A. Equivalent thickness of film
B. Thermal conductivity Equivalent thickness of film Specific heat x Viscocity
C. Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
D. Film coefficient x Inside diameter Thermalconductivity
E. none of the above
Related Mcqs:
- In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by___________________?
A. convection
B. radiation
C. conduction
D. both convection and conduction
E. none of the above - The concept of overall coefficient of heat transfer is used in case of heat transfer by________________?
A. conduction
B. convection
C. radiation
D. conduction and convection
E. convection and radiation - The unit of overall coefficient of heat transfer is___________________?
A. kcal/m2
B. kcal/hr °C
C. kcal/m2 hr °C
D. kacl/m hr °C
E. kcal/m3 hr °C - Thermal conductivity of a material may be defined as the________________?
A. quantity of heat flowing in one second through one cm cube of material when opposite faces ^re maintained at a temperature difference of 1°C
B. quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1°C
C. heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
D. all of the above
E. none of the above - In heat exchangers, degree of approach is defined as the difference between temperatures of________________?
A. cold water inlet and outlet
B. hot medium inlet and outlet
C. hot medium outlet and cold water inlet
D. hot medium outlet and cold water outlet
E. none of the above - The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit_______________?
A. temperature
B. thickness
C. area
D. time
E. area and time - Thermal conductivity of water in general with rise in temperature ____________________?
A. increases
B. decreases
C. remains constant
D. may increase or decrease depending on temperature
E. none of the above - The ratio of heat flow Q1/Q2 from two walls of same thickness having their thermal conductivities as ATj – 2K2 will be ________________?
A. I
B. 0.5
C. 2
D. 0.25
E. 4.0 - A non-dimensional number generally associated with natural convection heat transfer is________________?
A. Grashoff number
B. Nusselt number
C. Weber number
D. Prandtl number
E. Reynold number - The amount of radiation mainly depends on___________________?
A. nature of body
B. temperature of body
C. type of surface of body
D. all of the above
E. none of the above
