Nusselt number (for forced convection heat transfer) is a function of the _____________ number?

Related Mcqs:

1. Nusselt number is a function of Prandtl number and ______________ number of fluid in natural convection heat transfer?

   A. Grashoff
   B. Biot
   C. Stanton
   D. Reynolds

2. In forced convection, the Nusselt number is a function of ____________________?

   A. Re and Pr
   B. Re and Gr
   C. Pr and Gr
   D. Re and Sc

3. Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the________________?

   A. Surrounding temperature
   B. Average temperature of the fin
   C. Temperature of the fin end
   D. Constant temperature equal to that of the base

4. The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as _________________?

   A. D-1.8
   B. D-0.2
   C. D0.2
   D. D1.8

5. Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re 0.8. Pr n, is not valid, if the value of __________________?

   A. n = 0.4 is used for heating
   B. n = 0.3 is used for cooling
   C. Reynolds number for the flow involved is > 10000
   D. Reynolds number for the flow involved is < 2100

6. In forced convection, the heat transfer depends on _______________?

   A. Re, Pr
   B. Re, Gr
   C. Mainly Gr
   D. Re only

7. Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids ?

   A. Dittus-Boelter equation
   B. Sieder-Tate equation
   C. Nusselt equation
   D. None of these

8. A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________?

   A. Greater than that for un-insulated steam pipe
   B. Less than that of the un-insulated steam pipe
   C. Equal to that of the un-insulated steam pipe
   D. Less than the steam pipe with 5 cms insulation

9. Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place____________________?

   A. Between two bodies in physical contact with each other
   B. Between two bodies not in physical contact with each other
   C. From one part of a body to the another part of the same body
   D. Both B & C

10. For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area___________________?

    A. Increases
    B. Decreases
    C. Remain constant
    D. Passes through a maxima