where is the discharge given to compute the corresponding critical depth, is the gravitational acceleration, is the cross section area, and is the top width at the water surface.

What is the meaning of sub critical?

Definition of subcritical

1 : less or lower than critical in respect to a specified factor. 2a : of insufficient size to sustain a chain reaction a subcritical mass of fissionable material.

What is subcritical and supercritical boiler?

Subcritical boilers are boilers that work at temperatures up to 374°C and at a pressure of 3,208 psi (the critical point of water). Supercritical boiler (supercritical steam generator) is a type of boiler that works under supercritical pressure conditions.

What is critical flow in civil engineering?

Critical flow is the transition or control flow that possesses the minimum possible energy for that flowrate. Critical flow has a Froude number equal to one. Critical Slope is one that sustains uniform, critical flow (yn=yc).

What is the difference between open channel flow and pipe flow?

Pipe flow Vs Open channel Flow

Open Channel Flow is a type of fluid flow in a conduit with a free surface open to the atmosphere. The pipe flow is a type of flow within a closed conduit. The maximum velocity occurs at the center of the pipe. HGL(Hydraulic Gradient Line ) coincides with the water surface line.

What temperature is supercritical steam?

Supercritical water exists at temperatures above 374 °C and pressures above 220 atmospheres.

Which boilers are supercritical?

Super Critical Boilers are the boilers which operate at steam pressure higher than critical point. Critical point is 22.064 Mpa, 373.946 deg cen. at this point latent heat of evaporation is zero & there is no difference in density of steam & water.

What is the supercritical point of water?

At 373°C and 220 bars, normal water becomes supercritical water. “Supercritical” can be thought of as the “fourth state” of a material.

What is the difference between supercritical and ultra-supercritical?

The difference between subcritical and ultra-supercritical technology is that the total amount of flue gas emitted from the ultra-supercritical plant is about 14 per cent smaller, and hence the capacity of the SO2 control device can be about 14 per cent lower, resulting in savings in investment and operating costs.

What are two advantages of supercritical boilers?

Specific advantages include:

Steam temperature at the inlet and outlet of the reheater is nearly constant over a wide load range. The boiler feedwater pump power is significantly reduced at lower loads. Short startup times. Higher plant efficiency over the entire load range.

What is the pressure range of supercritical boiler?

What is Supercritical Pressure ? pressure above 22.1 MPa and 374 oC.

What is supercritical pressure and temperature?

The supercritical condition of a steam-water cycle is a state at which its temperature and pressure are above its thermodynamic critical point, where the pressure of the steam water is 22.12 MPa, the temperature is 647.14 K, and the density is 324 kg/m3.

What is ultra supercritical pressure?

Supercritical (SC) and ultra-supercritical (USC) power plants operate at temperatures and pressures above the critical point of water, i.e. above the temperature and pressure at which the liquid and gas phases of water coexist in equilibrium, at which point there is no difference between water gas and liquid water.

Why are supercritical boilers more efficient?

Ultra-supercritical technology uses steam with very high temperatures, up to 620°C, and pressure, up to 300 bar, resulting in a much higher efficiency than conventional coal fired plants. A unit burns much less coal, thereby generating less emission per megawatt of power output.

What is sub and supercritical water?

Firstly, the subcritical part, which covers temperatures between 100−374 °C and pressures higher than the water saturation pressure at the selected temperature; secondly, the supercritical part, which covers water temperatures and pressures higher than 374 °C and 22.1 MPa, respectively (conditions over the critical …

What is an example of a supercritical fluid?

Any fluid pushed to a temperature and pressure where it is no longer possible to differentiate between the liquid and gas phase becomes a supercritical fluid. For example, in water, the critical temperature is 374°C, and the critical pressure is 22 MPa.