21. The isentropic heat drop in the nozzle of an impulse steam turbine with a nozzle efficiency 0.9, blade velocity ratio 0.5 and mean blade velocity 150 m/s in kJ/kg is
    

1. 1. 50
      

   
   
   

   2. 40
      

   
   
   

   3. 60
      

   
   
   

   4. 75

   
   
   

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1. View Hint View Answer Discuss in Forum

   Blade velocity ratio =	u	= 0.5
   	v1

   
   or u = 0.5 v₁
   where u = mean blade velocity, and
   v₁ = Absolute velocity of steam at inlet
   

   =	150	= 300 m /s
   	0.5

   
   

   K.E. at inlet =	1	× m × v12 =	m	(300)2 J
   	2		2

   
   Nozzle efficiency = 0.9
   

   ∴ Isentropic heat drop in nozzle =	(300)2	= 50 kJ/kg
   	2 × 0.9

   
   

   Correct Option: A

   Blade velocity ratio =	u	= 0.5
   	v1

   
   or u = 0.5 v₁
   where u = mean blade velocity, and
   v₁ = Absolute velocity of steam at inlet
   

   =	150	= 300 m /s
   	0.5

   
   

   K.E. at inlet =	1	× m × v12 =	m	(300)2 J
   	2		2

   
   Nozzle efficiency = 0.9
   

   ∴ Isentropic heat drop in nozzle =	(300)2	= 50 kJ/kg
   	2 × 0.9

   
   

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22. In adiabatic flow with friction, the stagnation temperature along a streamline.... (increase/ remain constant)
    

1. 1. Remain constant

   
   
   

   2. increase

   
   
   

   3. decrease

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Remain constant

   Correct Option: A

   Remain constant

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23. List-I	List-ll
    A. Steam nozzle	1. Mach number
    B. Compressible	2. Reaction turbine
    C. Surface tension	3. Biot number
    D. Heat conduction	4. Nusselt number
    	5. Super saturation
    	6. Weber number

1. 1. A-5, B-1, C-6, D-3

   
   
   

   2. A-1, B-1, C-6, D-4

   
   
   

   3. A-5, B-2, C-6, D-1

   
   
   

   4. A-6, B-1, C-2, D-3

   
   
   

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1. View Hint View Answer Discuss in Forum

   A-5, B-1, C-6, D-3

   Correct Option: A

   A-5, B-1, C-6, D-3

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24. A cycle heat engine does 50 kJ of work per cycle. If the efficiency of the heat engine is 75%. The heat rejected per cycle is
    

1. 1. 16	2	kJ
      	3

      
      

   
   
   

   2. 33	1	kJ
      	3

      
      

   
   
   

   3. 37	1	kJ
      	2

      
      

   
   
   

   4. 66	1	kJ
      	2

   
   
   

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1. View Hint View Answer Discuss in Forum

   η = 0.75
   

   ∴ ηHE =	W	= 0.75
   	Q1

   
   
   or, Net heat input,
   

   Q1 =	50	=	200
   	0.75		3

   
   Also , W = Q₁ - Q₂
   

   or 50 =	200	- Q2
   	3

   
   

   ∴ Net heat required Q2 =	50	= 16.66 kJ
   	3

   
   

   Correct Option: A

   η = 0.75
   

   ∴ ηHE =	W	= 0.75
   	Q1

   
   
   or, Net heat input,
   

   Q1 =	50	=	200
   	0.75		3

   
   Also , W = Q₁ - Q₂
   

   or 50 =	200	- Q2
   	3

   
   

   ∴ Net heat required Q2 =	50	= 16.66 kJ
   	3

   
   

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25. For a compressible fluid, sonic velocity is
    

1. 1. a property of the fluid
      

   
   
   

   2. always given by √γ RT where γ , R and T are respectively the ratio of specific heats, gas constant and temperature in K
      

   
   
   

   3. always given by		∂p		1/2	s, where p, ρ and s are respectively pressure, density and entropy
      		∂ρ

      
      

   
   
   

   4. always greater then the velocity of fluid at any location

   
   
   

   5. Both A and B

   
   
   

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1. View Hint View Answer Discuss in Forum

   Here , Options A and B are correct answer .

   Correct Option: E

   Here , Options A and B are correct answer .

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