FLUID MOVERSMechanical devices – move liquid from one point to another point by doing work.

Fans < 0.07 bar (gage) and Compressors >2.5 bar.

FLUID MOVERSPower required = Fluid mass flow rate specific workPower = Wm (Watts)

Dynamic fluid mover: Energy is continuously added to a flowing fluid with the help of a rotor having blades by dynamic action (the fluid is accelerated).Ex: Ceiling fan

Positive displacement fluid mover: The fluid is drawn into a working space through a suction valve/port and then pushed or moved out through a delivery valve/port. There is a cyclic energy transfer. Ex: Cycle pump.

PUMPSThese are mechanical devices that move liquids (water, oil, etc.) from one place to another place.Pressure, velocity or P.E of the liquid is increased.

H – Total difference in level of water (total head = Hs + Hd)Q – Volume flow rate or discharge per second (m3/s)

PUMPSMass flow rate, m = .Q (kg/s)P.E. change of fluid = mgH = gQHPower required for the motor to dive a pump of efficiency,:P = (Watts)The rotodynamic (centrifugal) and the positive displacement (reciprocating) are the two common types of pumps.

Monoblock pump Submersible pump (multistage centrifugal pump)

HEAD Vs DISCHARGEDischarge decreases with increase in head.

CENTRIFUGAL PUMP

Very simple design

Two main parts are the impeller and the diffuser

Impellers:

- Bronze

- poly carbonate

- cast iron

- stainless steel

CENTRIFUGAL PUMP

The pump has a rotor with number of blades (vanes).

The rotor rotates inside a spiral casing with the help of a motor.

The casing is connected to the suction pipe which draws water from the sump.

The casing is also connected to the delivery pipe which takes the water to the over head tank.

PRIMINGThe suction pipe and the pump casing must be filled with water before starting.Any air in the pump is vented out.

SUCTION HEAD LIMITATIONThe suction head should not exceed 10 m of water column (head).

To overcome this problem in bore wells, special pumps called ‘deep well pumps’ are used.

Submersible pumps, Turbine pumps, Jet pumps and compressor pumps are the common deep well pumps.

Submersible pump is a multistage centrifugal pump.

Due to high rotational speed, there is a large conversion of K.E. into pressure energy.

CENTRIFUGAL PUMPADVANTAGES:

- Very efficient

- Produce smooth and even flow

- Reliable with good service life

DISADVANTAGES

- Loss of priming easily

- Efficiency depends upon operating design head & speed.

PROBLEM

A pump develops a head of 10 m of water column. The discharge is 600 liters/min. Determine the motor power if the pump efficiency is 50% and the fluid is water.

Answer: P = = 1.96 kW