Test: Dimensional & Model Analysis, Centrifugal Pump - 2 - Mechanical Engineering MCQ

Which one of the following is correct?  
In positive displacement pumps, the slip can sometimes be negativewhen the actual discharge is greater than the theoretical discharge.This happens in

Assertion (A): The efficiency of a pump is generally less than that of aturbine.  
Reason (R): Although the losses in the two types of machines are of the same kind, the losses in pumps are more due to eddy and turbulence.

When the specific speed of the pump is <2600, the type of pump is

Centrifugal pumps have which of the following advantages?  
1. Low initial cost
2. Compact, occupying less floor space
3. Easy handling of highly viscous fluids
Select the correct answer using the code given below:

A centrifugal pump driven by a directly coupled 3 kW motor of 1450rpm speed is proposed to be connected to another motor of 2900 -rpmspeed. The power of the motor should be: 

Which one of tile following statements is correct? 
When a fluid passes from tile inlet to exit of the rotor in a cerltrlfuga1pump, tangential momentum

Which one of the following types of impeller vanes are most commonlyused in centrifugal type compressors?  

A centrifugal pump is started with its delivery valve kept  

An aeroplane is cruising at a speed of 800 kmph at altitude, where theair temperature is 0° C. The flight Mach number at this speed is nearly 

The time period of a simple pendulum depends on its effective length Iand the local acceleration due to gravity g. What is the number of dimensionless parameter involved?  

Match List-I (Flow/Wave) with List-II (Dimensionless number) and select the correct answer:  

List-I gives 4 dimensionless numbers and List-II gives the types of forces which are one of the constituents describing the numbers. Match List-I with List-II and select the correct answer using the codes given below the lists:  

Kinematic similarity between model and prototype is the similarity of 

A model test is to be conducted in a water tunnel using a 1: 20 model of a submarine, which is to travel at a speed of 12 km/h deep under seasurface. The water temperature in the tunnel is maintained, so that is kinematic viscosity is half that of sea water. At what speed is the model test to be conducted to produce useful data for the prototype? 

A ship model 1/60 scale with negligible friction is tested in a towing tank at a speed of 0.6 m/s. If a force of 0.5 kg is required to tow themodel, the propulsive force required to tow the prototype ship will be: 

Assertion (A): Reynolds number must be same for the model andprototype immersed in subsonic flows.  
Reason (R): Equality of Reynolds number for the model and prototypesatisfies the dynamic similarity criteria.

A sphere is moving in water with a velocity of 1.6 m/s. Another sphere of twice the diameter is placed in a wind tunnel and tested with airwhich is 750 times less dense and 60 times less viscous than water. The velocity of air that will give dynamically similar conditions is: 

A1:256 scale model of a reservoir is drained in 4 minutes by opening the sluice gate. The time required to empty the prototype will be: 

A 1:20 model of a spillway dissipates 0.25 hp. The corresponding prototype horse power dissipated will be:  

A model test is to be conducted for an under water structure which each likely to be exposed for an under water structure, which is likelyto be exposed to strong water currents. The significant forces areknown to the dependent on structure geometry, fluid velocity, fluiddensity and viscosity, fluid depth and acceleration due to gravity.Choose from the codes given below, which of the following numbers must match for the model with that of the prototype:  
1. Mach number
2. Weber number
3. Froude number
4. Reynolds number.

The square root of the ratio of inertia force to gravity force is called 

Consider the following statements:  
1. Complete similarity between model and prototype envisages geometric and dynamic similarities only.
2. Distorted models are necessary where geometric similarity is notpossible due to practical reasons.
3. In testing of model of a ship, the surface tension forces are generallyneglected.
4. The scale effect takes care of the effect of dissimilarity between model and prototype.
Which of these statements are correct?

Why is multi-staging in centrifugal pumps used?  

Which one of the following statements is relevant to the specific speedof a centrifugal pump?  

Consider the following statements regarding the specific speed of acentrifugal pump:  
1. Specific speed is defined as the speed of a geometrically similar pump developing unit power under unit head.
2. At the same specific speed, the efficiency is greater with largercapacity.
3. The specific speed increases with the increase in outer blade angle.
4. The specific speed varies directly as the square root of the pump discharge.
Of these statements:

Assertion (A): With increase in discharge in a single stage centrifugal pump the BHP goes on increasing but beyond a certain discharge the BHP starts decreasing.  
Reason (R): Efficiency of the pump starts decreasing beyond a certain discharge.