91. The Blausius equation related to boundary layer theory is a

1. 1. third-order linear partial differential equation

   
   
   

   2. third-order nonlinear partial differential equation

   
   
   

   3. second-order nonlinear ordinary differential equation

   
   
   

   4. third-order nonlinear ordinary differential equation

   
   
   

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   Blausius equation:
   

   2d3f	+	fd²f	= 0
   dη3		dη²

   
   This order non-linear D.E.

   Correct Option: D

   Blausius equation:
   

   2d3f	+	fd²f	= 0
   dη3		dη²

   
   This order non-linear D.E.

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92. 

1. 1. 0.5C2

      Um

   
   
   

   2. 0.5C₂

   
   
   

   3. 0.6C₂

   
   
   

   4. 0.6C2

      Um

      
      

   
   
   

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   Correct Option: C

   

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93. A thin vertical flat plate of height L, and infinite width perpendicular to the plane of the figure, is losing heat t o t he sur r oundi ngs by nat ur al convection. The temperature of the plate and the surroundings, and the proper ties of t he surrounding fluid, are constant. The relationship bet ween t he average Nussel t and Rayl ei gh numbers is given as Nu = K Ra^1/4, where K is a constant. The lengt h scales for Nusselt and Rayleigh numbers are the height of the plate. The height of the plate is increased to 16L keeping all other factors constant
    
    If the average heat transfer coefficient for the first plate is h₁ and that for the second plate is h₂, the value of the ratio h₁ /h₂ is

1. 1. 2

   
   
   

   2. 1

   
   
   

   3. 3

   
   
   

   4. 4

   
   
   

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   Correct Option: A

   

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94. Consider one-dimensional steady state heat conduction, without heat generation, in a plane wall; with boundary conditions as shown in the figure below. The conductivity of the wall is given by k = k₀ + bT; where k₀ and b are positive constant, and T is temperature.
    
    As x increases, the temperature gradient (dT/dx) will

1. 1. remains constant

   
   
   

   2. be zero

   
   
   

   3. increase

   
   
   

   4. decrease

   
   
   

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   Correct Option: A

   

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95. Consider one-dimensional steady state heat conducting along x-axis (0 ≤ x ≤ L), through a plane wall with the boundary surfaces (x = 0 and x = L) maintained at temperature of 0°C and 100°C. Heat is generated uniformly through out the wall. Choose the CORRECT statement
    

1. 1. The direction of heat transfer will be from the surface at 100°C to the surface of 0°C.

   
   
   

   2. The maximum temperature inside the wall must be greater than 100°C

   
   
   

   3. The temperature distribution is linear within the wall

   
   
   

   4. The temperature distribution is symmetric about the mid-plane of the wall

   
   
   

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   Correct Option: B

   

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