## Heat Transfer Miscellaneous

#### Heat-Transfer

1. Thermal conductivity is lower for

1. NA

##### Correct Option: B

NA

1. Match the property with their units
 Property Units A. Bulk modulus 1. W/s B. Thermal conductivity 2. N/m2 C. Heat transfer coefficient 3. N/m3 D. Heat flow rate 4. W 5. W/mK 6. W/m2K

1. NA

##### Correct Option: B

NA

1. For a given heat flow and for the same thickness, the temperature drop across the material will be maximum for

1.  dT ∝ 1 K

So, glass wool has minimum thermal conductivity and therefore maximum temperature difference.

##### Correct Option: C

 dT ∝ 1 K

So, glass wool has minimum thermal conductivity and therefore maximum temperature difference.

1. Match Group with Group B:
 Group A Group B A: Biot number 1: Ratio of buoyancy to viscous force B: Grashoff number 2: Ratio of inertia force to viscous force C: Prandtl number 3: Ratio of momentum to thermal diffusivities D: Reynolds number 4: Ratio of internal thermal resistance to boundary layer thermal resistance

1. NA

##### Correct Option: A

NA

1. The temperature variation under steady heat conduction across a composite slab of two materials with thermal conductivities k1 and k2 is shown in figure then, which one of the following statements holds?

1.  Q = KA dt dx

 where Slope = dt = Q dx KA

i.e., slope is more for less value of K, therefore
 dt > dt dx Ⅰ material dx Ⅱ material

∴ K1 < K2

##### Correct Option: A

 Q = KA dt dx

 where Slope = dt = Q dx KA

i.e., slope is more for less value of K, therefore
 dt > dt dx Ⅰ material dx Ⅱ material

∴ K1 < K2