Mention all kinds of pumps?

Pumps are in general classified as Centrifugal Pumps (or Roto-dynamic pumps) and Positive Displacement Pumps.

Centrifugal Pumps (Roto-dynamic pumps)

The centrifugal or roto-dynamic pump produce a head and a flow by increasing the velocity of the liquid through the machine with the help of a rotating vane impeller. Centrifugal pumps include radial, axial and mixed flow units.

Centrifugal pumps can further be classified as 

end suction pumps in-line pumps

double suction pumps

vertical multistage pumps

horizontal multistage pumps

submersible pumps

self-priming pumps

axial-flow pumps

regenerative pumps 

Positive Displacement Pumps

The positive displacement pump operates by alternating of filling a cavity and then displacing a given volume of liquid. The positive displacement pump delivers a constant volume of liquid for each cycle against varying discharge pressure or head.

The positive displacement pump can be classified as: 

Reciprocating pumps - piston, plunger and diaphragm Power pumps

Steam pumps

Rotary pumps - gear, lobe, screw, vane, regenerative (peripheral) and progressive cavity

Selecting between Centrifugal or Positive Displacement Pumps 

Selecting between a Centrifugal Pump or a Positive Displacement Pump is not always straight forward. 

o Flow Rate and Pressure Head 

The two types of pumps behave very differently regarding pressure head and flow rate: 

The Centrifugal Pump has varying flow depending on the system pressure or head The Positive Displacement Pump has more or less a constant flow regardless of the

system pressure or head. Positive Displacement pumps generally gives more pressure than Centrifugal Pump's.

o Capacity and Viscosity

Another major difference between the pump types is the effect of viscosity on the capacity:

In the Centrifugal Pump the flow is reduced when the viscosity is increased In the Positive Displacement Pump the flow is increased when viscosity is increased

Liquids with high viscosity fills the clearances of a Positive Displacement Pump causing a higher volumetric efficiency and a Positive Displacement Pump is better suited for high viscosity applications. A Centrifugal Pump becomes very inefficient at even modest viscosity.

o Mechanical Efficiency

The pumps behaves different considering mechanical efficiency as well.

Changing the system pressure or head has little or no effect on the flow rate in the Positive Displacement Pump

Changing the system pressure or head has a dramatic effect on the flow rate in the Centrifugal Pump

o Net Positive Suction Head - NPSH

Another consideration is the Net Positive Suction Head NPSH.

In a Centrifugal Pump, NPSH varies as a function of flow determined by pressure In a Positive Displacement Pump, NPSH varies as a function of flow determined by

speed. Reducing the speed of the Positive Displacement Pump pump, reduces the NPSH

What is Bernoulli Equation?

The Bernoulli equation states that,

where

points 1 and 2 lie on a streamline,

the fluid has constant density,

the flow is steady, and

there is no friction.

Although these restrictions sound severe, the Bernoulli equation is very useful, partly because it is very simple to use and partly because it can give great insight into the balance between pressure, velocity and elevation.

How useful is Bernoulli's equation? How restrictive are the assumptions governing its use? Here we give some examples.

Pressure/velocity variation

Consider the steady, flow of a constant density fluid in a converging duct, without losses due to friction (figure 1). The flow therefore satisfies all the restrictions governing the use of Bernoulli's equation. Upstream and downstream of the contraction we make the one-dimensional assumption that the velocity is constant over the inlet and outlet areas and parallel.

Figure 1. One-dimensional duct showing control volume.

When streamlines are parallel the pressure is constant across them, except for hydrostatic head differences (if the pressure was higher in the middle of the duct, for example, we would expect the streamlines to diverge, and vice versa). If we ignore gravity, then the pressures over the inlet and outlet areas are constant. Along a streamline on the centerline, the Bernoulli equation and the one-dimensional continuity equation give, respectively,

These two observations provide an intuitive guide for analyzing fluid flows, even

when the flow is not one-dimensional. For example, when fluid passes over a solid body, the streamlines get closer together, the flow velocity increases, and the pressure decreases. Airfoils are designed so that the flow over the top surface is faster than over the bottom surface, and therefore the average pressure over the top surface is less than the average pressure over the bottom surface, and a resultant force due to this pressure difference is produced. This is the source of lift on an airfoil. Lift is defined as the force acting on an airfoil due to its motion, in a direction normal to the direction of motion. Likewise, drag on an airfoil is defined as the force acting on an airfoil due to its motion, along the direction of motion.

What is the different between pump and compressor?

The basic difference between a pump & compressor is : compressor is used to compress air at high pressure ,also when there is no load requirement . But in the other hand pump is used to deliever fluid or water to high head or through long distance under high pressure.A pump can't be used to compress air...(why?)

The main difference lies in the "compressibility" in the volume of liquid and gas. Liquid is considered "incompressible" (volume remains constant) when subjected to compressive forces, while gas is "compressible" (volume decreases when subjected to compressive force). The word "pumping" connotes "moving" a fluid (usually a liquid) from place to place without any perceptible change in its temperature but with an increase in the discharge pressure. Compressors, on the other hand, aside from moving the fluid, also reduces the volume of the compressible fluid (a gas), with a resulting increase in temperature and pressure of the fluid at the compressor discharge. For purely "moving" gases without compression, "blowers" are used instead of compressors. However, there is always a degree of compression however small that occurs for blowers since there is a pressure reading at the blower discharge (measured in inches-Water).

What is the first and second law of thermodynamics?First law

Energy can neither be created nor destroyed. It can only change forms.

In any process in an isolated system, the total energy remains the same.

For a thermodynamic cycle the net heat supplied to the system equals the net work done by the system.

