In centrifugal pump operation, the cavitation can be eliminated by maintaining suction pressure __________ the vapor pressure of the liquid at the suction temperature.

In vapor compression cycle having dry saturated vapor at the end of compression the refrigeration effect is given by? H1 – Enthalpy of vapor before compression H4 – Enthalpy of vapor before entering evaporator H2 – Enthalpy of vapor after compression

A

H1 – H4

B

H2 – H4

C

H1 × H4

D

H2 × H4

Cavitation occurs in a centrifugal pump when the suction pressure is

A

Less than the vapour pressure of the liquid at that temperature

B

Greater than the vapour pressure of the liquid at that temperature

C

Equal to the vapour pressure

D

Equal to the developed head

The ratio of existing moles of vapor per mole of vapor free gas to the moles of vapor that would be present per mole of vapor free gas, if the mixture were saturated at the existing temperature & pressure, is termed as the

A

Relative humidity

B

Relative saturation

C

Percentage saturation

D

None of these

The ratio of existing moles of vapor per mole of vapor free gas to the moles of vapor that would be present per mole of vapor free gas, if the mixture were saturated at the existing temperature & pressure, is termed as the

A

Relative humidity

B

Relative saturation

C

Percentage saturation

D

None of these

A centrifugal pump which circulates a hot liquid metal at 500 degree Celsius is driven by a 3600 rpm electric motor. The motor is coupled to the pump impeller by a horizontal steel shaft of dia 25 mm. Let us assume the motor temperature as 60 degree Celsius with the ambient air at 25 degree Celsius, what length of shaft should be specified between the motor and the pump? It may be presumed that the thermal conductivity of the shaft material is 35W/m K and that the convective film coefficient between the steel shaft and the ambient air is 15.7W/square m K

A

38.96 cm

B

54.76 cm

C

23.76 cm

D

87.43 cm

Impeller & casing of centrifugal pump handling corrosive liquid and frequently running under cavitation condition is most prone to __________ corrosion.

A

Uniform

B

Oxygen diffusion

C

Pitting

D

Inter-granular

Impeller & casing of centrifugal pump handling corrosive liquid and frequently running under cavitation condition is most prone to __________ corrosion.

A

Uniform

B

Oxygen diffusion

C

Pitting

D

Inter-granular

A centrifugal pump designed to pump water is employed to pump a more viscous oil. In the later case, the pump

A

Develops a lower head

B

Capacity is reduced

C

Requires more power

D

All of the above

N.P.S.H. the net positive suction head, is calc. by the absolute suction head _________ the vapor pressure of the liquid being pumped.

A

Plus

B

Minus

C

Divide

D

Multiply

Spherical bubbles of 3 mm diameter are observed in the bulk fluid boiling of water at standard atmospheric pressure. Assuming pure water vapor in the bubble and vapor pressure equal to 101.325 k N/m2, calculate the temperature of the vapor

A

100.217 degree Celsius

B

200.217 degree Celsius

C

300.217 degree Celsius

D

400.217 degree Celsius

In centrifugal pump operation, the cavitation can be eliminated by maintaining suction pressure __________ the vapor pressure of the liquid at the suction temperature.

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