End of term7
In the hydraulic calculation of pipelines, graphical methods are based on the concept of:
Hydraulic characteristics
Flow velocity
Hydraulic hammer
Centrifugal pumps
The head loss in a pipeline during turbulent flow is represented as ΔH = BQ^2, where B is the:
Head loss coefficient
Diameter
Length
Flow rate
The hydraulic characteristic of a pipeline represents turbulent flow when expressed in the form of:
ΔH = BQ^2
ΔH = B'Q^2
ΔH = BQ
ΔH = Q/B
In the case of sequential connection of pipelines, the cumulative characteristic is represented as:
ΔH = ΔH₁ + ΔH₂ + ΔH₃
ΔH = ΔH₁ + ΔH₂
ΔH = ΔH₁ΔH₂ΔH₃
ΔH = ΔH₁ - ΔH₂ - ΔH₃
In parallel connection of pipelines, the flow rates add up when the head loss is:
ΔH = Q₁ + Q₂
ΔH = ΔH₁ + ΔH₂
ΔH = Q₁ - Q₂
ΔH = Q₁ * Q₂
The cumulative characteristic of pipelines in sequential-parallel connection involves summing the
characteristics of pipelines:
1 and (2 + 3)
1 and 2
2 and 3
1, 2, and 3
Graphical methods are particularly important in analyzing the operation of:
Centrifugal pumps
Valves
Siphon pipelines
Hydraulic hammers
The effective head of a pump is the difference in heads caused by:
The pump
Gravity
Friction
Velocity
The power at the motor shaft is higher than the effective power due to:
Transmission efficiency
Pump efficiency
Pipeline length
Gravity
To put a siphon into operation, it is necessary to:
) Remove air from it
Increase air pressure
Increase liquid velocity
Increase temperature
In a siphon pipeline, a reduction in pressure at the upper point can cause:
Liquid evaporation
Increased pressure
Cavitation
Decreased flow rate
The hydraulic calculation of siphon pipelines is fundamentally similar to the calculation of:
Regular pipelines
Centrifugal pumps
Hydraulic hammers
Parallel pipelines
A sudden change in pressure in a pipeline due to a rapid change in flow velocity is known as:
Hydraulic hammer
Siphon effect
Cavitation
Pipeline surge
Hydraulic water hammer can occur when:
Closing valves quickly
Opening valves slowly
Increasing pump speed
Decreasing pipe diameter
The pressure increase during a hydraulic water hammer is due to the conversion of:
Kinetic energy to potential energy
Potential energy to kinetic energy
Thermal energy to pressure energy
Pressure energy to kinetic energy
The duration of the hydraulic hammer phase is determined by:
Time taken for direct and reverse shock waves to traverse
Valve size
Pipe material
Liquid viscosity
. To prevent hydraulic hammer, one measure is to:
Increase closing and opening times of shut-off devices
Increase pipe diameter
Increase pump speed
Decrease liquid viscosity
A special relief valve (Valve K) is installed to:
Release liquid and reduce pressure
Increase pressure
Decrease flow rate
Increase kinetic energy
Cavitation refers to the formation of regions filled with:
Gas (vapor) in a moving liquid
Solid particles in a moving liquid
Oil in a stationary liquid
Water in a gas
The formation of gas-filled regions in cavitation is caused by a decrease in pressure:
Below the saturation pressure
Above the saturation pressure
Equal to the saturation pressure
Unrelated to pressure changes
Cavitation phenomena can occur in localized resistances, such as:
Venturi tubes
Straight pipes
Pump impellers
Parallel pipelines
The calculation of cavitation involves determining the minimum pressure in the narrow section, denoted as
P₂
P₁
P₃
The cavitation number (σ) is used as a dimensionless criterion and is defined as the ratio of:
Pressure and velocity
Velocity and diameter
Vapor pressure and velocity
Pressure drop and velocity
The vapor pressure at which cavitation occurs is known as:
Saturation pressure
Critical pressure
Maximum pressure
Hydraulic pressure
Cavitation occurs not only in the flow of liquid through pipes but also during:
External flow around objects
Hydraulic hammer
Siphon operation
Pump operation
To exclude cavitation phenomena, it is necessary to aim for a cavitation number (σ) that
Increases with pressure
Increases with temperature
Decreases with pressure
Remains constant
At high rotation speeds, fluid flow velocities can lead to cavitation in:
Hydro machine blades
Straight pipes
Venturi tubes
Centrifugal pumps
Cavitation in hydraulic machines can result in:
Structural damage and vibrations
Increased efficiency
Reduced energy losses
Improved pump performance
In siphon pipelines, the pressure at the highest point should not decrease to the pressure at which:
Liquid starts to evaporate
Liquid freezes
Cavitation occurs
Hydraulic hammer occurs
The hydraulic calculation of siphon pipelines is fundamentally similar to the calculation of:
Regular pipelines
Hydraulic hammers
Parallel pipelines
Centrifugal pumps