The First Law states that energy cannot be created or destroyed; rather, the amount of energy lost in a steady state process cannot be greater than the amount of energy gained. This is the statement of conservation of energy for a thermodynamic system. It refers to the two ways that a closed system transfers energy to and from its surroundings – by the process of heating (or cooling) and the process of mechanical work. The rate of gain or loss in the stored energy of a system is determined by the rates of these two processes. In open systems, the flow of

matter is another energy transfer mechanism, and extra terms must be included in the expression of the first law.

The First Law clarifies the nature of energy. It is a stored quantity which is independent of any particular process path, i.e., it is independent of the system history. If a system undergoes a thermodynamic cycle, whether it becomes warmer, cooler, larger, or smaller, then it will have the same amount of energy each time it returns to a particular state. Mathematically speaking, energy is a state function and infinitesimal changes in the energy are exact differentials.

All laws of thermodynamics but the First are statistical and simply describe the tendencies of macroscopic systems. For microscopic systems with few particles, the variations in the parameters become larger than the parameters themselves, and the assumptions of thermodynamics become meaningless. The First Law, i.e. the law of conservation, has become the most secure of all basic principles of science. At present, it is unquestioned (although it is said to be criticized by people who do not accept the idea that the potential to gain energy is a form of actual energy).

Fundamental Thermodynamic Relation

The first law can be expressed as the Fundamental Thermodynamic Relation:

Heat supplied = internal energy + work done

Internal energy = Heat supplied - work done

Here, E is internal energy, T is temperature, S is entropy, p is pressure, and V is volume. This is a statement of conservation of energy: The net change in internal energy (dE) equals the heat energy that flows in (TdS), minus the energy that flows out via the system performing work (pdV).

Second law

The entropy of an isolated system consisting of two regions of space, isolated from one another, each in thermodynamic equilibrium in itself, but not in equilibrium with each other, will, when the isolation that separates the two regions is broken, so that the two regions become able to exchange matter or energy, tend to increase over time, approaching a maximum value when the jointly communicating system reaches thermodynamic equilibrium.

In a simple manner, the second law states "energy systems have a tendency to increase their entropy rather than decrease it." This can also be stated as "heat can spontaneously flow from a higher-temperature region to a lower-temperature region, but not the other way around." (Heat can flow from cold to hot, but not spontaneously—- for example, when a refrigerator expends electrical power.)

A way of thinking about the second law for non-scientists is to consider entropy as a measure of ignorance of the microscopic details of the system. So, for example, one has less

knowledge about the separate fragments of a broken cup than about an intact one, because when the fragments are separated, one does not know exactly whether they will fit together again, or whether perhaps there is a missing shard. Solid crystals, the most regularly structured form of matter, have very low entropy values; and gases, which are very disorganized, have high entropy values. This is because the positions of the crystal atoms are more predictable than are those of the gas atoms.

The entropy of an isolated macroscopic system never decreases. However, a microscopic system may exhibit fluctuations of entropy opposite to that stated by the Second Law (see Maxwell's demon and Fluctuation Theorem).

Third law

As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.

Briefly, this postulates that entropy is temperature dependent and results in the formulation of the idea of absolute zero.

What is the different between stress and strain?

Stress is defined as load per unit area.The difference between pressure and stress is stress is internal that is developed by the body.strain is defined as change in length to original length.This change is length is also called deformation.

Mention types of heat transfer?

Conduction- the transfer of heat from matter to matterConvection- the transfer of heat from matter to airRadiation- the transfer of heat from one point to another, such as boiling water.

Actually convection can also be any fluid medium and it can go vice versa ... the fluid can transfer to a plate.

Plus, you can't say matter, because "air" is matter.

It would be solid touching solid for conduction - but in reality there is a little bit of convection in there --- but that can be guessed to be zero.

Also, radiation is emitted by nearly everthing (unless a black body) - which its not point to point ... because that's duplicating what you've called Convection and Conduction. Radiation is the transfer of energy through electromagnetic waves, particles, etc.

Explain the air-conditioning cycle?

What is the meaning of “N.P.S.H.”?

Low pressure at the suction side of a pump can encounter the fluid to start boiling with

reduced efficiency cavitation

damage

It is the difference in pressure between the vapor pressure of the fluid being pumped and actual pressure on the suction side of the pump.

The Available Suction Head depends on how the pump is installed and pressure drop at a given flow rate for the fittings ect. on the suction side of the pump.

It is important because if the available suction head is less than the NPSH required the pump will cavitate. When this happens the fluid actually boils inside the pump or at least tiny bubbles form. When these bubbles collaspe the pump will sound like it's pumping gravel and will most likely be destroyed. Because the collapsing bubbles shoot out a jet of extremely high pressure and temperature fluid which actually cuts through the metal of the pump.

What is the difference between blower and compressor.?

A blower delivers high volume at low pressure. A compressor delivers low volume at high pressure.

What is advantage of fluid coupling over other types of coupling.?

Fluid couplings will not transmit shock. You have one in the automatic transmission of your car. They enable clutchless power transfer though they are less efficient than are mechanical clutch couplings.

what is the difference between a fan and a blower?

Generally speaking fans are axial, have high airflows at low static pressure

Blowers are centrifugal, have lower airflows than a tube-axial fan, but can sustain higher static pressures.

compressors can be of a number of designs but have the lowest flow and the highest static pressure of the three.

I have however seen a Roots type compressor called a "blower" by many people in the hot rod community but I believe that vernacular is not really correct.

compressors- Reciprocating, axial, centrifugal pumps-Reciprocating, axial, centrifugal