what is NPSH in pump????????

Answer 1

NPSH is an acronym for Net Positive Suction Head. It shows the difference, in any crosssection of a generic hydraulic circuit, between the pressure and the liquid vapor pressure in that section.

NPSH is an important parameter, to be taken into account when designing a circuit : whenever the liquid pressure drops below the vapor pressure, liquid boiling occurs, and the final effect will be cavitation : vapor bubbles may reduce or stop liquid flow.

NPSH = P0 + H − Y − Vt,

where,P0=PRESSURE inside the source tank,
(to be solved with coherent measuring units), where Y is the friction loss between the free surface of source of tank and pump center line, and Vt the liquid vapour pressure at the actual temperature at which the pump is handling fluid.
OR,
Suction Head
Based on the Energy Equation - the suction head in the fluid close to the impeller can be expressed as the sum of the static and the velocity head:

hs = ps / γ + vs2 / 2 g (1)
where,
hs = suction head close to the impeller
ps = static pressure in the fluid close to the impeller
γ = specific weight of the fluid
vs = velocity of fluid
g = acceleration of gravity

Liquids Vapor Head:
The liquids vapor head at the actual temperature can be expressed as:
hv = pv / γ (2)
where
hv = vapor head
pv = vapor pressure
Note! The vapor pressure in a fluid depends on temperature. Water, our most common fluid, starts boiling at 20 oC if the absolute pressure in the fluid is 2,3 kN/m2. For an absolute pressure of 47,5 N/m2, the water starts boiling at 80 oC. At an absolute pressure of 101.3 kN/m2 (normal atmosphere), the boiling starts at 100 oC.

Net Positive Suction Head - NPSH
The Net Positive Suction Head - NPSH - can be expressed as the difference between the Suction Head and the Liquids Vapor Head and expressed like

NPSH = hs - hv (3)
or, by combining (1) and (2)
NPSH = ps / γ + vs2 / 2 g - pv / γ (3b)

In pump operation, two aspects of this parameter are called respectively NPSH (a) Net Positive Suction Head (available) and NPSH (r) Net Positive Suction Head (required), where NPSH(a) is computed at pump inlet port, and NPSH(r) is the limit NPSH the pump can withstand without cavitating.

For effective pumping and cavitation should not occur ,
NPSHa>NPSHr
If above condition will not fullfilled, then cavitation will occur.there are two types of cavitation: suction cavitation and discharge cavitation.

You must visit to get more clear:
http://www.engineeringtoolbox.com/npsh-net-positive-suction-head-d_634.html

Answer 2

Net Pressure Suction Head.

This is the pressure head that causes liquid to flow through the suction pipe into the pump impeller.

When a pump takes pressure from mains, this is the mains pressure, less all head losses between the mains and the impeller. When the pump takes liquid from below the pump, the NPSH is atmospheric pressure less lift head and friction losses between the source and the pump.

Answer 3

NPSH stands for NET POSITIVE SUCTION PRESSURE, and this is the minimum pressure that the pumps inlet can be without cavitating. Cavitation is when the fluid vaporizes, forming bubbles which can damage or destroy pumps. You can find adeqaute formulas in Perry's Handbook for ChemE's, but in the real world you need only to calculate the NPSHa (available) at the inlet and compare to the NPSHr (required). NPSHr will be given to you by the manufacturer along with pump characteristic curves. You always want NPSHa > NPSHr.

Answer 4

The Net Positive Suction Head - NPSH - can be expressed as the difference between the Suction Head and the Liquids Vapor Head and expressed like

NPSH = hs - hv (3)

or, by combining (1) and (2)

NPSH = ps / γ + vs2 / 2 g - pv / γ (3b)

There are two components that must be considered:

Net Positive Suction Head Required(NPSHR)
Net Positive Suction Head Available(NPSHA)

The definition of NPSHA is simple: Static head + surface pressure head - the vapor pressure of your product - the friction losses in the piping, valves and fittings.

Hope this answers your query. If you want to go in dept, visit this link, which may be usefull.
http://www.mcnallyinstitute.com/11-html/11-12.html

................................................... All the best.

Answer 5

Net Positive Suction Head. A pump needs some pressure at its inlet so that the liquid being pumped does not cavitate. This is a fairly involved topic and I could simply go to some web site and cut and paste for you, however, I recommend a book, the author is: Sanks, Title: Pumping Station Design. In my opinion the finest text ever written on pumps, hydraulics and design of pumping systems. Read it and you will become an expert.

Answer 6

there is a great deal of hard artwork in getting that activity achieved and the cooling device could be flushed after that element additionally. i in simple terms did a water pump on a 1999 ford contour and it grow to be slightly worked given the area of that pump. as quickly as I have been given back homestead, i grow to be sore from my belt to my elbows for some days. a water pump could final approximately one hundred,000 miles form of. i could have charged approximately that plenty additionally. if that pump is inner to the block at the back of a disguise, the cost is going up on the topic of the hard artwork in touch.

Answer 7

Naturally Increase Penis Size - http://LongPenis.uzaev.com/?sToX