Dose NPSHr depends on liquid temperature in centrifugal pumps?

Let's clarify easily the relationship between NPSHr and Temperature..

First we need to define the NPSHr as it is "The minimum pressure required at the suction port of the pump to keep the pump from cavitating" .. Right! And it is a function of the pump and must be provided by the pump manufacturer.

Second to understand Cavitation, you must first understand vapor pressure as it is the pressure required to boil a liquid at a given temperature. Vapour pressure is strongly dependent on temperature and thus so will both NPSHr and NPSHa.

The temperature of the Liquid impacts the NPSHr of a pump. As the water (pumped liquid) temperature increases, the size of the cavitation vapor bubbles generated get smaller, thus creating less blockage. At a water temperature of210 degrees F, the NPSHr value will be reduced by about1 foot, compared to ambient conditions. This effect actually provides a small positive variation in the actual NPSH margin.

• Read carefully, use a paper and a pen, state the equations and find a mathematical relation between NPSH and Temperature.

Mohammad respond is correct :D thanks

NPSH is the absolute pressure in feet of liquid at pumping temperature available at the pump suction flange above vapor pressure. Since centrifugal pumps ... selection curve. For cold water conditions a convenient relationship between.

YES

No,it depends on the pressure difference at suction and discharge.

yes100 percent

  This is a relation between the NPSH and the temperature because by decreasing the temperature the NPSHa is increase because the saturation pressure is increasing  by the equation

npsh a = p suction - p saturation   

NPSH Required (NPSHR): The minimum pressure required at the suction port of the pump to keep the pump from cavitating.

NPSH available is a function of your system and must be calculated, whereas NPSHR is a function of the pump and must be provided by the pump manufacturer.

NPSHA / NPSHR margin is of1.1 to2.5 .

As NPSHr is given by the pump manufacturer, all process data is taken by him. Temperature of the fluid is an important parameter while designing pump as vapor pressure of liquid depends on it. Follow the below equation;

NPSH= Ha +/- Hz - Hf + Hv - Hvp

Where:

Ha is the atmospheric or absolute pressure

Hz is the vertical distance from the surface of the water to the pump centerline

Hf is the friction formed in the suction piping

Hv is the velocity head at the pump's suction

Hvp is the vapor pressure of the water at its ambient temperature