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Thermal Engineering 2 solved MCQs

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1. Nozzle is used to control direction or characteristics of flow.

a. true

B. false

discuss
a.true

explanation:-nozzle is used to control the direction and characteristics of flow.

2.  In fountains the type of nozzle used is

a. none of the mentioned

B. turbulent jet

c. high speed nozzle

d. laminar jet

discuss
d.laminar jet

explanation:-laminar jet nozzle is used to convert the fluid in laminar flow.

3. If mach number is less than one then its flow is                              

a. subsonic flow

B. turbulent flow

c. laminar flow

d. none of the mentioned

discuss
a.subsonic flow

explanation:-if m<1 then it is subsonic flow.

4. The steam leaves the nozzle at a

a. low pressure and a high velocity

B. high pressure and a high velocity

c. high pressure and a low velocity

d. low pressure and a low velocity

discuss
a.low pressure and a high velocity

explanation:-the steam leaves the nozzle at low pressure & a high velocity as the action of steam is best suited for turbine operations under these conditions.

5. When mach number is greater than one the flow is                  

a. subsonic

B. supersonic

c. laminar

d. none of the mentioned

discuss
b.supersonic

explanation:-when m>1 the flow is supersonic.

6. In rocket engines the amount of expansion in Nozzle determines the                      

a. exit temperature

B. exit pressure

c. exit temperature & pressure

d. none of the mentioned

discuss
c.exit temperature & pressure

explanation:-when the flow is subsonic, air in nozzle expands isoentropically and hence exit temperature and exit pressure depends on the amount of expansion.

7. De-Laval turbine is a                          

a. multi rotor impulse turbine

B. impulse reaction turbine

c. single rotor impulse turbine

d. none of the mentioned

discuss
c.single rotor impulse turbine

explanation:-a de-laval turbine is a single rotor impulse turbine.

8. The supersaturated flow of steam through a nozzle as compared to a stable flow, the available heat drop                          

a. increases

B. decreases

c. is unpredictable

d. remains same

discuss
b.decreases

explanation:-the supersaturated flow of

9. The Parsons’ reaction turbine has

a. only moving blades

B. only fixed blades

c. fixed and moving blades of different shape

d. identical fixed and moving blades

discuss
d.identical fixed and moving blades

explanation:-the parsons’ reaction turbine has identical fixed & moving blades.

10. What is the critical pressure ratio for initially wet steam?

a. 0.582

B. 0.546

c. 0.577

d. 0.601

discuss
a.0.582

explanation:-the critical pressure ratio for initially wet steam is 0.582.

11. The ratio of the useful heat drop to the isentropic heat drop is called                          

a. condenser efficiency

B. nozzle efficiency

c. vacuum efficiency

d. boiler efficiency

discuss
b.nozzle efficiency

explanation:-the ratio of the useful heat drop to the isentropic heat drop is called nozzle efficiency.

12. Rateau turbine is                          

a. pressure-velocity compounded turbine

B. simple reaction turbine

c. velocity compounded turbine

d. pressure compounded turbine

discuss
d.pressure compounded turbine

explanation:-a rateau turbine is a pressure compounded turbine.

13. When the cross-section of a nozzle increases continuously from entrance to exit, it is called a                          

a. convergent-divergent nozzle

B. divergent nozzle

c. convergent nozzle

d. none of the mentioned

discuss
b.divergent nozzle

explanation:-when the cross-section of a nozzle increases continuously from entrance to exit, it is called a divergent nozzle.

14. Aeroderivative engines have pressure ratios

a. greater than 30

B. lesser than 30 and greater than 20

c. greater than 50

d. none of the mentioned

discuss
a.greater than 30

explanation:-higher pressure ratios of greater than 30 are used in aeroderivative engines.

15. Aeroderivative engines are larger.

a. true

B. false

discuss
b.false

explanation:-aeroderivative engines are compact and smaller in size.

16. Aeroderivative engines release higher emissions.

a. true

B. false

discuss
a.true

explanation:-aeroderivative engines are smaller and produce high output as a result of which they release higher emissions.

17. Critical pressure ratio is ratios of pressures at discharge.

a. minimum

B. none of the mentioned

c. optimum

d. maximum

discuss
d.maximum

explanation:-critical pressure ratio is the ratios of pressure at maximum discharge.

18. Ratio of critical pressure to inlet pressure in known as                        

a. none of the mentioned

B. pressure ratio

c. critical pressure ratio

d. isoentropic pressure ratio

discuss
c.critical pressure ratio

explanation:-ratio of critical pressure to inlet pressure is called as critical pressure ratio.

19. In De Laval Nozzle critical pressure ratio is given by (2/y+1)^(y/y-1).

a. true

B. false

discuss
a.true

explanation:-critical pressure ratio of de laval nozzle is derived theoretically.

20. With the increase in pressure, the exit velocity                    

a. decreases

B. increases

c. same

d. independent

discuss
a.decreases

explanation:-pressure is inversely proportional to the velocity. so, with the increase in pressure, the exit velocity decreases. we know that the pressure is equal to force per unit area, this contradicts the above statement.

21. The Prandtl Number approximates

a. momentum diffusivity to thermal diffusivity

B. thermal diffusivity to momentum diffusivity

c. shear stress to thermal diffusivity

d. thermal diffusivity to kinematic viscosity

discuss
a.momentum diffusivity to thermal diffusivity

explanation:-the prandtl number is a dimensionless number. it approximates the ratio of momentum diffusivity to thermal diffusivity. it can be expressed as pr = v/ α(1). where α= thermal diffusivity and v= momentum diffusivity.

22. Pumps increase                      

a. pressure

B. velocity

c. momentum

d. heat

discuss
a.pressure

explanation:-pumps increase pressure rather than velocity. during the pumping process, a housing is provided for the pumping elements. these parts can change the speed. pumps create a passage way that will squirt the fluid passing through it. thus, pumping increases pressure.

23. Which among the following is the formula for volumetric flow rate?

a. q = v/a

B. q = av

c. q = a+v

d. q = a-v

discuss
b.q = av

explanation:-volumetric flow rate is given by q= a.v. where v is the flow velocity of the fluid, and a is the area of cross section of the surface. area of a surface is also called as the vector area. thus, the right answer is q = av.

24. Which among the following is the formula for mass flow rate?

a. q = m/p

B. q = mp

c. q = m + p

d. q = m – p

discuss
b.q = mp

explanation:-mass flow rate is given by q=m/p. this is a relation expressed for mass flow rate. when ‘m’ is the mass flow rate.

25. Compressible flow mainly deals with

a. solid dynamics

B. liquid dynamics

c. gas dynamics

d. solid and liquid dynamics

discuss
c.gas dynamics

explanation:-compressible flow is a branch of fluid mechanics that deals with different

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