10. In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the;

v. Reynold's number, Grashoff's number.

vi. Grashoff's number.

vii. Prandtl number, Grashoff's number.

viii. Reynold's number

7. Cold surface is facing upward inducing week natural convection currents and less heat transfer compare to the cold surface facing downward. True or False?

6. The temperature rise of cold fluid is equal to temperature drop of hot fluid in heat exchanger is only when heat capacity rates of two fluids are equal. True or False?

1. Thermal contact resistance caused by the perfect thermal contact between two layers. True or False?

2. Viscosity of gases increases while viscosity liquids decreases by increasing temperature. True or False?

3. Gases offer less thermal resistance to heat transfer True or False

4. Condenser and Boilers are type of heat exchangers True or False

5. For a perfect black body the absorptivity is less than 1. True or False?

8. Correction factor of LMTD for a condenser or boiler is F = 0.1, regardless of the configuration of the heat exchanger. True or False?

9. Which of the following statement is wrong?

i. Logarithmic mean temperature difference is not equal to the arithmetic mean temperature difference.

ii. The heat transfer in liquid and gases takes place according to convection.

iii. The amount of heat flow through a body is dependent upon the material of the body.

iv. The thermal conductivity of solid metals increases with rise in temperature.

11. Thermal diffusivity is a;

ix. function of temperature.

x. physical property of a substance.

xi. dimensionless parameter.

xii. all of these

12. When heat transfer by molecules collision, it is referred to as heat transfer by; xiii. Conduction xiv. Convection xv. Radiation xvi. Convection and radiation