96. In certain heat exchanger, both the fluids have identical mass flow rate specific heat product. The hot fluid enters at 76°C and leaves at 47°C, and the cold fluid entering at 28°C leave at 55°C, the effectiveness of the HE is
    

1. 1. 0.16
      

   
   
   

   2. 0.60
      

   
   
   

   3. 0.72
      

   
   
   

   4. 1.0

   
   
   

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1. View Hint View Answer Discuss in Forum

   ε =	Ch(Th1 - Th2)
   	Cmin(Th1 - Tc1)

   
   Here , C_h = C_c'
   

   ε =	Th1 - Th2	=	76 - 47	= 0.604
   	Th1 - Tc1		76 - 28

   
   

   Correct Option: B

   ε =	Ch(Th1 - Th2)
   	Cmin(Th1 - Tc1)

   
   Here , C_h = C_c'
   

   ε =	Th1 - Th2	=	76 - 47	= 0.604
   	Th1 - Tc1		76 - 28

   
   

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97. In a heat exchanger, it is observed that ∆T₁ = ∆T₂ where ∆T₁ is the temperature difference between the two single phase fluid streams at one end and ∆T₂ is the temperature difference at the other end. This heat exchanger is
    

1. 1. a condenser
      

   
   
   

   2. an evaporator
      

   
   
   

   3. a counter flow heat exchanger
      

   
   
   

   4. a parallel flow heat exchanger
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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98. Hot oil is cooled from 80 to 50°C in an oil cooler which uses air as the coolant. The air temperature rises from 30 to 40°C. The designer uses a LMTD value of 26°C. The type of heat exchanger is
    

1. 1. parallel flow
      

   
   
   

   2. double pipe
      

   
   
   

   3. counter flow
      

   
   
   

   4. cross flow

   
   
   

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1. View Hint View Answer Discuss in Forum

   θ =	θ1 - θ2
   	ln	θ1
   		θ2

   
   θ₁ = 50° , θ₂ = 10°
   θ₁ = 40° , θ₂ = 20°
   As given value is between these two, so cross flow is the best option.
   

   Correct Option: D

   θ =	θ1 - θ2
   	ln	θ1
   		θ2

   
   θ₁ = 50° , θ₂ = 10°
   θ₁ = 40° , θ₂ = 20°
   As given value is between these two, so cross flow is the best option.
   

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99. The practice to use steam on the shell side and water on the tube side in condensers of steam power plant is because
    

1. 1. to increase overall HT coefficient, water side velocity can be increased if water is on the tube side
      

   
   
   

   2. condenser can act as a Storage unit for condensed steam
      

   
   
   

   3. rate of condensation of steam is invariably smaller than the mass flow rate of cooling water
      

   
   
   

   4. it is easier to maintain vacuum on the shell side than on the tube side

   
   
   

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1. View Hint View Answer Discuss in Forum

   Air leaked into the condensor can be easily extracted.

   Correct Option: D

   Air leaked into the condensor can be easily extracted.

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100. In shell and tube heat exchanger, baffles are mainly used to
     

1. 1. increase the mixing of fluid
      

   
   
   

   2. increase the heat transfer area
      

   
   
   

   3. deflect the flow in desired direction
      

   
   
   

   4. reduce fouling of the tube surface

   
   
   

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1. View Hint View Answer Discuss in Forum

   Baffles are used to deflect the flow.

   Correct Option: C

   Baffles are used to deflect the flow.

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